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1 258 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d CH R 6 APT E e Dy e i r o s h ems T st namic Sy N a I T H LEN E TH R E STH E D nd LI A B . SM iv P t f rom a Dy n a m i c Sy s tems De v elo pm 276 e e t c pe rs e n DY ES I R 258 STEMS TH IC SY M NA EO a n rdi Coo l a nu a m Bi 297 n io t l o e 259 s s e ge: D a t eri l H ua ect v tel In e c o r l P a t n e pm l i l Sk s hat I W l? 298 F es ss on s f 260 gg E s rom l m r o Le a m o r f m r o F : logy yo br Em n St i a t n u o The M am M 263 hor p a t e re A 307 Y SUM M R 263 Epi ge n e s i s i n D e v e l o pm e n t a l Ps y chobi o logy S Y D N A M I C Y ? 307 CO NC LUSIO N: W H t s 266 nt ex tu al an d Ec ol o g i c Co l Theori s a R EFE R E N CES 308 T stems 271 n i k n i h y g s c mi na y D to n o i t uc od tr In An S t ica l ap p roa c h to Dyna m ic s y s t em s is a r e c e n t t h e o r e e me al pr oc ess a nd g e n eral s y st nt m s t h eo r ies. W e p r es en t mula- empor r y for a t he s t udy o f de v elop m e n t. I n i t s c o n t em w h w o nd sh les a ip inc r s p o t s y ic s m dyna f l o ia utor a t r o w s d irect l y f r o m a d v an c e s r ti on, t he t h i e o r y g n - u e d n nde th h t f g o in nd a t s r e u r e ep to yield a de d e y be us ma ey in st ea an di n g com p l ex a nd n d n s a sic y h s in p em t s y r s onl n be deas ca e i hes w t o h w o sh e e. W g n a ch of s e s s e c o pr l t ad r h c i nd r g a s a lon w o l i- fo o s l a t s, but i c i t hema t ma r s t a nd de v elop m e n t a p r o c ess as: us d to help us u e nde l l o gy a nd p s y c h o lo gy . T h e ti on o f s y s t em s t h in k i n g in bi o r s ) a c onc ep t u a l g u i de, ( b) a p (a o g r a m for r e d n h, a c r a e e namic s y st ems, in i t s m o s t g e n e s n a r m, m ic for r te m dy y (c) a b ma l t h e o r y . Fina l l sis for for , w e c onsi de r t he r e - a e r o sy st em s o f elem en t s t h a t c h a n g e o v e r t i m e. T he m i on be la l- e v hes to de c roa p s ap em t s y l s ica m en dyna e w t t a f s fer re ems, st y s l namic dy e, l us ica n h c te to a class o op m e t a nd ot he r t h e o r ies o f de v elop n e n t . m s- t hema t ica l eq ua t i ons t h a ma desc r ibe t i m e-b as e d s y t s i he h h in t on, bot i t a t en es r he p ut t o h g u ro Th ica l tor r ies. r e rop r p icula t t pa h t wi ms te l ess a c o r p nd in dy- a t n e m elop v g de udyin t s f o e g a t i r he e r l es wil hem y m i c s s y s t em s t h e o na : r r cu i t s e l f, t w o t u t De v elop m e n ca n only be 1. nde r s tood as t h e mul t i - e h t all f o n t p le, mut ua l, an d c o n t i n u o u s i n o eract i NA DY I R EO STEMS TH IC SY M ES m v o f t h e d e v elopin g s y s t le f r o els t h e m o l e cula r em, to h e cul t u r a l. t e en es r p e w , r e t hap is c th In n t t a t e o r y h o f de v elop m v t o c d an eral n e g y r e n n o sed ba e n t-indep enden t p r inc i- nde ca t n e m elop v De 2. d e t s e tood as n s r n only be u d les t h a t desc r ibe t he beha vi or o f p o m p l e x phy sica l a n c oc pr ma l- i m m o r les f esca m i t y n r e v ld o nfo u t a h es t ess p y o l o g ica l s y s t em s. T he ap bi l ica t i on o f dyna m ic s s t em s onds to y e a r s. li se c in n m elop v to de t p r o e c ess is r ela t i v ely n e w , em e r g i n g t e he pas t 20 y e in ma n y w a y s i t is a m ode r n r a r s. H o w e v , o r p t i t a h t is s m e t s y s c i m dyna f o ue al e v Th - o e h t des i v i c d i n gly , t h is c hap- c on; a i t r o ad r g t a lon f on o i t ua in nt co o , g n i z ali u t p e c n o c r o f s e l p i c n li a n o i erat , p g n i z ret i c a l p r i l r ica vie w o f t w o s t r a nds e tor te r be g ins wi t h a br ief h i s l ela d for ma l i z i n g t hes e c o m p an e x in t e r r t i ons o f t i m e , at c th e l l e t he in s m t for em t t s y ic s m for dyna e g a t i r he l a u is m t a t he or y i n t he s ens e a e It ess. c o r p nd a , e c n a t sub s r o e h es: t ri eo th elop- de f ies) o ud t l s ica r v nd empi ies (a p ie t o d if f e r en t s p e c ies, l d ap en) be as h d n a ( e b y ma it at th 258

2 259 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 259 Dy a m i c Sy n sis. B t i t i s a ls o a sp e- ut if t he ins t r u c t i ons to de v elop a r e in t h e g e n es, y B l a n a f o ins a r g d n a ins, ma do es, ag u e ci in k n o w l e d g e f r o m t h e i r e h in t s t is x y e t i x a l p m o he c es? If t n e he g ns on t r u o t wh g ns uma h w o h f o y or e h t c i f n i t h , 1994). er c t i y uld ab- o ism sh n a g he or yda t t des wha i c o de , wh t a e m ron vi en ons (e.g., T helen & S m ev ons i t ues e q hes t r e nsw y to a a he only w in? T a t e nd r a rb so e e y e k o v is to in t a n ot he r causa l a g en t wh o e v a l ua t es t h a a In t n e pm o l e v e ge: D tel s s e c o r l P t eri l H ua ect l ron vi ic or en t e n e g r e n t on, whe i t ma infor m t a l, a n d e h ma t be or- us mus ncul u m o r h e v cle e m o ons. S isi c es de k or [T]he indu i on o f n o v el beha vi t a l for m s ma y be t he sin- c t w i o g h win o n ile k e wh or sc l a t n e m elop v g a de in t a r t hes c o elop- he de l t l lem for a b o r p d e v l v s e r n u t n a t t impor s o gle m en- ly indef l ica g is is a lo h he end. T ut in t n o r u t a mus l t l W me f, 1987, p f l o . es. ( ienc sc al nt 240) sib le po si t i on; i t ot de- y s t h a t n o v e l t y r e a l ly do es n sa a h y t sa e when w n n a e m e t do w Wha f ism “de- on o i t c a r e t in n a g or n a t v elop , i t is t h e r e a l l a lon g. P o s t ula t i n g a s”? Usua v y a w l , but a r e g g bi s t e g t i t a h y t sa e w , y l l s ge ne s elop a n d en vi ron m e n t do es n ot r e m o v e t h is lo g ica l im- in in g we m e a n t h at it g e t s m o re c o m p l e x. I nde e d , t he def pass e. It m e r ely assi g ns t he p r e e x i s t in g p l a ns to t w o v i m w for e n f on o t ea r he c is t t n e m elop s. A de f o y t r e rop p so ur c es ins t ead o f on e. r ls a l e l c ica t den i f hen a mass o nd t a l l e gle c sin is g n i t r a t e s In th c hap te r, we fo ll o w a di f fere n t t r a d it i on. W e h nd ha a s, br r e v i gs, l for le s t poin - h t on he 3-m nds. T ag ree wi t h W o l f f (1987 ) t a t t he q ues t i on o f n o v el for m s ins, a e q ered w s an un t ea gr he t is s t i on. A nd w e a l s o c oncu r t when i t c bje g o vin o a m g n i k c a r s t top o s u t o ld infa n wh t ons— i t u l o l s ona i t i ad r he t t r- at th go es o ut o f si na t be c o m es a n 8-y ea r-o ld c h ild wh o ca n u r e, n u r t u r e, or in t e gh o w , o n o f b o t h— i a r e suf f i c ien t. T r ead a map a nd u nde r s t a nd s y he t r ad i t i on w e fo act l l m b o l ica l ly r e p r es en t e d lo- t th n n u o ca t wh uden t ld s r-o ea 18-y n a , r e t la , d n ons, a i t ca - ex n, io - a aniz g r o l a ic g o l o i s of b e i r o e h ems t st sy f o t a es o o r p y b s m w for e n f on o t ma he for ins t a pl ea r en c v nd e nd a a t s r de e for ma l t h e o r ies o f spa c e a n d f sel f t ess c - i e om ge pa t t er n g or a i n a g f-or l se By n. io t a aniz t z i on w e m e a n t h a t - r e he em es t v l o v ons in i t nsi a r e t hes t of ch a E . y r t o- g y o f n e w pa t t e r ns o f beha vi or f r o m p r e c u r s o r s t h a t enc mp o c e h ns of t o i t c a r e in e h t m o r f e g r e r em e d r d o an t t ex t o h t i em w st y lex s mp o ts of a c nen t e r ns. Whe r e do es u t hem s e l v es do n ot c o n t a in t h o s e pa s, n o i t c u it instr ic l p o s v e l t y c o m e f r o m? H o w ca n de v . t n e m ron vi he en t m o r or f f l e is n t sm i i n a g he or in t r e h eit elopin g s y s t em s th n a g f-or l Se y b t a h es t ess c ro p on— i t a z cre at e s o m et hi n g f r o m n o t h i n g ? i t h e i r o w n a c t i vi- ins o f t h is inc r e asin g c o m p l e x - U nde r s t a nd in g t he or i g t ies c h a n g e t hem s e l v es— is a f u nda m e n t a l p rop e r t y o f r de on- i t i ad r e. T ienc sc l a t n e m elop v f o t he hea t t y is a it li vin g t h in gs. F o r m is c ons l a t n e m elop v de g n i r d du e t c u r t n pr ess (Got t l ieb , W ahls t en, & Lickl i t e r , Chap f t e r 5, t h is es o c r u o he s for t d e look e v ha s t all y, de v elop m e oc t a l is e , m a e; Oy m u l o is v th , book nd Ha 1985). ne w for m s a i t h e r in t he or g a n ism or in t he en vi ron m e n t . f f s o em t s y ic s m Dyna les for for- c n i r p eral n e s g r i e In t he or g a n ism, c o m p l e x s t r u c t u r es a nd f u nc t i ons p i dea s o f bi o l o g ica l s e l f-or g a n i z a t i on in w a y s ism in ma l i z i n em e r g e be caus e t he c o m g n a g he or in t s t is x y e t i x e l p x t m o f a n e u r a l or g e n e t ic c ode. D e v elop m e n t c on- l- e v g de in nd a t s r nde ul for u ef ly us i r ina th at ar e e he for t r aor d n ons t l l t he or- - e r l a t n e m i r e p x g e in t c ondu nd for c ess a c o r p i l a t e e m op sis t s o f w a i t in g u n t i l t hes e s tor e t c u r t ins d r h. I a ism g n a g he or , t ely v i t a n r e t l t to do. A ism wha n ga se a ins c n t h is c hap t e r , w e ap p ly t hes e p r inc ip les m o s t s ab y m b g o w ne f in n r e t t nd pa e a r u t c u r t he s g t bin r o sp e c i f ica l ly to p e r c ep t u a l, m otor , a nd c o g n i t i v e de v e l- for o i eract t gh in u o r h t t n e m ron vi en l a i c o l or s sica y h s p it n e m op o es & n ood (e.g., J ildh h ly c r nd ea s a t n in infa t s n e wi n t. I n t he m o r e c o m m only a c c e p t e d m ron vi en t a h t h t Sm i t h, 1993; T helen, 1989; T helen & Sm i t h, 1994; e: Or g a n ism s ve rs i on, t he t w o p r o c ess es bot h c o n t r g T helen & Ul r i c h, 1991). B ut t he t hem e o f t he de v elopin ibut be c o m e c o m p l e x t h r o u gh a c o m bina t i on o s ap- na t u r e a n d or g a n ism a s a h o l i s t ic , s e l f-or g a n i z i n g s y s t em ha f on o f de v e l- nu rt ur e. F or ins t a nc e, t he g u i d in . t i pe a red ma n y t i m es befor e in bi o l o gy a nd p s y c h o lo gy g assump t he s o u r c es o f c o m - op m e n t a l beha vi or g e n e t i e s is t h a t B efor e w e desc r ibe a nd ap p ly dyna m ic p r inc ip les, w c f to t h o s e t h a t a r e inhe r e n t , pl ex it y ca n be pa r t i t i on e d si t u a t e o u r s y s t em s t h e o r y in t he wi de r p e r s p e c t i v e o in t he en vi ron m e n t. B u t inhe r i t e d , a nd ab s o r b e d f r o m sy st em s t h in k i n g in de v elop m e n t. T o w a r d t h is g o a l, o u r y inna t e whe t h e r de v elop m . n t is vie w e d as d r i v en b re vie w is s ele c t i v e a nd t hema t i c , r a t h e r t h a n e xhaus t i v e e on o f t h e st ru ct ur es, en vi ron m e n t a l d , or a c o m bina t i R eade r s a r e r e f e r r e d to e x c el len t r e vie w s b y F o r d a n input he f u nda m e n t r l p r em is e in t he t r ad i t i ona l vie w is tw o, t Le r n e r (1992), Got t l ieb (1992), Got t l ieb e t a l. (Chap t e a infor ma t i on ca n p e x i s t t he p r r o c e ess e th at “ 5, t h is Ha nd book , th is v o l u m e), Oy a ma (1985), a n d es t h a t g i v to i (1983). f ro e m Sa ri se f t a m a , 1985, p . 13). ” (Oy

3 260 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 260 n a m i Dy y es s s o n s f rom Embr y o log y: F o r m f rom a ti on is eq ua ll Le b i direct i o n a l b e t w ee n n u clea r p r o c ess . r e E g g m l Fo a nd ot he r c e l l ula r e v s s t en s Du i n g em br y o g en esis, c e l ls d i vi de, c h a n g e c h a r a c - r s le o a x ic e t a m a r is a d d r o t w mp r i ep or f t t s s r i ’s f y b a A b f l e s hem ze t i n e c - a g nd or e, a v o m , r te l l o c r e g r to la es in v mp l or a l for m. B ut n o e x a vi le o f de v elop m e n t a w beha ne ess ti v es o f t issues, or g a ns, a nd or g a n s y s t em s. T he p r o c a n em br y o no v e l t y is as c o m p e e l in g as t he em r g enc y o f l is h t n o e m e v s i ghly dyna m ic; t h a t is, t he c e l l a nd t issue m t a t e o f a s e em in gly h o m o g en e o us a n d fr o m t he in i t ia l s r As e x i t y . t hem s e l v es a l e s o u r c es o f or de r a nd c o m p mless sin gle c e l l, t he f e r t i l i r as- d e g g. A nd n o ot he ze for l t lo l g r ad ien t s gr ou ps of ce ca ls a r isin g f r o m d i f f e r en of ect p p l t e ely “g en e t ic” in c o m s s em e s t n e m elop v de o r ve a nd c o m e in to c o n t a c t mo h e i r n e w po si t i ons f u r t h e , t u r t e. u t c t he s t r r i c t u nfo ld in g o f sp e c ies-t y pica l s a n as ndu cti o n . w o n ess k oc r p i , er ract a h c eir h e g an ch t t u r y , bi o l o g is t s ha v e s t ud ie d t h is F or w e l l o v e r a c e n l v o n t a h is t e r t he n u o c c r a u to o t n a ele ly r a i c e t is esp Wha e f t e t ica r t in n to a in , r he gle sp a sin on o i t ma for s ran l e s t be- l l e gle c sin l on wil i g e is r h t t a h t l a n g he si es t v i g f i ul ly for m e d ona g a n ensi im l or e-d re th ism wi t h beaut if m f me a n e u r a l t ube or l i co b bud. Ra t h e r , i t is t he g r o up o d an h ga or e t g n i r es. Du p y issue t t d e t a i t n fere f i d - ll e w ns o ce l ls, a c t i n g a s a c l l e c t i v e a nd wi t h in a pa r t icula r po si- e w o cades, h w de e f t pas g- made si e v s ha r e h c r a e s r , r e v e e a on in t he la r g e r c o l l e c t i v ti t h t de t e r m in es t h e i r ul t i - nd a t s r nde u d r a w es to c n a adv t n ica f ni e- en imp he “ g t in n he h i r is c l l e e c on o e. N t fa e t ma i s tor y a t d ica l, but t r tr le b l a ck bo x” ( M a ab x, 1984a , p . 425) o f t h is l l e c t i v e a r e. spa t i a l a nd t empor a l d i m ensi ons o f t he c o a de elop m e n t v l p r o c ess. t is c ons ess: r u c t e d t h r o u gh p r o c t De v elop m e n r is t ic de- t is n o w abu nda n t ly clea Wha h a t em br y o n t e be nc t n e m elop v da e t ica r t in n is a w e en e v en t s in t h e v he pa o v on in i t T ina m r e t nd de on a i t c indu t h w a y s e a o l f t f f a f o g n i n r u he t nd on o cleus— nu pa t icula r g e n e p rod- r ieu-dep m f ies o r enden e l s ica tor s hi t g e n e e x p r essi ons t h a t l i em uc nd wha t on e w r i t e r has de a e d “ m u nda n e” bi o- s— t c o u p l e d to t h o s e m e c h a ar n ica l a nd m e e l ica hem c o n a h c l x, a M e ( f a r nd su body a l r e he c les in t ip inc r l p sica phy c a h t s t n e ev d an m r o f f o t n e m e h e hi ac e t n r e v o g y all u act t v r b a sic ma i n w a o r h de onsi ). C 1406 . , p 1984b e ls g t t h e i r pa h en t e w t y be la p r e t e is in e h e, t m i e t y on t t e r n. At a n e he sp h a g nd or s a t r ic pa f i c e ns t t ns— a l body p t em e r g e a r i o u s nd si e, sca ac pl f bor de r i n g c ze o o l l e c t i v es, a nd v a le, a a nd spa c e d i m ensi ons in t he f i r s t da y s in or de r ly t i m e n n c t i v e m o le cula r si g indu a ls n ot only ma in t a in t he pa t t e r ishe t so fa r es t a b l d but a l s o t r a n s for m i t in to a n e w pa t e r n . f a s r cu c o n r e t t e eks o f l i e. F o r m a t i on o f t nd w he body pa ) 26 . n, 1988, p ma Edel ( i g e d e z ut 10,000 il t he f d to abo de vi i has d g r e when t i e he c gh t u o h t l e, a m i is t h t y ls. B l ce e f- i d n u n a ls look l l k h Thi s p i c t u re i s m u c h di f fere e t f r o m o n e t h a t c a s t s t n heap d e t a i t n fere ons i t si in po d e k r eady ma r l e a r a y e h , t ng e u p e h t s p a s ne ge e t e e r , p u l l a i ng t h e r ig h t s t r i p s t h t a e m o c be e v ha y e h ons. T i t ca t body lo inc t s i t d ic ed pr at th t t im t t gh ri o c n on t r o l t h e ensuin g e v e n e s i n t he c e l ls. I a fo nde r g r o u f c e l ls. up o n a e t t e on i r ma he t r de onsi c e w , w vie c i m dyna pup- he t d h l d e r a e p t ap wha t a to be a d t ishe b a t es l l e w w o It is n r , m o r pe eer a s af fect i n g e ac h o t e h er e q u a ll y . O acc - u t on- homo g e n ou s fo u nde r c e l ly c or g r o up o f c e l ls a c t u a l l d e w , y l e rat e t t e n o i r a m e h d t n a r e e t e p p u p e h h t t i y w a w o a c ins v ta r a t s sub f o s t ien ad r le g ic h nd subt us a o i es, wh a n s alt n mo a s hip s n o i t la e r e h t g i t tan r o imp s i t Wha : r e h et g o f ry for m a ve ge n eral “ p re p a t t e r n ” o t h e s at h t e r u ct u r t an n b e c o m e sla c k . h t d e l l pu y e h t s a s g in str the r g e ( W o l p e r l t , 1971). T hes e g r ad ien t s a nd pa t- em e wil v on e r s in usin he pi g t on m en a be e e ha s t is g o l y br Em g o r en a t f n, o r u ns, in t r te m u nda n e” ef o fect t s o f m he “ r e f is l ly to m ic s y s t em s bot h for ma dyna ly a nd m e t a p h or ica l t h c e m e h r , y it av gr e in u t c u t r s cula e l o m f o s fect f e l a c ani r a le w b a t o t s o es. M ess c o r p l a t n e m elop v odel de m n e h s t a t l l a nd a t i t s su r f e c e (t he push in g a nd pul l i n g he c gton. in add H. W . t C is g o l o bi l a t n e m elop v de nt ne mi ree p r d pa r t icula r m o le cules a nd c of y s t a ls), or t he r e g ula t e in e W r uenc l ic inf t e n e he g s t a w t s e e t y in r ima r ’s p gton add o g y ica i on o f sma l l lo ca l f l u c t u t a t i ons in phys i o l am pl if m t on t issue d i f fere n t i a t i o n i n t h e e b r y o , h e e m er g e n c e r e , 1981). E v en m o r e r e, 1988; Gie ook ism (C l abo t e or m es— bon es, muscles, v t inc t s i ly d p r sha of e t issue t y p i m l p n r e t t epa r ia t i e in is o e s onc t a h le, is t ab k r ema r o l l. A l e gle c a sin m o r h u gh a g e n e t i - f on— o nd s gs, a n lu t cleus a r e t ula g e he r t , d e m for hem- t n g g e n i es in t he n u h oin . t s i r o e h s t em t s y g s ghg u oro a t o s l s a a w e h , t s ci e c lv y h p g n i g n a h sica hes t y f b f nd o d on a he tc es swi l se ess in W add in gton (1954) couch e d d e v elop m e n t a l p r o c h he n us, u de o i s t u o s t en v l e ica n a h c e nd m a cleus. T t f W ex ic i t ly dyna m ic t e r m s: “ pl e ca n s t il l c onsi de r de v e l- body fa t es a r e de t e r m in e d onc e t he in it i a l g e , n erali z ed u op e n t in t e r m s o f t he s o l m t i ons o f a s y s t em o f simul t a - r o m f e o s r u a o he c t e r e f i n e d t issue a nd or g a n d i f fere n t i -

4 261 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 261 Dy a m i c Sy n i ne us d i f f e r en t i a l eq ua t i ons” ( p . 238). Esp e c i a l ly in h o s r la e r w r i t in gs, W add in gton desc t ibe d em br y o n ic c h a n g e g in t he la n ua g e o f a t t r a c tor s, bif u r c a t i ons, op en s y s- in gton, m s, s t abil i t y , ca t a s t rop hes, a nd c hao s ( W add te is depic 1977 g u r e 6.1 is on e o f h ). Fi t i ons, in t h r e e d i - de m ensi ons, o f t he mul t i d i m ensi ona l spa c to d in e vi i subd n a n m b e r o f r e g i ons, su c h t h a t t r aje c tor ies s t a r t i u g a n y- e whe r e in on e r e g i on c o n v i r g e to on e c e r t a t , n end poin wh ile t h o s e s t a r t i n g in ot he r r e g i ons c o n v e r g e els e whe r e e (W gton, 1957, p . 28). T he f i g u r in sh o w s h o w t h e add gr ad ien t s es t a b l ishe d in t he e g g , t h r o u gh t i m e-dep enden t t d e t a i f i le, d ab t s e m o c es, be ess oc pr n fere es. t p y issue t t i add in gton w a s esp e c a l ly in W r i g ue d b y - f l e he s t t , depic t n e m elop v de f o e r u t na g n i z i abil st w o is n d on h e ’s classic epi e g u re 6.2 W add in gton Fi g e n e t ic la ndscap e. T h classic “epi e n e t ic la ndscap e” sh o e w n in Fi g u r e 6.2. T h g s pa h o f , g g he e t f o t r pa f y o tor t i h l a t n e m elop v he de is t l l a he b t v he de t f o y t i abil t g s asin e r he inc g t win o sh issue t p es. g t y elopin a de t en es r p e e r ndscap la s v elopin g s y s t em, whe r e t i m e t e m o n of S sio us c s s: A Di Gene h gy of t e e a r t e S Th m o Fr : e urc So n d whe r e l- t ns to w a r t he r eade r , a ru he dep t h o f t he v a d gy lo l Bio a c i t e r o e h ts of T c e p As gton, in add H. W . C y 29), b . ( p ind l l- a e in a v l, onc a he b (t y t i abil t s le y s is a n f ica t i on o r len & U l A y t 1957 b gh i len & y l p o win. C n 1957, London: A le y , is ha r d to d islodg e). F r o m a n in i t ia l u n d i f fere n t i a t e d r in t e d wi t h p e r m issi on o f Mr s. M. J . W add gton. Un win. R e in p n st he b a l l c o uld be a e (t ywhe r e on t he la ndscap e), de- at v elop m e n t g r ea t es h i l l o cks a nd v a l l e y s o f inc r e asin c elop v . As de y t i es p y issue t he t ds, t e e c o r x le mp co p t n e m d be o m e s epa r a t e b y h i ghe r h i l ls, si g n if yin g t he i r r e - c r a le na t u r e o f de v elop m e n t. H o w e v e r , t he pa t h w ve y s sib w buf t he la ndscap e a l s o sh o w do f e r in g; t h a t is, de v e l- n ly sim m op t p r o c e e d s in glo b a l e ila r w a y s despi t e s o m e- n wha t d i f f e r en t in i t ia l c ond i t i o ns, a nd despi t e m i n o r I pe ba ti ons or f l u c t u a t i ons a lon g t he w a y . ur n h is las t rt book l ishe d po s t h , pub m o usly in 1977, W add in gton u ca l l e d t he epi g e n e t ic la ndscap e a n “a t t rac tor la ndscap e” h (p 105). H e ask e d , “ H o w do w e f ind o ut t he shap e o f t . e e la e?” H e su g g es t ndscap d: “S o wha t w e sh o uld t r y to do y a w y n , in as ma ly t h g i , sl t r i e t l is to a d n le a ssib as po s l obs ve it s r e a c t i ons. W e wil er f ind t h a t t he s y s t em r e - y sis t s s o m e t p es o f c h a n g es m o r e t es tor s e s, or r h he ot n a r o se lf mo re q uickly a f t e r c h a n g es in s o m e d irect i it n s . th in ot he r s” ( W add in gton, 1977, p an 113). S i m i la r l y , in in gton ’s p h as e-spa c e d i a g r m Fi a g u re 6.1 W add f de v elop- o s a f i s r e r v ou a dyna m ic s y s t em on o c c o u n t , p r e h g t bin o ns a lon g t he z -ax is, f r o m p l a n e PQRS a t t he t i m me n t. Tim e r u e is a i s t e m ’s s t abil . t y sy l s o a c r i t ica l s t ep i l i t e f of r r he he ot ood. T h t h is adul ic wh ′ S ′ R ′ Q ′ to P n o i zat s s inc e W add in gton, t h e o r i S t s a nd ma t hema t i c i a n tw t em. T s y he s e t f on o i t si mpo o he c t t en es r p e ons r ensi m i h o d - e n e g o h p r o m f odels o ic m m us dyna ro e m u n d e e f f o e v ha r in si- mpo o us c uo t n o h has c ic , wh g g he e t di a g ram s h o w s ho w co issues. t c i f eci p s o t n i d e t ti on gr ad ien ts be a m es di f fere n t i for , 1981; r g enc y o he em f e m (s e e, e.g., Gie r e r sis, t a t e spa r c e a c t as a t t r a c tor s, pul l a i n g in me a e s in t So t he s a in, 1986; T apaswi & e ohen, 1969; M Goodwin & C k a by ne ar tr aje c tor ies. So urc e : Fr s: Gene e h gy of t e t o r t e S Th m es & P , 1986; T on m e, 1989, a t a g t a , 1983; Y m o h Saha us sio n of S o m e As p e c ts of T h e o r e t i c a l Bio lo gy ( p . 28), A Di s c u i he r s). T he c o m m on f e a t ot r es o f t hes e m odels a r e in t ia l H. W C. by - p o win. C n len & U l y gton, 1957, London: A in add sha c i t i ons c onsis t i n g o f v e r y ond l l o w g r ad ien t s, d i f f e r - r f ri gh t 1957 b y A l len & U n win. R e p on o issi m r e p h t d wi e t in gton. in Mr s. M. J . W add r essu r es or adhesi ons ica n a c c e m l a i t en l fa tor s su c h as p h

5 262 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 262 n a m i Dy r e he c e l ls, or bot h. T h e g in t ad ien t or for c e f ields a r p a s s e s o f di f fere n t i a l re e n t e d b y o n e o f s e v eral c l r s e f i m e . t nc t u as a f e g n a h ess c r p x h e ic ons, wh i t ua eq on o i of i t i on, wh ic h h So me b se ts i eq ua ti on s in vo lv e n i eral t la d a n d all ow s a sma l l lo ca l a c t i v a t i on to be c o m e enha nc e e e ons a i t ua he eq n. When t r r t t a pa f he n m t for ode o m p l e x spa t i a l pa t- so lv ed for v a r i e t y o f pa r a m e t e r s, c o y onsis te r ns ar e ge n erat ed, w h i c h m a y c t o f c cles, mul- al f c o m p l e x n e v e d an , s y e all v d an s ak ( pe le ract s ti p ns). C e o or m w g t in bin m o r r e t t t pa enden le-indep sca o e an gr c o u p l i n g ad ien ts wi th di f fere n t rat e s o f c h an g d r e t t pa x e l p m o ns, i n lead to h ons ca i eract t n i eir th ghly c o m p l e x incl ud in g s t r i p es, c o l u m ns, a nd s o on: “[ V]e r y c r a t r en elem f sis o a e b h e on t is y y a ns ma r e t t pa al re n t he pa le on t e sca c a f r body su f o fect f e e Th re 6.3 u g Fi t e s r n i m f i n g m e c h a ield-for ism s a nd t h e i r c o m bina ons” t e m for n ia l a m m s for ma ism n a h c e on m usi f f i on d i t c a e a r y d b 15). (Gie r e r , 1981, p . t i on. A sin gle m e c h a n ism ca n a co c o n t for d i v e r s e u at co lor a c f ul o e hes if nc nd fa ul a On t f t h g i t del s o he m t f e o r v a ues in t he eq ua- co at l t t e r ns, dep end in g on t he pa r a m e t e pa t a i h on is t i t ma for n r e t t pa f odels o m - t hema t he ma t f o a Fr urc So ons. o m Ma ti t h e mati c e l bi o l o g y (2nd e d., p . 445), b y : J. a D. Mu r r - y p o g. C la r e r-V e g in r p y: S n a m r in, Ge l r e , 1993, B y o v i des a n ele g a n t m odel o f t h e ci an J. D. Mu r r a y , wh o p r ri gh y S p r in g e r-V e r la g. R e p r in t e d wi t h p e r m issi on. t 1993 b a on e n y o f ma m m a l ia n c o g t pa t t e r ns: “ H o w t he le op- to ar d g ot i t s spot s” ( M u r r a y , 1988, 1993). T h i n k abo ut g dyna a le r ab k r ema he r nd t he zoo a t to t visi t las ur yo e o f m i c s o c cu r . As t he body is sca le d up o v e r 50,000 n r x nd s t r i p e s e spot g- e ), a r t n ha elep n e to a us o a m m o s a , f ly esumab r p es ( m ti l p m o he c w: T u sa o gs y in k r a m t a co pa f ies o r e r s ula zebr as, le opa r ds, a nd g iraf f es; t he simp le r s t r i p es o f y r e v f lor o o d c i l o he s es: T g r e ns em r e of t t a c r u le bif he simp hen t ls, t ma i n a l l sma ly shade d pa t t e r ns o f sku n ks a nd b adg e r s; a nd t he s o f t e h nd t ons a i t d c me un g ula t es. Mu r r a y sh o w s h o w a si ngl e me h a - m ifor n ly u r a e he n in, t a g a , so n gs, a n i t e spot t a elabor re mo r ma g r la y r e nd v a l l sma y r e , v d e nde I ls. ( i n e a g e la of at co n ism, m odele d b y a simp le n onl in ea r eq ua t i on o f t h e m m ma t l p r o c ess, ca n a c c o u n t for a l l t he v a r i a- a - n a l a e r n s.) I t a o d c i l o s e v ely to ha k i l e r o e m r ls a a de v elop m e n ima l on- i t c a e he r t f on is o i t ua he eq gs. T in k r ma t a o ons in c ti ls, sma l r a ndo m v a r i a t i ons in t he in i t ia l g r ad ien t t a e n h uld lead to t wo i c eab le ind i v i dua l v a r i a t i ons in c o a t n in i t ia l g r ad ien t o f s o m e e r e, whe p y on t usi f f di o g t s namic dy e h t t a h is t s e t a r r icula t r on pa e k a n t en) ca of o h p r o he m l (t ica hem c t c fa t n a t he impor n. T r e e t t pa h n o i t c a e r of f d i f f usi on in . n r e t t he pa t e t ea r ons c ti ac re i h v a r yin g r a t t es o w d e n i b com l a n e g o h p r o m f ns o a i c i t e r o e h nd t s t is g o esis o y br Em a clo se s u r f ace . l ica hem he c en t e w t ons be i eract t n i e Th ina d aor r t x , e on a t n e m elop v de g n i r du , w o h w o sh f f i d f o e t a s r t nd i on a ti ac re usi r e h i ghly n onl in ea r , - m o ly c i r ex t i- le in simp y r e v m o r e f is r n a ns ca r e t t pa l a r u a- t ds in a s e e c o r on p i t c a e he r es t im et m o s at h t g n ani me pl t s r u c ti a- le ma nn e r , but , a t ot he r v a l ues, t he r e a c t i on is u n s t b al c ond i t i ons in dyna m ic s y s t em s. T he pa t t e r ns t h a t t i r ea in onl is n h d. T e m t is for leads to en gm pi o nd n le a b gh y r esul t a r e n ot sp e c i f ica l ly c ode d in t he g e n es. A l t h o u a c t i on h or a pa h-l i k e pa t t e r n o f r d e p i r t s e v oons ha c c a l r l d a n d a e t e spot r ds a r opa le all e oot r a sm e h eit tc p c t s on t he su r f a c e. Cr i t ica l fa c tor s incl ude t he r e - rodu op- he le s on t for spot tai ls, t h e r e is n o de d ica t e d g e n e o t on r i ar d or s act r i p e d t a ils for r a c c oons. S t r u c t u r a l c a m p l e x i t y ly esumab r p , d e t r a t ess is s c o r e p h es; when t t n t be caus e l i vin g n d y r t e m o e he g hen, only t nd t l; a ro t n o ic c t e n e r g nde u a is c ons t r u c t e d du r i n g de v elop m e m t st sca le o f t he in i t ia l g r ad ien t is bel ie v e d to be s o sy e sub- em s wi h pa r t icula r c h em ica l a nd m e t abo l ic c on- i g m e n t ) p rodu c t i on to pa t- es in v st l an ce th at ac ti va t es m ela n in ( p st ra in t s spon t a n e o usly or g a n i ze t h em s e r in m n su c h s y s t em s, t he issue o f “ wha t caus es wha t te r y l ns. I ea g n i r e du c a f r in su he sk ls in t l e c e t y c o n ela y br em p en” is pa r t icula r ly t h or n y . When a l l pa r t to hap f t h e esis. en g o s o e erat p when a g es on a sy st e m c k a ls only t l e c f up o o r , o o ’s simp y a r r Mu f r o e w he po T in d e t a r t s u l odel is il le m pa on m on a i t si s po t i f t o x e t n o he c in t e t r fa icula t r g Fi ons o i t he simula t f o s t esul f s t w o h sh ic 6.3, wh e r u g he r le to ask whe t h e r t h is ot he r c e l ls, i t is simp ly n ot f e asib t t t i on wi t h s e t pa r a m e ua e r s, c h a n he eq e g i n g only t h d e or is “caus vi is beha h e or t ur ct ru st y es or b n e g y ” b t ica le o f su r f a c e o f sca he body o v e r wh ic h t he c hem l

6 263 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 263 Dy a m i c Sy n t en on a n d m odel in g , vi ron m e n t. T h ro u gh e x p e r i m e a n t No o n e w o uld assi g n a n y g e o lo g ica l p la n o r g r a nd h y - i p t he ef for ts of em br yol og is ts ar e direct ed t o w a rd a d e e p dr aul ic desi g n to m. ea r t s n i a t n u o m a n i s n r e t t a t e h r e t h e r , t ess. c o r p f g o in nd a t s r nde d u le i a t nd de a Ra e g ula r i t ies pa t e n t ly em e r g e f r o m mul t i p l he a r e h T s: tor i fa m l ica t i ons e Th o f em br y o l o g y for t h e o r ies o f p s y- e p h t m, ea r t ns w o d r e t a w he t f o w lo f f o e t c re st he t f o n o i t a r u g i onf c w ch ol og ica l d e v elop m e n t a r e p ro fo u e at h e r nd. Of t e n w e f ind t n re r u c e h t ed, b am i infa el v e s s ea r c h i n g for t h e “caus e” o f de v elop m e n t , o r , l l a r nd a e t a r n o i t a apor v e e in m r e t de t a h t ons rs t i ond c ou th he la or— vi beha e m o s es k a m t ha t e r u t c u r t s l a i t en ss e e n- an d t impor t a n t q u a l i t y o f w a t e r m o le cules u nde r p a r - , n u m b e r c onc ep t s— wha t i t is. T h us, - t a p t en r e f f i l d to in ze i n a g f-or el s o t s t n i a r t ons c w e, ag gu a k in g t icula r mu rd w o t ed irect d n e e b has h c r a e s e r l a t n e m elop v de h c a te rn s o f f lo w . B u t wha t w e s e e in t h e h e r e-a nd-n o w is jus t s c o v er i n g i n v a r i a n t s — t h e p r o g rams , s t a g e s , st r u ct u r e s e di pa r t o f t h e pic t u r e . T he pa r t icula r p a t t e r n s e vi den t a r , r t ons c n e e ns u y b d u t ha t odules— m r o hemas, sc es, vic de ons, i t a t en es e n- pr y n a m r c re e v o g in t c a s, t n i a al so p rodu c rl i h t f o t r a p d o o g A . s e g a t n fere if t d e a nc ma for r pe di f fere n t s s a l e s o f t i m e . T h e g e o l o g i c a l h i s t o r y o f t h e ie de r c h i s direct ed t o w a rd w h i c h i n v a r i a n t s a re “ inna t e ” t mo un ta ins de t e r m in e d t h e incl in e o f se he s t r e a m be d a nd a e t in d e r d-wi r a h ( e h t f o e t ima cl e g n a g-r lon e h T cks. o r to h ic” f o on si ro e e th (p r e s e n t at b i r t h), wh ic h a r e “g en e t v r icula t r a p o t d le on gi re i h w d n a on), i t c ele s ral u at y n b m te ys e s th t gy lo na a y b , h c nd a n i a n u o m he t n o n o i t a t e g e d . e c o n s e q u e n t p a tte rn s o f w a t er a b s o r p t i o n an th r u n o f f to g e n es, “de t e r m in e” de v elop m e n t a l o u tc o m e (e.g., Gel- t s a p r t w o af fect ed t h e e h t g n i r u d e t a m i l o c e Th r e y ma n & Ga l l is t e l, 1978; S p el k e , B r e inl in g e r , Ma c o m b e r , a e hes w on t h e m o u n tai n a n d th e r a t e o f m e l t i n g . T h o c o n - & J ac obs on, 1992). B u t e m b r y o l o g y t ea c sn t a h t us in t h e en fi gu rat io n o f t he m o u n t a i n jus t u p s t e- d e r m r e t de es— v l e s hem t f o d n a in ot— n do es e g th m inf l uenc e d ea v m e n t a l o u tc o m e. Gen es a r e ess en t see an c e w , er v reo o M elop n o o s d An . m a e r t s n w o d e rat w o f l i a l elem en t s in a . t ons c e hes t f o e nc a t impor e v i t ela e r th i n n- t i l- e v he de t s g in nd a t s r nde U es. ess c o r p f o ascade c c i m dyna n m a i n t a i a r a op e n t m e a n s u nde r s t a nd in g t ha t c ascade. - h t o n l, poo m o t n i s l l fa ck ro l l sma a f I . n r t t pa le ab t s a g in e a l d n r a e g r y t l e g s k c o r g n i l l a s f . A e g n a h c t a m g in , a r e g r a t n i t i l sp y a m m ea r t s e h t , t poin me so o t w o , o r c r e a t e a n St The M p a t e am M re hor i a t n u o n ne w, fas t e r c h a n el. Wha t endu r e s a nd wha t c ha n g es? t nd oc ess a c c o u n t s a ssum e Pr ha t beha vi or pa t t e r n s a for g o l o y br em m o r f on less r ge ar e l Th is gy lo o h c y s p y in s nt al act iv it y c an be u nde r tood me t h e s as s m r e t e m a a t s e h t is: th ies a g or d e elop v e d n i e e n- s e w t i r ula g e r e l b n th e d ies a n d r ip p les o f a m o u e t a i n s t r ea m. T h e y e x is t d t s e ek ism ena m o hen p he t s— w e s as p x- e o s t s i g lo o h c y nd l o b in t h e h e r e-a nd-n o w , a r t h e y ma y b e v e r y s t a e v e s p e c i f i c caus es t h a t ca n b e t o n t h g i m in— a pl h a B le, i t mul f easily c h a n g e d. p eha vi or is t h e p rodu c t o c dema r a tood s r nde u be y a m r he t a r but d e t la o s i d n a d e t h t i h ic wh f o h c ea uenc l inf g in ibut r nt co is- es, as h a f el s y only dyna m i c c ascade o f ma n a p r o c ess es op erat i n g as n n a c e w s a t jus t u B . y tor en d y l l ea r t t a is n gle t h e g e o - o s ov me . T hi s i dea c h a l len g e ti t he usua l n ot i ons o f sc i- er lo g i c h is t tor y o f t he m o u r n t a i n f ro m t he cu r en b g t a l o is y b sis, y l a n y in nd a t s r nde u e w t ha t e enc a r s he t f a w dra t o e a m b ed, w e al s o t a n n o n o i t a r u g i onf c c t g s — in g r e d ien t s a n d c o mpon hin t s — u n t il w e a r r i v e a t en d n a or vi beha e im l-t a e r he n e e w t be ne li t e im t e f i l he t th i l st uf f. Ex p l a n at i ons in t e r m s o f c o m pl ex t en ess e a o t n s i e r e h e, wis e k Li t. i o t e ibut r t n o c t a h t es ess oc pr t o e g p la na t i ons in p c ess es as op po s ro e d in ascad d c an x f es v l e s hem t s n r e t t a p e h t f o on i t a r epa s o m e ab- s m o r icul t f a li st of pa r t s i s d if f s o t e v e n for sc ien rm i s t s te st ract i o n o f t h o se p a t t e r n s . d i n gly , w e (s e e Ch i, Slot t a , & de Le euw , 1994). A c c or e a n u o he m T t r e a m m t t a p h or depic t s beha vi or a l in s r s e t fa r m a f ield , but a f of fe r a e me ta s t ph or i y ma t a h t r de m e n t as a n e pig ene t ic p elop o c e s s ; th at is, t r uly c on- v e h t x ess c o r p ins a l p e t i ut abo g n i k n i th t a h t e p o h we as i n h w s o . y t vi i t c de a em-wi t s y nd s it by ed ct ru st y a tor s u caus o f s t r e c t u r e . s tor y in de v elop- Th n e r a b le i dea wi t h a lon g h i is is a v e t ea in s a t n u o g m vin o t-m a fas f or is o h p a m. At e he m T t . n izi r eo h g l a t n me t e a he w es, t ac pl me so les. p p i r l l hly in sma oot s sm w o l r f t wh i r lpoo l or a la r g e t u r bulen t Ne ar by ma y be a sma l l y sh a hes T . y r es or sp v a w w o e es ma c a l r p he l ot il t . S ddy e v e l o pm e n t a l Ps y chobi o logy s s i n D e i Epi ge n e v en da y a f t e r da y , pa t t e r ns p e r sis t h o u r a f t e r h o u r a nd e s ap e on e u nde r s tood a s y s t em No p roa c h m o r de ep ly t h a n l, n el y sp r g d m or a lon tor r a s e t f but a y ns ma r e t t w pa e c a g o up o f de v elop m e n t a l p s y r h o b i o lo g i s t s w o r k in g r . Whe r e do t h e y c o m e f r o m? Wh y do t h a ap p e t sis r e p y e la e ia l ly T . C . nd 1960s, esp he 1940s, 1950s, a ely in t g r c y e nd wh y do t h e a c h a n g ?

7 264 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 264 n a m i Dy e Lor enz bel ie v e d t h a t beha vi or c o uld be brok en up in to o uo, wh g K n a g-Y nd Zin n, a a m r iel Leh n , Da la eir hn Sc s r tr ad t ly b y Gilbe r t e e w t a h t s t en nd elem a e t ly inna l o wh e r e w t a h t s t en elem uen t eloq s o y m on toda d e i r r on is ca i t i ’ h nd is book , th i s Got t l ieb (Got t l ieb e t a l., Chap t e r 5, t s a ies w ud t s s t s i g lo o h t e f cus o he fo gh t u o h t l , a d e n r lea Ha hes to or— vi a beha f m o he for s. T t r pa e t he inna en on t t of st mo lu m e). T vo e bi o l o g is t s us e d t he w o r d e pig ene si st x u y o r c icula t r le, pa mp a for e (s e e Ki tc h- n , in s, or y la isp ls or d l ip ca sh t r desc r ibe t he p r o c ess o f beha vi or a l on to g e en d- r , 1978, for d iscussi on o f t he v a r i o us m e h t f gs o n i n a e e h uma ns, fa c i a l e x p r essi ons— w a s bel ie v e d to be “ h a r f d e l l enz ca d. Lor e r i u q c ). T st si ene pig e m r te e tood as a s r nde t u on is bes r visi i e h is class o h t wi r ot a d ” a nd n h r s t w i t e ut be- t abo gh a u o h ic t f i t ien sc g n i l i a v e r he p t r e w y e h e t caus ns” be r e t t on pa i ve t c a d e x mo i f s “ nt nt me co d to em - or a nd i t s c h a n g e, a n d , in pa r t icula r , t he r e cu r r en t ha b he o e. T ienc r e p x ic e f i c e ut sp o h bel ie v e vi e r g e wi t nd or e. u t r u sus n r e v e r u t na f issue o je c t a r ien t a t i on o f t hes e d isp la y s ma y be lea r n e d lo du r i n g on to g e n y . Ge es e, for ins t a nc e, ins t inc t i v ely fo l- In th os e de cades, N o r t h Am e r ica n p s y c h s a gy w o i s t s. As is w e l l k n lo w o bje c t s on wh ic h t h e y be c o m o w n, t h e imp do m ina t e d b y lea r n in g t h e e r i n t e d , but t h e y o r e w a l o f psycho l o g i s t s wa s to el t u c i- l a t n me i r e p ex e s e lea r n go d to fo l l o h Lor enz ins t ead , if he sub s t i t ut e d h i m- r d e e shap r ls a ma i n or as a vi beha f o s w a l eral n ge he t te da se lf for t he m o t h e g o o s e a t t he ap p rop r i a t e t i m e . g r e p x e f y o t e i r a a v d e us s t is or vi eha e. B ienc r pe ex by - i T he epi e n e t i c i s t s, in c o n t r a s t to bot h lea r n in g t h e - o l ri s a nd e t h o lo g i s t s, ca mpa i g n e d to el im ina t e a t to- me nt al ani ma ls su c h as r a t s a nd pi g e ons, but t h e y be- s ge y li ev ed t at th er t he q ues t i on o f lea r n e d v e r sus a c q u i r e d. T h e t he p r inc ip le o f t r a i n i n g a nd r e infor c e m e n th e ere d t h e w i e esp a l ly c r i t ica l o f wha t t h e y c onsi de r c ap , t n e m elop v e ns. D uma g h in ud ies, incl c e l sp l d to a ie l p acc d i n g to beha vi or is t t h e o r ies, c onsis t s o f t he a n i - or t inna or s s a m e t h c su f o g n i n a e m d e in l-def l nd i ue a g va e r t em en t in 1953 is as eloq uen t inst inc t i v e . Leh r m a n ’s s - l a t n e m ron vi l en ica d a he r T . y tor s i h t n e m e c infor e l’s r ma t a ism o o beha vi or is t s is cap t u r e d in a s t a t em en t f r m a a nd r ele v a n t toda y as t hen: f cr n it ica l essa y b y Leh r a m (1971): T ins t i nc t ” is o b vi o he “ sly n o t p r es en t in t he zyg ot e. Jus t u ien t or is or vi beha he “ t l l ca e r t I he sic to wha ba so Al on” i t a t t in t , i ima n he a t f or o vi he beha l en es r is p as o b vi o usly t f, a nd s t a t em en t s is t he i dea t h a t sc ien t if ic e x p l a n a t i ons o e. T lem for t te r t he ap p rop r i a t e a g af he p r o b he in v e s t i g a tor s of sc ien t if ic insi gh t s in to, beha vi or co nsi st of s t n e m e t a t is: H ut? T m o or c vi is beha h d t i w d o e he us e o f e x p l a n a- abo v- he beha t r e l o ro t n o ins c a g r e t n e m i r e p x he e w t o v ut h abo ” e x i ly f l ica t e en nd “g ” a e t inna as “ h c ies su r o g e d y ca tor t io or abo ut h o w t he a c t i r, f t he subje c t ca n be p r e- ons o ob n e m elop v g de in t a g i t s e v in f o y t essi c e he n es t r scu t a l r e p x he e t f ons o i t c he a t y b ed ct di i m e n t e r . ( p . 462) v- t f s o ism n a h c e m l a u beha c to a t in gh in insi a to g ses es c o pr i t or a nd t h e i r in t e r r is ela t n ons. T h e p r o b lem o f de v elop m e i c e asp t n a t impor n a be to ues n i t on c g in n r lea gh hou t Al t str n f o t n e m elop v he de t f lem o o b e p - ac d an s e r u t c u r w e th of e h t g n i n i a l p x e in ly l a i c e esp s, t n u o c c a l a t n e m elop v de l v x e f on o i t c a r e t he in t f on o i t u - o s e he r t m o fr s n er t t pa y t i ti so ci al i zat io n o f c hi ld r e n ( B a ndu r a , 1977 ), lea r n in g t he- s in is i n g on es in t he or g a n ism a nd i t t t e r n a l en vi ron m e n t , o r ies. or ve lo st f a v o r a s g e n eral ies d e v elop m e n t a l t h e ha s o nd be t n e m ron vi r en e t u . t nd i ism a n a g he or en t e w t a ies In pa r n e p c i a l p x e to y t i inabil r i e h t to due s i s i h t , t s ( p . 338) a c tor y a c c o u n t s o f c o g - an di f fere n c e s d t o p ro vi de sa t i s f u ly ni ti ve an d l an gu ag e d ev elop m s i g in l b u o r t l a e q E . t n lo t: s of B e ha vio r D e v e namic pm en In hi s book , Th e Dy a th s . s o w n o v e l h ty ar i s e u l l te t o n s e o d e n o l a n i rn a e l t g w y l r icula t r d a pa e t en es An Epig ene t ic Vi e r , K uo (1967 ) p w o m t he 1950s a nd 1960s, a vie In f beha vi or be ca e o r p l a t n e m elop v de f t o en em t a t r s clea t s em s y a s m o r ess f c r popula a t s t ron gly op po s e d pu h e lea r n in g t h e o r ies. r t d n a x e l p m o or is c vi beha t a h d t ze hasi uo emp K . w vie l t he Eu n sc h o o l as- rop Et ho lo g i c a ea h e o r i e s ca m e f r o m t k a nd t le a iab r va r- e t in g n i g n a h ly c l ua in t n o e in a c c a l es p onr so s. Lor t uden t is s nd h enz a ad Lor enz’s K h t wi ed at ci nd e r na l a x t e n a l e v r e s b o e or w vi he beha t. T n e m ron vi en r le he ro s to t t s i g lo o h c y s p g n i t ien or e l in r ina m e s s wo wa k f n i n he a t f e o espons r l a he tot t ma o t r pa l a r l to g e t in is a c t a t i ons e ies-t y pica l beha vi or a nd a n i ma ls ’ adap of sp e d n e m ron vi he en t t , but t h e r e a r i f f e r e n t ia t i ons— or pa t- as h e i r en vi ron m e n t s. A nd a l t h o u gh e t h o lo g i s t s su to t c h g d ad f o s t r a p t n fere f i ien on m e a espons f r o — s te rn ed gr t t g to be impor in n r - e r de onsi enz c Lor l g a in n r , lea t n a d lea e: t he body . H e w rot e c a l s p wa ys wa or in- e t inna d e em or de vi de beha gsi lon a d g i t i v e. A c c o r d i n inc to Lor enz (1965), t h a t d st s t inc t i on f ica on, i t On to g e n esis o f beha vi or is a p r o c ess o f m o d i e a nd lea r n e d r p f s o w a e nc a t y impor r ima be t w e en inna t n s ran s for ma t i on, or r e or g a n i z a t i on o f t he e x is t i t g pa t t e r n espons of beha vi or g r ad ien t s in r e to t he impa c t o f n e w en- r s in u nde d t a nd in g beha vi or a nd i t s de v elop m e n t. I nde e ,

8 265 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 265 Dy a m i c Sy n , t m i l t ica t i r c t a es, for ins y t i v a r nd g a a nc e, ca n cascade e i a l t w spa uenc eq ons nd in c on; a i t imula t s l a t n e m ron vi e a n m an d , p e r- d /or s e r i a l pa t t e r n o f beha vi or g r ad ien t s is for e f m e de g r to la in e n t a l d i f v e r enc es. N o n o b v i o us a n d elop h o f t e n ma n e n t ly or t empor a r ily (“ lea r n in ic t im es ”) wh g n tor n onsp e c i f ic fa c s a r e impor t a t c onsi de r a t i ons in a dy- he e e e t t pa g n adds to t i t is x r ns o t f y o tor n v he in f beha vi or w as w s vie em t s y e ic s m na l . l cumula gr ien t s p r e v i o usly a c ad t e d du r i n g t he a n ima l’s de- de f le o mp a x ul e if A beaut t e h sis in t y l a n a l a n e m elop v l . K ( . y tor s i h uo, 1970, p a t n e m elop v 189) he w f o k r o sy uo is t nd K la a r i e n h c S f on o i t i d a r t s m e t s h eredit M rd i b f o y n e g o t n o e h t n o n i K w g An d an t s e W dre e w pa t t e r ns a r e s ele he l t g n i c t e d f r o m r Du i e spa n, n f e so n g. W e s t a n d Kin g ’s s t ud ies on s o n g lea r n in g in t h t i ns: r e t t am o n g a he r a n g e o pa f pot en t l r wbi co d n ies a t e l d subt e r e v o c n u e v e, ha t si a r , a brood pa d ess t is ues- e q a r t a h c o r p l a t n e m elop v he de ons in t i at ri va e o espons e v esis, e n e g to on f r g a t y s r e v us, in e Th e is de- y r g in n r lea g n o w: S r vie ie l r ic ea t s i l simp e r o ut a m ons abo ti imul t b o g n s, i t imula t i or s je t he s t y ot only b n d e in rm te c wa s e i t y e r d i r e c t e d b y a n inna t e t emp la t e or lea r n e d b h he s t , t x e o en l but a s b y t t he tot a l o vi ron m e n t a l f us o t a t n c i t a t i on o f ot he r sin g i n g ma les. Fi r s t , t h e y fo u nd a n im e an h ies, t t i c l capa ona i t nc u r f i e h nd t es a r u t c u r t l s ica om at er e ov whel m i n g ef fect o f c o n t e x t o n b o t h t h l e a r n i n g an d i o l phys o g i c a l ( b i o c h e m i c a l a n d b i o phy sica l ) c ond i t i on, s K he de v elop m e n t a l h i nd t tor y up to t h a t s t a g e. ( a uo, mp t he p e r for m i n g o f s g in ’ be les le, ma o a x for e gs— n . 189) 1970, p a hou d wi t h f ema les du r i n g r e se r in g a f fect ed t h eir s o n g gh f ot sin co nt en t. E v en t h o u g ema les do n , t h e y e x e r t s o - r ci inf l uenc e on ma les t h a t a al e s t ron g en o u gh to o v e r - n t a l sc ienc e, t a r g e t in n for a l l h In is ca e d de v elop m e , 1988). ic s s e g & W Kin ( e t la emp t y t or ens ri de a n y sp e c i f t i s t s to s t udy “e v e r y e v en t t h a t K uo (1970) e x h o r t e d sc ien e c ele ’ s les ema s to be f r a e p ism ap n a h he m T c - e e r v i t u in” as pa k es p l a c e u nde r a nd o ta t s i de t he sk r t o f t he be- ief win y br spons b e h t g n i r s) du t n e m e v es ( o g m in ick l g-f es g or vi ha r ad ien t , a nd n ot to look jus t a t glo b a l m e asu r a l n r ti me when ma les a r e lea r d in g s o n g. T he f ema le c o wbi a n t i t a - or g a n ism or en vi ron m e n of W]e mus t t a k e q u t: “[ g n o le s he ma espons he e t s shap e. F u r t he r- help r r y b r ti me as ur es o f s t imula t i v e ef fect s o f e v er y s e n s o y ve o mo e, e x p e r ienc e wi t h c r wbi r d f ema les is ess en t i for l a f t h e i n t erac - m oda lit y , an d m a k e q u alit at i v e an al y s e s o n ap rop r i a t e ma le ma t i p g beha vi or . When ma le c o wbi r s d t pa r t s o f t he en vi ron m e n t a l c o n t e x t ti ons o f t he c o mpon en is sa d ca- sue r nd pu to a g n y e h ies, t r na ca h t w ere ra wi e d t mp visi y r ina d aor r on, fash- o x uo’s e 190). K . p x” ( le or c na r ies r a t h e r t h a n f ema les o f t h e i r o w n sp e c ies. B ut t h is nd a c t a is g o l o y br em n h a as bot k r o is w om r f d ne io h m- o i s n pr e f e r enc e w a ot a r g i d imp r i n t in g , as t he o ld e t h o lo- v uenc l f n i direct a e v a h t o n d di , t s i g o l o h e on pa rat i c e p s y e st s u o -h y r na e ca d hes d. When t e n i a t in ma e v uld ha o s w gi h c f m o ea r t t ins he ma en- e m ca h be ic , wh gy lo o h c y s ild p u les in co wbi r d ma les w e r e h o ema s e d wi t h c o wbi r d f e t t a h t t t (1952) a e h t r wi g t nd la e, a m i ra pt u red wi t h Pia enc e. e h on, t as e ond s c e r s ei th e s e r y e d r t v e i r p r ef e r h e m h c a t t nd a by (1969) a owl B heless, a t e n o . N y r o e h t t n v on- g nd Kin a t e e, W denc i c r e he nd ot is a th om Fr s ue d wi t h a g r o up o f c o m- in t n o w has c s vie em t s y broad s m cl t ly de p i t ghly mul i is h t n e e elop r- v de g n o s t a h ude t o i b o t c y s p l a t n e m elop v e de v i t a r pa on- c e v o ha s wh s i g lo h l in t n o g c in be f e o ens he s ic in t m nd dyna d a ne mi y ua l e t uisi q x e d e t c du e t ica r t he in t f ies o ud t d s le i a t nd de a e. A n ies- c e l’s sp ma i n a c nd spa a e m i d in t e t c u r t ons c in , e n t s, a nd en vi- pa e r r ela t e d m e r t c h a n ism s o f o f f s p r in g ty ons in i t c n a w s o t nd i g a in r a e r f o t n e m ron vi l en pica hes e a , J ieb l t Got t r ude Gilbe e incl y e. T f i ly l r in ea t n ron m inf f e o c r u o le [a] s b a t vi e n i e as “ r a t n m ron vi en e at th - u l s d r a w o h, H c a b o hel T on, Et rons r A e t , Les t t Ro la enb l’s g enc , g t & Kin es W es” ( n e 1996 ma i n a n e a r e as a ). e y A lbe r t s, P a t r ick B a t e s ia on, l m Ha l l, Jef f r Mo lt z, W i l v e A nd be caus e t hes e dyna m ic p r o c ess es a r e s o in t r a c t i e W n e e b s a h z it w e rk u T d ral e G . s r e h t o d an , t s e h eredit M a a r a e p isap ies d t r e rop p l a t n e m nda u f , r ea in onl nd n when uo t pi e e r in c o n on in i t i ad r on -K la r i e n h c he S g t uin in t e r t u r b a ey ar e d - i sr up t e d. F or e x a mp le, e x p e r i th e n t a l p m h uma n infa nc y s t ud ies. g c ond he e t i ons, su c h as p l a c in ons to t ti x p g e c t e d r e a r in i n i is m k r o e w v i t a r mpa o is c h t f k o r a m l l e ha On n d a e t u i in es, on m r o h h t hem wi g t t c on or inje t a l o ls in is ima an r t de a i le d u nde s t a nd in g o f t he e x p e r ien t i a l c o n t e x t o f t h e a nd subt s fect g ef in le cascad ic a t . m a r h d bot e v y ha ma e n ot n e c- t h s t tor c g fa a in ud ism, incl n a g g or elopin v de a r u m ch ma n ipula t i ons o f t en il l Su ina t e t he in t eract i o n s i n r essa c r s ic- o r s to a pa r t e r us p o u i v b nd o a t n e r pa he ap ly t i r t y s t em, but t h e y mus t be in t e r p he s e t e d wi t h g r ea t ca r e . l c s. r ica t i r be c d e y inde , but ma or vi r beha ula ibutor n o t ut in T e insi gh t s r a is e caut i ons abo hes t e r p r e t a t i ons o f er ienc e ma y c e o n t r ibut e to on to g e n y in subt l “E xp s a ex ri me nt s wi t h infa n t pe nd c h ild r en be caus e t he in t e r- n 90), a y . e (1957, p rot la w r i e n h c s,” S y wa s a in w o s l d a e act on be t w e en t he e x p e r i m i n t a l ma n ipula t i on a nd t h e e n onsp e c i f i c . Sma l l t th at ar ef fect s o f t e m p erat u r e , l i g h ,

9 266 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 266 n a m i Dy t infa e o f t e n n t in t eract i o n i n t h at t h e v o c a l l e a r n i n g p r oc ess is r s a he subje t f es o ienc r e p x y e yda r e v l, e a rm no c cre t a n e m elop v e de caus e ons. B i eract t n i al ci o s y b ed at l t a h t s t es g g su h c roa p s ap em t s y ic s m n. A dyna ow kn un l abb es in b c n a adv ons a h e t e a l fa c tor s a nd t h e i r t i m e f u nc t i t s r x e t n o e c hes t e v i g e r ca t a h t s y a he w t e g n a r h c g n i u g cr it ica l asp e c t s o f p e r for ma nc e a nd de v elop m in t t e , 1999), s t s e in & W e t lds s (Go t n r infa i e h t to t ac re e n t . a m t en o t-to-m n e m o m , r cu c g to o in n r w lea e e for n g t ld- (1999; Go t s e nd W in a e t lds Go by ch ar se re nt ce Re t he s al st e in, Kin g , & W e s t , 2003) s t ron gly il l u s t r a t es t h so ci is i n t eract i ons a r e p r o b ab ly l i n k e d to t he m o n t hs- i en onc c t s m k r o is w h t. T poin he f o r f t n e m elop v he de es on t t a r t lon g s t a g es (Ol le r , 2000) t h a t r e l iab ly desc r ibe t r r ild h nds c u o he s t lan u ag e to t t s y ic s m a dyna m o r t. F n e m elop v l de ca vo of ar ye h o s g e t h a t s em o t r o i pr e k en ma l ma ch so u nds. P r el in g uis t ic v o ca l vie w , ma t e r n a e beha vi or a nd infa n t s ens or y capa c i t ies in- e sp d e r de onsi y be c t t or “ b abb eract t o g e n erat e t h e d e v elop m e n t o f m o r e adv a n c e d in- en v i de v elop m e n i r t to be d gh u o h g t ,” lon g n l n t fa n t beha vi or . T h us, t he pa t t , 1981), r ns o f in t eract i o n b e t w ee e ex cl usi v ely b y a r t icula tor ma t u r a t i on (e.g., K e n v g es on n e w si n if ica nc e when s t ud ie d f r o m a dyna m i c ta ca r e g i k e r s a nd infa n t s a r e a s o u r c e o f de v elop m e n t a l s a t n nd infa a r r e v i g e r e. When ca v i t c e p s r e s p sy st em e ch a n ge . s o - e d l a c v , e m i t al re n i eract t n i y e h t s a er h t e g o t d e i d u st l i y o endenc dep r e t nd in a y t f icausa t s mul w o sh t n e m elop v tu ex nt Co g c a l Theori s t s i o ol d Ec an al t in c e m esca les. M o t h e r s r a c ti onsis t e n t w a y s to t he b a b- i t i ad r he t T n s t i c i s t e g e he epi nd t a s t is g o l o y br he em t f on o bl be- g n i l abb b s nd a s, a t n infa r a i l i m nfa en u v e f g o in e d s ze si es uenc l gly inf ron t s e r o m t e i k i h-l c e e sp e r o es m m co ha emp n g i z a t i on f r o m mul t a i p le p r o c ess es f-or l mo s er s’ r espond in g (Go lds t e in & W e t , 1999). I nfa n t s bot h in t he or g a n i sm a nd be t w e en t he or g a n i sm a nd i t s th vi r a nd to t e e i r m o g c on m s a ip onsh i t ela cus is on r he fo t. T n e m ron s en v i g e r ca f ons o i t c a e he r to t e v i t ensi e s ar - h t a e, r g n a h c f ins o g i he or as t s t en r i e h t f m o ic for t s u o c nd a a t n u o pon he a t g n i g n a h s, c d soun m in- f t o e a s n a h t r e h st t abb l i n g in r espons e to c h a n g es in t he for m a nd t i m i n g on to b ru ct i ons. S u c h a vie w na t u r a l ly t u r ns o u r a t t e n i in t t e s l a i c o nd s l a sica y h he p t e in e t a l., 2003). of t h e i r ca r e g i v e r s ’ beha vi or (Go lds t d n s a t n h infa ic gs in wh r m e G o lds t e in e t a l . (2003) s t udy , to 8- f o s r he ot ch i l d r en a r e r a is e d , a nd i t r e q u i th r- nde u n d a le i a t es as de In st di ng of t he c o n t e x t as o f t he or g a n ism si t u a t e d an 10-m on t h-o ld infa n t s w or e w i r eless headp h o n es, a l l o w - in at in g t hem to r e c e i v e ins t r u c t i ons f r o m a n e x p e r i m e n t e r . th co nt ex t. Ex is t i n g de v elop m e n t a l t h e o r ies ca n be r ( , r e s clo g vin o m , g in il sm y b d esponde s r e h t o m When pl ac ed on a c o n t in uum as to whe t h e r t h e y a r e m o r e on- c i ce ed wi t h wha t is in t he c h ild’s head or wi t h t he sp e- ons, i t a z i l ca o v ’ s t n infa r i he t o t t en g n rn t on ) c ng hi ouc d t an ci n i t e g t. Pia n e m ron vi he en t f ls o i a , t de g n gi an h c d an c i f a th e infa n t s ’ b abb l i n g inc or por a t e d inc r e a s e d v oic in g a nd c o u n t s o f de- co vis gn t , a nd infor ma t i on-p it ro c essin g a c fas t e r c ons ona n t-v o w e l t r a nsi t i ons, wh ic h a r e de v elop- i t n t v elop m r- he pa on to t i t n e t t e le a t t i y l e, pa nc a t me nt all y m or e adv a n c e d for m s o f p rodu c , for ins i on. on- c n I tr u , t h e infa n t s o f y ok e d c o n t ro l m ot he r s , w h o t r na icula t r e o f t he phy sica l a nd s o c i a l w o r lds o f t as ild t on but nd a t s r nde hes is to u c roa p e ap hes t f o l a o imula he g en. T r i ch s l a i c o s f o t n u o m a e m sa he t d ve ei rec t h w t o nd h ind a m f ies o alit u q eral n ge a wi t h o u t c on t i n g enc y , d i d n ot c h n g e t h e i r b abb l i n g . I n- e caus e . B elop v de y e t e c rodu p nds u o s r i e h t t a h t ze i n g o c e r efor r he t e mus s t n fa t he p r o c ess es a r e assum e d to be u n i v e r sa l adap t a t i ons to to u o s r i e h t for r de or in t n e m ron vi en e h n t g nds n a h a c t he w o r ld b y h uma n br a ins, i t is im ma t e r i a l, for in- e i . ge n a ch ild lea h a c r e h t e, whe c an st e m o r e f enc r e inf v i t nsi a r ns t r a nd o r he g icks on t t s h t g wi yin u pl , or in a s t r u c t u r e d a l By n ipula t i n g ca r e g i v e r-infa n t in t eract i ons in r e ma u p f p e op le t a l k in g a n d a c t- o o r g g vin r e s b o y l, or b o o s sc h e, mul t i p le caus es a nd t i m esca les o f v o ca l de v elop- ti m he ind n a he b l as t dua i v i sic u cus is on t he fo g. T in i t o f r ea t e v o me n t me ca l c ev i e den t. T he m e c h a n ism s t o h a t c b o e v l ha l ls a dua i v i ind t a h e t ens he s sis, in t y al an m m o n c t e t a , but r t n he infa to t d e t c i r r s e ot r e n r a t n e m elop v de h i e h ond t y nd be a e v es abo ess c o r nd p es a ur ct ru st - r e f f i r d t z t he s y s t em o - a i l ca o v f ns o r e t f a t. P n nd infa r a e v i g e r ca g e es. ienc r e p x in f m u l t i p ea ti t ons a es, in- c r o f e l r e c r e d b y t he in t eract i o n o he ot ud g t he a r t i cula tor y ap pa r a t us, visua l a nd aud i tor y uum, a in t n o he c t f r end o he in t t s a t s i r o e h or t F cl s. T e t ot jus e n r a e r u t nd cul t a x e t n hes es in c ienc r e p x ’s e on rs pe p erce p t u al s y st e m s, a nd lea r n in g m e c h a n ism o elop de- f f o uf t s y r e he v e t r , but a t n e m v de f o e v i t por sup com pon en t s r e g u la t e a r e v i g e r ca y b d e t a l gu re e r nd a f av labi l i t y a nd r esponsi v e n ess. V o e uum, w in t n o he c t l de ai is end o h f. At t l e s t t o is n t n e m elop v v elop m e n t i ca an infa n t abil i t y , but a n em e r g e gr o up de v elop m e n t a l is t s wh r e w o r k in g in t he t r ad i- n t p rop e r t y o f ca r e g i v e r- o a

10 267 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 267 Dy a m i c Sy n y a u r t e ti on o f , J a m es Ma r k B a ldwin, J o h n D e w t he g e o g r a p h y o f la r g e sh ip s, t he m e asu r in g de vic es, t h e nd K ps ho N . s k s a t ered t n u o he enc nd t ls, a dua i v i ind f gy o lo yc o ; y k s t o g y S. V nd L. ia a r R. Lu , A. ly t n e c e r e r o win; m Le on , l tua x e nt co , l a c i g o l eco d as e labele r o a nd wh a cr s s - y- l a n ’ a ins h utc on. H i t a g vi he na es t e do lon t a or o e elem en ltu r a l th eo ri st s. I n add d on bot h pa r t i c ipa n t o b s e r v a t i on a nd c o mput e r i t i on, s o m e v e r s i ons o f li fe- s a sis, b e cu simula e rs p ect iv es (e.g., B a l t es, 1987 ) a l s o ha v e s t ron g w o h r— sp t t ma s t en e elem hes l t l w a o s h w o on, sh i n a pe t t s e vie hes l t l ons. A i t s assump em t s y nd s ic a t e n e g epi w he sma r t n ess o f na vi g a t i on t e a m s em e r g es, dep ends on, nd book , th is v o l u m i- ar e w e l l re p r e s en t e d in t h is Ha a nd is c ons t r a i n e d b y t he p h y sica l c o mpon en t s, t r ad e, in t he c hap t e r s b y Ov e r ton (Chap t e r 2); V a lsin e r (Chap t e . ti ona l ro les, a nd cul t u r e. N a vi g a t i on t e a m s are sma r t r 4); Got t l ieb e t t- Th eir act i v i t y i s e v e n t - d r i v e n an d g o al - d irect ed . Th e a l. (Chap t e r 5); Ra t h u nde a nd Cz i kszen s g a t i on t e a m mus t k e ep pa c e wi t h t he m o v e m e n t o f de r 10); S h w e d e r t r (Chap t e na vi mih a lyi (Chap t e r 9); Br adt he sh ip a t e r 13); Elde r , Bronf enbr enn e r , a nd M o r r is o gs g in h ess. When t r g o r in p a t in ma t nd mus et l. (Chap t a ron r t gh i he r r; t e v t o r a t nd s a t i u on to q i t op o e is n r e h t e g in aud t nd S , a r e g r es, Lindenbe t l a nd B r 12); a e t (Chap w , g r 11). A (Chap c f ons o i s r e v y n e ma r e a r e h gh t u o h t l on- e t de c isi on mus t be made a t t he m o m e n t. H utc h ins ’ w o r k t ons a t r e v o d e ibut r t s i e d r te xt ua l ism (s e e r e vie w s b y Di x on & Le r n e r , 1988; F o r d r- e sh o w s h o w t hes e de c isi he in act e & Le r n e r , 1992), t h e y sha r e c e r t a in assump t i ons abo ut e is r h l t l s a w o n k m o wh f e o on n ls— dua i v i ind f ons o i elop ma l s y s t em i t he op or is t lem. N b o r he p ut t abo w o n to k y n ma h t lap wi r e v ons o i t e assump hes nd t , a t n e m de v ly d nd for at ur es o f a dyna m ic s y s t em s ap p roa d up de vi i fe l ica g en lo lem has be b o r he p h t ic e in wh on c h. Fi r s t a e- dua vi i to ind d e n g nd assi s a t r pa e v usi l c x ly e l ua to mut in e en ind i- ls mos t is t he q ues t to el im ina t e t he dua l i t y be t w i l a pe r fect di visi on o f labor . Ra t h e r , na vi g a t i on t e a m s nd en vi ron m e n t , jus t as t he epi g e n e t i c in s t s dua vi a t ar s o m et i m e s e ch a ract er i z ed b y p a r t i all y red u n endea v o r e d to e r as e t n an a d he bo u nda r ies be d t e r u t c u r t en s e w ns o a nc t i on. ma- nd infor ons a i t c a r e t in f u r e t t pa g n i g n a h ly c d api r nd f s i t s i n t h e p a t ti e r n s o f i n t erac - on f l ow . Th e i n t e lli g e n c e t r o e h t l a t n e m elop v l de Al a h t e g d e t l w o n k c uld a o s w t s i rop r t ies q u i t e u n l i k e t h o s e ti ons in t he wh o le a nd has p e r l r be d o v e r n be desc gs ca in g be vin i he nd ot ns a ma hu i ls wh e t m p r is h a t wh o o c le. of t he ind i v i dua o a i r o t t he m o le cula r a nd c e l- on f z i n a g or f els o v le y n ma m s book utc h ins (1995) r e i h f he end o At t f l e c t , H s on l d lu y t vi i t c a l a r u e n f el o v le x e l p m o he c t h g u o thr r, a n a i- g o c d e ibut r t s i ly d l a i c o n a e r u t cul f o g n i n a e he m t nd s nd e x t end in g to n e s t e d r ela t i onsh ip s wi t h t h e beha vi or , a i e: on for c o g n ti t i v e sc ienc n t s (e.g., Bronf enbr enn , r e so al a nd p h y sica l en vi ron m e ci h 1979). A hes w t vie o s l ies a r o e e t l a t n e m elop v l de l nd a he ea T r ly r e s e a r c h e r s in c o g n i t i v e sc ienc e p l a c e d a be t t le v els as in eract i n g w i t h o n e an o t h e r . Th e d e e p di f fer - ma th at t he m odula r i t y o f h u t n c o g n i t i on w o uld be su c h t h a e r o nd m ism a l l- u t x e t n o en c e w t e be enc i v dua i ind a d a t t h e a , t x e t n o e, c r u t cul g f uld be sa o y c tor s i nd h n ely i o r e ep p d e z i l a u t onc e c r els a v he le t t a h hes is t c a o r p a ered t n ce in la ou a nd t hen in t e g r a t e d et t e r . f. T he be t d i d n ot pa y o f ts as mo r e th an - u s t i n t eract i n g ; i n s t e a d , t h e y a r e s e e n a s i n j h f s o t r c gs a in h e t hes T n a l e m nda u e f asp n o i t i n g o n c ma u t e te g ral ly f u s e d to g e t h e r . B eha vi or a e r a t n e m elop v s de t nd i e ly in a t mfor o ot be c nn nd ca a e v i t c b p s r e to a p in d e t a r g e t s a nd t h e me d e d a s ev e r-c ha n g in g s e t s o f re l a t i on s hip l p r dua i v i ind d e t a l o is f ies o t er l o p ract st b a s e g e l i v i r p at th o s e us, as m h e. T m i s tor y o f hi t h e r ela t onsh ip s o v e r t i n- m inds. ( p . 354) i ons o f simp le l i n- d r l ie ea r , w e mus t d isca r d o u r n o t ti on e Th l Sy e i r o e s s m ste era n Ge t y: T h a t en r causa l i e v ea t A or s t r u c t u r e X c aus e d We e v hes to de c roa p l ap ica t e elop- ha v desc r ibe d t h e o r e r- a p or B to ap vi beha r . Ra t h e r , causa l i e t y is mul t i p ly de t f y- em m o r on, f i t a me nt at di br fere n t l e v els o f or g a n i z e . n o v e i r t i m g g n a h ly c l ua in t n o nd c els a v le r e v d o ne mi hes udy he s ons for t i t ica l l imp ica ol og ica l to s o c i e t a l. T t e ap p roa c hes a r e b a s e d on d a r e v s i em st Sy deas ha he i le, t i a x or e ind. F m of t on assump mm co mp d n y a t i x e l p m o c ’ s em t s y ut s ons abo - r e is em e g d e l w o n k t a h dea t t e. H a nd t h a t h uma n beha vi or is s o c i a l ly c ons t r u c t e d in , r e v e w o ge g n a h c f es o d caus e t ela r r e nt le in p i t he mul t t er s emp ism n a g g or elopin v e d f o s c i t s i ract a ch he ha- ta sk a nd h i s tor y is beaut if ul ly il l u s t r a t e d in H utc h ins ’ s udy o f na vi g a t i on. N a vi g a t i on in m ode r t n , y t i r ea in onl on, n i t a z i n a g f-or el s s— w e vie hes d in t ze si (1995) r e c e n t ess, s abil to bi- d e in onf ot c n e r a e— g n a h d c n , a y t i t enn op na vies is a c ons i t c a r e t in f em o t s y s x e l p m o via a c d e v e i h s am n g es. a la r g e n u m b e r o f p e op le a nd m e asu r in g de vic ol og i c a l o y s t e m s . T h ey a r e a l s o f o u n d i n c o m p l e x phys - eract t n i e s e Th d b t h e e n i a t in nd ma y a d e e shap r ons a i ica l s y s t em s su c h as c h em ica l r e a c t i ons, glo b a l w e a t he r lit a r y p ract i b cul tu re o f mi ch an g es, m o u n t a in s t r e a m s, clo uds, d r ip pin g fau c e t s — c e an d l a n g u a g e , but a l s o y

11 268 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 268 n a m i Dy y whe r e v e r ma n c o mpon e n t s for m a c ohe r e n t pa t t e r n m s- h a n g e o v e r t i nd c e. T h e p r inc ip les o f dyna m ic s y a e t mula for ms te ema t nd ma a s t h is c i phys y d b t i c i a ns to l desc he beha vi or o f su c h c o m p ibe t e x phy sica l s y s t em s r ma y a l s o be t he bes t w a y to s t udy a nd u nde r s t a nd de- v elopin g or g s. ism n a e ce Fi r o c F i m a n d Dy n n a i w Le t r Ku f e o On lds. elop- t r l ies t e x p l ic i t ly dyna m ic for mula t i ons o f de v he ea ’s (1936, 1946 me wa s K u r t Le win nt ) topo lo g ica l fi e l d s u the o r y of pe ona l i t y de v elop m e n t. Le win w a rs n - n ab she d ly an t ired u c t i o n i s t . H o w , h e a s k e d, c a a p s y c h o l - h o r es en t a l l t he r i c gy p n ess o f h uma n beha vi or as t h e ndscap s ’s p win Le re 6.4 u g Fi ( p es, e c l spa s.) la ica g lo o h c y f t a e ic m t e po f ead o t ic ins ns” i t ien h sc i w , but “ st li ve no r o f f o s m e st y s ered y d as la e t depic ields wi f ce t h R = “ r e a l i t y ” g Eins o e h ’s t in e t r in enc r e f e 792)? R . win, 1946, p e (L e t i - l en t on be t w e t h e c e onn he c a nd I = “ I r r e a g t i t y ,” a nd sh o win i ca e s ropo ) p d: s, Le sic y h l p win (1946 , t en es r , p t he pas es in t c l for ona i t va i t mo he top e. T r u t u nd f a f t n el depic t s a l i f e spa c e o pa a y o u n g c h ild; t he bot to m, t h a o f d as a an o l r c h ild. So urc e : Fr om “ B eha vi or a nd D e v elop m e n t e o h et m e Th r e ff i d e h t t a h n t l i a e - c a f t n e c i t y al an b d l u o h s d . 798), b p on” ( i t a u t i l S a t o he T t f on o i t nc Fu y K. Le win, in v h s w h i c inf l uenc e beha vi or ha tor e to be sp e c i f ica l l y d is- r m ic hael ( E d.), 1946, N e w lo ld Ps of Chi l a anu yc M gy , L. Ca ho o ls a e v a h a ti e b o t ng uishe d. I n sc ienc e, t hes e t a d r p o C . y le i : W rk Yo d e t in r p e on. R y & S le i W n h o J y t 1946 b gh i y s t i e g wi t h in t h e s p e c i f i c t r icula t r pa r i he t n i d e t en es pr re n issi p h t wi on. m r e o n f act s w h i c h a r e c onc e i v e d si t u a t i on. A tot a l i t y o f c g e xi st i enden le fi e ld. ( p . 792) l a c s i t a dep r e t n i y l l ua mut as of d s t a nd p roje c t s m o r e in to t he im m e d i a t e f u pa t u r e t h a n en Ac g ha in t t e l s sica phy s v i win, a g to Le ng rdi co in h add c g- e spa e v nsi pa x e e r o he m t o f t he o lde r c ild. W t e o f t he ind i v i dua l me ani n g o n l y as a f u nc t i on o f t he s t a a p f ’s 1977 i l l u s t r a t i on o f ton h a s e-spa c e d i a g r a m o de- l t dua i v s h a t s e t t in g. C o n v e r ely , ind i t is x ot e do n s t i a in t r r t m elop v , sh o w n in Fi g u e e 6.1, is r ema r k ab ly sim ila r to n d. Le e y la isp e d r a y e h h t ic g in wh in win t t e he s t of e id s t ou e g i t nd depic on a i g e r e r r n ef r g p yin f i t den ’s in i win Le d i ons li fe s p a c e s — f ields o f a t ca l l e d t hes e f ields o f in t e r c v r e c is spa h gh t u o r h t t if r d e v essi g o r a p s a t n e m elop de . c le m o v e dyna m ica l l y for e hs. P op g n e r t g s yin r a v h t es wi t ro on in i t ca r lo i e h g on t in end , dep ield e f c is for h gh t u th e, t c win e L t r Ku . hor p a t e M s y a Theor stems Sy y t he spa ’s dy- h e i r n e e ds, a nd p r e v i o us h i s tor y . F o r c es ma lap r e v , o t c i l onf e, c t e p com a nd d h, but v c ue a i r e r e w s t ep onc ic c m na i g f f icul t to op- e h g on t in end , or sum, dep erat r h t i d to e he tc ly ma poor e r e deas w is i ze. H li a n o i e pe rs on ’s d ispo si t i on a nd t he en vi ron m e n t. Lea r n in g— l t he m e c h a n i s t ic f l a v or o f N o r t h Am e r ica n e x p e r i m e s- t a a nd de v elop m e n t— c onsis t o f f ind in g a pa t h w a y or d i n ps c he in t he l i f e spa c e. A nd as c h ild r en a ne i w n n- e he m nd 1960s, or to t he 1950s a t g n i r gy du lo ho yc co v e r i n g ly c c ca r v e n e w pa t h w a y s, t h e y a t u l- o h c y s p l a t n e m elop v de n a i t e g Pia f ons o i t ic assump st li ta a l r ea t e y e t n e w pa r t s e, a p f t l e le f t t i s l a gy w lo o h c y s ild p h on c t c is impa nd h a y, og of t he spa c e to e x p lor r o c ess o s e l f-or g a n i z a t i on. e v elop- v ut de abo g n i k in h t s m e t s y cades. S e de s o h t g n i r du Le win depic t d t h is de elop m e n t a l dyna m ic as sh o w n r 1970s v in de s t poin t n e r e f f i d t es a c spa e 6.4. Lif e elop- u g in Fi me nt u nde r w en t a sma l l r ena issa nc e in t he la t e t o r ce f ields, wi e h d i f- d nt me b t n e s e r p re e ar y l a y ered f a nd ea r ly 1980s, h o w e v e r , a nd t hes e v e r s i ons w e r e mu c h g de g r e es o f “a t t r y in c t i on” to t h o s e fere n t z o n e s for v a r yin mo re ex pl ic i t ly t i e d to t he n e w sc ienc es o f c o m p l e x i t a v ha e c spa e f i he l - t f s o r e t e m a r he pa ields. T f n di eral v e s e phy sic s, ma t h, a nd bi o l o g y . T w o aut h o r s, Ludwi g v o t i f i c i i y , s epa- ze o f ons: S ensi m t he spa c e, de g r e e o f sp e c Be r t a l a n f f y, a b i ol og i s t , a nd Ily a P r i g o g in e, a c hem is t , h l. rat i o n b e t w ee n re alit y a nd “ i r r ea l i t y e n t as y , a nd t w ere e s p eci al ly inf l uen t i a l in t h is r e n e w a ” or fa c es a ess c o r l p ica g lo o h c y h s p f e o uenc l inf e m i ss t ro e. T Ludwi g v on B e r t a l a n f f y (1968) has usua l ly be en eral n e G u li fe spa c e o f a y o g e n r c h ild is m o r e l i m i t e d a nd less d i f- ” . y r eo Th ms e t s y S credit ed w i t h o r i g i n a t i n g “ ired n i a t e d, an d it i s i n f l S inc e t he 1930s, he has he r a lde d a n a n t t u c t i o n i s t uenc e d m o r e b y t he im m e d i a t e fere

12 269 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 269 Dy a m i c Sy n a en n f f y , 1933). T h e tr o p y , an d, a s Pr i g o g i n e put s i t , t he “a r r o w o f t i m e ” a l r e on B s (v em t s y l s ica g o l o bi f w o vie t ru do u on. B i zat ani g r o s di rd a w o t — n o i irect e d ns in only on t to y r t is hem c m o r es, f ienc he sc l t l end in a r t t n ina m l o l o l bi l nd a s, a em o s to is a , w gy lo ho yc ps t s y s y n ma t a t e sma l l e r a nd sma l l e r elem en t s em s, l i v e in t h e r - s y l s ica g he s y em, but v on B e r t a l a n m odyna m ic n o n e q u il ibr ium. T h e y a r e t h e r m odyna m i - f f y f e l t t h a t u nde r s t a nd- s of t t i ca ron m e n t l l y op en: T h e y t a k e in en e r gy f r in g w o uld c o m e, n ot f r o o m e h t m r en t hes e s epa r a t e pa r t s, but f vi r o m e i ela he r t onsh ip s a on g t hem. S o, wh ile a n i ma ls a r e t s lea t is a t m i t f w o ro r he a t r— de r or i e h e t s a e r nd inc a m n t is a p r em ie r e x a mp le - m o c m o r t empor a f t e buil r ls a l e nd c ls, a l e nd c issues a t f made o ily r e v e r s e d. D e v elop m e r x i t y a o n cules, k le mo ex pl f t he m o le cules win he s t r u c t u r e o of a p r o g r essi v e inc r e a s e in c o m p l e nd or g a n i z a - g t h s ev en in t he g r ea t e s t de t a i l ca nn ot infor m us abo ut t he be- ti on. S u c y s t em s t a k e on sp e c i a l p rop e r t ies, incl ud in g t ha or o f t he a n i ma l. S o m e t h in g hap p ens when c o m p l e x he abi l r- ea in onl nd n ns a r e t t to pa ze in i n a g f-or l e to s y t i vi it i- e l o m a wh to for r e h t e g e to m o s c t r us pa o e n e g ro y or s t nd he a ensi t i vi t y to in i t ia l c ond i t i ons. Ag a in, i t is c r i t e is m at th a h l t ca s su t y s t em s a r e inhe r e n t ly “ n ois y ,” for or de r h a d c e ies n t r e rop em p t s y he s s. T t r he pa t n a h t e r o e i r ot be de nn ca t a h e t on on— i t p i r ium s f el o v w le ne ar is es f r o s, m su c h d e v f l u c t u a t i ons. I n eq uil ibr y s t em desc e mp he s y s t em as a wh o le r ut a - s- y e s hes e. T lon a s t en mpon o he c t f or o vi he beha t om fr e is da ois he n t nd t o d e y te ms pr inc ip les, in t u r n, a r e s o u n i v e r sa l t h a t t h e y ap p s, in em t s l ium s ibr il u q e n o n n ium. I ibr uil ins in eq ma y co nd o ra st , f l u c t u a t i ons ca n be c o m e a m p l if ie d a v e r - to wi dely d i v e r s e be nt in gs a nd en t i t ies: t he wh le s y s t em, sh if t i n g i t to o f on o i t a z n a g he or t ke ta i les ap p lyin g to s y s t em s in g e n eral , We ca n ask for p r inc i p g on. e w or de r o f or a n a n i z a t i sica y l, or ica g o l o l, bi esp y h p f e o r a ir e c t i v e o f whe t h e r t h e r A n u m b e r o f de v elop m e n t a l is t s im m e d i a t ely r e c o g- ica so v n o d c n on a i t ues is q h t e s po e e. If w r u t l na g o l c i o e- f r t s y s t i ic l p x e e hes t em e o nc a v ele he r t d e z ni inc ip les s p ni en t ly def in e t he c onc ep t o f s y s t em, w e f ind t h a t m odels, i s for a g e-o ld , y e t s t il l c r y- t ica l, issues in de v elop m e n t a l p s- inc i p les, a nd la w s e x is t wh ic h ap p l pr e n e r a l i ze d s y y to g ndor Br en t (1978), for ins t a nc e, sa w in P og r i- y. ol ch Sa h ms d n s, a t en , elem ind r k icula t r r pa i e t f e o v i t c e esp r ir te a gog e’s for mula t i ons o f s e l l f-or g a n i z a t i on pot en t i in r “ c es” in v o l v e d. (v on B e for t a l a n f f y , 1968, p . 33) l p m o c f ins o g i he or t f ons o i t ues y he q ons for t ti lu so t x e i g e to m nd sh a t s l a t n e m elop v e de on m o r f a s t if ad- e r v on B e r t a l a n f f y p r o v i d e d dyna m ic eq ua t i ons to il l u s- o nc va e d le v els. M o r e o v e r , Br en t bel ie v e d t h a t i deas o f n on- t rat e t hes e p r inc ip les: Wh o len ess or s e l f-or g a n i z a t i on, enn (s r a r e i nd h on), a i t a z i abil t f-s el y t i l ina uif ess, eq - op t a ly t ic” ca gly “auto in em e he s in t a l p x uld e o y c it ar ne li s ap p l a on ch t z i asp e n a g l or ica i on. I n h is d iscussi on o f s y s t em c t s o f de v elop m e n t , whe r e on e sma l l t r a n s for ma t i i- n a h c g n i t a r ele c c a , t uen q e s for sub t s ly a t he ca s as t act ly es. g l a i c e s esp a y w f f n a l a t r e on B , v gy lo o h c y s ons to p i t ca t r Br en t’s d iscussi on is s t i c ly t h e o r e t ica l. A r n o ld l o , g in on i t nc u f l a t n e m f odels o asis” m t s o e m o cr it ica h f “ w s m e r o deas m s i em t on- s y c e he n t d e i (1983) t f f ro Sa e on t i t n assump ia eud r he F i ly t l a e r s a ism n a g or t a h esp e c p g ely to de v elop m e n t a l cret hen o m ena. Sa m e ro f f has lon g to r nd s ons a ensi t e c e du in ek se ys wa f e o t a t ek a s e al n r r ild h c f es o m o utc o l a t en e m elop v in de d e t s e e t en in be t h eq e r , or g a n ism s a r e a l s o a cti v e ; uil as a n ibr ium. Ra u r m r a e n i l f e o r odels to il he fa ly in t r icula t r , pa isk at il u q e s i d f ind o in a k e v i l e t ium (wha ibr h em, t t s y en s op y t t pa red ic t h o l o gy f r o m a n p e c e den t c ond i t i ons. I n a n im- v i t c nd a y) a t i abil t ic s m dyna l l ca l we imu- ek s t e ely s wil a t por t r le nd nd Cha a f f ro e m , Sa r e pap l a i t uen l nd inf a n la nd f i on. T h is d i s e q u il ibr ium a l lo w s c h a n g e a e x ibil- t l sis ly puzzl in ind g f in t n e t g r e he p d t e t en cum (1975) do he i dea t h a t too mu c h s t abil i t y it y; t is in im ica l to c h a n g e v e nd u o r s a tor c isk fa us r o i r s y r e h t en wi r ild h e c som at th e de rec ur s in ma n y v elop m n t a l a c c o u n t s (e.g., Pia g e t , u bi l p m o y c r e v i , del y t i r i- t ema r , p ia x e or n g a in ud h, incl t r e We rn r) a nd is a n assump t i on w e a l s o f ind ess en t i a l for s, suf l a i c o nd poor s ons, a i t ca en vi ron m r o o n fered e t n a n nde r s t . t u nd in g de v elop m e t a le lon sus s r he ile ot es, wh uenc eq tt li ons m c r e g-t d e n i g ond e he s s t a e w in g o c i r a P t Ily is hem bel c o he N T o ri se e-a o r m e di c a l le caus imp nd-ef s. S t c e f us ef fect t eloq n nd a a y r o e h s t em uen s y ibutor to s r t n o l c ipa inc pr t a t odels o t d wi m e t n a l p t be sup e mus as e s i d f gh- u oro h h e r i ze r as w e l l (s e e, e.g., P r popula g o g in e, 1978; P r i g o g in i e m to Sa g n i e r f, whe f d r o c c odel, a ic m ism n a g g or oin g ro s p t e t s e r e t in ily in r ima r d a e w in g o g i r s, 1984). P r e g & S en t g en in on i t nc Emp u ely f v i t “ c a , c i t is l o hasis on a wh y t i s h m r t m t he p h y sic s o f s y ody- t em s t h a t w e r e fa r f r o e a vi- he en t h t ons wi i t c th at c ons t r u c t s i t s e l f o ut o f t r nsa r m na m ic eq uil ibr ium. R e ca ody- l l t h a t , in N e w ton ia n t h e t t f bi o l o g ica l de- ron m e n ies o is de r i v e d f r o m t he p rop e r y gy o f t h e s l s l s, a c i m t em s r u n to d i s o r na d e r . T he en e r 253–254). v elop m e n t ” (1983, p p . issipa se er s iv un r inc d t es o v e r t i m e. T he u n i v e r e as es in e

13 270 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 270 n a m i Dy e s lab- e t a h s t e g han c g n i r u d ly en e v i t la e n of r sio s cc a su e c du t y s assump- t i h t odel, wi s m em A s a s h c su f on o i t dop e h e t l s a e r inc r a r u t c u ’s str n o rs e o e p e h y of t rsit e v di or at t z ons o f wh o len ess, s e l f-s t abil on, i ti a z i n a g f-or l e on, s i t a i l a n o i t nc u t a p ir en- e h e h ns of t r e t d t an s c i t s i r e t c a r a h c an d f g ons for t ica l on, has imp i t a z i n a i l or ica h c r a r e i nd h a o h ns w m n o vir le m c a r e t t l in ta en i a i n t a inin g c o h e r e n t o r g a i - v , a c c o r d i n g to gy lo o h c y s p l a t n e m elop de f o t c e y asp er ev io l-f u t c u d str n an io t a niz u n c t r na l u n it y of t h e p e rs o n a s a a t m e ro f f. F Sa on mus i t a z i l a i c o s f ies o r o e h e, t nc a t or ins t l le. o wh ina . 49, i ( p a l ic s in or i g ) e t n o ghly c u oro h t e m o c be f on o i t o he n e t caus l, be a u t x he ind en s s t em s m e a ns t h a t t y i v i dua l is a l w a y s in op e h on, t i t i in he def T in t a in, imp l ies a l i f elon g po s- ma y t ran s a ct i on wi t h t he en vi ron m e n t. B i o l o g ica l vul n e r abil- a t h o u gh n ot inf in i t e) a n d sibil i t y o f c h l n g e, mul t i p le (a isk ot e cuum, but a t in a v it y or r x , in t h is cas e, do es n is a w h t pa l d t n e m elop v r de ea in onl n n ies, a t i u n i t on isc s, d y a v f k o or w t e n h c i he r e h t wi a m o r e or less sup por t i in t i- in he def e, t or m r he r u s. F m w for e n f e o t g r e he em t enc rod- oin t p e is a j m o e. Outc r u t cul y t i n mu m o ly a i m fa nd c t n e m elop v de t a h ies t f i c e on sp ti i f on o t nc u r a f e v e is n l a h y t e i c o he s t f enda o g , a r u t he cul nd t ild a he c uc t o f t e x t a lon e, but inde e d r esul t s as a f u nc t i on or c on pe o n t rs a - f l e nd s a g n i z i n a g f-or l e s s em ha t a nd t he tot s l s y on. Fi n th ei r dyna m ic in t eract i of g u r e 6.5 is F o r d a d st a . s c i t s i er act r a h c g n i z li i b c t r n f ies o r e as a s e g n a h Le l a n e m elop v de f odel o ’s m r e e, t he issue o f c han g e mo t i va t k es t he Li v e l o p - e wis de pr n abil i s t ic s t a t es, whe r e ob o n t ro l s y s t em s in t eract i c r (1992). I n r e a- me nt a l sy s t e m the o r y of Fo rd a nd Lenr e n t he cu us t h e t r es a t a t t. S r- e m ron vi he en nd t on a s r e he p s r so ni ng th at clo ely pa a l lels o u r o w n, F o r d a nd Le r n e r t re en r r h on cu d bot e s a em, b t s y he s t f on o i t a r u g i onf c nt h ns as “ be g in wi t h a vie w o f uma mul t i le v el, c o n t e x t u a l e s- at us a nd on t he s y s t em ’s im m st d i a t e a nd lon g-t e r m h i i t a z i wh a g or o n ) 7 4 . p ons” ( i t nc u nd f es a r u t c u r t s f ons o r he r ut t o gh u o hem h es t - e tor y . W e wil l r e p e a t t hes e t iabi n d s f l inds o g k yin r a t v ibi h ex i t r a nd v a y t i l abi t y a h t f r o inde ma . r e t hap is c nd be l vi i d n els. I v en le w t dua h in a bot e g n a h n c o ca wh e s i t ea r ’s t e; i r e n r nd Le a d r Fo t op us in sc o i t bi m is a e r t i r o e h e t hes to t n i d s o c c , a t n e m elop v de s: g o nd s l a ica g o elop v de gle de- l a i l to a sin in t n e m c t ies bi o a e l l e t n r in i e h . T y e m elop v r o e h s t em t s y s l a debt is l t u t c t s , t a h s t in v o lv e s inc r e m e n s a l an d tr ans fo r m a t io na l p r o c e e x e t n o nd c ic” a ism n a g he “or ly to t ect r di de- f o l o o h sc l a u t n s r e t c r a h c t n e r r u c ng o m a s i o i t c a r e t - n i f o w o l f a ough r th a o- ex t n o ts, p t c en rr u r c e h r s o d hi r an l a n o rs e p e h of t cs ti r v m e n t a l t h e o elop y , a nd less s o to phy sica l a nd ma t h e- a t ic s t is abil b o e p f ies o r e as a s e g n a h c l a t m n es. t elop v de f odel o ’s m r e n r nd Le a rd Fo re 6.5 u g Fi r

14 271 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 271 Dy a m i c Sy n s. Li a r i- e n e h e, t wis e r k ot p em t s y l s ica m l dyna ica t ma y t e r ns— a n o r g a n i z e d r e - t t a p m for s em t s y s x e l p m o c e hes a - ri ly c onc er n e d w i t h o p erat i o n a l v e r i f i c a t i o y s s f o n ma la i onsh ip a m on g t he pa r t s— r t in la r g ely a m y s t e r y . ema n ect direct l y w i t h t h e te c ms a p p r o a c h , n o r d o t h e y o n i th In e p as t d e cade or s o , h o w e v e r , phys - e h t a , m s t s i c ex l s ona i t a v r e s b nd o a t al nt me ri ud pe ies o f ind i v i dua l ia c o s d n s, t s i g lo o i b , s t is hem c ns, a i c i t ma a v- beha nd a l . t n e m elop v ild de ch e t s i t ien c s l a r io m e inc r e a sin gly in t o c e b e v a h s e r e s t d i y Thi s o v er v i e w o f t he h s- s tor ica l he r i t a g e sh o w s s t o f n e n a h m t i s w m e t y y s w o n h r i , o y t i x e l p com h c su in , s ms te p roa c hes to ha v e endu r i n g ap p e a e l to de v elop n- ap m r s. n e t t a p d e r de or e c rodu p o t e t a r e oop c s t r pa e, rs ve di elop is li st s. T h i s ma k es s ens e. As de v ta m e n t a l e r a t e s, w o t e s n o m m o c a t a h t is e i m ro s i- inc r p f Th e s c ien t i f i c p co f in y o ua l ly fa c e d wi t h t he r i c h n ess a nd c o m p l e x t i nt les n m a t hema a ica l for ma l ism s m a y desc r ibe d p t t e causa t a he elabor nd t udy a t l w e s w ism n a g he or eb be- s t im e, i r r esp e c t i v e o f t he i pa t t e r n s t ha t e v o l v e o v e r r ma- e t en a c t i v e ind i v i dua ls a nd t h e i r c o n in ua l ly c h a n g i n g tw s e rat t . bs u s l a i r te c t o n t r ibut i on o f t he dyna m i c n e c e he r s. T t n m ron vi en e r Ord e r f o m Com pl e x i t y t sy st em s t h e o r ies to t h is t r ad i t i - l ies a r o e h on is t h c su t a h ess, in w ica w s us to e x p r lo o r ds a nd in ma t hema l for- t a T he k e y f e a t u r e o f su c h dyna m ic s y s t em s is t h t t h e y a r e y e f e o enc g r e ess, em len o wh , n t i x e l p m o s, c ism l ma w co mpo s e d o f v e r y ma n y ind i vi dua l, o f t en he t e ro g e n e o u s y to e o p y e h on. T i t a z i n a g f-or l e nd s s, a v i de a w a m x - for r - pa r t s: m o le cules, c e x ls, ind i v i dua ls, or sp e c ies, for e l n a r is pr ess t he p r o f o u nd insi gh t t t a t pa t t e r n ca e wi t h o u h e r ly f l ica t e r o e h e t r s a t r e in he pa le. T p am bin o to c e m g n desi g n: D e v elopin g or a n ism s do n ot k o w ahead o f t i m e t ne a r ly inf in i t e w a y s. T he de g r e e s of f r e e d s- y he s o of m m e o r p f o t ess. c rodu is a p c r o . F end up l wil y e h whe r t y la r g e. Y e t , when t hes e pa h e t r em a t r t e to- s c o r m e us v a n d y e h t , r e h t ge r e to for m pa t t e r ns t h a t ohe l i v e in t c m e i i- i he or en; t e e s r ons a i t g m o le c ssib l po l ot a e. N c spa bina c o m p r e s s ed . B u t t h e p t a t s e r n l de g ree s o f f reed o m a r e na An tr od uc t i o n to D y na mi In s S y stems T h i n k i n g c . T he elabor a t e shap es or for m e d a r e n ot simp le or s t a t ic n u d em t a h t s m for r g e ca e nde r g o c h a n g es in t i m e a n g i n espi e v elop- D t e a lon g t r a d i t i on o f s y s t em s t h i n k in d - n i spa c e, incl ud in g mul t i p le s t ab le pa t t e r ns, d isc on t u n me i- c o s d n a e r u t cul f o udy t s e h o t t y og yol r b m e m o r f , t s m, but gly r it ies, r api d sh if t ndo o f for m, a nd s e em in a ema in e d m o r e o f a n et y, t hes e for mula t i ons ha v e r a in ua l ly de t e r h c su f k o r act m l l he ha es. T g n a h ic c t is m t s e v n i o t e d i h ract i o n t h a n a c o e re n t gu a r o n o i t a g st i ab sy em s is t h a t t h is s e q uenc e o f co mp lexit y t o simp l i c i t y st da an for me y n t hesis o f e x is t i n g s t a . D e v elop m e n t a l is t s s h t es wi g r e em y lexit mp o c to e esp r ut p o c i f ica t i on; t he pa t- r e n ee b s a h it t u b , e t at m s m st y s at h t e g d e l w o n ck a y ma o te w o sh m a e r t in s a t n u s r m es. Ou v l e s hem ze t i n a g ns or r g r r a c d n a n ea es r l ica r empi t u o y desi o t t icul ff di r c h a e, but e a nd for m a nd dyna m ic c h shap n g es o v e r t i m h e r inc inde r ip r p s em st sy of re co n a d o se ba les. I n t ema r m he w o le cules or in t h e m in t a r g o r p o e is n er th a t e ze i th is c hap t e r , w e sum ma r of a s e t o f dyna m i c p r inc i- l o e g r e v e o l t ima cl g f es o g n a h he c d or in t e b am re st ica o v p ap p l icab le to h uma n d e les elop m e n t a n d t hen sh o w a h t me p les a nd e d d ies. ti p odes t he r enc t i ho w r es ea r c h c a n be r- e t in nd a , d e t c ondu c , d e r inspi ns a e mpo o e c wis e k i e l r s uma De v elopin d o f a h u g e g h a s e o u r sum- p fr o m a dyna m i c p e r sp e c t i v e. W e ret ed b d es a mb er of t n e r e f f i nu t ess c o r nd p s a t r pa r ila issim d r ma r y o f dyna m i c s y b nd s t e m s hea vily on t h a o f e r le els o f or g a n i z a t i on, f v o t he m o le cula r c o mpon en t s m Ha k e n (1977 ) c a l le d syn e r g e t i c s . dyna m i c s s e t for t h b y i r t he c e l ls, to t he d i v e s of t y o f t issue t y p es a nd or g a n th te No he be e v ha s c i m dyna f en o s m e t s y s l ma for r ot at in sy t e m s, to t he f u nc t i ona l def s e d sub s y s t em s us e d in v s a h c u s , t n e m t elop v e d o t d ie l p ap ic s i g lo “ t’s r e Ge n a t s e g i on, d i t a r espi r nd s on. o on, a i t i n g o , c t n e m e v o on, m i “ca gr r Ma as a n d M o lena a r ’s e t a s t ro- ow th m odel,” v a d n ut beha B h co ely m e r e re n t a nd sup or is sup r e vi m ely co m - iscuss h r t o l il t S . y t uen eq s sub e d l wil e w t a h t ” y or he e t ph l c i l simp m o r y f t a i x e l p m ag lex, p o g c win o in sh m o r f y t i o (1993). T nd a h t i in nd u helen f e b n ca les p am ex Sm le mp co y t s m a e r t in s a t n u o m f on o i t a z i i n a g f-or l e he s . T x t ons s e h T im t n i s n r e eas t a p y b d e t inhabi is re tu Na e. t t a h n en in de- e t e r ue he g r a e t; w s e f i ns s is ma r e t t he pa a is- d n a le b m ass uds clo e, r u s d e m d e r de or n i ge n a ch e rodu a p o s l e a r ns a uma g h elopin v ons i t ela he r t f o t c a si pe rs e, t r e e s g ro w es k a l f w o sn ze, nd t e shap n i a t r e c o i o t r le pa p s. t mul g n am p la n t s a nd a n ima l s p a s s t h r o u gh for m a nd m e l t , m in ut e ns c r a m s a nd de v elopin g h uma e r e- Bo th mo un ta in s t n visib le to us, a n d s o c ia l elabor a t e l if e c y cles t h a t a r e i to a r s be caus e t h e y fa l l in t at e or de r f r o m d issim ila r pa e v e a l e d gr ou ps co me to g e t h e r a n d d isb a nd. S c ienc e h a s r s h l l e d op en s y st ems, or s y class ca t em s t a t a r e fa r f r o m secret s , ’ re tu na of ny ma b c s u t t h e p r o ce s s e s b y w h i h

15 272 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 272 n a m i Dy y th m r e h t t em is a t s ody- A s ium. ibr l qui namic e dy mo er simp el— le for ins t a nc e, t he a l t e r n a t in g c y cles o f r le v ic eq o um o t n e m na m f uil ibr ium when t he en e r gy a nd m ic a cl y is c h t. T e e he f t f o e c n a t n i on is a a swin nd s t r e t l g a e o e is n r e h t he s y s t em a r e u n ifor mly d i s t r ibut nd t d a ot t iab ve va r ec ll t is n ti he only on e. W e m co i gh t le, but i ot he r . F or ins t a nc e, when w e f l ow fr om on e r e g i on to a n muscle f ed so look a t pa t t e r ns o f al i r i n g or for c es g e n erat l iss t e sa l t in w a t e r , o t he m o le- add a l c o h o l to w a e r or d v i l o a c f e o oic h he c s. T t oin he j t at c t i v e v a r iab le is a c r l t - e e t t hea e nless w . U ely t e l h m o t c c a e x or r i ons m cules or i p r e t c a r a h ep in c t l s ica ic s m a dyna g n i z y s t em, but i t is i em is s t st em or add a n ele c he s y s t t ab le. , t en r r ic cu r sy t c l end c y dep ma t nd i ish, a l mp o on- c to a y eas s y a w ot a n h i n e g No t n e w ca n em e s m r t Sys . d e s o cl em is t s y he s e; t g r b l a n a f el o v si de y a he le sis to be u nde r t a k en. ly on t l s ica g o l o ds or bi be m a e r t g s vin o as m h c su e v l o v s e em t s y a nami t i l i b y At t ract o r s and Dy c St nd c h a n g e be caus e t h e y a r e c o n t in ua l ly inf us e d wi t h or a t is s m e t s y s n e p o , g n i z i n a g f-or l e s f o y t r e rop A c ri p ica l i e ran sfer e n er g y a s t he pot en t t a l en e r gy o f w a t e r a t t h , u s ran g e o f p at t e r n s i s h t h e o r et - g an e n o r m o th a t , alt h o u u n t a in is c o n v e r t e d to t he k i n e t ic en e r gy o f top o f t he m o a t l l y p o ssib le, t h e s y s e m ica c t ua l l y d isp la y s only on e o r i a t in e ma r s a em t s y l s e ica g o l o i B . r e t a g w vin o he m t d be- n f a v y l im i t e d sub s e t o er t hem, inde x e d b y t he beha vi or d caus e p l a n t s a nd a n i ma ls ab s o r b or in g e s t en e r gy , a n c c of t h e o l l e t iv e v ar iab le. T h e s y s t e m “ s e or to” in les t t i e is en e r gy is us e d to ma in t a in t h th r or g a n i z a t i ona l c o m - fe rs ” only a f e w m odes o f re beha vi or . I n dyna m i - c t e r “p ond la pl it y. Al t hou gh t he s e c ex w o f t h e r m odyna m i c s r st at e , be- l a or vi beha s i h t , gy lo no mi att a is ode m r a c t o n em is h ium, t ibr uil to eq n w n do u uld r o s sh t s y s t a h lds t ho caus i e a n t i ond c n i a t r ons— e c r nde u em— t s y s he t has a is only glo b l ly t r ue. Lo ca l l y , s o m e s y s t em s d r a w on en- h a t s t a t e. Ag a i n s i n dyna m i c t e m , t he s y s- r af fi ni ty for t gy a i e t as e r nd inc h er r or de r . e e s te m p r e f e rs a c e r tai n l o c a t i o n i n i ts sta t e , or ph a c s a e r e f r t n e pon m o e y n ma e r s, whe em t s y en s Op t i to , e c la p t ha t m ro f d e c la isp d ends t sp a c e, an d when onl t ela to r r e capab le ea r w in a y s, a r in n he ot h c to ea e h ret u r n t e re . t r e rop le p ab k r ema r of gy is e t en ien c r i f ies. When suf m T t a t e spa c e o f a dyna he s ic s y s t em is a n ab s t ract pump e d in to t hes e s y s t em s, n e w or de r e d s t r u c t u r es n c ensi m i d f o r e b m u y n ons a f o e c a spa f t o c u r t ons ly ap- r e m ot for n e r e w t a h t r a p usly ap o e n a t y spon ma e e t t he c t f es o a t le s ssib he po o in es def t ina d oor e c s o wh l- t t s t. Wha n e r pa e cules le o m f on o i t a g e r g g a n ut as a d o t r a a r i t c le iab le. F or e x v mp le, t he beha vi or o f a simp le e v a or ind - e r d e g e l i v i r i v i icula dua l pa r t r or p t r pa o n h t s wi t em su h as a p endul um ca n be de- c s y l s ica an ch me y suddenly p ons ma i t d n a e c ns in spa r e t t pa e la rodu c e ely in a t w o-d im ensi ona l s t a t e spa c l p m o d c ibe r sc t e y ula i t ies in t i g m e. T he s r s t em ma y beha v e in h i ghly re r d oor he c t e r whe e po es a t ina si t i on a nd v elo c i t y as s e en l de e pa on m o r f g n i t if s, sh y a w d com p l e x , a e t hou g h or r t- in Fi u r e 6.6. As t h e p endul g gs b a ck a nd for t h , um swin r e ck p g ons, n i t esis e, r m i g t in i t a b r u t te rn to a n ot he r , clo t t s m o t i on o on ca f n be p lot it e d on t h is p l a n e. T he m o i t an d g e n erat i n g elabor a t e s t r u c u r es. T hes e em e r g e n t f i t en elem e h t m o r f t n fere s i ly d l a e tot r ons a i t a z n a g or th c ons t i t u t e t he s y s t em, a nd t he pa t t e r ns ca nn ot be at p red ic t e d s o lely f r o m t he c h a ract er i s t c s o f t h e i n d i v i d - i l elem en s. T he beha vi or o f op en s y s t em s g i v es t r ut h ua t a ld ada e, “ T he wh o le is m o r e t h he o n t he sum o f to t g he pa r t s. ” t he c ondensa t i on o f t he de g r e es o f f reed o m o f a c o m - T de ex s t e m a nd t he em e r g enc e o f or y r e d pa t t e r n a l lo w s pl s he s y s t em to be desc r ibe d wi t h f e w e r v a r iab les t h a n t h e t mb f n eed ed to desc r ibe t he beha vi or o nu t he or i g ina l er elocity elocity V V mpon ca l l t hes e ma a t s. W e c r o s c opic v co r iab les t h e en l l ec t co ve va r i a b l e s (a ls o ca l l e d or d e r p a ra m ete r s ). C on- i uma r h de si in e d beha vi or . At i t e r m t a mul , g in de k l a n w Position Position with Friction Frictionless c r o s c opic le v el o f a l t he ind i v i dua — he m i l c o mpon en t s l t r ic p l w abo t e s, m y a endons, n ess c o muscles, t h e u r a l pa t es, Fi em. t s y ic s g um as a dyna endul le p A simp re 6.6 u m e a nd s o on— t he s y s t em beha v es in a h i ghly c o m p l . y a w x ibi r - t x e l i ic h um wil endul he p on, t t a li m it cyc le a t Wit ho ut f B oop hes e pa r t s c e r a t e, w e ca n def in e a c o l l e c - ut when t gle, i a c t o r . Wit h f r ic t tr to a sin le in t t e s l um wil endul he p on, t ve va r iab le t h a t desc r ibes t h is c oop erat i o n at ti m u c h a a po n t a tr i c t o r . t

16 273 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 273 Dy a m i c Sy n l a be r & R i g n e y , 1988), ele c t r ica e c t i vi t y in t he o l fa c- r g i dea l, f r ic t i onless p endul um p r esc r ibes a n or bi t or an t n tor y bulb ( F r e ema n, 1987 ), a e nd pa s t e r ns o f m t e v o m s r t cks i a r t t a h t e c e spa t a t he s gh t u o r h t h t pa r ula g e s on, 1989). t r e b o es ( s u t e n f uma in h R on to i t ic r add f e If w . y t i c elo nd v on a i t si po f es o g an ch l o on ensi m i d t n a t t impor s he m s, t t is a t n e m elop v or de F l a en v e l wil t um, i endul he p t t ly c o m e to r e s t , a nd i t s u - l re s t tor is i c a r t a t e or a of a beha vi or a l pa t t e r n p r ef e r enc look l l a spi e k i a l t wil bi or . r t t y is bes t ic s m abil i ti ve stab i l i t y . T he c onc ep t o f dyna bi r or cula r i he c T d n um a endul onless p i t ic r he f t f t o n a la re p r e s e n t e d b y a po t e nd- t i a l lan ds c a p e . Im a g i n e t um wi endul he p t f t o g poin in t s e t he r e h e t r on a i t ic r f h l t e l l a nd v ls a l i h h a b a y l ro l l in g a m on g scap e o f s, wi e h t , t en es r on is p i t ic r em. When f t s y is s h t f s o tor ac tr at l le as hem depic t iab r a v e v i t c e t l o he c t f e o t a t he s t g n i l e a caus be r t c a o ies tor r c aje r he t l t at tr ac tor is a po i n t a t t sh l l i a h f he top o on t l l a 6.7. A b e r u g (a o w n in Fi ) has a g poin o v e r c e on t h a t r e s t in n t , r e g a r d less o f e c he spa in t g l e r y sma l l en pot d e tor s f lot o en a i e r gy; wi t h jus t a v t em t a r t i n g poin t or in i t ia l c ond i t i ons. A l - ’s s t he s y s t l push, i wil l ro l l do w n t h e h i t l. T h us, t he s t a t e o f t he s y s- bi o l o g i- e f e um has only on endul he p gh t hou t i d poin t , x udg le. A t n n u y r e l, is v l a he b t y d b e t en es r p e em, r t y n ab e s t on n a h t e r o m e e poin only ha m m o s c em t s y l s ca v b), in c ( y e l l a ep v in a de l l a t. A b , islodg d l wil t s a r t n o e i s y st e m m a y re ac h o n e o f t h e s e v eral p o s s i - at t r act o r ; t h e t has v e t x e e g r ds a la e e nd n gy a r e en l a i t en le pot t r- i l y r e in b uil ibr ium poin t s, dep end le eq g on t he in i t ia l c ond i- i e g n a h t to c t s l boo na s po si t i on. T he la t a- t s y r e r is a v e t i l c ons. A l l t he in i t ia ond ti t i ons lead in g to a pa r t icula r l l r is ca e m he for tor; t b t t r a c e h le a e t caus be r o ll e rep a d e tor a . t t t a d poin xe fi r e ca l l e d ba sins of a t tr a c t i o n rac to si n sy s t em do es n ot w a t l- t on t he h i l l. A b a l l in a sha t - t he p endul um e x a mp le, wi t h o ut f r ic In i on, t he a t espond to a w w e l l (c) is m ode r lo t ely s t ab le, but wil l r a on- f he li m tor is o t rac t it cyc le or per i o dic typ e; i t wi l l c o suf e g w in ghbor i e he n to t g in vin l m y b t s t boo ien c i f l e ti nu al ly r e p a um is endul he p ons. When t i t a l l i c s s o t i t ot dw ile n (wh ck in be en). e w t o l l i he h on t g lon y r e v g n i l el r sl g h t ly p e r t u r be d , i t i e t u r ns, in t i m e, to i t s p e r i od ic be- e ndscap he la ls in t l a he b l t l e, a m i gh t u o g en a lon r e Ov en i en r gy f o t r ui q s s t e v i um is g endul , e t . Onc or vi ha he p n d spa c e pa t t e r ns cap t u r e a l l ot he r po ssib le t hes e t i m e a aje tr tor ies in t he s t a t e spa c e, a nd t h e y r e p r es en t s t ab le c y ll ti ve va r iab les for t he p endul um s ec s t em. I n bi o l o g i- co (a) (b) l or g a n ism s, p e r i od ic beha vi or is o f t en t he c o l l e c t i v e ca mpon esul f t he co or dina t i o n of co t o en t s ea c h wi t h i t s r ow n p r ef e r r e d pa t t e r n ( K u gle r & T u r v e y , 1987; S c h o ̄ n e r o & K o, 1988). C onsi de r h uma n lo c els m o t i on. T he c y cl ic w s alt er n a t i o n o f t h e le gs du r i n g n o r m a l alk i n g re f l ect r h u p l in g o f t w o le gs 180 de g o e es o ut o f p h as e. S u c he c t c oor d ina t i on dyna m i c s ca n be r e p r es en t e d on a p h as e (c) l t spa e c onsis t i n g o f a l c he po ssib le p h as e r ela t i onsh ip s e is a n m ic t e r m s, t h e dyna r be t w e en t he t w o le gs. I e st t t r a c tor a t 180 de g r g a es o ut-o f-p has e. Gi v en or d i - ron na r y c ond i t i ons, p e op le p r ef e to lo c o m o t e b y usin g r e a th ei r le gs in a l t e r n a t i on, h o w e v e r , t h e r ic r e a l s o p e r i od jumpin at ac tor s a t 0 de g r e es ( tr g) or 90 de g r e es ( g a l lop- (d) in g), but t h e y a r e fa r less s t ab le u nde r n o r m a l c i r cum- r st c es, a nd t h us a r e r a an ely s e en (a t lea s t in adul t s!). g u s. T re 6.7 St a b le a nd u n s t ab le a t t r a he s t abi l i t y o f c tor Fi a y r t at ic haot c he , t tor c a r t t ac f e o p y t l a i c e a sp , - l l Fina ls. T f he top o on t l l a he b l e w l a i t en d as pot e t tor depic c a r t t he a t s o f on in popula e c e , has r tor r t i n e t t a h c mu d e v i a c c o u n t he h i l sma y r e en a v v nd e , a gy r e en l a t en pot f ) has a lot o (a l t l i l n in ea r dyna m i c s. Chao s ha onl r t icula r t e c h n ica l s a pa lor l t e e is a r f p m o to he bot t t a l l a he b . T push wil l d islodg e i t; i o r r es a la r g e en e r gy boo s t to s end i t i v e t he s t ep h i l l ( b) r e q u m c s. Chao s desc r in dyna ng ani me ibes s y i s t em s wh o s e t uickly r he top . If p e r t u r be d , i t wil l q e t u r n to t he bot to m. It is e s clo t m a ndo a s look r or e vi beha d t lot , when p e but nc gla l a s ab le a t t r a c tor . T he b a t l in t he sha l l o w w e l l (c) is in a less r lon g t i m e on a s t a t e spa c e, a r e n ot r a ndo m a ov e e ela a u t le si ab st t i v ely sma l l p t r t u r b a t i ons wil l push t h e on. R i r u t c u r t ic s r t e m o e g x e l p m o ely c a em r t x y e la isp nd d es. en en ly end a b o r p l b all wil ar ou nd , a t l t h o u gh, g i e, i m i gh t u o b v Th n bi o l o g ica l s y s t em s y er e is g r o win g e v i denc e t h a t ma caus e o f i t s o w n s t o c has t ic n ois e. A be- he de up in t ep e r w e l l be y . t i l abi t s i t mul e y ha ) ma em (d ha vi or a l s y s t v mp x for e ic— haot e c ar le, hea r t r a a e f l u c t u a t i ons (Go ld- t

17 274 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 274 n a m i Dy gh n wil in g l end up in t he de ep es t v a l l e y , a l t h o e u i at ed b y h a rd w i red s t r u ct u r e s o r p r o g rams w i t h i n t h e ghbor la y all eys ma y be de ep en o u gh t h a t escap e f r o m t hem is e pushes to g r v r e v e k a s t tor c a r t t le a ab t s y r e em. V st sy a y a h ons, but t i t si d po e r r e ef r r p i e h t m o r hem f t ve mo e ve r y mu u n l i k ely . Fi g u r e 6.7d a l s o sh o w s su c h e r l t i stab le y o at ac tor h , wi dyna m ic a nd c h a n g eab le n o n e t heless. T h is is on e w a tr f s lor l e p e o r w nd t a s r o ract t t t a poin e e r h t t w e m b le d ” ( K u gle r & e en t hem. t f o em is “s t s y he s t t a h g t yin sa ly ass be t s , 1987 b i lit y o f a s y st e m c a n b e m e a s u red i n s e v eral t a e Tu rv ey Th ) r a t h e r t h a n ha r dwi r e d or p r o g r a m m e d. - wa y s. Fi r s t , s t abil i t y is inde x e d b y t he s t a t is t ica l l i k gh l i T he c o mpon en t s ca n ass e m b le in ma n y w a y s, a l t h o u e t t he s y s t em wil l be in a pa r t icula r s t en. t e r a t h e r h ood t h a only on e or s e v e r a l o f t hem a r e s t ab le en o u gh to be s e a l c onf i g u r a t i nd in e c ond , s t abil i t y r e - th an ot he r pot en t i a We ar g ue he r e t h a t , in a c t i on a nd c o g n i t i on, a ons. S on. If a sma l l p d sponds to p e r t u r b a t i de v elop m e n t , ma n y c onf i g u r a t i ons t h a t a c t l i k e p r o- e r t u r b a t i on ap p l ie ram es i t a w a y f r o m i t g v s, s t a g es, or s t r u c t u r es a r e s t ab le a t t ract o r s wh o s e s s t a t i ona r y s t a t e, i to t he s y s t em d r ina y e r som e t i m e t h e sy s t em wil l s e t t le b a ck to i t s or i g t l st abil i t af l i m i t s ma y inde e d be sh if t e d u nde r ap p rop r i a t e g u r e 6.7, when t h e cir eq uil ibr ium po si t i on. As s e en in Fi cum s t a n c es. T h a t is to sa y , ma n y m e n t a l c ons t r u c t s t he b a l l a pot en t i a l v a l l e y is de ep a nd t he w a l ls a r e s t e e p , a nd m o v e m e n t c onf i g u r t i ons— o bje c t p e r m a n enc e a n d in h m he sa , t t s a r t n o c n m. I to he bot uickly to t q n r u t e r l wil w alk e g , for e x a mp le— a r e a t t ract o r s o f s u c h s t re n g t r pe t l l e w l a i t en pot w o l l in a sha l l a d to a b ie l p on ap i t a b u r a nd s t abil i t y n ons ca i t a b r u t r e p e r e v e t s s o he m only t t a h t lon di up t t hem. T h e y look as t h o u gh t h e y a r e wi r e d in. ium be caus e t h e uil to eq n r u t e r to r e g sr e k a t l wil ibr l ons, Ot he r abil i t re s tor in g for c e is less. If t he b a l l is pushe d a w a y f r o m a usi i es— t r a nsi t i v e inf e r enc e, visua l il top ica- us, on h n. T r u t e r r e v e n l wil t i , r e v e w o , h e ind ll hi s tor c a r t t a e v ha le— mp a x ls, for e il t sk spor y n nd ma a s f on o ti a u l ma n t x e ipula- t n o c y t b e s is easily up y t i abil r e t af e m i e s s o wh t n o i t laxa e l r a c lo is h is t y t i abil t em s t s y t a sma n y b r o n , e c i t ract p f ck o ons or la o n . ti i e t at g n i y a p t o on. i t a b r u t r e p l l b Th , s t abil i t y is r ela t e d to t he s y s t em ’s r espons e to d le ird m e ly ass t o a s f le o mp a x e l a t n e m elop v ood de A g f r u t na a h t l l ca em. R e u - sy st em is t he infa n t lo c o m otor pa t t e r n o f c r e epin g on m o c t s y he s in t h t ons wi i t a t t c u l f l a e s h i b i t i ng p a tte rn s ar e en de- ly be l ona i t i ad r has t n r com p o s e d of e t t is pa h es. T e n nd k nds a ha ex pl ex s y s t m m a n y - o ois s has n em t s y s e sub hes t f o h c s. Ea em t s y s sub c i e ass o - o m o c n lo uma h sc r ibe d as a “s t a g e” in t he on to g e n y f c . It k l a w y e h e t l befor w a r s c t n n infa uma l h l ly a t as s a e on: N ti t o c has t ic r at ed wi t h i t , a nd t hes e in t r insic n ois es a a n emp es on t he s t abil i t y o f t he c o l l e c is is h le. T iab r a v e v i is t t t i n g to t h in k o f c r a w l i n g a s c e c essa r y p r e c u r s o r for an r- pa en ap v s, e em t s y s x e l p m o c t a h g t yin sa f y o a r w he t o to up r i gh t lo s t apis r e h l t sica phy e m o , s d e on; inde i t o m o c a bel e infa em t s y he s If t . c n t s mus t g o t h r o u gh t h is s t v g e for su c c ess f u l ie en t ly s t ab le on es, a r e n o n e t heless dyna m i ic t e r m s, h o w e v e r , s e c m for ndo a e r hes l, t l e s ens or im otor in ep w e nd de ep a e t des in a s esi r r a t i on. I n dyna m g t n e t t a pa , r o ract t t y a r a empor g as a t epin e r e c e n s ca we wil l ha v r l i t t le ef f e c t a nd t he b a l l wil l n ot f l u c t u a t e v e r y e r e ef r em p t s y he s t t a th nd t e h t f us o t a t t s en r r he cu en t v i mu c h a r o u s, g he m e a n a t t r a c tor pa t t e r n. I n t he sha l l o w d infa v i fect f e re o m e r a s ce r o f ll a m s e s e h t , r e v e w o h , ll we n t’s n e u r o muscula r s y s t em a nd t he infa n t’s desi r e to an e t t he b a l l sh o uld ro l l a r o u nd m o r e. T he si ge t som et hi n f he de ze o g at t ract i v e acr o s s t h e r o o m . W hen b abies via- , v do n t he s t r e n g t h or b a la nc e to w a l k up r i gh t ot ha - x , for e d e r asu e n be m e ca t a t tor s rac t t he a t m o r ons f ti e e - o t m enden on to indep i t u l o s d e l b em f-ass l e g is a s epin am p le, b y t he v a r i a n c e or s t a nda r d de via t i on o f t h cre t e. T he m o r e t a s — y t is t ica l p r o b abil i t y , but n t n in e v i t ab le s o - i bil a co ll ec ti ve va r iab le a r o u nd t he a t t r a c tor s t a ot a ns su h st a b le t he a t t r a c tor , t he sma l l e r t he s t a nda r d de via t i on lu ti on. I n fa c t , s o m e infa n t s us e a n o m a c o us pa t t e r l . r a w l i n g on t h e i r bel l ies or sc oot in g on t as c e i r bot to m s , ar o u nd t he a t t r a c tor h r l c pica y he t l. T l a t l a w a r r c e v e s n t n e infa m n a nd s o i l w a g s s b m se lie A t f So rac - d r ot a ha , but n tor pa t t d a e r r e ef r hen is a p t n r e t t tor is r e. g a t s d e r wi ica 6.7 ind e r u g As Fi a e t t g a pa in l l es, ca t n a t t r a c n f on o i t assump s to r e ef r em p t s y he s t e r ut whe t abo en em t a t l s ica t is t e t a s r o he c ly is t b m e ass ft So a c i m a dyna nd h e esis t a n t i t is to in t e r n a l a nd e x t e r n a l o w r de, a esi vie w o f de v elop m e n t. It b a n ishes for e v r r t he v o cabula r y t ab le as for c es. A l t h o u gh s o m e a t t rac tor s t a t es a r e s o u n nd sup- of p r o g r a m s, s t r u c t u r es, m odules, a nd sc hemas a s b s e r v e d , ot he r a t t r a c tor s t a t es a a- e s o to a l m o s t n e v e r be o pl a n t s t hes e c ons t r u c t s wi t h c onc ep t s o f c o m p l e x i t y , s t r t ab le. B e es e st ab le t h a t t h e y look l i k e t h e y a r e in e v i bil i t y , a nd c h a n g e. S t abil i t y def in es t he c o l l e c t i v e s t a t caus - i n t hes e beha vi or a l s t a t es a r e s o r e l iab ly s e en u nde r c e r t of t he s y s t em, a s s ess e d b y i t s r esis t a nc e to c h a n g e. Fl u c a a n c es, i t is eas e cir cum s t tu at i ons a r o u nd s t ab le s t a t es a r e t he in e v i t ab le a c c o mpa- y to bel ie v e t h a t t h e y a r e g e n r-

18 275 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 275 Dy a m i c Sy n e f a c t u a t i ons— t he e v - nd Fishe r n o t i c e d t h a t m o v e m e n t s sim ila r to s t ep s d i d u hes s. T em t s y s x e l p m o c f o nt me ni l t i f ead o t e ins supin e r e s w t n when infa r a e p isap ot d n e h up- e r a e— v i t c ly a l ica m em is dyna t s y a s t a h e t denc r t. T gh ri ce o f n e w for m s in beha vi or a nd de v elop m e n t . n ur so o i t a n a l p x em e t s y us s o v r e n l a t n e is made a c h o t e in a s g n infa t a h d t e c i t d n y e h , t r e h t . Ra ely k i l un o n s Ho w Sy ste Chan g e: Fluct ua t i s m api t a , t ly body fa l a i c e d esp n , a ht ig we a r d r a t e du r i n g and T ransi s n o i t ess ep pin g w a s sup p r t e d. T h e y r e a- r i od when s t e he p a s n r e t t pa l a or vi beha d e in def e v so ot hea We ha gs g le r i e th s a vie t i- m o onc ut a c o h t r wi a h t d ne le, ab t s usly o i r a v s e ta inc r e as he infa n t s had inc r e asin g sof t l y a s s e m b l nt d a t t ract o r st at e s . H o w d o p at t e r n s e in muscle mass, t t or in lea n in ly de- l ica n ha c di e m o he bi gs in t r le i e h g t in t f i l y t icul d n i o d y he v e r e H g? s t ff , a ge an ch r e elop m e n u l i n v o k e t h e n ot i o n o f n onl in ea r i t y , a ha m a r k o f dy- on is a i t si t depo ody fa e. B r we t s t po gh i r g up ma nd in l pa t e r n in a dyna m i c s y s t gr o w th c h a n ge t h a t is n ot sp e c t f ic to le g m o v e m e n t s, y e t A . s m e t s y s c i m na e m i s c ohe r- i n o f t h e c i mpon en t s . T h i s en t b e caus e o f t he c oop erat i it af fect ed t h e s y st e m s u c h t h at a q u alit at o v e s h i f t i n b e - o d ua- t c u l f l na r e t n i e h t e t despi e n i a t n i a m s i e enc r ohe c ha vi or r esul t e d. o n a l pushes on r e t x e l l sma e t despi nd a m e t s y s e h t f ons ti Cha n g e m a y t h us be en g ende r e d b y c o mpon en t s o f t h e e c t es, cas r e h t o n i , but , s iou obv n o n e r a t a h t m e t s sy on- e for r o ract t t a le ab t s y r e v a s i g in k l a w h caus be us, it . T h h y e h t o t c i f eci p s e b y a r m e t e m a r st em in q ues t i on. a p l o s uma tr n l o c o m ot i on, w e ca n w alk acr o s s t h e r o o m i n h i g h - i c s k i l h l t i w e a Fo r e xa mp le, p ract i c e o r e x p er ienc sp e c i e r a e w le i h w n e v e d n a es, c a f r su d e i r a v on es, o h s d ele he f s t i n g o r c h e w i n g g u m . B u t a s t h e s y st e m p ram et er alk o r h t on 10-m to 8- e, nc a t ins or F . tor c a f l - ica t i r c he t e b y ma a x e e th n t b a r r i e r to d s t n infa d ol e nspa a r t a r d n u ro a h c a e r ot n o a s e m o c e r he t , e g n a h c ons i t i ond c y r nda ou b l a n r e t s poin whe r e t h e o ld pa t t r n is n o lon g e r c ohe r e n t a n d t t a - e v a h s t n infa , ly l a m r o N 1990b). , ond m Dia ( oy e a t ev ri ret e v e w o H s. r e i r r a b t n e r nspa a r t h t i w e ienc er xp e e ttl li t a t i v ely n e w p a t t e r n . F or b le, a n d t he s y s t em f inds a q ua l i , r e s i p le, w e ca n w a l k up h i l l s ex but es, in incl us o i r a v f when Ti t z e r , T helen, a n d S m o t h (2003) g a v e infa n t am t s ica t i r c e m o s hes c ea r l il h e h t f o ess epn e t s e h t when l ra nspa r e n t bo x e for s e v eral m o n t h s , t h e b abies lea r n e d h s t mus va e f o e p y t e m o s o w ue, l t n o i ot m o c o l r u o t f i to sh if t t he i r usua l r espons e o f r ea c h in g i n t he d irect li n e i o bo he t f o g in n e p o e h o t t n g i n i h c a e r f o r avo f n i t h g x. s of n a l l fo u r s. T h is is a n e x - g bin im cl t— i a g l da e p u r uad q is In ca s e , infa n t s ’ lea r n in g t am p l e o f a no n l ine a r p h a s e s hi f t or ph as e t r ansit io n, he p e r c ep t u a l p rop e r t ies th r hi t ra nspa r e n t bo x e s t h r o u gh e x p lor a t i o n w as t h e c on t of o l . s m e st y s m u i r b li i u q e n o n f o c i t s i er ract a h c ghly u e t e m a r he pa ns, t r e t t otor pa m o c r lo n o f o e he cas t In n e h t g n i r ende g en e d g e . k o w f l o m for w e pa r a m e t e r r s ch ge wa s simp ly t he s t e epn ess o f t he h i l l to cl im b . t an em y es in a s g n a h l c l ot a , r ie l r ea d e iscuss d e As w n ro l pa r a m e l adua r d g e r ende g r en e t e m a r is pa h es in t g n a h l c adua Gr t e r , t if e sh as h e p ar l e v m o s. At s a ues o f a c o n t he slop ch g es in o u r w a l k in g u n t i l a sma l l c h a n g e in t an e n- us ma uo in t n o nd c a a e n i espond in a l y r em ma t s y he s t r l l t; a sma c e f ld ef o esh in onl N r. ne i- m r e ic t m r n n. I r e t t r pa u in o e g n a h e c g r es a la caus h is a t y t i r ea e g n a h c dyna no gy , t he slop e c h a n g es a c t e d as a co n t r o l p a ra m ete r in a s t esul ue r l a l v ica t i r a c t r a e t e m a r l pa lo t n o he c in t ro ly e r a y e h t r e h t s (whe r e t e m a r l pa ro t n o t. C if iv at it al qu on o u r g a i t s t yle. T he c o n t ro l pa r a m e t e r do es n ot r e a l e sh c s) or r e t e m a r pa l a t n e m ron vi or en , c i n a g or , c i f i e onsp n on t r o l ” t he s y s t em in t r ad i t i ona l t e r m s. Ra t h e r “c , i t is a c y t f or o vi beha e v i t c e l l o he c h t ic to wh r e t e m a r pa s t g n i n e t ea r h t y b s t if e sh s a h es lead to p ienc r e p x ic e f i he s e sp em is s - l- o gh c u o r h em t t s y he s es t v o us m h t t a h nd t a e v i t ensi m o l c l a t a h t l l ca e . R tor c a r t t t a en r r he cu t f o y t i t l t abi he s c f o r e b m u y n n s, a em t s y l s ica g o l o bi n es. I t a t e s v or- t le pl ex sy st em s ca r r y in t hem inhe r e n t f l u c t u a t i o ns. When i r e t t nd pa a t n e r ohe em is c t s he s t y e hes le, t ab n ons ca i t i ond c y r nda u bo t n a v ele les or r iab r a ic v ism n ga t e s r ns a ica be r i v ely n onsp e c i f i c , a nd o f t en ma y be c h a n g es in ela l- a l v t t i r c t a , r e v e w o n. H w do d e mp e da r ons a i at tu uc f l r- ohe s c t es i s em lo t s y he s , t r e t e m a r l pa ro t n o he c t f ues o t emp e r a t u r e, l i gh t , sp e e d o f m o v e m e n t , a nd s o on. t ered iab r a v e v i t c e l l o he c t s b r u le. At r e e p ois he n nd t e, a enc F or e x a mp le, T helen a nd Fishe r (1982) d isc o v h c f o y t i abil t he s es t m o c r e v e o ois is n t , t poin me so o t ro l - r e oop th at body w e i g h t a nd c o mpo si t n i on ma y a c t as a c o t t f e” o c n a r a e p isap “d n w pa r a m e t e r for t he w e l l-k n h or in- n r e e t pa o n w o y sh em ma t s y he s nd t , a n r e t t pa e v i at e m o s , r e v e w o . H y t i l iabi r va ed as cre ne l ro t n o he c t s es a im t wbor n s t ep pin g r espons e. N e wbor n infa n t s c o m m only a ue, t t- e y s em ma t s y he s l a l v ica t i r he c es t pass r , t gh i r e held up r a y e h s when t t n e m e v o g m pin ep t s e k ma pa r e m e t to r be f t e r a f e w m o n t hs, t he r espons e ca n n o lon g e t le in but a a ne w an d di f fere n t c o o rdi n a t i v e m ode. r ad i t l i ona l e x p l a n a on has be i e as h p l a or vi beha t e en t i ic el d. A t h o u gh t he t T he m o s t ele g a n t dem ons t r a t i on o f o ghe a in c e n t e r tr a nsi t i ons c o m es f r o m t he w o r k r br f K els o a nd h is i h y b x e l f e he r t f on o i t s, T helen inh ibi

19 276 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 276 n a m i Dy ies o vie de v elop m e n t ca n b e e n visi on e d as a s e r ies o f pa t- f odels o nd m ies a ud t s f , r e g s ues in a lon g ea ll co w o vin l o iss d nd a g vin l vo s e rn te h uma n bima n u a l c oor d ina t i on (s g e t he e x t ensi v e d i s- t poin y n a t a , d n a e, im t r e v e l- x- . y t i l abi t s f o s e e r g e d r icula t r a p g essin s s o p , e m i t in E cussi on in K els o, 1995). T he b a sic e x p e r i m e n t is as fo n lo in g o n t he pot en t i a l la ndscap e r ep r e s e n t a t i o nd w e i n- pa w s: P a r t i c ipa n t s a r e ask e d to m o v e t h e i r inde x e n g es, in a n t rodu c e d e a r l i e r , w e c a n depic t t hes e c f i ng er s e i t h e r in-p has e ( bot h f i n g - x nd e d a e x e l s f r ha pa r a l lels d to ende h as e (on e f i n g e r f l e x e d wh ile t g e t h e r) or a n t i p ab st ract w a y , i n F i gu re 6 . 8 o u r depic t i on clo s ely gton t he r is e x t ende d ) . T h e y a r e t hen to ld to inc r e as e W add in he ot ’s fa m o us epi g e n e t i c l a ndscap e ( Fi g u r e 6.2) o ) t he pa c e o f t he c y cl ic m o v e m e n t s. P a r t ic ipa n t s wh in h i t s ea r l y (1957 ) a nd la t e r (1977 inca r n a t ons. i bot T i r s t d i m ensi on in Fi g u r e 6.8 is t i m e ( M u c be h isk y , g in in t he a n t i p h as e c ond i t i o n usua l ly swi tc h to in- he f ph s e g n a h c o n h t g up wi in d e e sp y t b jus e a in pa e ndscap he la ). T elen, 1996 h le, & T o e, C w to f-S f o hk s r Ge t t e r ns. pr ies, but ess e v e r sib ly f r o m pas t to p r es en t , f r o m b a ck- r g es i r o Th us, bot h pa t t e r ns a r e s t ab le a t lo w f r eq uenc r e has he in-p only t n dy- ies. I uenc eq r r f r- he su t on— ensi m i ond d c e he s nd. T ghe ro g e nd to for ou gr i h t le a ab t is s u l o he c t f o t a h is t e— c fa v a r iab le o f re l a t i v e p h as e is na m ic t e r m s, t he c o l l e c t i v f e o r asu e le, or a m iab r a v e v i t c e l e e at t s e v i erat oop c he t uenc y . s ensi t i v e to t he c o n t ro l pa r a m e t e r , f r eq s e n i he l t f o h c em. Ea st y s e h t f o g t for i n in t n e m o r m icula t r a pa s t en es r p e e r ndscap he la t g Usin m h l- o is c nd h o a els , K t n e m i r e p x le e is simp m lea ues sh o w e d def in i t i e ely t h a t t he p h as e sh if t f r o g ti m e. T hes e l i n es depic t t he r a n g e o f po ssibil i t ies o f t h v t an t i- to in-p has e m o v e m e n t s w a s a c c o mpa n i e d b y a lo ss a r u g i onf he c e. T m i t in t poin t h t t em a st sy a h c ea f on o i li a h em up to t t s y he s t f y o tor s i he h t f t o esul is a r ne of t sy st em s t abil i t y . T he s t a nda r d de via t i ons a r o u nd a t c s a tor em c he fa us t l p , t poin h t s y he s ze t i r e t e m a r to pa g n i me an r ela t i v e p as e r ema in e d sma l l u n t i l jus t befor e i c o he s as t h c su e— m i he t t t at e , t x e t n o l c sica phy nd a l a ea c h pa r t ic ipa n t’s t r a nsi t i on, when t he de via t i ons in- h as r d d cre a m a t ica l l y . T hen, as t he pa r t ic ipa n t s e t t l e d e r to t has e pa t t e r in a f t e r t he sh if t , de via t i ons w e he in-p e n ag in sma l l. Li k e wis e, when S c h a lz, K els o, a nd S c h o ̄ n e r o (1987 ) p e r t u r be d t he m o v e m e n t s wi t h a sma l l t u g du r- v in he v a r i o us f r eq uenc ies, t h e y o b s e r v e d t h a t r e c o g t e r y r to t r e d f r eq uenc y w a s m o he desi e d i f f icul t a s pa r t ic i- pa n t s ap p roa c h t he a n t i- to in-p has e t r a nsi t i on. Disin t e - em c e rat i o n o f t he s y s t g ohe r enc e w a s r f l e c t e d in t di mi n ish in g s t r e n g t h o f t he a n i p h as e a t t r a c tor to pul l in e t aje c tor ies f r o m v a r i o us r r g i ons o f t he s t a t e spa c e . he t c De v elo pm e n t f rom a Dy n a m i pe Sy P e rs stems c t iv e g In th c t i on, w e is s i v e a n o v e r vie w o f dyna m ica l s y s- e g e n e t ic la g W ndscap e as a usin add in ms te gton ’s epi he ma me f il l u s t r a t in g t ns o in c onc ep t s. W e t hen us e t h e a de v elop m e n t a l p r o b lem o f lea r n in g to r e a c h as a n e x a m- d p h o w t hes e t hem es ca n be us e f to g u i de e x p e r i - le o me nt a nd r e s e r c h. Fina l l y , w e t u r n to t he de v elop m e n t s a of t , he o bje c t c onc ep t a n d , in pa r t icula r , us e t he A-n ot-B deas ma to d e t a por or y be inc in e i hes w t o h w o ror to sh er for t . n e m elop v nd de or a vi beha f ies o r o e h l t ma n nami c Epig e A Dy e t i c L ands c a p e a We v e t h us fa desc r ibe d s el f-or g ha n i z i n g s y s t em s a s r Fi g u re 6.8 An adap t e t i c n a t i on o g f W add in gton ’s epi e e em le, p i t mul m ro f ” d e l b ss a y l t f o “s or vi beha f o s n r t t pa e de- a or vi beha s t on depic i s r l is v h e 6.2). T r u g i F e ( ndscap la d o s e e r g e f s u o i he t e ro g e n e o u s c o mpon en t s e x h ibi t i n g v a r n e v e o l vin g a nd d iss o l vin g a t t ract o r s r o f m elop f v ies o e as a s t t lit b a t s i n fere f di y . m st abil i t y a n d c ha n g e. A c c o r d i n g to a dyna m i c s y s t e s

20 277 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 277 Dy a m i c Sy n f vin l-sca l on a sma visi us en h n t ca g in t h e v o l ndscap o nd s a , ild h he c t le la e o t a t l s ona i t n e t t nd a l a ona i t va i t mo e e e is r do ma in o f d to e t ela ndscap he la t f on o ensi on, i t a r t s u l r il u o n 6.9. I e r u g as in Fi me ti l a re on. T he t h i r d d i m l c de r beha p r or a sha h t t A wi t he dep t h o f t he v a r i a t i ons o f t he c o l onsi e c t i v e v a r iab le c - i t c a f o e m i t e s i r a l a vi s. T he dep t h r e p r es en t s e h on, t i t i t e p e r h t i W . y ca w de slo y r e nd a v on a i t va li n es, t he v a r i o us d i p s a nd v a l l e y g ld for a o esh r th t he s t abil i t y o f t he s y s t em a t t h a t poin t in t i m e, a nd in c t i v a t i n A is d i m - c he a e t caus d be ishe n i e ti v i t i t y h a s be en p r im ons c f on o i t bina m o r c icula t r pa at th r d b y p r e v i a o us a c t i v a t i ons. T he be- i d n s, a tor c fa g n n e r o le, m ab t s e r o es m m o c or be vi ha th us cap t u r es t he p r o b abil i s t ic r a t h e r t h a n r i g i d ly f i x e d d n , a d e t i ic easily el es. v m o s d e n r on has lea s r e he p t d— e t up sr i le to be d less ab na e- t a t e s i t i n g o nd c a l a or vi beha f o e r u t lausib ly p l ua eq n g. A in th t is t n h a t a c t i v a t i n g A o c c le a u Ne d Ti m e s c a l e s ste ld for a r m t f on o i e i t e p e he sa o esh r h he t e t is a t r gh mi t r i t ica l p rop e r t y o f de v e l- m. do e n, or bor o i t a u t on, habi i t a t ens in adap p , as hap act T he la ndscap e r e p r es en t s on e c he h s: T g n a h c f g o in t s e he n em t s y ic s m g dyna opin Be caus e t es on i s tor y o f a c t i n g in r e a l t i m e c o u n t s, c ons t i t i ond nd c a s t x e t n o he c les. T esca m i le t p i t mul a t i ons ma y d isp la y t h is im- t a h t he r e a l-t im e dyna m i c s o f n a t por de t e r m in e t he s t abil i t y o f a s y s t em a t a n y poin t in t i m e o, & els , K ck o (e.g., H s i s e r e st hy f o y t r e rop p t t t ons lead to d i f f e r - e h t f e o t a t he s ons for t i t i ond l c ia i i he in t e t u t i t ons ) c t ( Sc h o ̄ n er , 1993), when t he sa m e c ond i l a or vi t beha en sy s t e m a t t h e ne xt i n s t a nt of t i m e ( t + 1). Li k e wis e, t h e e t a i d e m he im g on t in end es, dep m o utc o p t t a t s s t e i in m r e t 1) de + t ( t em a t s y he s t f ies o t r e rop e a pr ev io us h i s tor y o f t he s y s t em. B eha vi or a l a c t s t h e r efor e em is t h us re i t e r a t iv e ; ea c h s ( t + 2), a nd s o on. T he s y s t ca r r y wi t h t hem n ot only t he dyna m i c o f t h e i r im m e d i - e r , d y e r (e.g., F um t n e m mo e, but a nc ma for 1983, e p at st at e is dep enden t on t he p r e v i o us s t a t e. v e y b d e t c impa s y a t w l em is a t s y he s t t a h t o 1992) s all c y a r e Mo st impor t a n t , t h i s reit erat i v e p r o ce s s occ u r s at r i n g , a lbe i t to v a of i o u s v i n g, mo vin g , a nd t h ercei in k ti m esca les. T h us, a l a ndscap e o f e v o l vin g a nd d iss o l vin g p u t e-b - m i n u t e a c t i vi t ies ca r r y wi t h y de g r e es. Jus t as m i st abil i t ies jus t a s e asily depic t s t h e dyna m i c s o f a r ea l- n i i i s tor y a nd build m o m e n t um, s o a l s o do t hes e a c - t a g n hem a h c rodu p , t c bje o n a for g n h c a e r as h c su ess, oc pr me ti enc t n e cumula s t en es r p e r t i as lem b ro p n t o i t i add n a g vin l o s or e, d n g a in n r lea f f o uf t he s t e t u t i t ons ies c tor s i d h se ndscap , s y a d , s r hou , e t nu i m r e u in o e n i l h c e. Ea g n a h c t n e m elop v de v o s e i t i l i b a e s ho t n i s ge n a ch r la s t- e depic in y eks, or m o n t hs. I n dyna m i c t e r m s , t he t i m esca les ma we g t he p r o b abil i t y o f t he s y s t em ’s s t a t es c o n t a ins i t s nc- a fr (G r ebo g i , O t t , & Y t r k e, 1987 ) o r h a v e a s el f- l be a c ow n f r a c t a l t i m esca le. T h i n k in g a nd a c t i n g a r e f u o F o r e x a mp le, f ons o ti i e m he sa t t a g n i t c nd a a g n i k in h t f y o tor s i he h sim ila r t t y a t m a n y l e v els o f o b s e r v a t i on. — h e h t f o y r et m o e g e h t al ract f y l l pica y t t a h t f o o s l is a t n e m elop v de at th me ti i s tor y . Habi t u a- e r a es in tl as co sca r in g , adap t a t i on, a nd de v elop m e n t s i t i h ic wh y b le n e h t on ely r i t en ends dep e in l t as co ti on, m e m o r y , lea n n he t , s r e t e m lo i c- a — e m i t r e v ess o c o r on p t eb buil mless w a e e s m on for me a s u red . R e p re s e k t ed o a s c a le o f desc ld. vi t ies in t he r e a l w o r co as t m a y be ti r ibe d a s a simp le cu r v e, but t h a t sim- t e d t r i m esca les r a d ica l ly c h a n g es o u Su ch w o f n e s pl ic i t y d isap p e a r s when t h e m easu r i n g sca le is m e t e r s or a vie s w vie o , y l l pica y in. T a he br ” in t d e t n e s e r ep r t is “ wha f ce nt im e t e r s. N o n e t heless, t h e s imp l e c u r v e is th e c o l l e c - in h ti o n o f sma l l c o v e s a nd i r r e g ula r i t ies ap pa r - r e p e e t to t n h nd n w alk i n g o n t h e bea c so as w e l l as to t h e l l sa sma e t en r o e f if d a g n i t inhabi b cra m e t r i c sca le. Li k e wis e, g Stability a ue, wh ile p e r c e i vin g , a c t in g, an d t hi nk i n g o cc u r r we g Landscape a r o w n t i m e s o f s e c onds i n d f ract i o n s o f sec onds, t in h e a c cumula t e d a c t i ons c ons t i t u t e t h e l a r g e r c oas t l i n e t hes e ” “A n t a l c h a n g e (Sa muels e n & Sm i t h, 2000). v m of de elop o w , ea c h beha vi or a l a c t o c cu r s ove r In a dyna m ic vie ation v Acti iles Prof o f a c t i v a t i on, p e o sh , me win u r s e o a k , a nd de ca y , ti g a c h c nd wi t h v a r i o us le v els o f s t abil i t y ass o c i a t e d a t h ea wi T ime t in t em m e, but e v e r y a c t c h a n g es t he o v e r a l l s y s t poin i t a s tor y o f a c t s o v e r i i m e. T h us, r e p e a t in g nd builds a h h c e. Ea m i t r Ef fect o f re p e at or o i n g beha vi v Fi g u re 6.9 e - c a c t es ca t u n i onds or m n lead to ha- e or in s vi beha e m he sa x h e n e on ma t ti y a c t to p r im e or to lo w ti e r t he t h r esh o ld for t va g in n r on or to lea i t a u t bi be- t n a t e ins on f o y t vi i t c he a as t , m t s e r o or m vi beha e k a m y a a- d l o h s e r h t ered w on. A lo ti ti pe re t t l a ca as a lo g r n i c le, a b o . ract t e co m es t he s t a r t i n g poin t for t he a c t i vi t y o f t he n e x t. W

21 278 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 278 n a m i Dy , r pr e a r c h e r s p r es en t in- em is es. When t h e y t r a i n e d m e m o r y , t he c o m p e t enc e s e n e m elop v e de v i t i n g o c f ies o ud st t s r fa o n s do k t n ld infa h-o t n o m - e, 6 wis e k d. Li e l a e v e w wa e h t t ess wha to ass d e n g sks desi a t h t en wi r ild h nd c s a t n s p t c bje o sh at th a o w infa n t s t a l ly k n o w . T h us, e x p e r i m e n t en r r ild ch s t h - h c r a e t in s ien ic e def r a y e h but t , t sis r e e , po ssib le v e r sus impo ssib le phy sica l e v en t s pu r por t to r e - - e nd r a r e v o g a c vin o m e r , t u o g n i h c a e ly r l ua t c a g— in t h e t e v o m e sk to r a he t g t in g n t. Cha c bje he o g t n i v e tri ve al whe t h e r infa n s k n o w t h a t o bje c t s a r e s o l i d , ca nn ot e cup y t he sa m e spa c e as a n ot he r o bje c t , o b e y t he la w s e o f l a e v e t r en mpon co ch ar se t he ess en t i a l k n o w f o oc g d e l d o c t p e r m a n n t um, a nd s o on (e.g., B a il la r g e on, o u bje g c h ild r en ma y t h enc us po e. V e r y y e m o nd m y a it av gr s- n t e p el m o e c v i t i n g o le c b a r de onsi ess c s Sp k e, & W a ss e r ma n, 1985; s e e a l s o C ohen & Oa k es, - e p m o he c e, but t enc a m t h e i r p e r for ma nc e wi t h a s e r ies 1993). Or , on t he b f otor , m y r o sis o e m e r u t ma im f e o caus t enc e is h i dden be g n ls, la il a v e” t he abil- to “ of co sk lor e d rods, c h ild r en a r e assum e h on. i t n e t t e, or a g ua d inf r enc es— to inf e r a t h i r d r ela t i on for- r e nd p e a e v i t nsi a r t e k y to ma it enc t e p m o en c e w t on be i t inc t s i e Th is d e has be e he g t n a h r t e g ue rod is lon l he b If t s. (“ r he o ot tw om fr ma nc r en a m aj or for c e in de v elop m e n t a l t h in k i n g n e nd t he g r e en rod is lon g e r t h a n t he y e l l o w rod , is t h e for t he pas t 20 y e a r s (Gel ma n, 1969). I n do ma in a f t e r rod a e in, r il on en fa r ild h rod?”) If c w o l l e he y t n a h r t e g ue rod lon do ma bl e s e a r c h e r s ha v fo l l o w e d t h is t r a in o f lo g i c: n es l sica y h p f o e g d e l w o n he k t e v ot ha do n y e h s, t t a o d , e r u t c u r t s ge d e l w o n k e som of e enc s he t e s i f De t hes e t e p o- oro u gh t a sk a n a l y sis, s t r ip a w a y t he sup por t i n g th r p rop e r t ies o f o bje c t s or t he abil i t y to t h in k abo ut t w o ma r for r e nd p ess a c . e h t e whe e nd s les, a iab r a e v nc th i n gs a t t he sa m e t i m e y ss ess t he “ess en t i a l ” k n o w le dg e. B ild t hes e r en po ch T he c o r e assump t i on he r e is t h a t k n o w l e d g e or abil i - i t i v e c o m t- pr oc ed ur es, r e s e a r c h e r s ha v e u n mask e d c o g - t ies a r e s tor e d “ t h i n gs” t h a t a r e t i m eless a nd e x is t o u n r a ie l r ea t es a enc t pe ond inly be a t r e es, c g r a ie l y r nd ea si de t h e i r he r e-a nd-n o w p e r for l a t n e m i r e p x e n e. A nc ma ta th t r e f l e c t s a “ t r ue” r ead in g o f t h e os e p ropo s e d b y Pia g e t a nd h is fo l l o w e r s. I n add i t i on, ood only as i sk is g t t poin e on s i t inc t s i e d nc ma for r e p / e enc t e p m o he c s to help w on vie m m o is c h e. T r u t c u r t s l a t n e g m lyin r nde u em ha s r u n in to s e r i o us d i f f icul t ies, h o w e v e r , bot h empi r i - y e h c e m he sa y t Wh : g a l ca de n a i t e g in Pia a pl ex ild ma nds o f ca l ly a nd t h e o r e t ica l l y . Fi r s r he ot t n a t nd a sk a a e t el in on v e le v i t i n g o e c on t m a for r pe , l i t e r a l ly t h o usa d to t en ies ha v e dem ons t r a t e d t h a t c or e g d e l w o n ’s k r ild h le v el in t a sks bel ie v e ud ap in to a sim ila r s t r u c t u r e. st y d ui l ely f em r t x es is e r u d e c o r in p a t r e e c to us t i r abil ei th Ag a in, t he d i f f icul t y l ies in t he abi l i t y o f t he t a sk to a c - e ghly dep r u t c u r t dden s i he h t l a e v e ly r al tu r- e. p x he e t f t o x e t n o c e r i t he en t on t enden i nd h a r e p x he e t f e o c a l he p g t in ud on, incl i t a u t l si a t en im m es a dyna y do Wh u c c ic a n t r ende r t he c o m p e - , t n o e m i e r t ica l ly insuf f i - n- e t t nd a on a i t a v i t o o r m e h on as t i t i e h ues, t nd cl ons a i t c u r t he ins t t enc e / p e r for ma nc e d i s t inc caus i d le b m me . helen & T sk ( a he t ons in t i t a i r a le v subt y r e nd v on, a ti c ien t? B e in t e beha vi ass s y a w l or is a e e t is t wha g n i t c u r t ons c de f y o a l w ica g lo o h ere Th Sm i t h, 1994). F or e x a mp le, b a s e d on t he c o lor e d rod is n t en “ess s c t is nd wha a e r o t c en n a m r e nd p eless, a m i l,” t a ta sk , Pia g e t c oncl ude d t h a t p r esc h o o l e r i e k ot ma ld n u o a- t t i v e inf e r enc es. H o w e v e r , when Br y a n t a nd T r nsi l a t n e e m caus e t. B n e m o he m t f nd o e a nc ma for r e only p ra o (1971) d r il le d p r esc h o o l e r s in t he p r em is e infor- act ba ls in a t n e m nda u f m ss r f e m i in t d e elop v y has de it iv o i t i on u n ti l t h e y lea r n e d a nd r e m e m b to e m i t l a ma in r d e i t s y a w l nd is a on a e h t “ at h t ered p erce p t i o n a nd a c t e h e t n i an l e r s esc o o y a l w ica g lo o is n e r e th r he p e,” t en on e r he g t n a h r t e g ue rod is lon bl , t x e t n o c l a rn te x e d n a l a rn e l d ma k e t hes e inf e r enc es. S i m i la r l y , t he fa il - 6 f e o cou u to d r a w a l i n e be t w e en t hes e c o n t in uo us p r o c ess es. T h r e g d Pia s le t c bje dden o i for h h c r a e s to s t n ld infa h-o nt mo e , y r o t ess enc m of kn owl ed g e i s n o t di f fere n t f r o m t h e m e t t ie v e a tte nt i on, s t r a t e g ies, a nd m o t i v a t i on t h a t c ons to bel i t u t e t h a t infa n t s ca nn ot m e n t a l ly r e p r es en t o bje c s f ut o e o r a y e h when t o in ek e on, s i t i add n g. I win o kn g a c n e t f e o enc t e p m o c e r e h t t a , t e 1954). Y , t e g Pia t ( gh si g sa e a g e, infa n t s a c t su r p r i s e d when t h e y wa t c h o bje c t s m n i h tc a es w o sis. D y al an k s a t n i e s erci x e an o t s e c u red t t bje o f e o r asu e ue m r he t t e t u t i t ons c r a e p isap s d c c bje o d isap p e a r f r o m e x p e c t e d lo ca t i ons. h o w c h ild r en ca n - i r e p x he e d in t e w lo l e a r ues a cl y n w ma o e? H enc an rm pe r t a n g e r esul t s — To ex pl a in t hes e s th ia t ien c i f e suf r ls a r on t i t a z i r a i l i m fa y n ma w ho r o , t n me kn ow in gs in on e si t u a t i on, but n ot a n ot he r— de v elop- to p s al nt me ha v e p ropo s e d t h a t t he c h ild has t he “ r ea l ” t is e el a w a y t h e sup e r f l uo us p e r for ma nc e imp e d a n c es? c t m e a n t h a i co mp e t enc e a l l a lon g , but t he fa il u r e l ies in s o m e p e r for- t bje Do es n ot be in g ab le to r e t r i e v e a h dden o o e he cas t t n . I y t i e abil nc ma t is h e in t t a r epa g s win o n s,” or is k w o n k ly “ l a e ild r h he c t nsi i v e inf e r enc e, Br y a n a r t f a f s n a e w r u il he fa t t a h t d e on as e (1971) r o ass ab r nd T ot in cas e f r o m k n o win g in or de r to a c t? On e da n g e r o su c h l t n e he m r g t a in ck la acc o u n t s i s t h at , i n t h e q u a g mire o f d e f i n it i ons a nd t a sk s t r u c t u r e, but in r e m e m b e h g t in e

22 279 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 279 Dy a m i c Sy n e e is lo s t. H o w do es h t o eral v e s re he te no We r re s e a r c h p r o g rams t h at f s l t ess i c o r p l a t n e m elop v sis, de y al an ic it a t n e m elop v de f g o in nd a t s r nde u n ek a e ly s t i l pl ex so al is h t t es a es as he or she do v ild beha h is c h t t a h en t p hap ge tor y , or , e w to f-S f o shk r es (Ge s y l a n a f els o t n o is c h in t nt me mo v le d e t s e in n an ch e x t? Wha t in t he c h ild’s h i s ild h en in g e n e r a l, leads to t hes e pa t- in t he h i s tor y o f c ild h a c t a h t d r o y w r e v w e o h w o 2001, 2002) sh r es t g n a h c r e t ut r s te l, a v ie r t e l r ica x le f es o ess c o r ns in t i m e ? he p s he s le t n enab r u in t t a h es t g an ch y t em to p rodu c e ma n y en ki . s i s y l a n A f ls o e , d Le ere y La c d su api ds in r r o t w Ta er ff di ng ti me se ri o usly c essi on. Li k e wis e, A d o l p h v esca m i le t p i t mul r e v g o in t a r g e t ns in a e m so al ere V e v r w e ep t y s o h w o ut (2003) sh ro h nd S en, a ijk v- nd le les a n ta en do w n a n incl in e p l a n e c h a n g es t he body dyna ens els o f a k a l y sis. N e u r a l e x c i t a t i on, for e x a mp le, hap p m- nd wha s a ic e c onds. R e l a c t i on t i m r es a in m i l is e o f t he or de r o , n- u h f y l l es. Fina ut slop s abo w o n k t n infa n t a s e ds o f m i l l is e c onds. P e op le lea r n sk il ls a f t e r h o u r re , T hom as a nd Ka r m ilo f f-Sm i t h ’s (2003) r e c d n t w o r k on h s o f p m d ay s, an d ract i c e . De v - c o e g n a h c l a t n m o n t de v elop m e n t a l d i s o r d e r s, a nd pa r t icula r ly W i l l ia m ’ s e elop s cu r s o v e r w e eks, m o n t hs, y e a r s. T r ad i t i ona l l y , p s y c h s ynd ro m e, c o g e n t ly ma k es t h e poin t t h a t u nde r o t a nd in g lo- t nd in t n e m elop v nd de a , g in n r on, lea i t c a d e r de onsi c e v s ha st gi de v elop m e n t — a e r v en in g ef fect i v ely— r eq ui r e s g o n is u e m i ism t n a e l p i t on mul e g n a h c f es o ess c i- r w p o g h in nd a t s r nde u he or ut for t es. B ess c o r t p inc t s i as d h t o h c a e h t i w eract t les in esca m ti f i he d e t r , as a t n e r ohe nd c a ed fi els in t v le t n e r e f - l e v e d e h t e t a cre o t r e he s y s- a r v em. E t y s t ep a n infa n t t a k es, for e x a mp le, is bot h a h op me nt al t r e j e ct o r y . Th eir g e n eral p r o g ram o f re s e a r c f he le v el o f n e u- a h c f r o e c rodu nd a p a t c rodu p ic m t a t s t a h dea t he i d on t e s a odels o is b n br a in f u nc- g e— a t t a ti ibe r sc um c r i d to c e p e map r ons a i ut deas abo nd i ons, a i t d v i t o nd muscles, m ls a l a eb y rons, e t nc u f e r whe g— in on o w f o y r nd u e h e t t e l p m o es. A c c a f r nd su a e c spa i g e in r a br n udy a t he s e for t t a i r p inap e r a ons— - - e g r in k l a rop es in r i qu r de ud r e d r o g g e - s i d l a t n e m elop v de f g o in nd a t in s, incl s v- e le hes l t l a t a e g n a h c f s o ism n a h c e g m in t a r g e t ynd els. T udy o f de v elop m e n t , t hen is n e c essa r i ly he s . e m ro t ’s s m ia l l i as W h c es su n o d e s ba y l l a c i t ne es a n d a t d i f- l- e a ly de l ica p y t f ins o a he br t t a h ue t g r a y e h , t r e h t Ra c onc e r n e d wi t h h o w c h a n g e a t d i f f e r en t t i m v e v els o f a n a l y sis in t eract . a t c a t s in t r pa h t ins wi a br l fere m r o ot n e n r en a r ild h g c opin n t l n i l l u s t rat i o n o f th is is p r es An f o k r o he w d in t e t a nd pa r t s impa ired ( a s en s t h e c a se i n i o r m al adul t br a i n y) but br Ne , 2002 r e i l e v a le & B vil e N e e ues (s g lea l o r c nd he le a vil inju r a ins t h a t ha v e de v elop e d d i f fere n t l y th ro t n e m elop v l de a t na t s nd po esis a en g o y br ut em o h g u . for r e vie w) on t he n e u r a l a nd beha vi or a l de v elop m e n t o f N m o r ons f usi oncl he c t f t o en isc n mi Re - ud t ies le’s s vil e dea f ind i v i dua ls. G r o win g up dea f leads to d i f fere n t o u t o r e-f u n c t i n br of a in de v elop m e n t in t he dea f, s t r u c t u com es in vi su a l p r o c e s sin g wh ic h a r e r ead ily ap pa r e n t in r e a p rodu c t o f a de v elop m e n - a l map pin gs in t he br a in a ev en t-r ela t e d pot en t i a ls ( E R Ps) in r espons e to p e r i p h t R E h c su t a h nd t u he fo s. S t en v l e visua vin scade in ca g p l o v r o c ess es a t ma n y t i m esca les. T h e visua l o r Ps f eral m t f-Sm f ilo m r nd Ka a s a m o h T y ies b ud t on s i h f for dea i a h t g n i r for hea r e g r es la m i 2 to 3 t e r e eas w ar t simula n n fere f i e d hes ins t a l p x le e vil e ls. N dua i icula i ind t r de pa i v o r (2003) p v to in s t gh ul insi ef ly us r s m r e in t s e c of c t he com pe ti ti ve pr oce s s e s t h at o p erat e i n d e v elop- aje r t l a t n e m elop v l de pica y at f ut o o w o r h g ic ies, wh tor d f nt be t w e en visua l a nd aud i tor y c o r - n e g f o n o i erat p o me an g n mi i t e h t n i s e c n fere di ll sma t ica l r e g i ons. B u t s e s s oce r p eral i c s o f k abo t t h is m e a ns in t e r m s o f t he dyna m on, & s n h o es, J t a B ut wha , n a m l E o s al ee s ( th in i ienc g e. T he m o m e n t-to-m o m en t e x ). h, 1996 t an f-Sm f ilo m r Ka p e r es o f ind i v i d - ch ua l dea f c h ild r en— in t e r n a l n e r de he or on t y t vi i t c a l a r u n e wis has e x t ende d t he i dea o f Le e s t e d le v els to t h v e mi of ll is e c onds— is d i f f e r en t for a visua l s y s t em de l- . H e e o w do w e r s ona l i t y st udy o f em ot i on a nd p asks: H elopin g wi t h i i o h t g wi opin ut aud on t h a n for on t e de v y n if t f r o m be in g hap p sh to sad when w e a r e to ld o f a n u - t f f- ond d c e is l l i e m i hes aud i t i on. T he a c c r ue d ef f e c t s o le in (e.g., de- t e oods s y do m nd wh w a t t? H en v e y p hap o i t c a l a r u e in n s e c n fere e at cre m r e t ng o l e h t r ove y t vi )? Wh pr essi ons, c o n t en t m en t y a r e s o m e o f us m o r e i t r m g e t h e ch hen de t t a h y t t e v i t an c e onn c l a r u e es in n in hes w do t o s? H r he ot n a h ods t o e m hes e to t ron p y p e hap t s P R he E t in t den i v e y t i v i act ral u e n di f fere n t p a f t e r n s o o r- nd u nhap p y odes a nd t hes e m a ods c r ea t e o u r p e epis he or de r o f m i l- f adul nd dea t s. E v en t s on t of hea r i n g a ona l t u o y a nd p a e t ea r ies c t i l s r e r p u w do o o ies? H t i l ona s m r t a lon r e v o d e t a e p e onds, r c se li i g esca le caus e e odes, in o in o r em ot i ona l epis u u r m o od swin gs? U nde r- g r o w t h (n eu rona ch an g es in bot h slo w e r p l r o c ess es o f es u st di n g e m o t i on r e q u i r an nde r s t a nd in g h o w p r o c ess es y) a t i v i t c e onn c e p r o c ess r t fas o s l nd a f n e u r a l a c t i v a - es o c ot he r . I n a r e c e n t h uenc l les inf esca m i t t en fer f di at e ea ti R E on ( Ps). l t y de v elop m e n t , ona s r i nd p on a i ot em f o y r o e h w t ne e

23 280 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 280 n a m i Dy l pa- a t n o 2 m t g a pin n g es in t hes e a n a t o m ica hs, but c h l ona i ot en em e w t ip be onsh i t ela he r ens t k i wis (2000) l Le t i l r causa cula r i to c y t i l ona s r e nd p oods, a odes, m epis ram et er s ma y be fa r less impor t a n t in t he t r a nsi t i on to y di er z i ract a h c t a h es t s y l a n a f les o a c s t n fere f e s s o acr indep enden t w a l k in g a t 12 m o n t hs. At t he la t e r a g e, a l - he la es. T in tl as co r n g e t h to a f ies o t r e rop opic p c s o r c le or ma e-sca g r t hou gh infa n t s n e e d suf f i c ien t le g mass a nd s t sup r w t e s insulas— n e he p es, t dg i he r s, t y a he b t e— in l t as co e por t t h e i nc e i g h t , t he abil i t y to ma in t a in b a la t i r he c y be t on ma i t ep c o i r rop nd p on a g visi usin ond opic c s o r c i le or m l-sca l he sma ons for t i t i he c t - m o l c ica en o- oc ess es— w a v es, t i da l for c es, e r o s i on. B ut t hes e m i c r pon pr t. Li k e wis e, a l t h o u gh fo cus e d a t t e n t i on ma y de t e r- t g-s he lon e to t ibut r e t n o ly c l ies causa t r e rop opic p sc g n w sk il ls, as g in nd a mi ne su c c ess in ea r ly s t a g es o f lea r n in le o r o i ibut r t n o c e v i t ela he r t , c i t ma auto e r cula r i c f n mp a x e n is is a h ies. T t r e rop opic p c s o r c ma sk il ls be c o m e m o y s r nde . U t i l causa d. ishe n i m i on is d i n e t t a of t l- e v de y t i l ona s r e nd p on a i ot g em in nd a t r s en mpon o he c e t caus Be t hem s e l v es ha v e a de v elop- y l r cula i c f ind o k e m he sa ut t g o in k r o es w r i u q e r t n e m op t on ona nt al hi s tor y a nd r ela ot opic em c s o r c i he m m t ro f s— ip onsh i t ela l r causa l t i onsh ip s a m me g t hem a r e c o in- t n i ua y alt ered, a f u ll er re p le ab t s e r o he m oods to t m f le o dsca i he m gh t ll o r h es t at st r e s e n t a t i o n o f o u r dyna m i c u pe h ’s t wis zes Le i r ma 6.1 sum e l b a . T t y a h 6.10 T e r t u g Fi e k i uld look l o e w ndscap la i on depic f les o sca e e r t i l ona rs top o f e a n ot he r , sh o w s t h r e e la ndscap es la y ered o n on em ot i ona l de v elop m e n t , sh o win g pa ral lels a nd d i s t inc- ro mpon en t s o f t he dyna m ic s t em s ind ica t i n g t h a t t he c ti ons a c o ss sca les a nd t he cu r r en t u nde r s t a nd in g o f t h e y psycho o g ica l a nd n e u r o b i o lo g ica l m e c h a n ism s. a dyna e l es ha v l e s hem t m i c . T he a r ro w s c onn e c t in g t h e v g be T hes e de v elop m e n t a l pa t t e r ns f i t t he la r g e r i dea be- in l p u o he c t t a h t w o sh s r e y la is s t en mpon o he c en t e w t x a i h e. T m i t r e v o e g n h y c nd ma a , nt ge n i nt co d n a s e l p com h ind t he la ndscap e in Fi g u r e 6.8: T he c h a n g i n g s t abil i t y t s an me r v e r ma n y sca les o f t i m e. Ea ns o c h l i n e on t h e d an , l a n o i direct i t l u m s y a w al s i g n i l p u o c e h t at h of pa t t e la t s- y ca r ma he ot n e a on on s m e t s y s e sub h f o s ect f f e t a n r e t t pa l a or vi a beha f es o t a t he s t s t en es r p e e r ndscap th cade o onden- xpr ess e d as t he c o l l e c t i v e v a r iab le; t h a t is, t he c e v e r t i m e. T o c o n t in ue o u r infa n t s t ep pin g e x a mp le, t h t inc g n e r t g muscle s g le asin e v- r beha le to a simp r in s t en mpon o le c p i t he mul t f on o i t sa h e h in t y t vi i t c gh a u o r t v io ra l e x p r essi on. K n o win g t he beha vi or o f t he c o l l e c t i fi r s t m o n d hs o f l i f e fa c i l i t a t es s t a n d i n g , c r a w l i n g , a n e i a l f i r s t s w ep in d isc o v e r in g t h e t in spa- e g n a h es c c on indu i t o m o c t lo enden ndep g. I in alk va r iab le is a n ess en t s ti s m o v e a r o u nd n e as infa caus ly be b a b o r on, p i it gn co al pr o c e s e s of ch a n g e. B ut a m o r e c o m p l e t e u nde r s t a nd in g t ir s k r ndma la l a i t r spa i e h on to t i t n e t t a e r o y m pa ey th al so re qu es t h a t w e k n o w abo ut t he beha vi or o f t h e s t co s t h a t c ons t i t u t e t he c oop erat i v e e n mpon e m b l e . en (A cred o lo, 1990; B e r t en t h a l & Ca mpo s, 1990). B u t v- n t a l s t ud ies Th is is esp e c i a l ly impor t a n t in de v elop m ch an g es in c o g n i t i on a l s o f e e d b a ck to lo c o m otor beha e e nd w ons a h i ibut r t n o he c e t caus be t g i s o f t hes e elem en t s i or as m o r e sk il le d infa n t s e x p lor e a nd e x p loi t m o r e a n d e f n t a s p ect s o f t h eir s p a t i al e n v i r o n m e n t , c h an g fere di - n o c t n fere f di n i d an e m i t er v o e g an h c s e v l se hem t y ma n n i n g , a r y e ab le to ma k e nd a api d adjus t- mp a x or e s. F xt te th ei r m otor p l a le, le g ma ss a nd fa t-to-muscle r a t i o ma r n to u s t n me be pot ep- f on o essi t r p x e s l a or vi s to beha ibutor r t n o t c en . s t n e v e ed t c e p x e ABLE 6.1 T M l ona s r Pe ood t ode l Epis i ot Em y i ona esca le Se c onds to m i n u t e s Ho u r s, da y s Ye a r s Tim a s esc r i p t i Rapi d c o l ona i ot e-em v i t a t e r p r e t g in in t La n v e v i t a t e r p r e t in f t o en m n i D r o t g en in t Las e r g enc e o f c o g n i t i v e n t r p r e t in a t i on wi t h e ot i ona l s t a t e bia s habi t s em i d o y m r a empor T tor c a r t At t e r p em t s y ic s m Dyna r e t in f e o r u t c u r t t s n e n a m r Pe e i t a e t a t s f on o i t ica f v st ma l ism spa c for at e spa c e e Po ssib le e m o s f g o in hen t g n e r t nd s n a Co r t ica l c ohe r enc e m e d i a t e d b y o i t c ele S bic m i l o c i t or l-c a t ron f to bi Or u d bic im l o ic t r o d c n l a e n i a r t on en i t a z i n a g l or a en t r a i n m en t , m otor r ehea r s a l, a n d ica t r o c o c i t r co ne r ob io l o g i c t ron f to bi or a l an c me ism e n o m or roh u e wi d n inde a t e, sus enc r e f f ea pr s t cui r i bic c m i l h t c onn e c t i ons, p r u n in g o f ot h r s, lo ss o f he pl s i t i c i t y a i ghe de r f l In te nt i on, g o Hi l In te n t r or ona l or ien t a t i on S ens e o f s e a m for

24 281 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 281 Dy a m i c Sy n v els o a x or e on. F i t a z i n a g or f m- t le en r e f f i d y r e v t s a ism n le, b p d y isc o v e r in g t h a t t he depo si t i on o f body fa t a c t s as e a c ro l pa r a m e t e r in t he d isap p t a r a n c e o f n e wbor n n o ep pin g , w e ha v e sup p l ie d a m e c h a n ism o f c h a n g e. A st phys i o l o g i s t m i g h t a s k a b o u t t h e me t a b o l i c p r o c e s s e s l p th at ac c ele r a t e t he depo si t i on o f fa t in t he po s tna t a e - e ri od , a nd t h a t c o uld a l s o c ons t i t u t e - x e d a p as ess-b c o r abo pl i on o f c h a n g e. B ut t he m e t at l ic e x p l a n a t i o n n a o u ld n ot be c ons t r ue d as a n y m o r e b a sic a nd m o r e r e a l sh el. I an on e a t a n y ot he r le th nde e d , be caus e le v els a n d v pr oce s s e s a r e m u t u a ll y i n t eract i v e , it i s impo ssib le to as- e si n on e le v el as t he ul t i ma t g causa t i on. D esc r i p t i ons o f en mpon ch an ge of ma n y c o t s a r e n e e d e d s o t h a t mul t i - l le el pr oce s s e s an d t h eir m u t u a v i n t eract i ons ca n be r fu ly in t e g l a t e d . s a ism n a g g or elopin v De . y t i l a us ica t x e l Mu l p m o e c r sy st o mpo s e d o f v e r y ma n y ind i v i dua l elem en t s em- em s c d wi ron h in, a nd op en to, a c o mp le x en vi dde m e n t . be t r e c mpon en t hes c o n t in uo usly in t e o a c t wi t h ea c h ot he r T s nd in s o doin g c h a n g e ea c h ot he r a nd t he s y s t em as a a s o is is t he i dea o f mu lti c a u h a l i t y . As in ma n y le. T wh he r c o m p l e x s y s t em s in na t u r e, su c h s y s t em s ca n e x - ot s a ibi ohe r e n t beha vi or : t h r t t c r e c oor d ina t e d wi t h o u t he pa an ag en t or a p r o g r a m t h a t p rodu c es t he or g a n i ze d pa t- lely in t te Ra th er , t h e c o h e re n c e i s g e n erat ed s o n. he r ela- r ti ip s be t w e en t he or g a onsh ic c o mpon en t s an d the n co nstr a i n ts an d o p p o r t u nit i e s of t h e en vi ronm e n t . Th is is n ered g u re 6.10 T he epi g e Fi e t ic la ndscap e as a mul t i la y e he i t t dea o f a n op en s y s t em, on e in wh ic h t he en vi ron m n ot he r em whe r e t he c o mpon en t s mut ua l ly inf l uenc e ea c h st sy y in c h a n gi n g w a s . ua (t erat n e s, in g r he l ot l l to a - eq , t en mpon o sk) is a c a he t a o n t i h ns t z n a g f-or l e is s h e. T enc r ohe g c in a t a i on m sin- e x or e l a n e e t in t— en gle elem v e r y le v el mus t be c on- r I mpor t a n t ly , e x p l a n a t i ons a t . y t i r o i r l p has causa l— a n r e t ze, t ly t e n t a nd ul t i ma t ely r e c onc ilab le. T h is is esp - r a h e c r a y e h sis i n a g f-or l e s s em t s y s x e l p m o c h c When su e c i a l abil o y t i abil t or ins y t i t s e v ti a l re e h t y b ed z i er act r i e h t f impor t a n t when c onsi de r i n g t he n e u r a l b a sis o f beha vi or . st e ies o r e as a s d e on visi n be en ca t n e m elop v e es. D at f S inc e t he t i m o f My r t le McG r a w (1932), t h e r e has be en vin l o iss nd d g a vin ol ev ic s a- t m g dyna yin r a v f ns o r e t t g pa a t r ad i t i on in h uma n de v elop m e n t a l s t ud ies to s e ek e x - t b el, to look for s v le l a r u e he n t t on a i at an pl s e r v e d e o m bil i t y , r a o h e r t h a n a n in e v i t ab le ma r c h to w a r d ma t u r i t y . n e r ohe is a c g n i an ge in beha vi or as ca u s ed by a p recedi n g an d d e t e r - e to s us l t n infa t ch h or t vi beha t Th us, c r a w a in. F or e t t s ien - i d oor nd c a h t g n x a mp le. Go ldma n- c i f suf e v ha y e h when t e t o m o c lo e mi ni ng ch an ge r in t he br a e vi n e, a r u t s es po e n nd-k nds-a e a ha on to assum e v massi a h d t en t es g g su e v ha s r he nd ot ) a ic (1987 k Ra na t i ron- t f on o i zat i an rg reo o nd to m but a , t en em v o f-m l e s e t a a t t i por to sup nt me v i t l a t ron ef r he p ons in t i t c e onn ic c t ynap s as sy t em n ot y e t b a la nc up- d a co rt ex ar e t he r e s on wh y 8- to 12-m on t h-o ld infa n t s nd s t ron g en o u gh to w a l k e a i t s in spa t n e m e v ro imp w o sh a t. Cr gh ri w f on o . s h t n o m eral v e or for s vi le beha ab t is a s g n i l i t ibi on, inh i t i n g o c l t B n t s lea r n to w a f k , t he c r a w l i n g pa ut when infa t e r n be- pr epot en t r espons e t endenc ies, a nd e v en t h e ons e t o l e ek to e x p l a in Pia g e t i e. T a n - k l a nd w a g n i d n a t s f ns o r e t t he pa t y d b ze i abil t es des com g ua g n la h a t c h e r a nd ot he r s s o d in t e h le b m e ass g n i l w a r m for c a r g r p o e is n r e h g. T in st ag es as a r esul t o f y t vi i t c in a a es in br g n a h e c k i el g a t s v (T tc he r , 1991, 1992). s zes a i n a g f-or l e em. It s t s y us s o ha r e he n d in t e r es or wi n ge a s n a h c f s o ism n a h c e he m for t h c r e a e ul s f ess c c A su g o l u t i on to a p r o b lem in a t a sk c o n t e x t (m o v e a c ro ss t h e n e m elop v de g n i y r r du e a ma t roo m), la t e r to be r e p l a c e d b y a m o r e ef f i c ien t s o l u t i on. q u i r e in t e g r a t io n of m e ch -

25 m 282 i c Sy s t e m s Theori e s Dy a n ete r o g e n e ou s S y stems an d Deg e n e ra c y . T hes e H g eas abo t icausa l i t y , s e l f-or ut mul a n i z a id t i on, a nd op en- ouch V ision T ess f i i t em e r g n g i d eas abo ut n e u r a l de v elop m e n t. T h e n r br f ma n y d i f fere n t p a in is made up o t s an d p r oce s s e s , a t i w n o i eract t us in uo in t n o is in c h c but ea s t r a p r e h t o e h t h m an d, thr ou gh t he s ens or y - otor s y s t em, wi t h t he w o r l d hla r c u (e.g., Ch nd & S ejn o w sk i, 1992; Cr ick , 1994; Da ma- enlo o, ma n, 1987; H u t t o, 1994; Edel c h e r , 2002; K els si 1995; K c y t r e rop has a p o s l in a a he br vis, 1994). T & Da h o r th a r u e h in n ic wh , cy a l ene g de ls l ) ca n (1987 ma Edel at ct d st ru e i r r n be ca on ca i t nc u gle f y sin n a t a h ns t a e e m ur d g i onf e c on n a h t e r o m y ut b o u ls a a n g si l a r u e n f on o i t a r n s al mb u n a n i e t a p i c i t r a p o er s r e t s u l c ral u e n t n fere f di at th e g e di n erac y cre a t e s red u n d a y n c ff ere nt of fu nc t i ons. D Fi u re 6.11 Il l u s t r a t i on o g t he t i m e-lo ck e d map pin gs o f f ss o he lo t h t en wi v ons e i t nc u em f t s y he s t t a h t h c su e on f t tw or y s y s t em s to t he e v en ens s in t he w o r ld a nd to ea c h s o he r t in- B e caus e visua l a nd hap t ic s y s t em s a c t i v ely c o l l e c ot . for ma t i on— b y m o vin g ha nds, b y m o vin g e y es, t he a r ro w s c c e c t in g t hes e s y s t em s to ea onn h ot he r a l s o ca n s e r v e as r te ac hi ng si g n a ls for ea c h ot . he

26 283 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 283 Dy a m i c Sy n he s r e a c h t wi t a in s t imul us ( H a r r i s on, 2001). F or e x a mp le, - o ot jus nd n u en fo w be o has n y t i c i t as l in p a Br t in t he le ma l o el he sm d or t e r h t wi d e t a i c o t be ass gh i r A m e t t f t es in sub- ens ic s t a m o in s o s l , but a x e t r o y c or ens s to l , a nd m otor espon- r r o l c oda ss-m o r le c ssib l po l ot a s. N r e w o he f t co rt ica l a r eas a nd in t he visua l, aud i tor y ead n k y s a nd ot he r ma m m a ls ( K a a s, 1991, co rt ic es in m o , t s n es. I ienc r e p x ic e t he t s e n y s s up a w o es sh denc e t th al ey t end to c onsis s o S t ei n & M eredit h , 1993). T hes e dem ons t r a t o t or mu- s r e t le d e lor o g c vin i e c r e p f i ons see in a s nd nde for u t n a t impor y r e e v r a y t i c i t as l t p adul of t g sica l n o t es or c o lor e d s o u nds a nd t a s t es. S y n e s t hesia w a s r s i r r Ha e e ica (s ot x l e ica g lo o h c y s p d e r de onsi g c lon t e t h a t br ons dem y e h ) t e (a caus be t n e m elop v de a i n t a on, r r o n be “g ca t a h e t s o h en t v s, e n o i g t r ap h ica l l y re p r e s e n t a be- t e in pa — d e t a g i t s e v ly in l ica t ema t s y ot s nd n 2001) a ” d to a ca t e d , a r e dyna m ic p r o e n i a r t ons c o e s e d i v o r p y e h b) t nd ( es, a ess c r es a ienc r e p x ic e t he t s e n y e s caus lo o y n e m elop v h de ic wh y es b ess cl ues to t he v e r y p r t c ma fe w odd k inds o f c o r r espondenc es, h i ghly ind i v i dua l i s- a l p e k ta dua gh C as i . e c t ic (wh ile s o m e ind i v i a h ls m i gh t p e r c e i v e e ue), a a n g e, ot he r s m i gh t p or r c e i v e i t as b l nd be caus e he n e T e p e r for o w classic e m e d b y x p e r r e s w t n i m e w adul r ve t s r epor t su c h c r o ss-m oda l s ens or y e x p e ry i - f ues on N zen e k n o ld m r o w W e y g lea l o is c nd h h a ic r Me s, enc es. H o s e v e r , r e c e n t beha vi or a l s t ud ies wi t h adul t w wh v e r ela t i v ely u n f issu r e d br a ins wi t h a clea r s o - h ha ic o m sh o w t he p s y c h lo g ica l r e a l i t y in p hen o ena su c h as t p ha e v i t ensi r s i e h nds. A f on o i t a t en es r e totopic r ma fect pop-o ut ef s i n s e a r c h t a sks a nd r e c e n t ima g i n g s t ud- he s t n a r e g n i he f on on t i t ensa d t f g o pin map g n i k a pa ins o g g es- win e g r e a r e h T . y t i l a e r l a r u r e he n t w o ies sh g su espons r h e l a c i g o l o i phys ro ct ele to s ea ar nd es on t ha e ti e M ond lo c h & Mau r e r , 2004) t h a t t hes e ons (s a f r l su ica t r co f s o d map le i a t en c a t de d adj e l a e v e e r c t e r a t ons in adul i t c e onn ic c t he e v s e n y ic s t a r ync s s- io id s i v i dua l t a h eas t ar w e r e sim ila r , but n ot i den t ica l, in ind ti g he de y in t t i v i t c es o f t he e x ube r a n t in t e v r c onn elop- e zen mo ey Jen k ins, M e r nk ic h, & R e ca nzon e, 1990). s ( t n l ma t u r e, a n in t e r c onn e c t i v i t y t h a t p l a y s a n me ly im a , Th e a r eas a r e p l as t i c , n ot a n a t o m ica l ly r i g i d hes t at n e- he c nd in t ess, a c o r p l a t r e m elop v le in de ro t n a t impor when t he e x - wa s dem ons t rat ed i n s e v eral w a y s . F i r s t , epa em at i on o f t he s e em in gly s s in ma- r a t e s ens or y s y s t n i ze d pe ri me nt er s a mput a i e d d g i t s, t he map s r e or g a t r k e w i t z, 1994). e tur or g a n ism s (s e e a l s o T u g so th at adj a c en t a r eas enla r e d to f i l l in t he f i g e r n input w a s el im ina t e d. S e c ond , when t h e spa c es whe r e n De l t i m o d al Pr o c es ses i Mu Cog n i t i v e v e lo p m ent . r zen ic h g r o up f u s e d t w o f i n g e s y e k Me n o t m adul f s o r f ons On e dem t r a t i on o t he de v elop m e n t a l po w e r o f he t- e n o he m , t r h t e g to k e y s ’ br a ins el im ina t e d t he bo u nd- p e g e n o us s y s t em s c o u er l e d to ea c h ot he r a nd t i m o v i t p e c e he r nd t s, a t i g i he d en t - e w r e v ields o e f t ies be ar m e lo ck d to t he w o r ld c o abies es f r o m a s t udy o f h o w b in-f usi on w lap s su r g ica l ly c o r rect ed, e d. When t p he sk a . enc r nspa a r nd t a t s r nde to u me co r a nspa r enc y is a T y e a f on o i t nc u f d e nc d. Enha e n r u t e eas r di st inc t i v r d i g i t a in m ob lema t ic c onc ep t; t h pr k o hem- f bi r ds wh o ha r t n i n i a r gh t u o r gle f h t sin l ica t r o s c t i d r e g n i e r enla g g y is se lv es b y t r yin g to f ly t enc r o u gh windo w s. T r a nspa r h when pr es en t a t i on, wh re h a g a in c o uld be r e v e r s e d ic e en visua l cues a n d t ela r r o e c caus lem be b i o r a p ons be t w en when n as a t n e m i r e p x e o l v e , y l l d. Fina e ce ng ni ai tr c n er e r s t u o u o f o t s o m e z i er ract a h c t a h ic cues t t he hap t n e ons w i t ipula n ma en- es r p e t r i g i d f o s r de bor , d e s impo e r t he w e k i abies, l b o e. S is cas h in t k r o ot w ld do n r o wi t h e h ons c n g e d s o m e wha ti t o v r t i m e, p r ta esumab ly a a bi ds, a r e c onf us e d b y t r r nspa r enc y . I n on e s t udy , Dia- n i g n e r . i re he f t f y o tor s i e h e us l t a i d e m he im t g ect f dden u nde r m ond (1990b) p r es en t e d infa n t s wi t h to y s h i n e e a nd ot he r e x p m i r e T f ds o r o he w in t , d e l a e v e hes s r t h de— e si g on on en op n s a a e w r e as t t a h t h c es su x bo in h, A l la r d , a nd Jen Me t r zen ic the “ a h ins (1990) t k r r h t i e e r e es w e bo hes 6.12. T e e u g d in Fi e t a r t s u l il x s- a io ns ’—of t t h n e s e r p e l ‘r a c i t r o ls of c i ta e ic d if ec sp e di t o a tr ib u t e d , s e le c t i v e r e s p o n s e s of c o r - s e e r ns—a t r u l ne c i n U l i s h e d an d a r e c o tab t inu a l ly r emo d e le d B Y O R 195; emp hasis a n d EXP ER IEN C ES th r ough ou t l i f e ” ( p . capi . ) l ina g i ls in or a t t to a a poin h t on wi i t w e is s h end t We i e g n uin g r t in n c n a n m e is a r s t hesia in adul t s e n y dea: S i e asi v r e v he p t f t o t i m oda l na t u r e o f in t e r c onn e c t i v i t y a nd e x ube r a n t mul e he de g e he r as t d e in is def sia u h st ne Sy in. a g br elopin v t - x g u re 6.12 A to y ( b a l l ) h i dden u nde r a t r a nspa r e n t bo Fi f e o ienc r e p x n y e r a t n u l o v r in la d le, a b a r , du l a n r e t x e in an n opaq ue bo x in t he Dia m ond t a sk . T he op en d a g is ind i- t ca e d b y t he a r ro w . e e ge ne r ic p r c ep t i ons in s ens es n ot c o m m only ass o c i a t d

27 284 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 284 n a m i Dy a n he in- t t a h t o s opaq ue— h i d i n g t he to y— or t r t nspa r e fa nde r t he bo x. T h e k e y r esul t is n t s c o uld s e e t he to y u on 9-m at th v e i r t e le to r r ab e e h e t t t e be r s a t n ld infa h-o t r . r o m t he opaq ue t h a n f r o m t he t to a nspa r e n t c o n t a i n e r y f r nspa a he t t h t lem wi b o r he p T r in- t a h r is t e n i a t n o c t n e t to r o r h , t ly t c e r i y d he to h for t c a e emp t t s a t n fa u gh t h e h a r su t ind- e r nspa ra t c e, r a t h e r t f a n s e a r c h in g for a nd f n g. in g t he op en in t n nfa I b o w lem, h r e v e r , if is p h e t v l o ily s ead s r o n th ey ar e g i v en e x p e r ienc e wi t h t r . s r e n i a t a o c t n e r nspa t ld b t z e r , T helen, a nd Sm i Ti h (2003) g a v e 8-m on t h-o - a t a r t s u l Il re 6.13 u g nd El Fi ck a sk . On e l is t a r u he T t f on o i bies e nspa l s to p t e ck bu t n e r y a i t h e r a s e t o f opaq ue or t r a l t ia r t h c ea ssi- ly as po d pi a as r r e nsw e, to a m sk is t a he t he sa t n e r a e. P m v o h t a h t wi i en n o ins t r u c t i ons ot he r e r e s w g b h e q ues t i on: “ Is t h is a pi tc he r . le t l f t he pa r t ic ipa n t s a n - ” Ha hes to put t an th hem t g n i k x, ma y bo he to in t s r e n i a t n o e c sw e r “ y es” b y p r essin g a but ton on t he r i gh t a nd ha l f b y ipa essin g a but e ton on t he lef t. P a r t ic h n t s a r e fas t e r when t pr t s w e r e av ai lab le to t he infa n t s du r i n g p l a y . T he infa n e. t s de a si e m he sa le is on t es” r nd ha espons y he “ n w hs t hen t e s t e d in Dia m ond’s t a sk when t h e y e r e 9 m o t ue c o r e n i a t n o s en opaq v i en g o had be abies wh he b ld. T on r e n t to r es jus t as fa d e t r ie v e o bje c t ile r o m t r a nspa s f e pi tc he r ( y es) or i t w a s n ot (n o). R espons e t i m e w a s t h w in t o t n infa , r e v e s wh o . H udy t ond s m l Dia ina g i he or e r t c bje l o ely visua r is is a pu e h e. T r asu o t m enden g- c dep r a nspa r e n t c o s s o u gh t o ut a n d a t n e i r pl ay ed wi t h t he t n r h a r e t c mu e fas e s w t n ipa c i t r he pa t , t e . Y sk a on t i t nit e d ly fo nd t he op en in gs a nd r r e t r i api v e d t he o bje c t f r o m u z i n g t h e o b j e ct i f t he but ton p r ess e d to ind ica t e ni g o rec n t a nspa r e r t es. x bo he t r s ’ tc he t he pi de as t si e m he sa s on t a e w espons es r he y Wh i a t n o he c t h t wi y a l r p i e h abies in t e b hes y? T n- ha le, as if s e e i n g t he ha nd le p r nd e d (a nd r ead ie d ) t h e im he in t e r-r ela t i on o f s e e i n g a nd to u c h i n g— had er s— in t s m e o f r e a c h i n g to t h a t si de. S i m i la r r esul t espons otor r i in- s i d t a h l cues t le visua he subt ze t t n g o c e to r d e n r lea nd in ha e be en r epor t e d wi t h a wi v a r i e t y o f o bje c t s a de v r o m n o su r f a c e wha t s o- g uish s o l i d t r a nspa r e n t su r f a c es f m e sks usin g s e v e r a l d i f fere n t ta t h ods. I n g e n eral , p e o p l e e d t h a t su r ev f a c he visua t h t es wi l er a nd had lea r n o a e fas t e r in visua l r e c ar g n i t i on t sks when t he r espons e e rop p t ic cues t he hap d. T i l o e s r y a enc r nspa a r f ies o t r a r - he o on on t i t c a l a e b h t le wi b i t mpa o to be made is c t r nspa a r he t e g n i h c u to om fr n t su r f a c es e d u c a t e d visi on, t a h us t l l e t s t esul e r hes t. T c g i t i on is a je n o c e l r visua on e h a d u c a t e d r e a c i n g a nd to s t n infa g n i l h, enab c nd visi u r is is i t la c as, a e g ua g l a n h e t in e m he sa f, in t o e c pie n on. T in en he op ind t to f r a nspa r e n t c o n t a i n e r s. T hes e r e - gs in t he i a t map ho w i t mus t be u nde r t pin dea o f r e en t r gs, n o e sul t s sh w h o w infa n t s ’ mul t i m oda l e x p e r ienc es in t h f ut o o t on is buil i t i y b d e t a c u d nd e n g o c e l r visua e r whe a t - bje gs, o in en ut op abo e— dg le w o n k e t ea r ld c r wo r e c t m it s t i e-lo ck e d c onn e c s. i ons wi t h a c t i ons on o bje c t nspa r tr n t su r f a c es. v a l, a ie nd t r a e e m i r e p Ex uma n c o g n i t i on su t g g es t t h a t n a l s t ud ies o f h ie , n y c onc ep t s a nd p r o c ess es ma y be inhe r e n - i t ly mul t De v elo p m ent a s S e l e c t io n . In a n e a rl ma r s ect n o i em we p ropo s e d v e r y g e n eral p r i n c i p les o f dyna m ic s y s t s m oda l in w a y s t h a t f i t w e l l wi t h Edel ma n ’s i dea o f r e en- onc c f y o a as a w t- a e: P g n a h c l a t n e m elop v de g n i z i l a u t ep t ran ce (e.g., B a r s a l o u , 2005; Glenbe r g & Kasc ha k , p te r ns ass e m b le d for t a sk -sp e c i f ic pu r o s es wh o s e for m 2002; Go g a t e, W a l k e r-A nd r e w , & B a h r ick , 2001; Lick- e li r, 1994; R i c h a r ds on, S p i v e y , B a r s a , & McRae, u o l a nd s t abil i t y dep ende d on bot h t he im m e d i a t e a nd m te r o t di an t h i s tor y o f t he s y s t em. W e emp hasi ze d t h a st a dy- 2003). On e l i n e o f e v i denc e for t h is c oncl usi on is t h a t p l e g on m a y t ui in t n o t be c e mus r e h t t a h t t n a e w m ic vie m na ev oda n im ly u t i ic l p x t to be e n a e sks m a en in t l, mul t i ies c t r- e t x nd e a l a n r e t h in em, bot s y he s t f o s t en mpon o he c t m oda l i t o n t r ibut e to p e r for ma nc e. F or e x a mp le, vi- c g e r t c bje o l a su n i t i on ap p e a r s to auto ma t ica l ly a c t i - o na l, a nd a m on g t he t i m esca les o v e r wh ic h t he s y s t em he o bje c n n on e s t udy , i va te t he a c t i ons ass o c i a t e d wi t h t o li v es. C o n t empor a r y d isc o v e r ies o f br a in or g a n i z a t t. I tc he r su c h as c i m e dyna hes t h t wi t n e t onsis ghly c i e h r on a i t nc u nd f a e r u t n a pic w o sh e r o e w s t adul f a w a t e r pi pr t s simp a sk w a he t 6.13. T e r u g in Fi d e t a r t s u l il at th le, to inc ip les; inde e d , t h e y p r o v i de insi gh s in to t he p r e c i s e a pr me c h a n ism s o f ch a n ge . ess a but ton ind ica t i n g whe t h e r t he o bje c t w s a

28 285 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 285 Dy a m i c Sy n ec of ve su ck in g i t s e l f— a nd i t is c o n t in ua l ly upda t e d as e x p e - i t sel as a t n e m elop v t to de poin t a h ies t t r e rop P i d b y e t en lem p g is sup in d e e es. When f t cumula c e a ienc r , e v a t c e l l o ic c m in is a dyna a he br t t a h t e t ica ess ind oc pr t is de- s e l f-or g a n i z i n g a nd dyna m ic p rop t wi e r t y be ma ” t e to ea im t “ y r o g e t he ca e, t nc a t le, for ins t bot ies; i h ies o si gn ed t o e x t ract c o h e re n c e f r o m e l t he bot t f t i l a u q l a u t ep c r e he p ude t to incl d e g r enla m u l t i p le, t i m e-lo ck e d in a o c c s to a t n e m e v n on. I i t nc u f y d b e n i a t m- on is ma i t a z i n a g s or t nd i input; a o g m in ck he su t in t en m t adjus n nd a o c c g a win o l l he fo t ghe i le. H p p i e n h es in t g n a h c e t m oda g d e l w o n r k de r-or ld Edel- a r vily on Ge ely hea r e w , t n e u r e rop p t c bje o , g in d e e ut f abo y o n or he t ) “ ’s (1987 n ma e u rona l g r o up s ele c t i on” f or o vi he beha nd t ies, a t f a r i m dyna g n i t ia t n a t ism ins n a h c e m ( TNGS) as t he n e u r c l y yda e v gh e u o r h on t i t c ele s y b t us buil h ns is t uma r h he ot hea , g vin o m , g in look ies— it iv act e n de t . elop a or vi beha v l m . g n i h c u nd to , a g n i r t l assump i i ons a r e c r i t ica l. Fi r s t , Se ve ra t l add i t i ona Edel ma n (1987 ) clea r ly fo l l o w s Pia g e t (1952) in be- g a e n e t ic a nd epi g e n e t ic p r o c r o g e t on ca i ess es du r i n g h e r ies a t d e is assum li e vin t h a t t hes e ea r ly p e r c ep t i on-a c t g t f r u t c e t i h c r l a a b he glo t e c rodu gy p o l o y br em ral u t e o o r n e r s ton e o f de v elop m e n t. I n pa r t icula r , t he em e r - ne he c ima r y a r - e t he br a in (s e e Edel ma n, 1987, 1988). I n t h a t g enc e o f ca t p g o r ies is a sp e c i f ic cas e o f dyna m ic pa t t e r n r e, h n infa in y t i l iabi r a us v o m or e is en r e h t , r e v e w o ur ect it ch for ma t i on. T he t a sk fa c i n g n e wbor n t s is to r e du c e g h t - c e onn r c i e h nd t rons a u e l n dua i v i ind f o r e b m u he n bot t he de r e es o f f r e e d o m a t ma n y le v els: I n t he e x t e r n l a ti wo t he pot en t i a l ly inde t e r m ina t e na t u r e o f t h e r ld— vi t y . S e c ond , c onn e c t i ons be t w e en n e u rons a nd g r o u p s t ies; is is don e b y for m i n g p e r c ep t u a l ca t e g o r rons a st - r e v o n e is a r e h , t d r i h e. T gh us u o r h e t is r imul i— of ne u h rons a u e n f e o nc nda abu r e t he in nd in t a e ly inde l ua he eq t ld— r o w l a n r m ina t e na- t g on m ons a i t c e onn le c ssib nd po e h e b is is don h t nd muscles— a s t oin le j p i t he mul t of re tu t hem, a nd t us sp y c i f i c i t y a r is es t h r o u gh c o m p e on. i t i t i t ina d oor otor c m f ns o r e t t g pa in ek se ro l. At n o t nd c on a s Im in e, t hen a n e wbor n infa n t wh o ag e f i r s t e x p e i - r a t t impor s o h nd m e, a m i t e m he sa t ma t tc mus y e h , t t n t enc r ld incl ude n u r sin g a o t he br eas t. Ass o c i- he w es in t r in t e r n a l dyna m i c s to t h o s e o f t he w o r ld a r o u nd th ei f t e s m e v o n m w ’s o y b a he b t n ons o i t ep c r e he p t h t wi ed at hem; t t n ies a r o g e t ca l a u t ep c r e r p i e h t e k t ma mus y e d h w s, ton g ue, a nd t h roa t a r e t he t a l t e o f t he m i k , of l i p s, j a s o g e t on ca i t c r a ei th r ib x e l on in f i t nc u t to f uen r g n o ies c le, h u gh t a nd sm el l o f t he m o t he si e r ’s sk in, t he s o nd o f he r t r e h, p c roa p ic ap m r dyna u o n s. I y a w e v i t adap c on, a i t ep c - p le body t a t n o c f e o enc i r e c x ile e t c a o he wh nd t e, a ic vo t ti a nd c o g n i t i on a r e n ot d isj oin t e d; t h e y a r e pa r t o f on, a d an e erat n e g he de t f e o caus e h. B t t m r a a nd w ran t n ree sin g ula r p r o c ess. e onn c f eb o w t i ons, t hes e p e r c ep t i ons a c t i v a t e t i m e - c e Th r e he t e t s o o h c e w r m h t whe t a h t e v ie bel e us, w i , l r ela t e d g r o u co p s o f n e u rons m eshe d to g e t h e g in k n rr pa t t er n fo cqui a ry go te ca or , n o i t dina or co or n, io t a m r si- b r e s ens or y epa ly s l ina g i he or t y t d e t c e t ns de r e t t he pa t a we , n n o ti g to t he sa m e dyna m ic p r o c ess es r r e f e e r ar i h hes st em s. It is a l s o h i ghly l i k ely t sy a t t e r ons a i t ep c r e e p f-or g a r i ze whe e b y c o m p l e x he t e ro g e n e o us elem en t s s e l n em o r f s t e n l a r u e m h t wi d e t a i c o ass - a v i t o nd m l a ona i ot n t- ic pa m e. Dyna c nd spa a e m i e in t enc r ohe c e rodu to p c l p r a b le f ti el in gs ( D a m asi o , leasu a n g si t a h s t r e t n e l c ona e t , e e l n be f ns ca r te i g or v e r y s t ab le, but n , m o s t impor t t n a ck a su h c ea h t i ). W n, 1987 ma 1994; Edel d n , a w o l l a nd sw nd s ey - ar e t i m e dep enden t a th e a mless. B y ti me d e p e nd ed nu r sin g epis ode, o v e r lap pin g , but n den t ica l, re at pe ot i t a h t n a e m we t, en in a he br t in t en v e h c a nd body has a ea gr v ps of ne u rons a l s o be c o m e a c t i ou a t e d. C o m m on as- ef nd-n r e-a o w , a h i s tor y , a n d a n he fect o n t h e f u t u r e . B y o m e s t r e n g t se e d; less-us e d pa t h w a y s be- l ies be mb c hen m e t hes t at th an me we , s s amle se i hem- e t r ins a ma do e e co he s t r u c t u r e is r e en t r a n t , me less s t ab le. B e t caus on. T h t n e m elop v de f f o uf t he s is i t up r r e t ut in o t es wi lv se e n t s a r e e x t ract ed f r o m t h e s l e e e m co mm al u t p perce on ep o a e t he dyna m i c s f p e r c l t i on, a c t i on, a nd c o g n i t i on in r er ov ons t ela r r o i r c i e h t y b d e k r e ma r a t a h s t g input pin lap t he p es- ti m e. Wha t t he infa n r s e es, t h in ks, a nd do es in t l-w or ld t i m e. T h is map pin g o v e r he t e ro g e n e o u s in r e a des t he f - en t p r o v i u he a l im en t for wha t t he c h ild is in t ess; n e w r ela t i onsh ip s a r e e x - input is t he c r i t ica l p r o c i a e tur e, jus t as wha t t he c h ild d t d in t he pas t is t h e sub s t r ed a nd s t r e n g t hen e d be caus e t h e y o c cu r to g e t h e r . cit nd a T us, for h o w he or she s e es, t h in ks, a h c t s r i gh t n o w . e p e t i t i on, su c h a p r o c ess o f s ele c t i on b y f u nc- Wit h r u e y we ca n en visi on t he n e d b rona l p r o c ess es po s t ula t l lo w s t he n e wbor n infa n t to r e c o g n i ze a c ons t e l l a- ti on a f t on, TNGS as a sp e c i f ic for m o i dyna m ic pa t t e r n for ma es a s a h i ghe r-or de r ca t e g o r y: “ Tim e to ti on o f f e a t u r g t t on wi t h t he pa t t e r ns be in i he ca t e g o r ies o f p e r c ep d n o w b y only ea t. ” B ut i t is a dyna m ic ca t e g o r y , in v o k e v i r a nd a c t i on t h a t for m t he de ghe elop m e n t a l c o r e o f h l pa a r t on, i t si g po sin i a nd inc o m p l e t e f e a t u r es— t he n u r t gh nt al fu nc t i ons a nd t he pa t me e r ns o f t h o u t t h a t x a for e le, or t he si gh t a nd sm el l o f m o t h e r , or t he a c t mp

29 286 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 286 n a m i Dy n ef a l i ze d t h r o u gh- fect i v e f o r m s o f re ac hi n g e m er g e . W h a t i s re m a rka b l e r e nd g a x e l p m o gly c asin e r inc e m o c be e a o ut infa nc y a nd c h ildh ood. in t he de v elop m e n t a l pa t t e r ns o f t he c h c ea t h h en is t r ild t ghly u nd a s o l u t i on— a nd e v en fo u a l ly c o n v r g e d to h i e f i y d l l dua i v i g ind win o l l y fo b ons— i t u l o o n ot k n s e o ho d w r e n r n a lea ca w Ho . n o i t ra lo Exp s r ila sim w t n fere d a wh a t t h e re is to l e ar n ma na g e to lea r n t n fere f i d e lor p x e y e h s. As t y a w h t pa l a t n e m elop v de a y? T h is is a yw n nt i y d b e t ia t i ons in t c a d e l l ro t n o c n r u i e h in t s— me ve mo mo re di ff icul t q ues t i on t h a n e h . T r a e p t ap s r i t f gh i m t i usin issue is whe h e r on e n e e ds to p r esp e c i f y - t he lea r n in g i n i ered v o isc d h c y ea he t y— he to t f t o gh g si t t he a r o y t en g he a t r e h t ls, whe a o g g in n r he lea nd t sks a ta s de- ti all t or i di f fere n t p a t t e r ns, ea c h had a d i f fere n t d e v elop- e e t n wha w o n has to k r e n g si l v n. E r to lea d e t en g - n r ds to be lea me nt al ta sk to s o l v e. T he less on for build in g in t e l i g denc e us o ut o f t h is en- e builds r t a t h em t t s y l s oda m i t A mul : r is clea s t en s ag i n e m elop v n de uma h m o r e f t b n d isc o v e r bot h t h e ds to e e ons only n i t ela r r o c d e ck e-lo t ran t map s f r o m t i m t a h g t win o sh y b abies ca r nda a qu y h s e t a sks on to t i t u l o he s nd t a d e n r sks to be lea ta o e t in m o t i on, to m o v e abo ut broad ly , e v en r a ndo mly , be s a - o th ro u gh e x p lor a t i on, or n o n g o a l-d irect ed act i on. I n to lea r n a nd t h r o u gh su c h e x p lor a t i on to d isc b v e r bot h o e sks a a h t es bot t ea r c t n e m e v nd op- us m o n a t bies, spon ta sks a nd s o l u t i ons. a r t ons e dem g. On in r ies for lea t i n u t por n ns r e onc on c i t e a he po w e r o f m o v e m T n t as a m e a ns for e x p lor t i on is t t be or & T g n i h c a e r f udy o t he s t helen, 1996 ). T h e (C a n m i r e p x e an y b ed rat t s u l l i o s al t al p e r oced u r e k n o w n a s ek de k we ek -b y - w e d e v c a r s t a abies w b r u fo f o t n e m elop e & t a g onju c t n e r e infor c e m infa n t ” ( R o v e e-C o l l i e r “ od as t i r e p h t on 3-m a r e ov d h e y t r a nsi t i on e f r o m n o t g as 3 m o n u o s (as y t n nfa ). I e, 1987 yn Ha n t hs) a r e p l a c e d o n s o f d e - r e t t a p t n fere f di y r e v r u o F re ac hi n g t . re ac hi n g nd t c i bbon y b d on t h e i r b a cks a a r h e i r a n h kles a r e a t t a e e m o d. S e v - e s b o e r e w t n e m elop v h c ea onr he n abies in t b r s, o t n nfa head. I r e v d o ende h is susp ic bile wh o f to a m ly e r a r m s a t in l l, but sa t p l a c i d i h t d e t f i ly l d r od ha i r e g p a i n k . As ons, d i act n w o r i e h t ough r th e, v s r cou e o isc r t h is l e wa n g t he w o r ld. O t he r b abies w e r i m o r e h i gh-s t r u n g tc h o he infa n t s k ick t h e i r f e e t , a t f i r s t spon t a n e y e h , t usly t c t i v e, f l a l i n g a nd f lap pin g a nd a l w a y s m o i g. a nd a vin act at e t he m o bile. I n a fe w minu t iv s, th e y l e a rn t he c on- e to s o l v e v e r y d i f f e r - T hes e d i f f e r en t b abies had to lea r n nd t h ng enc y be t w e en t e i r foot k icks a ti he ji g g l i n g o f t h e b lem s to lea r n n to r e a c h o ut a nd g r asp a . t c bje o en r o t p s h p mo bile, wh ic r es en t s in t e r e t in g si gh t s a nd s o u nds. l c i t c less a e m o e, to T he f v a i le r w o uld ha v e to lea r n to be esponds c o he m T ons: i t c a ’ s t n he infa ely to t t bile r g onju a i to m hem in he p e. T g t in nds, to br is ha r h e w lo in i c a l l d d he m T o r e infa n t s k ick a nd t he m o r e vi g oro usly t h e y is to be m r e he n a r e, to r to lea e v uld ha wo by ba v i t c a e r o on a h mo v e, t he m o r e m o t i in t nd s o u nd t h e y p rodu c e e e h t m o r hem up f t t f i nds, to l ha r ons on he i t si l po r usua i in g i e h e t as e r s inc t n on, infa r k i t a u t is si h t n bile. I mo ick a g be t a h on t i t u l o g a s in ind n, f r d lea si de. Ea c h b a b y d i n t e n e o us le v els ap pa r e n t when n i l e s a he b t e spon v a to abo t x t h e p lor a t i on o f wi he m o v e m e n t spa c e . o g m o m n o a n t ly look a abies simp b be- s t n ’ nfa bile. I vin T he c o u r s e o f lea r n in g for ea c h b a b y ap p e a r e d to be i x l e ia t i in f e o l is on ro t n o r c - e h t r e v o isc d y e h or as t vi ha i t c ele he s nd t on, a i t a lor p x l, e usa o r a f e o on o l u t i ons s on o f f y o t e i r a de v a wi f on o i t a lor p e he s nd t ons a i t c a n o i t c le on spa fr th at ex p lor a t i om c e. I n b a sic for m, t he de v elop- he in e t t e k to ma n r e t t l pa ma i t he op t of e s t in g e v en t s — r a i me nt g al pa t t e r n is t h is: T he p r es en t to y i t en n c f on o i t a n t o v e m e n t o f he m he m o bile— o c c u r . t t s o f usin o r is a n onp rodu c t i v e a c t i ons, g a ic i t s a l nd el l s o r t a n a t o n d n a , k s a t l a nt e m i r e p x e n s i Al t hou g h s h i v d i l ons in d i f fere n t b abies. u d i act i d n i t n fere f di y r e v an a er yda y r ea l-w o r l d o n e , i t i s a v e r y ap p rop r i a t e m odel ev ons a , o v er t h e p l ace T hes e a c t i all r e f i r s t , q u i t e l i t erall y a l-w or ld lea r n in g. T h e m o b i l e p ro vi des t h e infa n t for r e r t- wi t h n o clea r c ohe c enc e in for m or d irect i on. B u t b y a e ck e-lo m i t r n ma h t wi e o M ons. i t ela r or c f o s n r e t t pa d y e h t f e o g n a le r o he wh e t lor p x e t a h s t t n e m e v o m y b , g in infa impor r ela t i ons h t r e v o isc d es v l e s hem t t a n t , s n t e m iq n n u w r o is or he in h y b a ue h c e, ea mo e v c spa nt e b t a x t en em v o m y tor a lor p e e n ow r i e h t h g u o thr h T ns. r e t p y— t h t wi t c a t n o he to k r ma e t or la r e oon on, s i fash es c n infa he t h t i w y l t en g n i t on c g vin o m e r a es v l e s hem t s t g e ng in g in to or br ush in g a ba a ins t i t or swipin g i t. T hes r a h d n a r e t r- fa he t ; e l i mob de o g vi e r o m he t , ick k y he t r s mom e nt s of co , e c is spa h s in t nt e m e v o m e som t c e l e s t c a nt t a s t n infa for s i s i h T . s y a w s d n a gles g i j e l i b o o usly m h e e vin as- e r inc h t wi d e t a e p r hen r e t r a t a h ns t r e t t ut pa g o ca t a sk; t h e y sm ile ghly nd lau gh a n d o f t en be- en g a g i n g hi a eq r g f in a s— a ro usa l b y e p e cle r y he c eks, t e w r e Ov . y t uenc enc o me an gr y when t h e c on t i n g co y i s r em v e d . T h us, t h e o l c ona casi c nd o on, a i t c a , y to e m o c s f t o gh he si t t. a t n k ex e r i me n t a l pr o c e d u r e li p e t h e wor l d pr o v id e s com p l e x , Ov e r c y cles, inc r r e ef f i c i en t a nd m o r e le, m ab t gly s asin e o re e at i n g e v e n t s y et all per - p l act x e er v e n d an , e s r e v di y

30 287 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 287 Dy a m i c Sy n Rao, 1997 ) ha w n t h a t in t a sks in wh ic h p e op le a r e v e sh o s i t i d n A ons. i t c a n w o ’ s t n infa h t fe c t l y t im e l o c k e d wi e n es, t r ua q s f o s y a r r a e g n a r r a ex p lor a t i on, spon t a e e o u s n on t a sk -r ela t e d m o v em en t , y o f f-load t h e ask h i r e d to r e f. i t h o u t spon t a n e o u s m o v e- f s i h n). T ca o y W h ld (when t r o he w to t y r o m e m m r e t-t or sh ess c e p th ts tar s at th ro n f r o m ld ap- r o nd w en body a e w t e be c a f r e t he in g in t in f-load of me n t , w i t hou t e xp l o r a t io n , t h e r e i s n o t h i ng t o lea r on a n c t i n g o n d uma h f o t c e e asp v asi v r e to be a p s r a pe th e m o b i le. i v end a lot o en— r f h g c in ud incl ls— a m m g ma un Yo i- n g o el c sp r-le ghe i h f o t n e m elop v he de l to t ica t i r y be c ma ild n t g o a l. T h e y m o v e, t h e y in he bind ons or in t i t nc fu t a h t s t en t n o c l a t n e m f ve ti g o me in beha vi or wi t h n o ap pa r e ti ar s epa r a t ed in t i m e . w o r h nd t gs a in h t e c n u bo y e h , t nd u o r n a u r y e h gle, t g ji e e t epor ly r t n e c e h (2005) has r t i Sm t hem, a nd g e n erall y abus e t hem in w a y s t h a t s e em, to w o e on h denc i v d e t u is beha h t , r e v e w o e. H ood us g o n e v inds, to ha m e r v- ma t he body— a nd t he body ’s c o n t in uo us c o u p l in g to e v en t s only ca m e com r, io n- v g in in to build l a i t en is ess , y a l p d e l l in t he w o r ld— ma y p l a y a k e y ro le in w o r d lea r n in g. T h e l i g enc e t h a t a r e op en to n e w s o l u t i ons. e d b y s r i sk f a a t m o r es f v i r de ti ve for t us s o f in t e l ex p e r i me n t a l pr o c e d u r e m Ba he pa 6.14. T e r u g in Fi d r- t a r t s u l nd il ldwin (1993) a e ild h g c n u o y y r e e v r s a a c subje g n i t ipa c ti nd ies— bod in re a m te ys s s ou rv Ne . s r a e en 1.5 to 2 y r ent m bodi Em t e p x he e e. T ag of t h e n e r v o us s y s t em is c onn e c t e d to it is t h ro u g h t he body le, b a a t t ild a h e a c befor s t si r e t n e m i r n a es en t s t he c h ild wi t h on e o bje c t to p l a y wi t h a n d e i n g a f fect ed b y ) t h e w o r l d . Th ere nd p d r a g n i fect f h a bot ( b t b n i s y a w e h t n o h rc a e s e r d an n o i nit g o - g sin a e r inc is o o w he t t , ild h he c t f t o gh si f ond. Out o c e a s h t hen wi rec o a h ic wh n e r s a nd t he t w o c o n t a i n e r s n o to c hen put in e t r s a t c je t i d n a ly ep de e r a t— n e m elop v e d d n a on— i t i n g c e u n i t on c r u o f o a c rodu p e h t ely t le m co i r e p x he e le. T b a he t on t d e c t ar e p l to looks in r e t n e n o i eract t in d mp wi h t h e p h y sica l - w or ld t h ro u g h o u r bod ies. T h is t t t e n- on e c o n t a i n e r a nd sa y s, “ I s e e a dax in he r e . ” T he e x a i n t he s t udy m i r pe t on- he c in t t c bje he o ild t h he c w o ot sh es n do r e t n e ti on to t h e body ’s ro le in c o g n i t i o n i s s e e n L r f f o k La 2002; , k a h asc K & g r Glenbe (e.g., e g ua g n la of tai n e . & a te r th e o bje c t s a r e r e t r ie v e d f r o m t he c o n t a i n- p n i 1999), on, s n h Jo vin r o a g m e m y nd l o s lem b ro er s a t a h t e c i t o e is a dax. N h on ic d wh e ild is ask h he c nd t in- nd a n o i t n e t t a t oin j n i . d e ienc r e p x ly e t oin r j e v e n e r e w t c bje he o nd t a e m he na t 000), 2 , y e v i p S & n o s d r ha ic (R Ho a hen ca n t he c h ild j oin t he o bje c t na m e to t he r i gh t nd in n e w a p- w t 2004), , d r a l l a B & u Y ( g in ead n r io nt te ild t e enc g i l l e t in l a i c i f i t r a l g as 24 n u o o en as y r w h c t a h d t e a bje c t? B a ldwin sh o p roa c hes to a d e v elop m e n if t he na m e to r e f e r to t he un - is, t e r u uld do t o hs c nt mo erat t i l is h t in dea h i y e k A 001). 2 , r e i e h c S & r e f a fe (P k i n g a is m i t e m he sa t t a t e ck he bu en in t had be t a h t t c bje o n e se t h e t c o g n i t i o n d o e s n ot jus t r esi de in or g a n ism s, but w o is? H h t o d n dre l i h c d di w o H . fered of , s wa me na he t n a ( d l r o w e h t h t i w s n o i eract t n i ed l p u o c eir h t n i s e d i s re if o i t h a t is l s o t h e hea r t dea f Gib s o n i a n ap p roa c hes to a on, s Gib e, e s on; i t ep erc p 1979). On ica v elop m e n t a l imp l t i on is t h a t t he phy sica l e de r a e r v es as a c r u c ia l m e c h wo n ism in de v elop m e n t a l ld s a. l t s e l f. N ot a l l k n o w ess i e d g e n e e ds to be put in to t h e pr oc m o ons. S i t a t en es r p e s, or r ism n a h c e d m e t ica d , de head e b. kn ge ca n be r e a l i z e d ed he body , a fa c t d r a m a t i- owl in t l ly il l u s t rat ed b y p a s s i v e w alk er s . K n o w l ed g e o f t h e ca c. er m o t i o n — alt n a t i n g l i mb m o v e m e n t o f b i p ed al l o c o to a c kn tr ad i t i ona l ly a t t r ibut e d ge ed e n t n r a l pa t t e r owl d. I see a dax in ge n era tor— ap o e a r s to r esi de in t he dyna m i c s o f t w p here. m up d p endul um s ( McGe e r , 1990). S co le e o f o u r in t e l- o e li g enc e a l s o ap p h a r s to be in t he in t e r f a c e be t w e en t e Where is the dax? c body a nd t he w o r ld. T he p hen o m en on o h a n g e b l ind- f h t n ess is o f t en c onc ep t u a l i z e o le do n op e P . y a is w d in t ls o t is r re me mb er t he de t a i gh f wha t befor e t h e i r e y es i t f Fi g he c u re 6.14 A sc hema f e o s r u o t ic i l l u s t r a t i on o m be e y do n ot n e e d to r e m e h b e r wha t t h e y ca n e t caus e h t s in t he A-n ot-B t a sk . Af t e r t he dela y , t h ev i d i n g bo x is en ely look a t a nd s e - m i m i oë, 2003). S & N n a er g e e (O’R g t a n t to r e a c h a nd s e a r c h for he infa mo ve d for w a win lo l d r . y dden to i he h t ook la r l y , B a l l a r d a nd c o l lea g ues ( B a l l a r d , Ha yh o e, P , &

31 288 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 288 n a m i Dy de m o uld y o u c on- i r e p x e e t. On n e ev e n t a l t a sk t h a t sh o w s t h is is t he “ H o l - l vic a i c i f i t r a n g a in build e r e e w on e, w lyw st e v i p nd S on a ds r a h c i R f s o t n e m i r e p x es” e r ua ood Sq y e h t w o n ld k u o c t a h is, t h ld do t u o c t a h e t vic a de ct ru es bje o n d to a ie l p ap h t es wi m i t t en r e f e m na f i d t d a e t en r p e r e le w op e (2000). P en es r ly p l sica y h ot p n t c t when l t me wa s of fered ? - a c o al i t a p s t c n i t s di a m o r f h c a e , s o e d i v t n fere f di ur fo na he ti t e r e s w t c he subje , t en es r p s o de vi o n h t wi , r , y r t t gh i e m on t a h ons t i t u l o s Th er e a r e a n u m b e r o f e on. La t e - ud in g r e a s on in g a nd r e m e m b e r in g abo ut wh ic h o b ask incl d abo ut t he c o n t en t o f t h o s e vi de o s. E y e t r a c k i n g o e ut o f wh ic h c o g in r e nsw when a d e le look n t a i n e r s a nd abo ut t he l i k ely m s ca t c je ca m e r a s r e c o r d e d whe r e p e op t h y e f h when t s r t hes e q ues t i ons a nd t he r esul t s sh o w e d t h a t o h e y s y s t em- e k ea sp f ons o i t n e t in t i es. Sm m na r e f w e v e r , t h a t y o u n g c h ild at ica l ly look e d in t he d irect i o n w h e re t h e re l e v a n t infor- r en s o l v e t h is p r o b lem sh o w e d , h o t i h simp le r w a y , e x p loi t i n g t he l i n k be c w e en o b - d. e t en es r usly p o i v e r en p on had be in a mu t ma h is - l a (B s r e t n oi p c i t c i de f o dea i he t o t d e t ela r all s i s Thi h je c t s a nd lo ca t i ons a nd spa c e. Wha t c ild r en do in t a la n a t ly impor l ona i t nda u nd fo ep a a de f e o us e k sk is ma ta r d e t t l., 1997; H u r for d , 2003) a n d i s o n e s t ron g e x a m- i he w in t y t i r ula g re s- ly d l a u t ep c r e is p t c bje o l a e ld: a r r o pl e o f h ow s ens or y - m otor beha vi or s— whe r e on e looks, t i on; i t t ti ng uishe d f r o m ot he r s b a s e d on i t s u n iq ue lo ca wha o n e s e es, whe r e on e a c t s— c r e a t e c ohe r enc e i n o u r it ys c e v i t i n g o c d e t ela r r he t e g o t g in bind em, t n s io on- gn co mus t be a d i f f e r e n t p l a c e f r o m a n y ot he r o bje c t. T he k e y c t inc e h t f o t is d r he ot m o r f e t a r epa s hem t g epin e k nd s a on- nt te t fa c tor in t he B a ldwin t a sk is t h a t in t he f i r s t pa r e me i r e ly p ex r essa c e n ot n s e o d e on sum, n I s. nt te e d mu c h pr o c e d u r e, on e o bje c t is p r es en t e d on t h e n l a t n i he c on- to s m e t y s l ia t n e r e e- r p o s l e a r a s r e n i a t n o c t. T he lef r on t he he ot t , t h g ri inf or e g d e l w o n k t n a v ele t-r n e nt co s he na nd t y a a t e m he sa t ed t n se he r e is a e a sie r w a y ; b y w n ect o n e i d e a to a n ot he r . I n s t ead , e h t h t d wi e t en es r is p e m ’s ex me nt er on, i t ca e lo on . d l wor t a h t to s r e t poin ri body e h t nd a d l r o w he t g usin t or a t e ck e bu to on g in in look pe o l v es t h is t a sk b y he r mp a x for e le, on t i gh t. T he c h ild s ield p m e f o s An em e r g i n g f bod dea i e hes t to t n e n i t r e i- m li nk i n g t he na ca- lo t a h t h t wi d e t a i c o ass t c bje he o to t e g bot ic s ( Zla t e v & B a epi k en ius, 2001). is nt me l n e e t i c r o be ti e k n o w t h is is t e on. W caus e w e ca n m o d i f y he cas o r f s t esul r ield f is Th e- d f o t en hem c o r p ap r l ua mut e h t m l t pe ri me nt in se v eral cr u c i a ex e le, on p m a x e r o F . s y a w he elop m e n t a l p s y c h o lo gy a n d r o bot ic s, wi t h a f o cus on t h e v r do e he r t t e s to g t c bje dden o i or h s - e n i a t n o c d e e ot n es n i p pr o l o n g e d e g e n e t i c p r o c e s s t h r ough w h i c h i n c r e a s i ngl y a sul h on t t c bje o t e g r e he t t t en es r ely p r e n m e ca t. On r g e i n t c e s y st em g lex mp o c e r mo nit i v e str u c t u r e o s e m e h t i h t wi y a l nd p end to a t t en a r ild h c e v r e h nd ha t a gh ri t e, s w t h t h e p h y s i c a l a n d s o c i a l e n n o i t c as a r e s u - i l t o f i n t e r a c bje t on t he lef t a nd ha v e o r e t c a r t s he d t t en es r hen p t i e n e t i c r o bot- & ronm vi v t la e (Z t n e B a l k en ius, 2001). Epi g h l ild r en a t t end to a nd p l a y wi t ch i t t h e r e. T hen, wi t h a l ic s a l t n e m elop v de to t n a v ele r deas i y e k e e r t zes hasi emp h o bje c t s r e m o v e d , wi t h only a n emp t y a nd u n ifor m t a b l e pr o c ess es in bi o l o g ica l a nd a r t i f i c i a l s y s t em s: at i ’ n dre l i h c direct n a c e n o , w e i v n o ace rf su t n o i t n e t s of en t dim o b em he T 1. h e sy s t e m t t e r i gh t a nd o f f e r t he na m e (dax) or to t he lef t a nd o f f he r s e n d e tuat si s It 2. n e m ron vi en l a i c t nd s l a sica y h in a p s o t n e t l iab ly l i n k t h e ly a onsis en c r ild e. Ch m he na t e nd r ene pig e d e g lon o r A p c na m e to t he o bje c t t h a t had be en a t t h is lo ca t i on. o r l p ta en pm lo e v e ic d h g u o thr s s e t 3. asin g c h ild r en ’s s o l u t i on to t h is t a sk is simp le, a i wh ic h inc r e un gly m o r e c o mp le x c o g n t i v e s t r u c t u r es Yo f t o esul em as a r tr ick in a s ens em e, t h a t ma k es v e r y y o u n g c h ild r en look h t ons wi i ract e t in e r g e in t he s y s t a e t n a h t r e t r sma t he p h y sica l a nd s o c i a l en vi ron m e n t y p e r hap s r e h l ly a r e. B ut i t is a t r ick t h a t k wil w o r k in ma n y t a sks. Lin l i n g o bje c t s to lo ca t i ons n e t at g n i irect o n t o l i nk re - i o t o t h at l t o n c a t i a nd t hen d ina r y de v elop m e n t a l r e s e a r c h Th is n e w i n t e r d isc ip l c la e d e v en t s to t h a t o bje t t p r o v i des a n eas y w a y to bind o o t t e g Pia m o fr s si ene pig e m r e t e h t s w ro bor ely s p r pu c l., 1997 o bje u- le ro op e ). P a t d e r a l l a B es ( t ica d e r nd p s a t p r v elop m e n t de t e r m in e d de r n o cti a r e t in he t y b ily ima u t s e , g usly o i onsc c n ly u t n e r pa nd ap , a ely n ti e on h t e wi r a t t w e e n t he or g a n ism a n d t he en vi n ha t r he ron m r , t n e be ea ha but , y tor t in a s is on g nd when sp rot he p t f o g n i k a n es do ield f s i h t n i h t i w h c r ea es r t en r r Cu es. n ge by t o o y t h t he ot he r ha nd when sp ea k i n g wi f t he a n t a g o n i s t. B s jus or ens ze hasi al ci o s o s al t u b s n o i eract t in otor im emp t i on, t y e h l i t n e t t a f on o i t c e r i nd d es a r u t s e nd g ha n k n - ess es wi t h pa r t icula r a t t e oc t i o n t o t he i dea s o f V y pr er s . A m er i c a n S i gn L a n - tor to t s a in ts en ev he ch y a ract h g c i t e n e epi in t wi udy t s f o s topic t en r r Cu (1962). go ts ky h gu e for ma l ly us es spa c e in t g is w f a y in i t s s y s t em o a ro bot ic s t y- t s h o uld be o f in t e r e s t to de v elop m e n t a l p s ha o m e n as a m e c e spa us o s l le a in op e ns. P u o ron p g look , c i n n ch og is t s a r e j oin t a t t e ol t i o n ( Björ n e & B a l k en ius, f a p a st a in t he direct i o n o h t r e b m e m e help r o t t n e v e t a d o b s e r v a t i ona l 999), 1 n l a ha c S ( n o i t a t i im 2004), ,

32 289 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 289 Dy a m i c Sy n y Cha a t enb y , & r a c t eri ze t he Beha v i or a l A t t r ac t or St at e s . G a , r G aum, sb h c u B l, zea ea Br ( g in n r lea t Bl t n a t is impor t e, i g n a h c f udy o to g a s in inn g e be efor B 005). 2 , g r be m u t s le nde u e iab r a v e v i t c l l o he c t f es o t a t s d e r r e ef r he p nd t a r P o t y r o e Th om Fr s e: A Dy nami c Sy ste m c i ract fere at f fere n t poin t s in t i m ons. i it d n o c t n e f i d r e v nd o a di proac h c r a Ap s e R o h t e ud t l s ona i t c e ss-s o r c e r ere H e- us y r e n be v ies ca is whe t es, i m i t e m o ul. S f r g t h o f T he s t d le il w sk o h w o n ul to k t helpf s o is m a dyna m ic ap p roa c h is i t s g n r ea t g e n e r a l- e sks u adul t s or c h ild r en p e r for m t he t a nde r v a r yin g c on- y n ss ma ro c on a i t ica l p ap l a i t en s pot t us i h nd t a y it c de- a i t , or spa y c a r cu c , a d e e g sp in r e f f i as d h c ons su ti di do ma ins a nd le v els o f a n a l y sis. F or ins t a nc e, a dyna m i l n g abo ut p ap a e r o is m t n e m elop v to de e h y o t f o y t i abil t he s le t mp l to sa ica t i r c a w o s l nds. It is a ma h c roa f t h in k i v y r o e h ic t f i c e a sp n , p e r s ona l i t y les esca m i e t t a i r rop p es, to pick ap g a t n fere f di at m e st sy f, sa a h t t n e m elop y de o elop a r e v e w o g. H in on as e l r ma for f on o i t uisi q c he a or t in a de v , m e n t a l s t udy . If t h e r e a r e bi g d i f fere n c e s be- dyna m ic ap p roa c h do es su w e r f ul r e s e g r c h g es t a po e tw e en 8 a nd 12 m o n t hs, for ins t a nc e, a nd v e r y l i t t l a st rat e gy for in v e s t i g a t in g pa r t icula r do ma t e f i r s ch an ge af te r 12 m o n t hs, in t ensi v e s t udy w o uld be d i - ins. W s in a dyna m ic s t r a t e g y , sum ma s i ze t he p r inc ip le s t rect ed t o w a rd t h e t i m e o f ra p i d t r an ep i t i o n . r d to h c roa p is ap h t f on o i t ica l p ap n e a t a r t s u l il e hen w nd t a As w e m e n t i o n e e a r l i e r , t he s t abil i t y o f a beha vi or a l v tr tor is inde x e d b y i t s v a r iabi l i t y a r o u nd a n a ac e r a g e at t he de v elop m e n t o f a f u nda m e n t a l m otor sk il l. n e h o w q uickly t h e va l ue: H o w e asily i t i s p e r t u r b e d a Re ca l l t h a t t he ess en t i a l issues a r e t he s t abil i t y o f t h d a - a t s a o t s n r u ret m e t s sy g f n o c e l b u rat i o n a f t er p e r t u r b sy st em, as inde x e d b y t he beha vi or o f s o m e c o l l i e c t i v e mpon ti on. P e r for ma nc e t ha t v a r ies g r ea t l y w i t h i n t he sa m e in- me asu r e o f t he mul t i p le c o en t s, a nd t he c h a n g es in t st i t y o v e r t i m e. A c c o r d i n g to dyna m les, ip inc r ic p di v i dua l a nd is ea si ly t h ro w n o f f c o u r s e ind ica he t t ha t s e abil nc at ac tor s t a t e i s w ea k . C o n v e r t ely , when p e r for ma tr e t ra nsi t i ons to n e w for m s in v o l v e t he lo ss o f s t abil i t y t h a s all y f r o m di f fere n t o s e g er nv ns. At r e t t d pa ze i n a g f-or l e w s e n f on o i t ma he for le t enab n st a b l e v a l u e , e s p a eci co s ma y r e v e a l nd a s tor c a r t is d f o e enc es r p he wh n i ic d n a ons i t i ond c l ia t i in h o f t h e i r c o mpo- t t ra nsi t i ons, s y s t em p ll s is a c o n t ro l pa r a m e t e r or a c r i t in en l elem ica t ot he r nt e r t u r b a t i ons, t h e a t t ract o r w e ne is de ep . t u h (1994) o t i nd Sm helen a e. T g an ch e - x e f ies o r a s d e in l l ic pl e h d in t le i a t e de r h a ic n, wh g desi h c r a e s e s for r ep t s t i De sc ribe t he Dy n a m i c T r aje c t or y o f t he C o l e c - i m ons. i t c e s g sub win o l l fo ti v e V a ri a b l e . T he hea r t o f a dyna c a n a l y sis is a e map o ia c u r le. A c iab r a v e v i t c l l l o he c t f o y t i abil t he s t f h t t ic s m on in a dyna i t assump e gy is t r a t t he ind i v i dua l a Ide n t i f y t he C o l l e c t i v e V a ri a b l e o f I n t ere s t . In a t ) a nd a n y beha d or a l c h a n g es o v e r (or t he fa m i ly u n i dyna m ic s y s t em, on e or t w o v a r iab les ca n be i den t i f i e vi nda u he f t on in e r a e m ti tur m m o . It is c udy t s f o t e t he de g r e es o f f r e e d o m o f a mul t i d i m e n- i n u l a t n e m th a t c a p s t h ild r en a t t n e m elop v de ies to c t s l em. I ud o mpa r a e g r o u p s o f c si ona l s y n a de v elop m e n t s t udy , t he g o a l is to de- e c l l o is c h es in t g n a h he c ibe t r sc t i v e v a r iab le o v e r t i m e . e t ela e-r g a m o r f t n e m elop v e d er f n d an s e g a t n fere f di d i e c n or in e m i t r e v le o iab r a v e v i t c e l l o ind a c to f y ot eas It is n fere f di o up p e r for ma nc e. S u c h c r o ss- r e g g a r e v in a s r a n ea r , c h a n g i n g s y s t em. P e r for ma nc e m e asu in es a t onl e h g t in t i im for del t n a t e impor r ies a ud t l s ona i ect s t e r a g e be- e h ut t m abo ot infor nn ca y e h e, but t g n a c f ies o r nda u bo on e a g e ma y n ot ha v e t he sa m e m e a n i n g a h a la t in onl n ons i t ela he r nd t em, a t s y he s t f o s t en mpon o he c e t caus l i t en he ess e. T g n a h r c ende g en t a h es t ess oc pr a r ea a be g e. B ut t h is is a p r o b lem o f a n y s t udy l in pul s r o ract t t a t a h ns t a e s m em t s y ic s m dyna f o e r u t na t w e en t hem, c h n ov e i t a v i t o l m ica t e r o e h he t r t v e t e, wha m i t r e on. tr aje c tor ies f r o m a v a r i e t y o f in i t ia l po si t i ons. T h i s i i v e v a r iab le is t h a t c t n a t mpor i e On r t e r i o n o f a c o l l e c t me a ns t h a t c h ild r en ma y end up wi t h sim ila r beha vi or s e r v a b l e v a r iab le, n , t a it sh o uld be a w el l-def in e d a n d o b fr om ve ry di f fere n t s t a r t i n g poin t s. At t he sa m e t i m e o ons t r u c t. Whe r e a s “ n um be r o f w or ds n t h e l e x - de r i v e d c ev en v e r y sma l l d i f f e r enc es in t he in i t ia l c ond i t i ons ca in u a g e p ro c essin g c a- ic on” is op e r a t i ona l l y s p e c i f i c p “ l a n g lead to wi dely d ispa r a t e o utc o m es ( F i g u r e 6.7 ). G r o u , i - c a n n o t b e def in e d o u t s i d e o f pabil i t y ” i s n ot , b e caus e av era g e s ca nn ot d isa m b i g ua t e t hes e pa t h w a y s; t he u n t a t n me ot he r e onc r e t e beha vi or a l m e asu r es. I n s o m e be- so ly nd u o f o r y be p s ma ism n a h c e m l de r lyin g de v elop m c p p rop r i a t e c o l le c t i v e v a r iab le ma y r). ila ly sim ab k r ema (or r t n fere f di ha vi or a l s t ud ies, t h e a l a n a us imul t s a n e e w t be g n i m i t he t — hip s on i t a d re a be Th us, u nde r s t a nd in g de v elop m e n t a l t r aje c tor ies r e - fere n t p a r t s t h e ely t a i r rop p ap f t ls a dua i v i r espons e, be t w e e n m o v em en t s o f d o f qu ir es lon g i t u d ina l s t udy o f ind i g r i n g a s o c ia l d ia dens e sa mp l i n g in t e r v a ls to cap t du r e t he t i m esca le o f n i k a n t r u t l ua mut r o , body lo g ue. u

33 290 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 290 n a m i Dy a ask e w be- whe t h e r t h e s h i f t f r o m n onc ons e r v a t i on to c ons e r - t for ins , y nc infa n e. I g n a h c t nc n a v ele r e, when n i c l A odel. m he rop t as t a a y b d e in la p x e e b n ca on ti va ons - t a v r e s b ekly o e en w v e , ily da t s o m l a r a e p s ap or vi ha t nsi a r l t ica t i r he c iss t f o r be um n a for y m ma e denc vi e g ron t s ind f ot n d i d y e h t gh hou t nsi- e, t f i r in l e t ons. La i a r s y be r ela t i v ely p r o lon g e d a nd mu c h less f r e- ti n i s m te s y s f o s e x e d n i l fu e s u e ar g a l f e th , s g a l f e th ons ma i e f Th . n o t i s ran t l a g s ar e : q uen t m e asu r es a . d e d e e e n r r Lon t u d ina abil- g l s t ud ies a i e desi g n e d to p r o be t he s t str on r o c l s da Bimo • r e h t i e is e nc ma for r Pe n: io t u ib e di e v e w o e; h m i t r e v o s m e t s sy f ly t o y it l e e r r e s t in g a a e w , r m e f f, wi t h o ut in t r or o e d ia t e for m s . m w t d t r e v s o em st i e t ela o r esca les. T h e o b v i o us on e is sy m e. Less e x p l ic i t is v elop m e n t a l t ch an ge ov er ag i e or de o l t y ; i n t e r m e d i a t e oda bim i t d e t ela R : y t i l i sib s cc Ina • e r i m e n t a l t a sk . B y ass essin g p e r- t he r e a l t i m e o f t he e x p e h nd e l b a t ns u e r a y e a t le, essib c c a ot n e r a es at st r ia ls a nd c ond i t i ons wi t h in t h e for r v a e r i o us t v ma nc e o ra l y see n . re e-to- t n i he m ut t ask abo e on, w u s l a t n e m i r e p x gle e sin essi m o r h f tc le swi p o Pe s: en jump Sudd • - n m to a e for on i hin wi em t s y t f y o tor s t he h us, t h s. T c i m dyna te nu mi he s es. ot he r r api d ly wi t h o ut in t e r m e d ia t e s t a t a n t. Ef fect the ex p e r i m e nt a l s e s sio n s y be v e r y impor t ma for r e e h e on t nc ma • Hy st e r e s i s : T he dep endenc e o f p a ls a nd t h e i r or de r a r e a l s o inde x e s of t h e nu m b e r of tri a ely pas t a i d e m im e le, r mp x or e e. F nc ma - for r e p t y e n a h e c nc ma for r e es p o . D g t i l abi t em t s sy e h t of ’s s i spons es m i gh t be d f fere n t when t he t a sk is sp e e d e d ons, or is i r te r ma n y e p e t i t i af t s t ab le wha t e v e r t he p r e- t mpa o ds as c e e sp f e o g n a gh a r u o h up t r to when i d e r ce di ng t a sks? r a e m e. he sa gh t u o r h t n w d do e w is slo g n Pr o bin g t hes e t w o t i m esca les is impor t a n t be caus e s i Di v e r g enc e : T he s y • t em ma y r espond d f f e r e n t ly to l a e en in r v t i l f e: When th ey mus t be in e x o w r e t ly in icab r n t r o l v a r i a b ch les. g e s i n di f fere n t c o an y poin t in t i m e , h nd c s a t n infa ve er obs r we ild en a t a n g s ine e of l enc g r e v Di • r r e s t es a g su y t i r ea in onl N : e s n o p l e n- r lon ei th h t bo s t c e f e or r vi r beha ei th g-t e r m de v elop m ro th sma l l c h a n g e in a c o n t a l v - a r iab le or p e r t u r b a a t sk a he t in t h t y wi tor s i e h t a i d e m im r i e th d an y tor s i h l ta . ti on ca n lead to a la r g e ef fect a h c l a t n e m elop v e, de wis e k on. Li essi s il- h t c c e l f e es r g n l r m i- • Fr e f o y r qui ecove r d ye a l ibr ium : De o m e a r l ie r t e x dr ’s r e p e a t e d e v r yda y e en p e r ienc es, wh ic h t hem s e l v es e i t a elax w r , a slo gy lo no on. i t a b r u t r e r a p e t f a e m i on t e m t e p r for ma nc e dyna m i c s. It is us ef ul t h e e efor r odula s onsi i or h s, namic insic dy tr in ’ s- t n ipa ic t r he pa r t de to c o • An o m a l u s v a r ianc e : In cr ea s e d a nd u n usua l v a r . y t i l iabi he e u a t n e m i r e p x l h t ic nd on wh o r g ck a he b ies, as t tor ram e ter s n t i f y P ote n t i a l C o e n t r o l P a Id r insic dyna sks a r e impo s e d: T he in t ta m i c s a r e t he p r e- r e v i he pu T t he c l l t f o s c i m o he dyna g t pin map f e o s o p e fer red st abil i t y la ndscap es, g i v en p r e v i o us h i s tor y a n d c o isc le is to d iab r va s c em t s y when s r e or g a n ic c ond i t i ons. v h a t x e he n e. T g n y st r t a e. Wha g n a h c e e h y t nd wh w a o ut h nd o ep is to f i beha , c i n a g he or t io t a h s t tor c fa l a t n e m ron vi l, or en a Ide n t i f y P o i nt s o f T rans it or n . T ra nsi t i ons ca n b e vi h e s t if sh l a t n e m elop v r de ende g en d r o t w s r i f e ? s t h a c u , s s m r o f w o n s t t f hi s e v i at t i l a qu t nsi a r t a do to y t i abil e h t or en spok t gh hou T is n n g desi l a t n e m i r e p x ul e f e e e d or , ask t e enc r e inf e v i d to i den t i f y n s s. I r e t e m a r l pa ro t n o c l a i t en pot o m e cas es, t he po ssib le - th e y c a n b e q u a n t i t at i v e c h a n g e s in t h e c o l le ct i v e v a r i o y ac a r u acc e h t or d e e sp in t s k . - c a r le, p mp a x us; for e o i v b ly o r i e fa r a e g n a h c f o s t en ag f i h s a as h c su le ab t a f ons a n a r t n i s i m e t s y s a when e caus e b l ica t i r c e r - i t nsi ra T ti ce fa c i l i t a t es lea r n in g to r i de a bic y cle or doin g a r i t h- m s t n i on i t si d a d e i f i t den i be n a c e g n ha c f o s n ha c e me ti c. Bu t, in ma n y ins t a nc es o f de v elop m e n t a l c h a n g e , ism em t s y s le ab t S d. e t ipula n ma t en v nd e es a ess c o r l p ica t i r he c t n d us a o i v b o n o e n r a s when only ; e g n a h c ot n o d s ohe th o f t he c o mpon en t s is w e a k en e d a r e t he t only in- s r i f t em a e s t a h t s t en mpon o be in c d e y inde ma e c e r enc n e m. t s e d. W e look r e v as to be o e c la onp m m o c o l, or s a t den ci co mpon en t s ab le to r e or g a for i ze in to a m or e s t a b l r s ibe r desc , g in n r lea d d gbi n o an d Kin g ’s (1996 ) s t udy o f m str a t ca s a n w o n k s i c dyna f o h nc ra e b Th y r o he t e h p o mp w- e c t i on, is a g ood e x a r s le: F ema le c o in a n ea r l ie f r o m w on e h t i sudden if d e n r e onc c sh y l r icula t r pa is t s s o e c i t ica l de t e r m ina n t r f bi r d s ’ subt le win g f l icks a r n o t h e r . T hes e sudden jump s a r e ass o c i a t e d for m t o a le is T m n t. A n ot he r e x a mp e helen a n d ma le s o n g de v elop o f wi t h a n um be r o f ca t a str o p h e f la g s or ind ica tor s t i t i on o f t r eadm il l s p ep pin g in in- Ul r i c h ’s (1991) desc r d iscuss e d ea r- sh if t s wi t h o u t i n t e r m e d i a t e for m s . A s r e t s in t r eadm il l s t ep pin g w e n e fa n t s, whe r e imp ro v e m a s a nd M o r lena (1992) ha v e ap p l ie d a li er , v an de r M a an s l a t e d t o o v erall c h re g e i n d o mi n a n t muscle ton e. e r o y to Pia g t i a n c ons e r h t he rop t s a t ca v a t i on t a sks to e

34 291 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 291 Dy a m i c Sy n dens ro iab les— in l o is t r o l c sa a b f les o mp l sa ina d u t i g e lon r d e t c le a n o c t n l v a v ele r r e v o isc y to help d a e w On t e asu r e r m i e h nd t s a t h e r s. C o r t is o l le v els in infa n t s de- t n infa o in add i t i on to infor m e d g uess es— is to a c t u a l ly m ch h ed s a cre e h t h t g wi lon les a iab r a em v t s y s f o r e b m u es in a n g s, m h t y h n r ia cad r i c w o ot sh n d di d an e g a t i an w t c h infa n t had g r ea t v a r iabi l i t y f r o m m e a s co but ea ec ti ve va r iab le. T h us, if t he beha vi or o f in t e r e s t is, u r em en ll en e em r asu e to m i v a r iab le c e l l o s, a c t n l in infa a v ie r t e r t c bje o y l l dua i v i ind e r e , w ely s r e v v n o s, c r sa y , e h t o t. M t ve mi g h t b e c o r rect ret r i e v al s o f a - n i an h t re o m r e h t o h c a e m o r f fered f i le, but d ab st ry hi dden o bje c t. B ut be- v . c e l l o e is a c nc ma for r e p l a v e i r t e e r caus e o f ma n y t t n to infa t n fa i a h t ma y c o n t r ibut e to c h a n g e, indep en- es t ess c o r r p ot he den t , i hen c on or Ma n ipu lat e P ut at i v e C o n t rol P a r a m e t e r s t o E x - onc o m i t a n t m e asu r es o f visua l a t t e n t t mo ry , for ins t a pe nc i m e nt al ly G e n e ra te T r ans i t i o n s . Map pin g t he e, ma y r e v e a l c o r r ela t e d jump s r of me c v l a t eaus. mpo- o c r e h t o d n a le iab r a a e v i t nd p le l o c e h t f o s dyna m i c ne f s t ls poin a e v e le r iab r a v e v i t c e l l o he c in t y t i abil st In o nt s only p r o v i des su g g es t i v e a n d c or r ela t i ona l e vi- t h (1997 ) g t ra nsi t i on. T h us, Ge r shk o f f-S to w e a nd Sm i denc e for po ssib le c o n t ro l p a r a m e t e r s. M o r e c o n vinc in a f t map p e d c h ild r en ’s w o r d r e r i e v a l e r ror s a s a f u nc t i on o is to ge n erat e d e v elop m e n t a l t r nsi t i ons on a r ea l o r d e- a r e t c a r a h c h t w o r g y r cabula o d v api he r t od i r e he p t f ic o t is v elop m e n t l t i m esca le b y ma n ipula t i n g t h e s u g g es t e d is t v f o ons i t simula e hes T s. r e t e m a r a p l ro nt co elop m e n t a l l dua i v i e, ind m i de h t g n i r hs. Du t n o nd 24 m en 15 a e w t be y t t em na m es sh o w e d a s he t e caus c be on i t nsi a r t f o s t poin at rk wo ge an ch ch i l d r e n ’s r e bje n o w o n k f o l a v s e i r t on. Ch g f fect ed b in be to le m a is us h t nd a e l b y en r ild a i t up sr i d f od o i r e ek) p e w - ief (3- to 6 br a t s t o n is enab o n l-k l e to a w t d poin l u wo ons. r v t e in en t i y e th t a h ) t t ca , y (sa t c bje o n w o had na e d c o r rect l y m a m i t y n e s i n t h e a st an d mi s - m t e nc a t mpor i l ica t c a r p nd a l ica t e or he t h bot f o is It p ons a r e e f fect i v e i n a d e v elopin g e i t (e.g., du c k ). T h is t r a nsien t d i sr up t i on in le x ica l m na kn ow when in t e r v en t i r sy mly en to r ild h l c dua vi i d in ind e t ela ly r l a empor s t a ess w acc en- i f o s is or vi beha d ishe l b a t es when d n a em st o t c rodu p d r o w w e n f a e t a r d e as e r inc an S ead H e h T t. icul f if d s i n o i t n e v r e t n i t ha t d he enc tr r t g n i t es g g ons, su i t p am x e r o f , ram g o pr he le x i c on is th at t he r a t e o f n e w w o r ds be in g adde d to t l o o h c s e r y p l r a e e h o t t d e t ge r a t s a w le, m r o n t ro l pa r a m e t e for t hes e w o r es, ess c o r p l a v e i r t e r d ye ar s b e caus e r es ea r c he r s d isc o v ered t h at e n r i c h he c e n t t i c r lde o h t i w t en pot less s wa ld r e n w h o s e e d u c a t i ona l l ica x in le e g n a h c l a t n e m elop v h de f o r e v i r he d us, t th an d, eady is i r e p e v i t ensi a e Onc d. e m for od r l a e r e w s t habi acc ess p r o c ess es. s d e in m r e t Tr ad i t i ona l l y , v a r iabi l i t y in beha vi or a l da t a is a r e - de , d e v elop m e n t a l c o n t ro l p a r a m e t e r s c a n be h i f i c e p s g n i id v o r p y b d e t s te nt e r v e nt io n s t i a t m a y e n - se ar ch er ’s n i gh t m a r e. T oo mu c h wi t h in- or be t w e en- c g n a h c l a g ende r lon g-r a n g e beha vi or ea- r l ica h t e or F . subje c t v a r iabi l i t a y sw e m p s a n y e x p e r i m e n t a l ef fect s . e n . s t en m h ic enr y l l usua e r a ons i t e e k sks to ma a e t s o o h ely c t a r ibe s del r e h c r a e s e us, r Th s ons, t hes v i n t e r he e t op le look a l i k e. B ut beha vi or in r e a l c h ild r en is n o In t pe x a mp le d iscuss e d ea r l ie r , Ti t z e r e t a l. (2003; t. ile a g a r ly f b a t o is n t , i t ’ s t n infa enden e t a r ele c c , 2005) a r e h & Gass t i a h e t lik Sm t dep x e t n o nd c se e a l s o d t n o c t n e r nspa a r t m o r s f t c bje e o v e i r t e ies to r t i abil Ab il i t ies s e em in gly c o m e a nd g o, a nd e v en sk il le d s r e n i a adul gh es to x glas bo i x Ple f y o t e i r a a v h t hem wi g t in id ov pr n a Y ( e m i t h c ly ea t en r e f f i sks d a m t for r e t p i m s t by i he r , 2002). Dyna m ic s y s t em s t h e o r y t u r ns v a r pl ay & Fisc wi t h a t h o m e. N o r m a l ly , 10-m on t h-o ld infa n t s ha v e - sk o a le t gly simp in em e he s t h t wi y t icul ff s- y ic s m dyna n g. I lessin to a b e in g r u o a sc m o r f y t i abil di r g a vin ie r t e f o te th eo r y , t he m e t r ic is n ot whe t h e r a c h ild has s s m e m x is he bo t f g o in en he op x when t glas bo i x a Ple m o r y f to ep t. Ra t h e r , as s y s t em s s t n infa , w vie l l u y is in f he to gh t u o h t l de. A he si on t st at ic abil i t y or u n c h a n g i n g c onc eir ela- xi e l P e h t o t n i k ac m s — t h g i s f o e n i l direct - h t n i h ac re ar e a l w a y s in f l ux, t he impor t a n t d i m ensi on is t he r ot in nd n a glas— x v e r t i m e (v a n a- e l. r a t e r e z t g. Ti in en x op he bo to t t o ti ve st abil i t y o f beha vi or in c o n t e ne lo h t h t e wi ienc r e p x e d e ck s la t n e infa caus , be t a h d t e so Ge e r t , 2000). N e w m e asu r es o f v a r iabil i t - e w r y l a a r t f ies o t r e rop p nspa l r usua i e h on t d e i l e r y e t or he sh t r e v o e g n a h c f ies o tor c aje r e t e s to s er ch ar se h t , y enc r on- e esca les o f p r o b lem s o l vin g or o v e r a lon g e r de v elop- y s e e. T he c m ti pa t t e r n o f r e a c h i n g s t r a i g h t to wha t t h for de v elop m e n t a l c h a n g e w a s t he r e or e x a mp le, Y a n a nd Fisc he r (2002) - me nt al spa tr ol pa r a n. F e t e r m a t n o c d adul ke rac t t n e r nspa s a r t f o g n i l nd ha ed at pe t lea r n in g a n e w c o mput e r p r o g r a m a n d g in n r nd lea a s r e n i t u d he c a e ot r gh but n o r h en t e uld be s o c t a h s t t c bje ut o abo fo u nd t h a t he p e r for ma but , d e i r a on v s r e p h c ea f e o nc v th t he pa s t t e r ns o f v a r iabi l i t y d i f fered b e t w ee n n o at i c e th ro u gh. T he e x p e r i m e n t e r s p r o v i d e d 8-m on t h-o ld in- x nd e o r a t e p fa n t s wi t h v a r i e d t r a nspa r e n t c o n t a i n e r s a nd to ld t h e s. A l s o, D e W e e r t h a nd v a n Ge e r t (2002) c l-

35 292 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 292 n a m i Dy y pa t he c o n t a i n- r e n t s to a l lo w t t h e i r c h ild r en to p l wi a vi de t r a i n i n g , enr ic h m en t , or inc r e as e d pa r e n t a l sup por t h u i p e to sh o w m o r e adv a n c e d p e r for ma nc e; t er s for 10 m i n ho t es t wic e a da y , wi t h n o ot he r sp e c i f c h o s e t h a t in- ins t r u c t i ons. B y 9 m o n t hs o f a g e, infa - n r i t he e x p s in t e cre as e a t t e n t i ona l or p r o c essin g dema nds or o - m a r e f f e t fa c i le in r e t r ie vin g to y s t h a n a me a l g r o up w e less t a r t ons dem l ons wil i ract t s i i or d imul t us s o u g bi e r e m o r n ot ha sk le d a c t i ons. Wha t is d i f fere n t a b o u t a dyna m ic s s- en- e v il d n i o d wh e ag of s h nt o m 0 1 of p ou r g l o r nt co y ri ch ed ex pe r ienc e. Enr ic he d e x p e r ienc e pushe d t he s y e h s in t t n e m i r e p x e e hes t f g o in t a u t he si is t h c roa p p s- s m te a v la c o n t e x t o f t h e o v erall c o ll ect i er e dyna m i c s s o t h a t . s m w for e to n em in t rg c d de le ip inc pr isi In ons ca n be made on when a n d wha t to a sim ila r v e in, Ge r shk o f f-S to w e a nd Sm i t h (1996 ) e ipula i n i n g to in v e s t i g a t e t he d isr up t i on o b s e r v e d in - x us e o i v e r e p h t n ons. I essi s l a t n e m i r e p x in e e t us n ma a d t r wo am hes T . r ie l r d ea ibe r desc e h w ic s, wh ror r l e a v ie tr re rd e p les, t he in t e r v en t i ons w o r k e d be caus e t he e x p e r i - a l on as e r d s r o h aut e t h a t t he d isr up t i on in w o r d r e t r ie v me n t e r s k n e w f r om o t he r da t a t h a t t he c h ild r en w e r e in f wi t h a c c ele r a t e d v o cabula r y g r o w t h w . s t he p rodu c t o pe ri ods o f r api d c h a n g e a w de d wi t h ma n y n- e w a nd u n s t ab le add i- a le x i c on c r o In t he fo l l o win g s e c t i on, w e r epor t on a de v elop m e n w de d le x i - ti ons. If t he r e t r ie v a l o f w o r d t e w ly c r o ta l s t udy desi g n e d a nd c ondu c t e d usin g t hes e e x p l ic i s in a n t r i e v a l is c on is easily d i sr up t e d be caus e w o a dy- d r e dyna m ic s y s t em s p r inc ip les. W e dem ons t r a t e t h a t r h r ela t i v ely u is t g n i r s du ror r e g n n p ract i c ed, t hen na m i na m ic p e r s p ect i v e re v e al ed c h an g e p r oce s s e s t h at w e re e t r i e v a l . as e r c uld de o od sh ri pe t h p r a c t ic e a t w o r d r n ot di s c o v ered f r o m c o n v e n t i o n a l a p p r o a c hes. e wi e e, t n a h c l a t n e m elop v r for de g t e m a r l pa ro t n o he c e er H y A D y nami c S ste m s Ap proac h t o h c a e R o t g nin r a e L eei s at e p e he r t s wa ed e h t y b s ct e j b o f o g n mi a n d an g n e d h-o t on 17-m d e i v o r s p r lds t n e m i r e p x e e hes ild. T ch ac aspin g o b je c t s is a fo u nda t i ona l Re hi ng for a nd g r p n es. m na t c bje o f t o e e s on g i c rodu n i e c i ract p a tr ex wi th h p ep t u a l-m otor sk il l t n h a t is c r i t ica l for n o r m a l erc uma f When t e c h ild r en ’s r a t e o hes p rodu c t i v e v o cabula r y fu nc ab i on in g. N o r m a l infa n t s f i r t s t r e a c h o ut a nd g r c be a n to a c c ele r a t e, t he r e s e a r g h e r s o b s e r v e d inc r e as e d in r e 3- to 4 - m o n t hs-o ld. At h th gs t e y s e e when t h e y a s for ma rd re tr ie v a l e r ror wo n ot for ds but n r o n w w o n k y t, fi rs y e h e poor; t r l a ro t n o d c n on a i t ina d oor r c ei th n t o r ds t h a t had r e g c e i v e d e x t r a t r a i n i n g. T h is t r a i he w i n e of en m iss t h e i r t a r g e t s, a nd t h t i r m o v e m e n t s a r e je r k y i e e w s o es h t a r t ons udy dem st g m nd na n o bje c t s ma y a i g n h an i n d h c mu e m o c be y e d hs, t t n o m w fe a n i h Wit . irect nd less p e r u r b a b le le x ica l t be t he caus e o f m o r e s t ab le a he f mo sk il le d , a nd b y t he end o f t i r s t y e a r , t h e y ca n re y ma f l e s t em i t s y he s t o y t vi i t c he a w t o h d an , al v e i r ret f es as t v shel t e k r ma r e he sup f t f gs o in h ab t gr e r a y e h a be t f de v elop m e n t e o l c h a n g . e he caus ele d b y in sh op pin g ca r t s. whe in 1933) ons for i t en v r e t m in r e g-t as lon e v i t ma ly as infor l ua Eq Th e p io n eer g w or k o f H a l v e r s on (1931, a n d c (1962) t ha t d e t en um c o d has (1991) en t s f o H n o v f o ly l a i , e esp te st in g c o n t ro l pa r a m e t e r s a r e wha t V y g o t s k y e m t , infa n t s ’ o s r i f e s o h t in h t wi n t t hs o f r e a c h i n g ons ca l l e d mic r o g ene si s ex pe ri me nt s (e.g., K u h n & Phelp s, r . h e s b e , o m e m o re acc u rat e , st ra i g h er t re ac a n d s m o o t h e 1982; S i e gle r & Jen k ins, 1989). T he e x p e r i m e n t e r s t r y c e h t in d e v l o v in es ess c o r p l a t n e m elop v de he t t Bu e r- e m to push c h ild r en in to m o r e ma t u r e p e r for ma nc e b y ma- d l pa n o le c ssib po g n i t ipula n r a m e t e r s o v e r a sh or t e r t- i l t e in ema r e v ha t n e m e v ro imp s t i nd a l il sk he t f o e enc g ro is g n i h c a e R tood. s r nde e u tl u ti me pe ri od , s o m e t im es wi t h in a n e x p e r i m e n t a l s essi on. f a t en mpon o c y n a m f o n o i t c n n es x a mp le, T helen, Fishe r , a nd R i d l e y -J oh ns on (1984) st ru ct ur a or e d p ro c ess es, incl ud in g t he phys i o l o g i c a l , F e me t abo l i te , a n d b i o m e c ha n ica l p rop e r t ies o f t h e muscles st ed th ei r h y pot hesis t h a t t he c o n t ro l pa r a m e t e r for t h c t s , t n s t a t e o f t he c e n t r a l n e r v o us s y s t em, visi on o n l-k l e he w t f e” o c n a r a e p ep pin g n isap e wbor n s t w an d j oin “d he o t hes e l l A on. o s d n a on, i t a v i t o m on, i t n e f t a l visua d an , t us fa o e n a subcut f on o i t si d depo api he r s t a e w espons r t if l f o r ea y t s r i f he t g in r u d g in g n ha c e r a s t a- e en y e h . If, t y v ely hea v i t ela gs r ’s le y b a he b t g n i k ma elem r e, m o s e— . o d, t he w e i g h t o f t he le gs w a s c r i t ica l for whe t h e r b a - s er et ram a p l so r t n o c e h t e r a at h W ne e rat d i p a r r e h rat a at t y s e t a t s w e n o t n i m te s s e th e v o m t a th bies s ? ep p e d or n o t , c h a n g i n g le g w e i g h t s sh o uld m i m i c t d i d. D t e c r easin g n a l c h a n g es, a nd inde e d i de v elop m e nd t t helen a es, T ess c o r e p hes n a d To be g in to u nde r s e subm y gs b he le l load on t ica n a h c e he m t gs he le t g n i g r he r c lea f e o enc g r e he em t f udy o t a s d e n g ues desi g l o g in w e r inc r e as e d s t ep pin t , a nd add in g w e i g h t s de- a e h les. T ip inc r s p em re ac hi ng usin g e x p l ic i t dyna m ic s y s t espons t d e as cre e. he r fo cus w a s on r e a c h i n g otor n em e r g e n t p e r c ep t u a l-m as a We h t ma a n y de v elop m e n t a l s t ud ies in t a g ze a hasi emp r pa t e r n a c q u i r e d t h t o u gh o ut t he s o f t ass e m b ly o f mut u- pot en t i a l c o n t r ma n ipula t e p t a h e t s o h s. T r e t e m a r l pa ro o- mpon t s wi t h in a c on- o le c p i t en h t g wi in t c a r e t ly in al mul

36 293 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 293 Dy a m i c Sy n a i il l to te for t x t. A l l o f t he c o mpon en t s a r e ess en t l (T helen, C o r b e t t a , & S p enc e r , 1996 ). Ov e r a l l, t he in- he sk ca e d on r e g r e v n o c y e h s; t r he c a r r e t t be e m ela- s be t n fa y ma s t en mpon o c e r o e or m e, but on v ro nd imp a e g r e em he end o t e y hs b t nd pa h ha oot nd sm a t h g i i d t a s r e t e m a r l pa ro t n o as c act a f t ely s v ti f r en t poin t s du r i n g de- e h t f r n t. T he o v erall desi g n w e r for ma nc e r esul t s a r e c onsis t e n t a s to m e asu r e beha vi or hes . T r a e t y rs fi e p v elop m e o e at ed ly a nd in t ensi v ely in a sma l l n u m b e r o f c h ild r en e g a h t wi t n re m e v ro g imp win pe sh s t epor us r o i v e r p h t wi on H e f ns o r e t t to pa l a or vi m beha ro els (f v le le p i t mul at (v muscle o f s t en, 1991). B ut t he pic t u r r e v e a l e d b y t h is nd de- r- su e r o nd m , a r e h c i mul t nd a on) a i at iv act i t p le t i m esca les (r ea l t i m e a dens e lon g i t u d ina l s t udy is mu c h r t e). i t l a t n e m elop v pr isin g , t h a n m h a t pa in t e d b y p r e v i o us w o r k . o l v e d fo u r infa n t s, N a t h iel, T he s t udy in v Mo st no ta bl y, t he dyna m i c s o f r e a c h i n g p e r for ma nc e a n, Gabr c g ov er t he f i r s t y e a r w e r e h i ghly n onl in ea r ( in c o n t r a s t to ea h in Jus t in, a nd Ha nnah, wh o s e r e a c h i n g nd n onr a gly l m m o v e m e n t s w e r e o b s e r v e d w e ekly f r o m 3 w e eks e less dens y b d e l a e v e r t n e m e v ro imp r a e n i ar in em e he s t nd g up da h . T r e t f ea r e h eks t e g w in t a n r e t l nd in a eks, a e l 30 w ti un a e r o t a ). Fi r s t , infa n t s d i f f e r e d d r a m a t ica l ly in c l t i p le c o mp o nen ts in look in g a t r e a c h- r udy t st a k e d mu t he a g e o f t he f i r s t t r a nsi t i on (f ro m n o r e a c h i n g to r e a c h- c s (t im e-spa c e pa r a m e- t in g p e r for ma nc e: T he k i n ema t i in g). Whe r e as N a h a n r e a c he d f i r s t a t 12 w e eks, Ha nnah in d nd Jus on i t ina d oor he c ies, t tor c aje r t t n e m e v o he m t f s) o r te a t i d n ot a t t a in t h is m i les ton e u n t i l 20 w e eks o f , t t- e g n a h d c api r f ods o i r e p d e w o s sh t n he infa , ond c e e. S ag be t w e en t he a r m s, a nd u nde r lyin g torq ue or for c e pa l nd e v en r e g r essi ons in p e r for ma nc e. A pl l in- at eaus, a te r ns m o vin g t he j oin t s, t he pa t t e r ns o f muscle a c t i v a - a c he r s a t f i r s t. B ut t h r e e o f l he fo u r fa n t s w in- e r e poor r e ti on th at g e n erat e t h e f o r c es, a nd t he e v e r yda y po s t u r a t nd Gabr nnah, a n, Ha ha t a N s— t d a n fa a e w o sh o s l a iel— a nd m otor s t n udy ad- t he s on, t i t i add n I . y b a he b t f es o t x h t n ess a nd sm oot h - i r e p epo he e , t ek e w h c Ea . s e l a c s me ti e l p lti mu d e ess dr n ess ap p e a r e d to c h whe r e s t r a i g d t me er s p r es en t e s ct e j b o e v i ract t t a h t s wi t n he infa nt n ge t w o r s e a f t e r s o m e imp ro v e m e n t ( labele d a s A in Fi g- i n, Jus h t a s in N a e w r e h t , y l l ). Fina 6.16 e ur t in, a nd Ha n- su c h a w a y t h a t t he r e a c h w a s em be dde d wi t h in a la r g e r a t r le nah a r a t h e r d isc on t i n u o us sh if t to be t t e r , less v s a essi on, a nd m otor v a r iab les w e r e r e c o r d e d s o t e h t iab a h 6.16 on p t nsi t i on f r o m n onr ea c h in g m o v e m e n s to r 295). . ra e e a c h i n g r u g T in Fi y d b e t ica ind e ( nc ma for r pe t t i l abi t on to s i t nsi a r iel’s t Gabr d t r a nsi t i ons on co uld be cap t u r e d. T h us, t h e y r e c o r d l, but e adua r g e r o s m a w y ly n ia m esca les: (1) t he r e a l t i m e o f t he t tw e h t e r l whe r clea r i onl in ea r o v e r a l l. T hes e p h a s e sh if t s to d i f fere n t o t t n e m elop v he de nd (2) t a , d e t en es r s p a y w to s le, esca m i t l st at e a w ere c o n f ir m e d s t at i s t i c a ll y . v . e v l o iss nd d e a v l o v y e ma f- i d y r e looks v g n i h c a e r f e o s r u o c l a t n e m elop y he de T t i abil t s f ns o r e t t whe r e pa n f tor e r a e g n a h c fere ies o t when t he ind i v i dua l t r aje c e sa mp l i n g. A l t h o ep in a gh a l l fo u r infa n t s p lot t e d usin g dens Co ll ecti v e V a r i a b l e D y n a m i c s . T he f i r s t s t u r l- a l ues b y 1 y e a r , t h e y co nv er ge d on r ema r k ab ly sim ila dyna m ic s y s t em s ap p roa c h is to def in e a r e as onab le c o v l e c t i v di d n ot g e t t h e r e b y i den t ica l m e a iab n t hes e c o l le c t i v e v a r e e h t e r u t cap t a h es t r u s a e m les— iab r a le or v ns. Ca e- r es. P g n a h c l a t n e m elop v s de t nd i p t s y he s t f e o at st s c i m les dyna iab r va em a - n es u ess c o r he p t to t gh de insi i v o r vi g t us desc r i p t i ons (e.g., F e t t e r s & T odd , 1987; Ma t h e w lyin r de e r g? A n i h c a e r f o t n e m e v ro nd imp t a e he ons o l v d t ook , 1990; v in- r u l fo l on to a m m o e c r a t a h les t iab r a & C ro t n o e c er th on H o f s t en, 1991) su g g es t e h a t im- fa c o uld be desc r ibe d b y t w o m e a- h n g es? c n fere f i l d dua i v i r ind i e h for t s t n u o c c i t a s? Wha t n pr ov em en t in r e a c t d re s o f t h e p a t h o f t h e h a n su o t h e o s t I : y o t fered f The Fi st ig ht n ess a nd i t s sm oot h n ess. A s t r a i g h t-ha nd pa t h ra r s t T r a n s i t i o n: The On s e t o f R e achi n g . lo l a n g l desi ina d u t i g t m o r a f e c n a t s i d t s e t or he sh es t k ta f t he m o v e - t r t o ues g lea l o d c n helen a d T e w he s T he lon o ly a e n y r e in a v e v o ’ ha s t dul t: A e g r a he t to t to pinpoin t wi t h s r m e a c cu r a c y t he f i r s t p h as e sh if t , t h e nt me nds m st c a e ul r f ess c c su f o e c n a r a e p ap ess is a m g in t c a t n o nd c for a g n i a- e h n h oot hes. Sm ac re irect for d h t pa ht ig ra r hes e o f h o w o f t en t he m o v e m e n t s t a r t s a nd s top s or e r e w t e ons f eks o e e w su t t a h e t ot N ( . y to d e r e f f he o t i m hes t f ons o i t a v r e s b t o is l a r u t na e r o he m t y d b e r e onf c slo w s do w n a nd sp e e ds up . I nfa n t s ’ je r k y m o v e m e n t s er i z ed b y acce l e ra - on, i t nsi a r ma t l a t n e m elop v a de d e i f i t den g i vin abies.) Ha b e n y “sp e e d bump s” c h a ract ha v s he n s to look for po- a w h c roa p ic ap m ep in a dyna t t x e t ti ons a nd de c ele r a t i ons. I n c o n t r a s t , adul t s ’ m o v s t n e m e p to a r d a d i r e c t t a r g e t sh o w only on e a c c ele r a t i g on a n d n o r t s e k a te n t i a l co nt r o l w a r a m et er s . R e c a ll t h at w e m n i a r ele c e de on on. assump t i ons o f c o t t in ui t y a c ro ss le v els a nd t i m esca les; o l l e c t i v e e t hes t o c f o s c i m dyna l a t n e m elop v he de T w d isc on t i n u i t ies mus t a r is e f r o m, a nd be pa r t o f, t hes e e va co nt in uo us dyna m i c s . r iab les for t he fo u r infa n t s a r e depic t e d in Fi g u r 6.15

37 294 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 294 n a m i Dy oot ess a ess o f r e a c h t r aje c tor ies o f fo u r infa n t s fo l l o w e d lon g i t u d ina l ly o v e r t h e n t h g i a r t he s es in t g n Cha re 6.15 u g Fi h nd sm n nd s a les a r e n u m b e r o f m o v e m e n t u n i t s (f e w e r = a sm oot he r r e a c h) a iab t r a i g h t n ess inde x, whe r e a v a l u e v r f i r s t y e a r . T he c o l l e c t i v e s tar t to t a r g e t. So urc e : Fr om “ T he D e v elop m e n t o f R e of c h i n g du r i n g t he Fi r s t Y e a r : T he R o le o f 1 = pe r f e c t l y st r a i g ht f r om a t a , a nd J . S p enc e r , 1996, Jo ur na l of Ex p e r i m e n t a l Ps yc ho lo gy: H u t an P e r c e p t i o n an d e b r o C . helen, D T . E y ,” b eed Sp nt me ve Mo m y t he Am e r ica n Ps y c h o lo g ica l Ass o c ia t i on. R e p r in Pe e d wi t h p e r m issi ons. r f o r m anc e , 22, pp. 1059–1076. C o p y r i gh t 1996 b t t e y a r e Wha t is c o n t in uo us for y o u n g infa n t s is t h a t r e t f en a v s e t n e m e v o m m r h in h c ea onr ue as n n i nt o c t a th g a helen e al wa ys mo vin g t h e i r l i m b s, f r o m t a d e l. (1993) look a t s. T r a e p or ap vi w beha e is n th bi r t h a n d e v en befor e. h he c n t in u- ’ s t n infa f ess o c o r a p s a g t m o r f e g r e t em m, mus w for e he n t , g n hi c a Re n i c a e t r s r i on to f i t nsi a r he t t o h f g t h i e c r e nd p g a a t o c cu r be- ou s pr o c e s s e s of m o vin on- n d e i r a nd v a y n ma “d isc o v e r in g ” a r e a c vin r o m am o n g n i e c t e d r e a c h— re ac hi n g m o v e m e r t s . a nd i he f s m t for r e s p t n e infa for l-d a o t g r

38 295 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 295 Dy a m i c Sy n n i e d a t to y c o n t a c t , a nd sp e e d o f n onr ea c h in g m o v e m e n t s for t he fo u r infa n t s in Fi g- g Fi g u re 6.16 Av era ge sp e e d o f r e a c h , sp e p e h i n g du r i n g t he Fi r s t Y e a r : T he R o le o f M o v e m e n t S c e e d ,” b y E . T helen, D . R a ur e 6.15. So urc e : Fr om “ T he D e v elop m e n t o f m e n t a l Ps yc ho lo gy: H u m an P e r Co e p t i o n an d P e r f o r m anc e , 22, pp. 1059–1076. rb e tta , a nd J . S p enc e r , 1996, Jo ur na l of Ex p e r i c o ia t i on. R e p r in t e d wi t h p e r m issi ons. c ica g lo o h c y n Ps ica r e he Am t y t 1996 b gh ri py Co l Ass e d s t a t es o f in- l l sk for a a he t s. T t n e m e v o ul m f e c less for , r e w d slo an T hes e aut h o r s fo u nd t h a t t he p r ef e r r ea e o e: T m he sa s t a abies w e b th fa n t s ’ m otor s y s t em s in n onr g c h in g m o v r i he t s— t e m e n t t h e i r ha nds in t h e dua i v i ind d ly inf l uenc e d ro u n p s— c i m insic dyna r t l in vic i n i t ies o f fo t he desi r e d o bje c t s. B ut t h f- i had d y e , fere t p r o b l e m s t s o l v e t o d o t h is: Gabr iel a nd N a t h a n n r icula t r pa n g. I n i h c a e on to r i t nsi a r he t t f o e r u t he na t o fered i n t h e am p l s to t n e m e v o ul m f e c r for i e h t n w mp do had to da t ude, a nd esp e- he fo u r infa n t s d i f it o ci al ly in t he vi g o r , o f t h e i r spon t a n e r m e c rodu in had to p t nd Jus nnah a l; Ha ro t n o in c ga e o us a r m m o v e m e n t s a t o infa w t. T e h ons c a e us to r o i v e r hs p t n o he m in t s, d n n e c in spa d r a w for s m r r a i e h end t t x to e e c muscle for if i e v o us m oro g nd vi e a g r n, had la a h t a nd N iel a Gabr ho ld t hem s t - f ly a g a ins t g r a v i t y . Ex a m na t i on o f t h e nt me r he e tw o ot he t s; act ua l torq ues us e d to m o v e t he a r m s e gm en t s sh o w e d w ere q u i e t e r an d g e n erat ed fe w r

39 296 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 296 n a m i Dy i th at Gabr iel a nd N a t h a n w e r e usin g t h r muscles p e r Shi f t s i n C o n t rol du ri n g t he Fi r s t Y e a r . Re c a l l i- r l c i m le dyna iab r a v e v i t c e l o he c s, t t n infa e e r h in t at th - s e n e g s ce r o f al i t er n i e v i s s a p e h t eract nt cou to ly ri ma i F ( r a e t y s r i he f t r e v e v o d m i p ra e h t y b ed at e o s r u o r c ea in m n g n i k i r t had a s e t s o f t h e i r a r m s, wh ile - g n onl od o i r e t p inc t s i a d h t e 6.15), wi ur abil Ha nnah a nd Jus t in w e r i t y e usin g t h e i r muscles to c o u n t e r - t g ins in em e s f e l a v it y . act he in- t t a h t o s l a l g ca r . R y t i abil t s f od o i r e a p y d b e w o l l fo fere f i d y r e s had v t n l infa dua vi di Ma n y c o mpon en t s a r e n e c essa r y for infa n t s to be g i n - e v o insic m r t n i t n i c c i t s i er ract a h on to c i t ela ly in r l a i e s, esp c m dyna nt me to r r- a r t he y (or ot he to e t e le to s t be ab mus y e h h. T c a e e ge ) a nd lo ca . t e i t in spa c e. A nd t h e y mus t w a n t to g e t i t sp e t ds. S t ud ies o f adul t r e a c h i n g ha v e r e p e a t e d ly sh o w n a v i t o nd m l a he visua t T c s o f r e a c h i n g a r e e l asp ona i t th a t t he sp e e d o f m o v e m e n t s— r ef le c t in g t he a m o u n t o f t ro l pa i- pr oba b ly n ot t he c o n en er g y d e l i v ered t o t h e l i mb s— is a c r i t ica l pa r a m e t e r in r a m e t e r s be caus e ot he r e v h t infa n t s ca n lo ca ma n t asp e c t s o f m otor c o n t ro l. F a s t e r m o v e m e n t s a r e e o bje c t s in t h r e e - t a denc e su g g es t s y e is less m ensi ona l spa c e r a t h e r w e l l, if n ot p e r fect l y , b y di g e 3 ge n erall y less a c cu r a t e, p r o b a b ly be caus e t h e r a o w k mo nt hs, a nd t h a t t h e y g r asp a nd m o ut h o bje c t s a nd sh ti me to ma e f i n e adjus t m en t s ( F i t t s, 1954). R e a c h hem. M i k ely , s ele c t in g t he c o r rect m u s - l e r o in t t s e r e t in tr aje ct o r i e s m a y re q u ire di f fere n t s t rat e g ies o f c o n t ro l t cle pa ely t a i r rop p on ap i t a v i t c he a t g n i l nd sca ns a r e t a nd d i f f e r en t pa t t e r ns o f muscle a c t i v a t i on, dep end in g r s t r e a c hes f r o m t h e i r i r f i e h on t i s to fash t n- Fla ly ( d api ly or r w d slo e m for r e e p r a y e h r t he t on whe n infa ow all o . w r a s, & Ag o c r o , C ieb l t nn, 1992; Got un direct ed m a v e m e n t l, de r s & H e r r m a s r m e n t s p rodu c e mu c 1989). S h la i y m i , v e r y fas t m o v e I nde e d , a na ly sis o f infa l n t s ’ muscle s y n e r g ies f r o m r m t c ele y g r ap h i c ( EMG) r e c or d i n s r e v ea l t ha t ro ea c h - w on slo n a h es t c for e v ssi d pa e t ela on-r i t o r m e t ea gr es g e s us po h nd t e mus- l ona i t nc u f in es g n ha c h t i w d e t ia c o ss a s a w t e ons g in n t p r o b lem s for n e e u r a l f c o n t ro l do, a r f i d e, cle e. S p enc e r a n d T helen (1995), c o mpa i n g EMG us ick n r Ze , r de i e n h c , 1991; S ieb l t ash & Got at (L r g in h c ea r n t- s n r e t t pa c Sc d hm id t, be a e befor s t en em v o m g in h c ea onr n nd a & Ha r t , 1989). C o uld m o v e m e n t sp e e i d , t e ons h ac re er e d a an r in t hes e de v elop m in- e n t a l sh if t s ? g n i h c ft in g as a c o n t ro l pa r a m e t a e r when t a h t d e r e v o isc fa r he fo es t t a r t s u l l 6.16 i infa n t s ’ c h a ract er i s t i c e r u g Fi e u nt s f re q u e n t l y recr u i muscle, d i o t l e d r o i r e t an ir e h t d t s sh a lon e a nd in c o m bina t i on wi t h ot he - v a w o r . Plot r a e t y s r i r f i e h t r e v s o t n e m e v o m f o d e e sp muscles. ( T h i s e h o ulde r muscle r a is es t h e u p p e r a , g in h c ea r e efor B m.) era g e an d pe ak s p eed o f t h sh re ac r it se l f , a s w e ll a s s p eed o r m s, but t h e y us e d a r i e h t d e is a r o s l a es im t e m s s t n infa at t he s t a r t a nd t e r m ina t i on o f t he m o v e m e n t. I n add i- n ot y t i abil e h T is. h t - n no f o d e e sp ’ s t to d infa e t epor ) r l. (1996 a t helen e on, T ti do he r c o m bina t i ons to muscles f o a re ele s a v i t c a ely v i t c s t n s infa t n e m e v o he m t e a nd l t l is, a t a h s, t nt me ve c o n t ro l t h i s muscle g r o u p w as mo g hin c n ed at ci so as ls when p rodu c e d du r i n g t he 14 -s e c ond sa mp l i w g t r ia i t h g o al - d irect ed m o v e m e n t s . e a l e d s e v eral th ere ey n ot r e a c h i n g. T h is a n a l y w sis r e v T helen a nd c o l lea g ues sp n r s lea t n infa t a h d t e t cula e d on m sp c i f ic f u nc t i ona l muscle pa t t e r ns t h r o u gh e x p e r ienc e in e e g r e v n o s c n infa , t s r s. Fi t esul le r ab k r ema r o r e or t a e e r hs befor t n o nd m eks a e he w t g n i r g du vin mo nt a n d co nt a c t sp e e d; i d t w a s n o t o go r ila less sim mo v e m e - c a g n i h c m tu ly em e r g es. I nfa n t s ’ r e a l-t e a c t i vi t ies o f al o vin g— p- a ly or too r w too slo r e h t i y e he to ab t r l to g ona i t nc fu im is c h in t g vin i e c r e nd p a s c i m dyna b m i r l i e h t f o ” l e e f he “ g t ensin s h t , wi ond c e . S ly id i- on, ind i t u l o s d e e on sp m m o e t eq uenc es o f t h e i r m o v e m e n t s— a r e t i m e-lo ck ons d he c s c i m insic dyna r t or in s e i t ali n o s per d e e l sp dua vi e d e - r e t s a fas a iel w le, Gabr mp a x or e e. F g a r e v , on a d e in ema r input to t he de g e n erat e an d ree n t r an t n e u ral n e t s w r t - r r o c e s s clo a e w r e h , t d r i h nnah. T Ha n a h espon- ve mo sc r ibe d in a n ea r l ie r s e c t i on. As a c ons eq uenc e, ca t e eed l p s t n e m e v o m c i t s i er ract a h en c e w t e be denc a l t he po ssib le - h ac re n i go r ies o f l i m b pa r a m e t e r s em e r g e f r o m e t i ons t h a t a r e ap p rop r i a t e to t he spa t i a l lo ca t i on bina m t o n e r e hes w c a e he r s. T t n e m co v o g m in h c ea onr nd in n g a in t e o . y he to t of l a t e d f r o m is he on g oin g p r ef e r es a nd habi t s o f t h enc c y fa ma s t en mpon o em c b s y r s he es in ot g n Cha abies, but w , y l l s. Fina c i m e dyna s o h t m o r d f lde o m e r e e t a t i l i t - is d isc o v e r y . F or e x a mp le, T helen a nd c o l lea g ues fo u n d pe ri ods o f th t e r m o v e m e n t s w e r e ass o c i a t e d wi t h ins t a fas he c in t y t i bil c uld a l s o s t abil i ze l. ro t n o poor c g y e h l t i t n h u c a e ot r d n i s d t n infa at th n i t ica les, ind iab r a o v e v i t c e l l o i gh t n a h t g n e r t , s ly ssib o on. P i t si e po in l d d r heads in a m ei th Al t hou e he fa c tor s t h a t le d t he infa n t s to m o v w o n k n t u e r ly a w slo e r o uickly or m q re mo e befor y r essa c e e n r nd head muscles a ck a e n f l o ro nt co e as y is h n, t eed es he a r m ca n be l i f t e d indep enden t l y . S t ab le head a nd e y ov erall s p t v a r i a b l e clea r ly a c t s a s a c o n t ro l pa r a m e- l i i c fa so al z l ca e lo t d a r cu c es a t a t i te r on t he s t r a i g h t n ess a nd sm oot h n ess o f t he r e a c h t r a- e h c ea he to-be-r t f on o i t a e dua c t s o f r e a c h i n g a r e fash i o n l a d i v i in, ind a Ag . y tor c je e o bje c t in spa c .

40 297 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 297 Dy a m i c Sy n r y he s at t he m o m e n t a nd ca r t y wi t h t hem t he s t a t e o f s- Gabriel 100 h m t em a t t h a t m o m e n t , wh ic h, in t u r n, is de t e r in e d b y t e 90 y s . t tor s i ’s h m e sy 80 70 60 50 nu io t Bi m a n a l Coo rdi n a 40 30 e is s Th is in t c r p la y b e t w e en t a sk a n d i n t r insic dyna m i 20 Percentage of Reaches 10 s us eq ua l l y w el l i l l t r a t e d b y a n ot he r a sp e c t o f infa n t ’ 0 a h o w t or e n o h t i w e r nds. h c a e re ac hi ng : Whe t h y r t h e 28 4 48 44 40 36 32 52 24 20 16 2 1 8 (1939; he t t ha Ges el l t Ges el l & A m es, 1947 ) f i r s t n o t e d Bimanual eeks) Age (W Unimanual fere p la t eral s y m m et r y an d r re bi n c e o f infa n t s w as v e y Nathan l un s t a b e e a n d f re q u e n t l y s hi f t ed f r o m u n i m an u a l l i m b u s 100 90 o t e n ere f e r p ed c to bima n u a l , a nd f r o m s t ron gly la t erali z 80 n (1996 . sy mm et ry . T he fo u r infa e t s i n t he T helen t a l ) 70 60 g Fi u f r e 6.17 s. st udy a m p l y dem ons t r a t e d t hes e s h i t 50 o h s ) 1996 helen, T & a t l t be or (C dua i w ies uenc q e r v i ind s f 40 30 o of on e- or t w o-ha nde d r ea c h in g. N i t e t h a t , i n t h i s s ua- t 20 Percentage of Reaches w c ti on, to y s o o uld a l w a ys b e g r a s p e d b y o n e h a n d , s o t - 10 0 g i t o N on. i t nc u f for y tor a ha nde d r ea c h in g w as n o t o b l 28 4 1 2 16 20 24 8 32 36 40 44 48 52 only r e ef r l but es, enc p d i d ind i v i dua infa n t s h a v e m i x e d Bimanual Age (W eeks) Unimanual no tw o infa n t s w e r e a l i k e i n t he i r de v elop m e n t a l c o u r s e . Hannah d r helen As in t h e sin gle-a T m t r aje c tor y , C o r b e t t a a n 100 90 ls (1996 ) d isc o v e r e d t h a t o n u a l c oor d ina t i on w a s a bima 80 ca s e in , is h inf l uenc e d b y infa n t s ’ in t r insic dyna m i c s— t 70 o m s b im l r i on e h t r e h t i ash f d le up o whe on- n in c a n i d e v 60 50 t re ac hi ng mo ve me nt s a s w el h When infa n t s r ea c h e d wi l. 40 d w slo tw o h a nds, t h e t w o a r m s t ende d t o s p e e d up a n 30 20 l s nt m e m m y s ere s w b m i l e - i r et ; do w n to g e t h e r in a l v m o Percentage of Reaches 10 t a d h e t o s n a w g n i l p u o c ca l l y c o u p l e d . I n c o n t r a s t , n o s u c 0 20 44 40 36 32 28 24 48 16 2 1 8 4 52 n t d ti me s when infa o t s p r e f e r r e d to us e only on e h a n Bimanual Age (W eeks) u o a l s y m h m e- s f bima n c gr ab t h e t o y . F u r t h e r m o r e , epo Unimanual J ustin in i - pe h c a e r n o n d n g a n i h c a e n r try h t i w ed at ci o s s a ere w g 100 e, nc ri o d s o f hig h e r s p e e d mo v e m e n ts. Gabr iel, for ins t a 90 80 up e d t w o h a nds a n d had c o d le us m o v em en t s a l m o s t 70 ab thr y o u g hou t t h e ye a r , a n d h e w a s t he m o s t en e r g e t i c b . 60 50 n u Ha nnah, in c o n t r a s t , w as la r g ely u ima n ua l a nd u n c o - 40 d o t for t p e c e x i r e p e h slo he t n i pl ed (a nd m o v e d ly), w 30 r e d mi dd le o f t h e y ea r when he as m o v em en t s p e e d inc r e 20 Percentage of Reaches 10 s a d e m n t n e v o M . l l e w an d h er m o v e m e di t s y m m et r y 0 48 40 36 32 28 24 20 16 2 1 8 4 52 44 m on sp e e d w a s a c f t r o l pa r a o e t e r for bot h t he ef f i c ienc y Bimanual eeks) Age (W li th e m ov em en t a nd th e s tr en gt h o f b il at eral c o u p . n g Unimanual in t hou gh t he infa n t s had a n o Al v i o us t a sk g o a l b en t a g es o f u hes for c a e a r Fi g u re 6.17 P erc n i- a nd bima n u l o r ab a to y , t h is dyna m ic a c t em e r g e d re ac hi ng ut to g t 6.15. he fo u r infa n t s in Fi g u r e c e m e n t. T he s t a t e o f a m o fr d of o n g k o i n oun g mo v ba g r r o t h e i r body a r - r f t n e g m s em a s w em t s y s ’ s t n he infa t e o m h o w ch it ect ur e, m e t abo l ism, a r o t i v a t i on, a nd f r te rn th at se l f-or g a n i zes f r o m mul t i p le c o mpon en t s o v e nd m e. I n su c h a th ey had be en m e vin g in t he m o n t hs befor se v eral t i m esca les: T he he r e-a nd-n o w dyna m i c s o f t h o on e pa r t o f t he s y s t em is p r i he in- t f o s c i m m dyna v ile g e d— t he r e is n o vie w , n o ta sk a nd g o a l, a nd t he lon g e r-t e r a t- g n i h c a e fa n t s ’ h i s tor y o f m o vin g a nd r e is a pa c h i n g . n. R i a he br ode in t c g n i h c e d r e t ica d de a

41 298 P PM 02 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 298 n a m i Dy v n o r t o ls of C e l e l of L e d o A M Tr ansition to Stable f o t n e m elop v he de d f w o ic vie m A dyna t e l a e v e r g n i h c a e r Goal Le el Control v Reach T rajectories c e l l o he c a es in t g n a h e c k i el ag st r v e e m he sa t t les a iab v i t T v el Control iming Le t n o c ti me th at re ac hi in- wa s em be dde d in t he infa n t s ’ ng l Control e v Load Le e uo us a nd on g oin g in t r insic dyna m i c s. I n t h is s c t i on, w e Goal Le v el Control e em f odel o ic m m t a dyna en es pr t c o n t ro l t h a t r e g on- n r e c e mul i p le le v els a nd mul t i t le t i m esca les b y hes les t ci p T v el Control iming Le p t y a r e dyna m ica l ly cou e le d. h t p ropo sin a h g t el Control Load Le v l? l i Sk s W hat I ef ul he r e i g to d It is us Wha : nd ask ly a ief ess br r t is in- 7 9 1 0 1 1 1 6 5 4 3 2 12 8 g t vo ed in c o n t ro l l in lv he a r m (or a n y body pa r t ) for su c- Age (Months) m ess f ul a nd adap t i v e c o v e m e n t ? e Ac rdi ng to B e r n s t co in ( B e r ns t e in, 1996 ), on e o f t n o g c asin e r inc f odel o le m A simp re 6.18 u g Fi e v r l o ro t t x e l to f y t i he abil is t y t vi i i- c d a le il sk f ks o r a m l l he ha d c r S e t Af . g n hi ac v ha e (1994), w er ̄ n o h e def in e c o n t ro l as re r ons. t i ond e c r u t u nd f t a en i r s to cu t n e m e v o t m ly adap b e rot e c t in g t h a t le v el f r o m p r t u r p b a t i ons f r o m t he ot he r le els. v nd e T v el in v o l v es t he in t e n a l a he load le x t e r n a l for c es a c t i n g r i t il ons t es sk t c Wha u t le d p e r for ma nc e is n ot jus t a r e - t nd t on t he l i m b s a he ass o c i a t e d s g r e t c h r e f l e x es. T he t i m i n i t y to a c c o t ab t nd s le a ab at le pa pe t e r n, but t he abil m- e n e he g es t v l o v el in v le i i he t d t n y a tor c aje r a t f on o i n t g o f a m r a ul, but ef c a r nd g d a api r h t wi l o el g v gh-le i e h m o ish s pl l t e t s a nd muscles to e x e c ut e t he t r oin aje c tor y . T he g o a l le v he j i f l ex ib le s o l u t ons t h a t ca n be r e c r ui t e d onl in e or in a n - i t he spa is t a f t a l o ro t n o in c a ly g l adua r s only g t n nfa t. I e g r l n es. C onsi de r , for e x a m- a t s cum c i e c r u t u f f on o i t ipa c ti r els. e le hes t v on t t r ia n wh o s e g o a l is to s t a y ues d eq le il le, a sk h p e c ho in ile lead e, wh r u t s ul po ef g a r in a g a t in nd ma e a rs h l in t he h is cas e o r s e t h r o u gh a n t t ende d c o u r s e. Sk il in in r espons e v e m e nt , su c h as s e t t in g t he c oor d ina t i on pa t t e r n o f mo me a ns ma k i n g m i n u t e, onl in e adjus t m en t s a nd muscles, a e m i he t t g n i c rodu nd p a s t oin us j o i r a e v th es in g n - h c g n i t ipa c i t n ile a s wh t n e m e v o e’s m s r o he h to t aje r t e c spa in. r r e t t be hes mus c a e r , a y l l m. Fina r he a t f y o tor c he t e t e m a r pa l a o l g g b he glo en when t v d e ze i abil st n i t i v e or s o - a I nde e d , in m o v e m e n t , as w e l l as in c o s r c n ci al ac ti vi t ies, w e ca n def in e sk il l as be in g ab le to d e c la isp ly d d e t e p x e is u t e g r a he t when t e— g an ch ui t e h t t e e m t a h ies t g e t a r t e s t a i r rop p t ap r c e ly r d api r (adul t s ma k e t hes e k i nds o d n uickly a q s t en m adjus f gi sm hly; Jea nn e rod , 1988). Usin g G r e g or S c h o ̄ n e r vi- ’ s l en sica phy , or sk a l, t a i c o he s t f nds o dema ng oot an ch m f els o v e le hes e t in n def ca e w , y g o l o in m r e (1994) t on- ron c e n t. F or r e a c h i n g , g ood c o n t ro l m e a ns be in g ab le tr a- els. v le l a go nd a , g imin , t load he t s a l o to ef fi ci e n t l y re ac h i n all direct i ons, for m o vin g or s t v o r y o bje c t s, when t he l i gh t is br i g h t or d im, f t e n r els a ona e le hes ons, t i t c d a le il t sk adul y r ina d or In r o m ti le; t b a r epa s or d e on s t a c d a n a , k in h e, t v i e c r e le p op e s- i is, p t a an y po s t h u r e, wh ile o u r a t t e n t i on is fo cus e d t t e l a e v e e r r l a ro n o c f els o v ld. Le r o l w sica y h he p in t it un d ract ed, an d s o on. On f u r t h e r a n a l y sis, w e ca n i den t i f y r t x gh e u o r h only t t ons, i t ipula n ma l a t n e m i r e p x e y r ina d aor he sou rce s o f p o t e n t i al di s r u p t i o n a s af fect i n g o n e o f n n c f ipa els o v le ree th t ro l o f t he r e a c ic t r pa l l e s t r e t n e m h. As depic i r e p x le, when e mp a x t e for e d in Fi g- t s to o e ly a c h i n g mus t be s t abil i ze d f i r s t a g a ins t t r a ur a - n e ho ld a l i m b po si t i on c ons t a n t when t h e y ap p 6.18, r r- e t x e n na t m , or to r e a c h to a t a r g e t t h a t is suddenly d i s- l load f o s m us for sien o e c h a n ica l p e r t u r b i a t i ons— v a r in a w a t dul d. A e ac pl t e r n a l for c es a c t i n g on t he m o vin g l i m b s a y t h a t , t c e rot e, p t a l o to is , y l l ona i t n e t le, in e ab r ex a or vi beha eral v e s t ies a t vi i t c r a i e h l t ro t c aje r y o d t ende t he in end to push t uld t wo tor f n o or c f c o u r s e. els. v le l Th els o r e v e r y g ood a t ma in t a i n i n g l ro t n o c f s v he le s, t t d adul le il , in sk t a h ns t a e is m a t adul t a h t w o n e k (W ar ot t le bump t t i l f o e c he fa y in t tor c aje r t t n e m e v o r m ei th s e n i gh t ly c o u p l e d; t he g o a l le v el is n ot a sla v e o f t h e a l d i, & b; e.g., m i he l t t ins a ag Hoga , Bi z z i , n Mussa -Iv ar m ’s bi o m e c ha n i c s a l t h o u gh t he load le v el c o n t r ibut es v e le hes t t a h ze t hasi t emp mus e n g mus t be s i ze d in abil Flash, 1987.) S e c ond , r e a c h i els to t he m o v e m e n t. W t o di f fere n t t a s k dema ar e s t r i c t ly a f u nc t i on o f f he impo s e d t a sk dema nds. nds o f t he t i m i n g o f ce fa he t t h e t

42 299 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 299 Dy a m i c Sy n t h l ly in t he ab- t , t s ge e sy s t em ’s d isc o v e r y o f a s t ab le t r aje c tor y s o l u- nc i u ly or f l ica m o t a n t a is x ot e do n y e Th ona a i c e rot p d n a on i t la o s o i e h t is, t t h t on— ti sks. a he t t f e o enc s n o f t he t i m e - f spa c e pa r a m e t e r s o f g e t t in g t he . y o t n e e s e h t to nd ha t l e men l o r t n Dev e op l t of L e v e ls of C o s w ere n o l o n g e r b u f fet ed b y t u s , b y h Th i s a g e , re ac h e o dyna e v load-le m i c s . I nfa n t s c l uld r e a c h s m oot hly a n d i n a , do n ot s t a r t o ut wi t h t h is abil i t y t s I nfa n t s, in c o n t r , a r t l ro t n o c uld o c y e h t nd a he r e nn ma t h g i a r t s ely v i t ela t to p rot e r t e c e asp e c t o f t he t a sk a g a ins on t p u r b a - g se c for l ia t m e n t s a g a ins t t he i r o w n i n e es. r c ha ons— ti t is, to c n t ro l t h e i r a t t i ons a g a ins t u n a n - o ina d r or nde s, u t n ld infa h-o t gh 8- to 12-m hou t Al on y r c t r s f bump ) d e t ipa vi- he en ti o ipa t e d (a nd e v en a n m t i c r e v nd e a e , s r he c a ood r g y t t e r p e k i ons, look l i t i ond y c yda ron e e n t. I nde e d , wha t w e w a n t to a r g ue he m r h a t t h e is t o a t n e v ha y e h t we ca n c r ea t e c ond i t i ons t h a t r e v e t l t h a ync ia i e is h t a t l s in t i e r s a t n e m e v o m ’ s t n ic; infa ghly s t e r ghes i y to he abil t l— sk f el o v t le t i he h t d e r e t t mas ye il o u p l e d to lo w e r-le v el dyna m i c s, a n d in i t ia l ly t i gh t ly c t m rot e c t t he g o a l f r o p he lo w e r-le v el dyna m i c s. I n t h e gh e x p e r ienc e a nd or g a n ic c h a n g es do es a only t h r o u r l l l o win g s e c t i on, w e fo epor t on s t ud ies whe r e t he g o a rot g . e r e ic em m dyna l a o el g v r-le ghe i h d e t c e ly p l fu e clea r e x a mp les o f t h is in ea r ly spon- y r e e v n s ca We le v el— t he lo ca t i on a nd t he na t u r e o f t he o bje c t to be — ou - r a e v ha e gs. As w nd le a s m r he a t of s nt e m e v o m s e n ta re ac h e d w a s per t u r b e d . Th e s e e x per i m e ed al e v re s t n ib th h is u n s t ab le p e r i od , infa n t s w e r e n ot f l e x , in t le; at gu ed pr ev io usly , when y o u n g infa n t s inje c t suf f i c ien t t h w s y t th ey we re held cap t i v e, s o to sp ea k , b y t he a r m pa en e r gy in to t h e i r l i m b s, t he r esul t i n g pa t t e r ns su g g es a d o s c i l l a tor s wi t h r had p ma- ey th a p i y for tor c aje r r t i e h d. T e c rodu usly p o i v e c s o f c o u p l e t he dyna m e r i od ic for c- r t e l l o he c t be t mus s c i m h dyna c u on. S i t nc u g f in i v e c e - ti e h ck in t u t s e r e w y e h le; t ib x e l ot f ood but n s g a on w a e us r o i t habi r e t s o f c p r e v e h t h t on wi i t bina m o ns in c r e t t pa l a r u e le n simp f t o sul - bje cus on classic o fo e hes. W c nd t sp n g l i k e p rop e r t ies o f t he j oin t s a nd muscles a i h e r . A dy- ror r ot-B” e A-n t’s “ e g Pia s— nt me ri pe ex al ev tri i c s r ona i t i ad r he t es t g len l a h t c n u o c c s a em l t s y ic s m na ef fect s o f g a v it y — t h e load-le v el dyna m . r in g at an pl ex h a t o bje c t r e t r i e ons t v a l i t a sks t ap in to endu In n e f ir st mo nt hs o f l i f e , infa t s a r e la r g ely t h e th , w dg ow kn s ut o bje c t s. Ra t h e r le e su g g es t t h a t infa n t e abo e v i t cap , l e w l o r t on c t o n n a c y he T . s c i m dyna e hes t f o s l e w t g be in l p u o y c tor a g i l b d f es o c a r t w o sh o a l a o he g en t n or t a l l , t he po si t i ons o f t h a e h t or e c spa in s b im l r i e aje ti ro t n o y c tor c l. r t f els o v le ng mi h s t n me g e s e e t f o g n ti h t us, h T t. en em v o m g n i r u d i m e s t n infa t a h t lem b ro t p rs fi f o l ro t n o c is e v l o s o t v a h cs of t Th a s k Dy nami e T h e A-N ot-B Er ro r e k a en w to in g e b t mus y he t ; s c i m dyna el v oad-le l e hes t in w e h t nd a l e v le load e h t en e t e b g l th e o bl ig a tor y c o u p abo On e o f t he p r ima r y t a sks o f infa nc y is to lea r n e ut t h o hi r l e v els ghe f c o n t ro l. k abo ut t hem, ies o t r e rop p o f bje c t s to a c t on t hem, t h in t r By t he t i m e infa n t s f i r s e a c h a nd g r asp , a t a g e 3 or 4 a l ly abo hem. Li k l ut t t erall y f t , t h o u s a nds o an d, ev en t u a mo hs, t h e y mus t ha v e be g u n, t h nt o u gh t h e i r r e p e a t e d r ut t en abo t t i r en w be p- e r t c bje o f o e r e v s ha r e pap u t he na ct ge ve me nt s, to n erat e a t r a j e mo o r y i n t i m e an d s p ace t o nde r s t a nd re se nt at i on: When a nd h o w b abies c o m e to u o t hes a c a e r r i e h ut t e. B e s y e h g t in h t e m o in s tta a il l n r t e s t t i a l a nd t empor a l p e he spa m a n enc e o f o bje c t s. On e r n t ro l lab le indep enden t o f he load le v el dyna m i c s . t fu l ly c o en us g u ’ s t n e infa r asu e to m d e n has be t a h sk t a e t r u t a n - si oot t f s o t n nfa , I en r e a c h too fas t or too slo w ly; t h e y o v e r sh t a t s r f o bje c nd s asks infa n t s to r e t r i e v e a h i dden de g o in t c or inje s a in s s t a r t s, lead in g to t h e t s r top gy bu r nd s e en e c ic t a m a r nd d s a ror r e h c r a s f ns o r e t t t. Odd pa bje o c t e t c a r a h c o on s i t a r ele r nd de on a i t a r ele c c a f ns o r e t pa is- - v elop m e n t a l c h a n g es c h a ract er i z e p e r f o r m a n c e b e de ic d e r odel p is m h . T g n i h c a e ly r r ea f ic o t o wi t t a h u t h t s t n tw en t he a g es o f 6 a nd 12 m o e t hs. W e br ief ly r e vie w uld de- t he a r m, t he r e a c h t r aje c tor y w o g ood c o n t ro l o f o he e o u r dyna m ic s y s t em s a c c r u n t o f on e o f t hes e s e a r c h m e o ade when m gr s a e fas t. T h is hap p ens be caus e r t n e v ror er e h, t i ror (Sm r ot-B e A-n n a i t g ssic Pia he cla s, t i fas e m e n t s c r ea t e in e r t v a l for c es be t w e en t he s e g- t m o e enc p , & McLin, 1999; S r e z t helen, Ti T t h, & T h e- i , Sm r ic e n t r o l — s o m e - s me nt s of t he ar c m, wh o h re q u ire p reci he c on e r helen, S , S c h ̄ ie r len, 2001; T h, 2001; t i & Sm , g sk il le d m o v e r s ha v e c o n t in ua l l y . A n d , inde e d , t h is th in T i t h, 1994). helen & Sm d ibe r desc s r he c a u r t n infa r he fo d in t e n e p t hap is wha e a x e n t a n e s e r p We . ror -B Er t o The A-N ea r l ie r : When m o v e m e n t sp e e d inc r e as e d , r e a c h t r aje c t o- w o h f le o mp y a y i l causa i t mul f o s t ep onc ic c m he dyna t d e us ). e 6.16 r u g i F ( t h g i a r t nd less s e k r je e r o m e m ca ies be r we ha v t a e m elop v t a classic issue in de visi e to r n- m i t d e t s e nd n e e d ram at i c t r an s i t i o n t o s m o o t h e r a n d st ra i g h t er Th t ues l p s y c ho l o g y . T he q ta i on or i g ina l ly po s e d b y Pia g e t g w at h u t g n hi ac re n o r a t a w a s e d a g e 7 m o n t h s i s , w e s u -

43 300 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 300 n a m i Dy b - o f t o ep onc he c e t r i u q c s a t n when do infa s “ a (1962) w t-h c in g bje le o a simp d e vis de e e?” H enc n a m r e p t i c je d Specif ic a f n e e ons o l g a r e v e s y d b e t en adop h has be ic , wh sk ta t r i a n z i n g to y a des a t i h r e t n e m i r e p x l he e s. T er ch ar se re t i nd t e nde r a l i d a t lo ca t i on A a u he infa n t r e a c hes for t h ask T T . es. m is A-lo ca t i on t r ia l is r e p e a t h e d s e v e r a l t i to y h t e t n e m i r e p x he e l: t ia r tc l swi ia c u r he c e is t r e h hen, t T r c t a t n e w lo ca t i on, B . At t h is poin t , 8- to hi des t he o bje Look a cu on e t h-o ld infa n t s ma k 10-m r i o us e r ror . If t h e r e is a e a c h n o t t e en h i d i n g a nd r e a c h i n g , t h e y r sh w or t dela y be Plan bje , but b r a e p isap d t c a he o w t sa y e h t e ck to A, to whe r whe y e fo u nd t he o bje c t p r e v i o usly . T h is A-n ot-B h t e r Reach d ror is esp e c i a l ly in t e r e s t in g be caus e i t is t i gh t ly l er n k e i s i ghly c i r cum sc r ibe d de v elop m to a h n t a l p e r i od: I nfa t n e Remember y o n t h e cr u - o r th an 1 2 m o n t h s o f a g e s e a r c h c o lde r rect l r ci B t r ia ls. Wh y t h is d al a m a t ic sh if t? u Fi g y re 6.19 A t a sk a n a l sis o f t he A-n ot-B e r ror , depic t i n g t h s k i n g t h a t t 10- w o m Do 12-m on t o n e h-o ld infa n s l i de h i d i n g e v en t. T he bo x a nd h i d ica n g w e l ls c on- a t y p A-si g mo only a t a h d t e t es g t t su e g ot? Pia s do n t n ld infa h-o nt it n he c t in ua l l y p r es en t visua l input. T he sp e c i f ic or e t o ut st ra nsien t input c onsis t s o f t he h i d i n g t f t he to y in t he A w e l l . o t o bje c t s ca n e x is t 12 m o n t hs o f a g e do infa n t s k n o w t h a t g t win lo l d a n a g n i d i en h e w t d be e s y is impo A dela he infa n to i enden indep su e v ha s r he t ons. O g- t c n a w r o i e h t ly o t f se s in t c bje e o h t t looks a t n he infa s, t t en v e e hes t g n i r h. Du c ar a t t n , infa od i r e p h t on 2-m t s sh h t g n i r du at th ed st ge if he cue vie w , r e m e m b e r s t d lo ca t i on, a nd u nde r t a k es a p l a n - e, c ei r r e p r es en t a t i ons o f spa c th h a n g e t he f u nc t i on in g o f v i t c he a g to t in ess lead oc pr ng ni on o f r e a c h pa r a m e t e r s, i a t t es, th ei r p r ef ron t a l c o r espons ic es, lea r n t r ibi to inh f. Fina l h s t r e b m e m e r t n he infa t , y l l e l e s t i g n i h c a e r y d b e w o l fo as e t h e sk a he t t f g o in nd a t s r nde u , or inc r e ch a n ge t h eir r he cu r a m e t e r s o f t h. c r en t r e a pa th cred i o a t en es r p e r r ei ons (A of th ng re st lo, 1979, Br em- t ne r, 1985). n e ca n e x - input Th er e is m e r i t to a l l o f t hes e i deas, but n e m o c be to ield f he t s w o l l a h c i h w , r e h t o n a e on to o t ghly he f u l l pa t t e r n o f e x p e r i m e n t a l r esul t s (Sm i t h , a in t r e x e l l i w t poin d e t a v i t c a pl i h A . g n i z i n a g f-or l se a ibi inh g ron st a T helen, Ti t z e r , & McLin, 1999). T h is m i gh t be be caus e , t i nd u o r a s t poin he t r e v o e uenc l inf y l- tor a t hes e a c c f e o c n e s b a e h n t d i e n i a t n i a e m o b t n o i at v i t c n a g win lo o u n t s s e ek a n e x p l a n a t i on in t gle a sin f s o m r e f caus h e r e is n o sin gle caus e. W e o e when t f input. r a for ma l ex te rn al e ry eo th t c a f o on i t n l o v e e h t es t a r t s u l il 6.20a e r u g Fi i o t a v i o n l., 2001) to a t helen e T odel ( ield m ic f m he dyna , t u tri A st ir y f er th e v ex pl a in h o w t he A-n ot-B e r ror is t he em e r g e n t p rodu c t o f - b o y n a n e e s s ha t n infa he t e efor . B al h es in A he t h bot t a ield f he t n i n o i t a v i t c a s i e r e t dden, i e h les. T esca m i t d e t s e n r e v g o in t c a r e t le caus p i t mul je c t h oc acc nt , be g ins wi t h a n a n a l y sis o f t he look in g , r e a c h i n g an d B l ou at i o n s f r o m th e t w o c o v e rs . A s t h e e x p e r i m e n t e r v e y r o m e nd m a i i n g t h e t o d y , i t d e t a r t s u l , as il sk a he t e t is r p m o c t a h y h t s t en direct s a t t e n t i o n t o t h e A l o c a t i o n b e 6.19. ield f e h t hen T A t a n o i t a v i t c a t nsien a r t gh, i h a s e c rodu p . in Fi g u r . p ol ve s a de c isi on o v e r t i m e ev When t h e a c t i v a t i o n ea k a m i c s . Th e dyna h k D s y n cr os se s a th r esh o l d , t h e infa n t r e a c hes to t Ta a t lo ca t i on. m i c f ield simula t es t h e i t ca lo to h c ea r o t s t e- t n i y b B r o A on de c isi ons o f infa n c s n e infa onc t a h t is t n u o t c is a h l for t ia uc cr st Mo rat a r i o u s inf l uenc es on t h a t de c i - g , o v e r t i m e , t he v g in a h be ac h, a m e m o r y o f t h re t r e a c c o m es a n ot he r input he t f , d e r o si inspi y l l a r u e n is odel m ield f e h T on. t he s e c ond A t ia e r e is h l, t to t he n e x t t r ia l. T h us, a t r y i ll y b y A m a r i z i er ract a h c nd a d ibe r desc pe ty c an al a t ed t so me inc r e as e d a c t i v a t i on a si t e e- r he p t f e o caus A be ica d ot t a n . c i f i c e p s y l l n m n a t c a r o t s ab is t i but ), (1977 a o is c h e. T r e h t y t vi i t c us a o vi cue g n i d i e h h t h t es wi bin m a odel e Th ha s a on e-d im ensi ona l m c t i v a t i o n f ield , ia ls to A, r n y e h to A. Ov c a e ond r ma c e a s e c rodu to p t r a g def in in a pa r m e t e r spa c e o f pot en t i a l act i v at i o s e t a t s n r a s ron g m e m o r y o f p t e v i o us a c t i ons builds up . Ea c h nd B). I nput (i hi s c as e t he lo ca t i n t ons o f t a r g e t s s A a p al em be ds t h e h i s tor y o f tri r v i o us t r ia ls. N o w , c on- e b d i r l o c a t i o a nd t h e i r inf l uenc e o n e t n e s e r ep e r ar e t h y n r i - si de r t he c r u c ia l B t r ia l in Fi g u r e 6.20b . T he e x p e e th ield. M o s t impor t a n t , poin e d i v o r p ield f e f h t in s t cue a h ut as t B . g cue to B ron t des a s i ov pr er nt me t

44 301 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 301 Dy a m i c Sy n h T S m i t h , 2001; Sm i t & e t a l., 1999). T h e e r ror helen, ca n o c c u r (a nd n o t o c c u r ) e v e n when t h e r e i s n o t o y to i be i dden (Sm i t h e t a l., 1999). Di rect h n g a t t e n t i o n t o a n c in-vie w o bje c t A h e i gh t ens a t i v a t i o n a t t he lo ca t i on, t t c bje o w in-vie y l l ua in n o c t. a h t to h c ea r s t n infa d an eq bs l Su y t uen , when t h e e x p e r im en t e r d irect s a t t e n t i o n to c if fere n t n e a r b y in-vie w o bje a d t B , infa n t s w a t c h , but g hen r e a c h b a c k t o t he or i t ina l o bje c t A. Ex p e r i - e me t e r s h a v e a l s o made t he e r ror v a n ish b y ma k i n g t h n al i r t B e h h t n o s e h ac re e t m o r f y a w e m o s n i t n fere f i d s A e tr r ea c hes. I n t h e m odel, t hes l d if fere n c e s d e cre a s e ia th e inf l uenc e o f t he A t r i a l m e m o r ies on t h e a c t i v a t i ons in h e f ield. t On e e x p e r i m e n t a c h i e v e d t h is b y sh if t i n g t he po s t u r e infa of t he infa n t (Sm i t r- t du o sa wh t n h e n ., 1999). A l a t in g t ia ls w o uld t hen be s tood up , as sh o w n in Fi g- he A t r t 6.21, to w h t he h i d i n g e v en t a tc B , du r i n g t he dela y e a ur r i n g t he s e a r c h. T h is po a t u r e sh if t caus es e v en 8- nd du s nd 10-m t h-o ld infa n t s to s e a r c h c o on rect l y , j u s t l i k e a r on t h-o lds. I n a n ot he r e x p e r i m e n t , t he sim ila r i t y o f 12-m ac d nd B t r ia ls w a s c h a n g e d b y put t i n g on a n re hes on A a ki t of f w r is t w e i g h ta s ( Die d r ic h, Sm i t h, & T helen, ng “ 2004). I t s wh o r e a c he d wi t h n hea v y ” a r m s on A t r i- nfa a ls but “ l i g h t ” on es on B t r ia ls (a nd vic e v e r s a ) d i d n o t m ma t he e r ror , a g a in p e r for e i n g as if t h e y w e r e 2 to 3 k mo nt hs o lde r . T hes e r esul t s su g g es t t h a t t he r ele v a n t g me r ies a r e in t he la n g ua mo e o f t he body a nd clo s e to f t i v a t i on in t he p l a n - Fi g u re 6.20 (a )T he t i m e e v o l u t i on o c a n h t e r o c s r nde u y e h on, t i t i add t he s ens or y su r f a c e. I e he o ni f ield on t he f i r s t A t r t c bje ng es as t s i on r i t a v i t c he a l. T ia hi c e n t r a l i z e d na t u r e o f e r ror : T he r ele v ghly de a n t z is h dden a nd due to s e l f-or g a n i i i n g rop e r t ies in t he f ield is p n i d i he h le, t b a he t on t s r e v o he c ude t es incl caus , t en v e g t f t a i n e d du r i n g t he dela y . ( b) T he t - a v i sus c a on o i t u l o v e e m i n i t h g i e is he r e ti on in t he p l a - n i n g f ield on t he f r s t B t r ia l. T h vi i t c a t he pas t , y he dela t t he infa n t , a nd t o he f e el o f f y t t y r o m e t due to m en en e d a c t i v a t i on a v A p r i or to t he h i d i n g e t t he body o f t he infa n . he o for p r i or r e a c hes. As t bje c t is h i dden a t B , a c t i v a t i on r i s e s h Th icausa l i t y dema nds a r e t t in k i n g o f wha t is is mul rop- B, but as t h is t r a nsien t e v en t ends, due to t he m e m o r y p at 10-m on t h-o ld a me an t b y k n o w l e d g e nd de v elop m e n t. D o e f o n o i irect he d d in t le on is pul i t a v i t c is a h , t ield he f t f ies o rt i h y ma infa e t h e when t t n e r e f f e d g n i h t e m o s w o n s k t n k e t he lon g e r-t e r m m A. d r a w ies, to r o m d y r e nsw he a ot? T h t wi is e r mpa o ror c er do n when t h e dg es if w nd k n o win g as y c e onc ep t u a l i ze k n o w le e a g u m m o r em e f t n e m o m e s reci a p t e l p i t l or made a t n e r de n i g A be t ons a i t c he a t f o ca r o m e g m in r e g n i he l s, t y y - i d he im nd to t sk a a he t on to t i e t ela in r s t en mpon co m o - c he de t t if e, to sh m i t r e v i d n , a ield he f t e t ina m to do , t vi i t c g a in d e c e r ely p at s y he s t f o y t em. Wha t do 12- l si l r odel clea he m de. T A si y a u t he habi ck to t a on b mo r e ca n e h-o t on 10-m t a h t w o n lds k h-o nt lds do n h ot? T ed t r e h t: T enden dep e m i ror is t r he e t t a h t pr s ic e is a e o sin gle caus e, n o sin gle m be n c h a n ism, a nd n o on e f ely a t a i d e ief p m od im i r e t when en v e g n i d i e h h r t e t br a ow h-o t on uishes 10-m g in t s i d t lds h e t r u t c u r t e s dg le kn c r a do e uld s o s sh y e h t d e nd inde , a ly t c e r r t c h infa n o 12-m on t h-o lds be caus e t h e r e a r e ma n y caus es t h a t fr om a l., 1987 (W el l m ). n e t a r a r a e p ror ap , bot he e t e k ma h 10- ead t n . I r a e p isap nd d s h t g m odel as a g ui de, e x p e r i m e n t e r s c a n ma i k e Usin s t e s em t s y s x e l p m o as c d e d r a g n be r lds ca h-o on nd 12-m a is r th e e ror c o m e a n d g o. T h is a c hi e v ed b y c h an gi n g e h t at l ia r t s t a jus , r e v e w o . H sk a he t t g n i r ze du i n a g f-or l se th a y e rop ies p g abbin r on-g i t n e t t r t he t g in en t h g i he y b , dela sk dy- dyna m i c s a r e n e s t e d in t a sk dyna m i c s, s o a r e t a b , an d s y inc r e a sin g a h t of o r e v o c e r t h e nd h i di n g e v e n t elop na i c s n e s t e d in de v m m e n t a l dyna m i c s . he t g asin ic e b r c de e m u n r o f p r i o r r ea c hes to A ( Die d r h,

45 302 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 302 n a m i Dy t n i n g for a B t r ia l. a l a ia r A t n g for a in t t si t n infa An re 6.21 u g Fi nd s d s s (1998) simula t es de v e l- a t a k na ), Mu odel s m em t s y ic ror has r ot-B e he A-n T . s c mi na y D l a ent m p elo v De g en impor t to de v elop op m e n t b y s t ron g e r s e l f-sus t a i n i n n m e m o r ies for t h e t be m e n t is t e i caus be a y r o e h t l a n t . y t h e nc . H hs in infa t n o w m e to a f d e k n i ly l t gh ti o w e v e r , hi di n g e v e i g If s e l f o s e ess c c su he t e v i r d ies r o m e m f n i n -sus a t a ne f ral u odel su g g es t s t h ield m t t he dyna m i c s t e- r c t a h en, r ld i h c r lde o . m o r f e m o c y e h t e r whe sk a t mus e w hen t r at he e r ror in infa n t s a r e b a sic p e t o c ess es in d v o l v e in r imp t a h t y a d y r o- v e g oin d s t n infa e r a t Wha l r i e h t es v o e g i g n a h c y , b d e nde es. I g l a l n t ons a i t c a d e t c e r i l-d a go a O ? y r o m e e po m on i t ssibi l i t y is t h e i r ca s el f-lo c o m o t i on. n e t a sk , r e s e a r c h e m o s c ror r he t e v i t a v r e es r p e k n ma s ca r e t a w l i n g ap p e a r s t o i mp ro v e t h e spa Cr i a l m e m o r ies o f in- ild s. n t as in infa s, jus t nd adul en a r t h r c lde in o o nd g a r o ls a e r a e fa he t t u B 1990). s, mpo a C & l a h t en t r e B ( s t n Re nd c a r e enc p n a d , S ly nt ce e o l lea g ues (2001) in v e n t i s he r e v ro mp i l ro t n o c otor m e in f r i e h p o ssibil ot t ies. T w i y lds b r-o ea le for 2-y b a t s sui a h t a h sk t a ot-B t A-n d i n g n t’s f i r s t y ea r . r ma t n i r du ly d e k h e l a s t p a r t o g f a n infa e o s s t en es r nd p he sa t f a c a f r he su x. T ndbo in a sa y to o Pe r hap s m or e e x p e r ienc e p e r c vin e i g bje c t ipu- n a m d n a s e e t e ica un ifor m f ield , s o t h h r e a r e n o ma r k e r s to ind t t g n i t la e ic ot n o t s t n infa f o y t i l ibi x le f e h t es v o r imp hem e tw le h i d i n g lo ca t i ons. Ex p ssib r i m e n t e r s g a v e tod- o po vi- e r a r i e h t to d e i t less to be or s t e g t r di f fere n c e s in t h e p dl er s ma n y t r ia ls a t lo ca t i on A, a nd t hen h i d t he to y a t t sk t a e p e r a t ot-B n - A e h - g n i c i ract p ly mp i S ons. i act s ou he todd le r s, ha lo g t i on B . W i ca t h a dela y o f 10 s, t vin Dia ( e nc ma for r e p es v 1990a r imp ly ed is h t n I ). , ond m o dden a wa tc he d t he to y be in g h i t lo ca t i on B , s t il l r e - ie , wa r e a l-t im e a c t i v i t y i n t he t a sk is u n if y d w i t h d e v el- i tu ed to lo ca t i on A to d rn g in t he sa nd for t he to y . I n - t i m e . D e v elop m e n t a l c h a n g e m ro f s e v l o v e l he t op m e n t a , t r e de h e r e a d e ma n y ot he r si t u a t i ons in wh ic h bot h re t n infa e h t f o ies t i v i t c a e . im l-t a a r w in- e n e t t despi ck on a habi ild b l l fa s t nd adul en a ch , ma t i on ( B ut le r , B e r for h i e r , & Cl if ton, 2002; H ood t t a c i mpl I s o c i m A dyna roach. p p c A i m a n a Dy f n o i o asada Ca r e y , & P r , 2000). N d n e t heless, in t he s t a nda r s o l v e a n ap- sy st s t h e o r y o em f de v elop m e n t help s to r e g 2 ot-B t a sk , infa n t s c h a n A-n e t h e i r beha vi or o v e r t ica l c o n t r a d i c t i on. At a v pa r y glo b a l le v el, r e n t t h e o r e e y inc r e as- mo is is simula t h odel, t ield m he f t n hs. I nt e d b r bi t d n a e g a i r l he ica g o l o u o y d b e s s impo t n i a r t ons he c t t e es i k s ma i h ield. T he f t f on o i t a v i t c g a in t s eas- he r g t in t esul em to r e s s t n e m ron vi n en uma ies in h t i r ila he sim t by o r he input f r for t ie cue to for m a n i d i he h t g m utc l ila r de v elop m e n t a o in sim o m es. A l l in t a c t h uma n in- t f-sus l se t wi t h t he A m e e p m o e B to c t m- a k a e p g n i n i a g fa t s lea r n to w a l k , p r o n r ess f r o m ma k i n g t he A-n ot-B o a dyna or y . S i m i la r l y , in he r m odel o f t he e r ror (a ls m-

46 303 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 303 Dy a m i c Sy n e a g ua g e, a n d nd t i m e” o u t s i de t he m o m e n t o f k n o win g. K n o win g , jus t n la i t r na i e h k t ea , sp t i g n i k ot ma ror to n er v t t y ic s m a dyna of uc d o pr y r a t n e m o he m on, is t i s- c e a lik t e looks a ut when on s. B ip onsh i t ela r l a i c o e s ens t m in for e s e em s fa r less nd hla c r u on. Ch i t c a v de f ls o i a t he de t f e o le caus iab c o iss ot a d em, n t elop m e n t , t he pic t u r m in . Ch ild r en f r o m t he sa m e fa de t e r c y: a is w h t t ) put i (1986 m i ly g r o w up i t is a z in gly d i f f e r e n t f r o m on e a to be a n ot he r . Ch ild r en m ic adv t s o c i a l a nd e c on o m h a n t a g es s o m wi e t im es fa il in a B]r [ pa on for i t i n g o c e r n r e t t f ess o he busin ot in t e n r ins a e r e, whe f li as t h o s e f m impo v e r ishe d b a ck g r o u nds su c- r o t t n g o - c on, as a c e r n r e i t i pa f o e r u t he na nd t e, a k n sa w it s o t n o he c s r nde t be u ins, mus a br y d b ishe l mp co tood in t f t o x e l h n in ea r i t ies m i gh t be r c f onl e c t e d in de v elop- c u d. S ee e o le in h s ro it a n o i ut l o v l. E ro t n o otor c e m v e i h c ins a w br t me a s s t ag e l i k e s h i f t s a nd m i gh t u nde r l ie t he d r a m a t ic n n in t i t is, pa t t be r n r e c o g g wha i t i on is t h e r e to sub s e r v e e di f fer enc es be t w e en 10- a nd 12-m on t h-o lds in t t a he s n - e na i on . . . . [ I ] f w e i g n o r t m otor c o n t ro l as t h e i d otor c m oor r is made f t n e m elop v ut if de . B sk a ot-B t da A-n d m o r t nd pa a t s r nde u e h w ic in wh h t wi t t e nt e co r n r e c o g n i t i on, x en t s, t hen t hes e n onl in ea r i t ies m i gh t a l s o re a l-t im e e v g i ru n t he r isk o f g e n erat n g b i o l o we i c a ll y ir re l e v a n t s o l u - d l l sma y r e en v v enc r e f f i l d dua i v i e ind at cre es. E - r e f f i 474) ti ons. ( p p . 473– l a t n e m elop v enc es a t a t g s in inn g es in be ies tor s i h nd in de i v i e ind g r nd lead to la y a if l p m n a ca es. If enc fer f i l d dua o h l nd a in as a g y be g ma win - n us, k t. T c k to a in th We t hen a t l wil t n e m elop v el, de v o, t e l o r c i he m is is s th be y wa ys s- be a n inhe r e ic s t ly s ens or im otor a c t. Ou r dyna m n e - l a e ic r t r a r ync s o i d he i to t nd v d e i t h c mu y r m essie a ms ac co un t t h us s t a nds on c o m m on g r o u nd wi t h Pia g e t te t. F n me ac ti vi t ies o f t he infa ti r o m a dyna m ic p e r s p e c- in t s but a y t vi i t c otor a im or l ens t in s gh u o h t f ins o o g i he or y ti e, i t is impor t a n t to u nde v es b ess c o r he p nd t a t s r r ela , T h o m p- J s h t nd wi u o r on g m m o on c on (1987 n h o ); V a t wh he e v e r yda y a c t i vi t ies o f c h ild r en c r ea h t e de v e l- ic r on, a o sc h (1991); Ch s u nd R c hla nd (1986 ); a nd Edel ma n he u n i v e r sa l a ttai n m e n a n d ts op m e n t a l c h a n g e— bot h t (2005) a s ) in t he n e w e r i nd Glen- (1987 u o l a deas o r a B f v i dua t h w a y s . l pa t he ind i a r r g a nd Kasc ha k (2002) t es in t h h e be t c o g n i t i on em e g or ens s nt re ur le a rec c i on to be enab t a h ns t r e t t t otor pa im e W s K n o w i n g? Wha t do l l t h is m hat I a n for Pi- es a . d i gu y ed u t p perce all h i n g h is o w n c h il- ag et ’s or i g ina l c oncl usi ons f r o m w a tc es”? Wha dr e a r c h for o bje c t s in t he “ w ron g p l a t c en s mi t Dy na c S y stems an d O her Theori e s o f D e v e l o p- s n d n on a e g r la il a B f o t esul he r for t a e is m h l t l es a do e o s as a t em t s y l s ica m t is dyna en r h f f i w d Ho . t n me r y e s t n infa t a h nd t u fo e v o ha wh s r he nd ot r (1988) a abe Gr d helen a c roa p r ap he ot m o r hes? T f t n e m elop v de of n se em to k , in o w t h a t o bje c t s s t a y whe r e t h e y a r e put n r e i t Ba e c e n t ly c es (2003) r onsi de r e d t h is q ues t i on a nd t h a ta ic h t h e y only w sks in wh tc h but do n ot a c t? H o w do es y e h 6.2. T e l c - b a d in T ze i r ma e sum r ons a usi oncl f c i e sp i th m ic s y s t em s a c c o u is dyna t f i t wi t h Mu na k a t a , Mc- n m a r l f ica t e r o e h g t win o l l he fo t d e de onsi ly c l ca r ks: or w e gle e nd , J o h n s on, a nd S i e la r (1997 ) a nd t i r c onn e c - h Clel on is t a c c o u n t , in wh ic h in t e r n ti a f ons o i t a t en es r p e r l r o t s r esi de in on e s e t o f la y e c s t h a t del i v e r input to a bje Ch o m sk y ’s (1968, 1975, 1988) na t i vis t t h e o r y o f la n- 1. h a r t e s y s t em t epa a t a c t s ? s gu ag e de v elop m e n t (wh ic h has inspi r - o e h t t vis i t na d e ssib he A- t t a h ons is t i t ues e q hes to t r On e po e le a nsw l ies in ot e on, s iscussi for a d l— e e ins as w ma r do he r h e ut r ly abo ror is simp i n g— n ot abo ut t he o a b - r ot-B e n c , 1983) odor F n e is a h t o t g n rdi co Ac , g nsw i w o kn ut ot abo nd n a t c je r . n a on i t ep c r e p f o y r o e h t Gib - r e p d 2. E. J. (1969) s o n ’ s en n- t s in t he A-n ot-B t a sk r e p r es n t o bje c t s in d e p e infa ce pt sis) l d e v elop m e n t (wh ic h i s empi r i c i s t in emp ha ua c t i on s ri g h t f r o t m t he be g inn in g , a l - r f y l t n om h e i r a de 3. go ts ky ’s (1978) t h e o r y o f c Vy g n i t i v e de v elop m e n t o hou t . l a t e a t a k na as Mu , t o y n ons ma i t a t en es r p e e r s o h gh t is s w o c i a l f r a m e or k (a t h e o r y t gly em- ron t h t a in a s g - l a o t g por gh to sup ) su (1997 o g en ron t be s , t es g u in f t s i c i r pi d n a x e l p m o inly a c a t r e is c t gh i u o h t , r o v a l h l r ect ed ma n u a a c t i on. T di is a nsw e r d i v o r c es k n o win g p ap t s i c i r empi n a f le o mp a x g e in t s e r e t in ) h c roa he o t e r s whe w o n k t n he infa g; t n ti ac om fr bje c t is when i t t t 4. g e t’s (1952, 1970) c ons t r u c t i vis i- h e o r y o f c o g n Pia nn o n t ro l t he r e ot c a c ca t but jus , dden in B i is h h. red ve ’ y toda o t r o s s ece s p irect (a d t n e m elop v de ti ie he p g is t win o n g. K ron is w r e nsw is a h t e v We bel o- r i ) e r g e nt em s t a ppr o a ch i le v ele c y s t em s ess o f dyna m ic ass e m b ly a c ro ss mul t d s a l. (1996 ) o ma n e ut in El t 5. C onn e c t i o n ism as la i d e r r e- p in t he s e r vic e o f a t a sk . W e do n ot n e e d to in v o k e bje t ” or “e x t ende d in spa 6. Dyna m i c s y s t e m s as la i d o u t i n c helen a n d S m i t h (1994) as “o h c su s t c u r t ons c ed nt se c e T

47 304 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 304 n a m i Dy t T s ABLE 6.2 A T axo n o m y o l Theori f D e v e l o pm e a n e g y T helen /Sm i t h El ma n / B a t e s k s t o g Vy n o s Gib y k e s hom C y r eo Th Pia t on e erce p t u al Emp hasi ze d m e In te rn a l iz a t i o n C onsr u c t i on Se l f-or g a n i z a t i o n Em e r g e nc i / lea r n e d c h a n ism o f Ma t u r a t P e ons r n in g c onn lea c t i ch a n ge No Ye s Ye s e s Ye s Ye s Ex p e r ienc Ye s s Ex t e r n a l infor ma t i s Ye s Ye Ye Ye s Ye No on No No No s Ye No No l a i c So s No Ye s Ye s Ye s Bi ol og i c a l c o n s t r a i n t s Ye s Ye t n a in de v elop m e Br No No No No Ye s Ye s s No t Ye s No Ye s Ye Em bod im en No Ye a (n ot in l r e p r es en t a t Ye s i ons Ye s No Ye t n Me s s No tr e) ens l s ona i t i d a No s em t s No l s ica m Dyna ( y No Ye s Ye s es) No y /simula t i ons Ye s No No No Ye s Fo s rm al m odels Ye y s t em s: A r e T h e y R e a l ly Dif f e r en t?” b y E . T helen a nd E . B a t es, 2003, De v e l o pm en ta l S c i enc e , 6, dap t e d f r o m “ C onn e c t i o n A nd Dyna m ic S ism a –391. 378 pp. h r e g a r d to (1) t h e i on inhe r en t in a r i c hly s t r u c t u r e d en vi ron m e n t. T h i s act T hes e si x t h e o r ies w e r e c o mpa r e d wi t ima le ima r y m e c h a n ism o f c h a n g e, (2) t he s t r u c t u r in g ro is p r pr r i ly a p r o c ess o f per c e p t u al l e a r n i n g , or a n in- c in- i a cre a s i n g abil i t y to d isc e r n r ele v a n t f e a t u r es in t he p e r- i l of ex te rn al infor ma t on, (3) t he impor t a nc e o f s o ua a on, (4) t he ro le o f bi o l o g ica l c ons t r a i n t s, (5) t h e ce pt i l a r r eract y a nd t h us to t u n e a c t i ons ap p rop r i a t ely to t e o f infor ma o us t i on abo ut br a in de v elop m e n t as a t h e o r e t hem. V y g t- r Fo n. io t a iz l a n r e t in on y r o e h is t h t buil y k s t n i nd l e a v i t n g o he c t f o y n ma , y k s t o g Vy r a i n t , (6 ) emp hasis on s ens or im otor p r c ess es, i ica l c ons c- u r t ic s t uis g t o tur h a t ma k e us h u ma n a r e f i r s t p l a y e d o ut in t h es t r es en p e r l a t n e m f on o i t a nd elabor hasis on a ) emp (7 t a - e n v i eract t s as a s in l a or vi beha f m o al re ons, (8) in ti o u r c e o f em t s y ic s m dyna f on o i t ca o t. adul t n e et p m o c a h t i w o By pa r t i c i pa t i n g in s o c i a l in t e r a c t i on, t he y o u n g or a n- e e, (9) us g n a h nd c e a r u t c u r t s f on o i t na la p x /e on i t causa g e p e o inc m o r es f v o ism m r m of ma t hema t ica l for ma l ism s, a nd (10) us e o f c o mput - l a n r e t e, in enc t e mp o e to c enc t l a i ons as a too l for t he s t udy o f de v elop m e n t . simula izi ng t he r ele v n t s t r u c t u r es u n t i l he or she ca n f ina l t y t e rodu c t hem on h is or he r o w n. A l p h o u r e h c i is is a r h gh t n cha Me - e o r w d t e k o v y in sk m o i- m r e t de l a t n e m ron vi en f m o d for e t ica t s i h p o s re o m d an Ch ge. n Cha f s o sm i n na i on t h a n on e f inds in ma n e y w r g n a h i c t in gs b y ma n y o f l a t n e m elop v t for de n u o c la t e d m e c h a t ism s to a c t empor n o t c is or vi ’s beha ky ts go Vy r n, Eu- ica r e a a nd t he ro le o f t he en vi ron m e n t: pa r a m e t e r s e t t in g a n d ies (Am a t to t i on is c e rop t a inly a ea n, a nd R ussia n), in t e r n a l i tri g g e ri n g. Tr i gge r i n g re fe rs z - t s i x e e r a p f o e s elea he r r t u he o t m o r f ” - n ot u t (n en v e l a t n e m d vi en n a y on b i t op l a or vi g beha in pushe is “ t a h ism t an ch me ron t’s e g de. Pia i s lik se he t r i g g e r i n g o f t he p r o c ess es t h a t lead to ma le e h hasis on t emp t n e t onsis is c s h a on w i ibut r t n o l c na mi e t ni d r s e y b e r , whe t n e m elop v e d e v i gnit o c f o re u t a n l a n o i direct bi ge elea ta l ia in t he em br y o b y t he g e n e t ica l ly t i m e of os t hen adjus d t n on) a i t la i ld (assim r o he w t on t c en a r ild ch te st te ron e). Pa r f m o d for he ic enr n is a g n tti e s r ete m a r tr ge ri ng , a p r o l c ess whe r e b y c h ild r en us e en vi ron m e n t a th e i ig act i on sc hema t a in a c c o r d a n c e wi t h t h e i r de g r e e o f h e c o r rect p a al ram et er s for t h e i r na si i v e gn s t o s e l e ct t su c c ess or fa il u r e (a c c o m m oda t i on). T he m e c h a n ism o f t e g ua g n la s i n o i t c e onn in c ge an ch a m ma t ica l op t i ons. I n inna e g r e r a t n e m elop v de f o s t n u o c c a t f y o a r r a n a m o r f t g sub- elabor a t in g t hes e i deas o v e r t he y e a r s, Ch o on m s a t h g i e on w i t c e onn es in c g n a h ly c l ipa inc pr m sk y has c on- t la ies in t i r u g e he r t t a h t h c odes su n e k i ron-l u e ic n ol mb sy sis t e n ly s t r e ss e d t h a t lea r n in g is h i ghly o v e r r a t e d as a r beha ma e do s o h t for t leas t e, a g an ch of ce ur so vi or s e ess c o r p l a n r e t he in t o t in d e t a f t he w o ins o ld a r e inc or por at on, or Gib ies. F c e he sp for t t n a t ly impor l a i c e e esp ar s th th at c onn e c t n odes to ea c h ot he r , a nd input to o u t put. a n ge a r e ch i l d r en ’s e x ons l t he p o- r ima r y m e c h a n ism s o f c h So me m odels be g in wi t h f e w c ons t r a i n i n g assump t i p h ei r en vi ron m e n t a nd t he d isc o v e r o y o f ma tc hes - c e t i rat n o f t abo ut a r c h i t e c t u r e, whe r e as ot he r ’s b a s e t h e i r a r c h i l nc t be tur e o n cu r r en t u nde r s t a nd in g o f n e u r a w pa t h w a y s or as a e en t h e i r cu r r en t abil i t ies a nd t he a f for da es for

48 305 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d s t e m s Theori e s 305 Dy a m i c Sy n l r k a t a , t in s g n i t esul ons, r i zat i an rg reo u c t u r es t h a t ca nn ot be ly & Mu e O’R e e e (s enc i r e p x e f e o uenc eq ons c i na y 2000, for a c l a n r e t ld. Ex r o w e d i s t u o e h t n i infor- l direct ed ect t de n ). I l ia utor nd t a w vie e r e v ehensi r mp o e n a h c e l m pa i inc r he p t , po- or he inc e t caus ism be n o i t r e v e w o l, h al c onn l to c ica t i r on is c i t ma is in- n a h c f ism o e g r a t i on o f s t a t is t ica l r e g u la r co e h ld is t r o he w por t i r ula g e l r ica t is t a t s f on o i rat i t ies in t he lea r n in g ies in t e t s o h in t e g n a h f s o ism n a h c e l m ipa inc pr c ies. Ex- r o e en vi ron h m e n t . ic s y es dyna w do Ho s t em s d i f f e r wi t h r e g a r d to t h e m te rn al st ru ct ur e is c r i t ica l to dyna m ic s y s t em s t h e o r ies nd a h , a nd ha t sk a a ic t f i c e he sp t , d l r o he w e t caus be pr inc ip le caus es o f c h a n g e? T he c onc ep t s o f s e l f - s- i y e g enc e p ropo s e d in dyna m ic s y s- nd em on a r i t a z i n a g or tor y of in t eract i o n i n t h at w o r l d, i s o n e o f m a n es caus y ron g a n i z i n g t he s y s t em. H o w e v e r , in dyna m ic s or s t em s, a r a s bea ry eo th ms te ip to onsh i t ela l r ica tor s i g h t ge in e x t e r n a l s t r u c t u r e ma y r esul t in a c o m p l e t ely otor Pia g e t’s c ons t r u c t i vism, t he emp ha sis on s ens or im ch an oc on- es is sha r e d wi t h Gib s o n i a n ap p roa c hes, a nd a ess pr di f fere n t endpoin t , but t he endpoin t i t s e l f is n ot c c t i on- st ru ct ur in g ro le for t he en vi ron m e n t wi t h c onn e t tai ne d in t he en vi ron m e n t. T h is t hen is a sha r e d poin c whe hes ha v e ism. C o n t empor a r y dyna m ic s y s t em s ap p roa wi t h na t i vism: H o w e v e r , r e as na t i vism s e es t he ma in c i a l in t eract i ons, but c o u ld in p r inc ip le s n ot c onsi de r e d s o caus e as t he c ons t r a i n i n g p rop e r t ies o f t he s y t em i t s e l f ; s dyna i t nd na y (a sk m o 2004). Ch , d r a l l a & B u Y e e (s em t vism) y s x e l p m o a c f y o tor s i he h es t e s s em t s y ic s m eract r e t x e d an al n r e t n i g n i se t in ny ma of t u t o s to be lef em but is he r t i ic l p x e e r e a r e h ly? T . s t en mpon o c al n l a e , t ma l t h e o r ies o f c h a n for e in dyna m ic s y s t em s c onsis t e n g y , i r e g g i r a t h t wi n g m e c h a n ism o f c h a n g e. S p e c i f ica l l n Im o rt anc e of S o c i al I p te ra c t io n . Of t he si x t h e- Ya h i a nd B e e r (1994) sh o w e d h o w t he dyna m i c s o f mau c o y e r o is t e h ’s t y k s t h g y le 6.2, V b a d in T ze i r ma ies sum or e r ghly m i us t uo in nt co i h e t a r e n e n g ks ca or w t e t n en r r cu e i usly as a o e s n o i eract t in l a i c o en s k a has t t a h e t only on r t n st inc t pa t t e r ns o f s q uen di i a l beha i t if , sh or vi be- g e st of ce ur so y m o t. Ch n e m elop v e de v i t i n g o sk e in c ur ct ru e t r a c tor s t a t es, in r espons e to a n e x t e r- a t n e r e f f i en d tw t a l a r u t c u r t s t n a t y impor n l y a l s p tor c fa a i c o s t a h ies t den sk y ’s g e na r i g g n e r . T h a t is, Ch o m eral s r e g g i r t f dea o i l t ot as- ro le in la n g ua g e de es n elop m e n t , a nd Gib s on do v l a e be r l l e uld w o gs c in t t e s r e t e m a r nd pa a in a dy- d i z e a c si n y p r i v ile g e d s g n t a t us to s o c i a l fa c tor s. Pia g e t a - a m e w or k as a m e c h a n ism o f c h a n g e . na m ic s y s t em s f r f e ow le dg e d t he impor t a nc e o kn s o c i a l fa c tor s in t h u icula c ons t r c t i on o f t he m ind ( p a r t r ly in h is w o r ks on s t- n g ua g e a nd cul t u r e— la e e Pia g e t’s r ema r ks on V y g o n f E x t r e The St n. o i at m r o f n I l a n r u c t u ri g R o l e o in Pia o ot s d n i ), but d 1986 , t e g t s w ’s vie y sk c i a l udy s a- h c e he m t h t d wi e t ela r r o gly c ron t on is s ensi m i is d Th w pr , to da t e , a h t e g d e l t o n k c es a t a nd B helen a es. T ess oc f e s o e i u ot q is n t gh i u o h t l a t , d ibe r t desc jus g n a h c n ism c i a l s tor c dyna m ic s y s t em fa s ha v e fa ile d to r e c o g n i ze s o h l he sa m e t h in g. N a t i vis t t t e o r ies t end to do w n p a y t h e ess. o r p l a o t n e m elop v e in de r u t c u r t s c f e o c r u as a s st ct ur in g ro le o f e x t e r n a l infor ma t i on, wh ile empi ru i - r ci th eo r ies t end ( b y def st i t i on) to vie w t he en vi ron- in me n t a s a pr i m a r y sou r c e of st r u c t u r e. T h us for The R o l e o f Bi o log i c a l C o nst ra i n ts . Of t h e s i x p o s m sk y , t he en vi ron m e n t t l a y s a l i m i t e d ro le a nd a c Ch r eo th only t s i s ’ y k s t o g y V he e l b a T in d e r mpa o c ies 6.2, gh t u o r h ly t i r a m i pr e r i n g. I nde e d , Ch o m sk y has c on- i g r g t o r n e o l t t i l d a t h ha t e on b y a a s o t g n i h - o i f b e o l o e r h t t u o f n a l ly emp hasi ze d t he pau c i t y o u t he en vi ron m e n t. F o r ti s t a B d n a helen T . t n e m elop v e d n o es t n i a lo g ica l c ons t r en i- a i c o he s , t t s a r t n o in c , y k s t o g Vy t i r is a c t n e m l ron vi t s a y be m o r e a r esul t o f m he issues o f i h t ha t t es g g su t y b d z gh u o r h ild t h he c t ca l s o u r c e o f s t r u c t u r e, in t e r n a l i e he ma in in t e r e s t to V y g o t s k y t h a n a p r inc ip le d den ia l o f t wis ci n t eract i on. Li k e i e, for Gib s on, t he c h ild do es so al l ro le o f bi o l o g y . l l c on t empor a r y a t n e m elop v de us o i r e s A t n ot n e e d to build c o m p l e x m e n t a l s r u t en es r p e es to r r u t c r t i ro le o f bi o l o g y . th T h e o he ies d d e g d e l w o n k c a ies r o e f- c i eady r r l is a t n e m ron vi he en e t caus be t n e m ron vi he en t h s e f r o m t o st r o n ge r (na t i vis t ) to w - c e onn c t e o (m r a k fer ma in infor - e is r th n I . t v o isc g only to be d in t i a on, w i ered i n o ti c i f i c e p s g in in m r e t de in gy o l o i f b e o l o r e h t n i ) t s Pia r t in ua l ly emp hasi ze d t he s t r u c t u r e d na- o t c e g , d ga n o la i t mul l, icausa t mul s t i in s y- e t s y s c i m Dyna es. m o utc m tu s re o f t h e w o r r e h r o s hi s e l erci x e d l i h c e h t h c i h w n i d es hi p ap l t a ic r o ered, c h s e roa bi o l o g y a nd en vi ron m e n st otor sc hema t a l inna ma ni mi , usin g infor ma- t e s ens or im ua eshe e ens s o n s e k ma It le. b a r epa ins nd a d m y l l in t n o c as tc t t r in is or he en h e w t h be e isma ut a m on abo ti i ons a n d n in in m r e t de t s o m or t n a t impor t g. s o m is h c i to ask w h ium) to m o g n a h c t a v i t o e. H ibr uil eq is on (d i zat i w- al re e i n g o c f t o he endpoin , t er ev l op- (for t n e m elop v e de v i ma t u Br i n D e v e l o pm e n t a s a S o a r ce o f C o n s t r a i n t s . i ons) r e f l e c n erat ons a i t ma for s n a r t f ies o r e g s a lon s t d f he fo u r cla ssic o e n o n t t h t e t o es n t a nd B helen a T a

49 306 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d c Sy s t e m s Theori e s 306 n a m i Dy y k sk y— made th eo ri st s— Pia g e t , Gib s on, V y g o t s , Ch o ta t i on in t he s ens e o f Ch o m sk y , Pia g e t , a nd V y g o t s k y m b r n e: A k i on-l i t a t en es r p e e is r r e h hen, t s. T he g ot on am l- o i y o r u e n l a t n e m elop v de m o r on f i t a m infor f e o us h c mu r less us s fa a e w r e h , t r i ut to be fa B y. og l ef n r e t in ul infor t i on (or y t i abil t e s m o s h t em wi t s y he s ma t in t en v e a f t he t w en t i e t h c e n- o the e th t a th ) e i s t ca n poin t to as c o r r espon- c n re r u rec r av a i lab le in t he f i r s t 50 to 60 y e a r s o tur In o- l p x e n en a e has be r e h s, t r a e 20 to 30 y t he las t . n- e s e r ep r is is “ h . T or vi in beha y t i r ula g e e r m o to s ng di y infor d ti on” in t he s ens e o f c onn e c t i o n ism a n d T helen a n si on o f ta m a t i on abo ut p l as t i c i t y , a c t i vi t y -dep enden t is ha t on, i i t i in is def h r t nde es. U t Ba s e n i g to ima d a r fa c tor s in br a in de v elop m e n t , a nd t he bi d irect i o n a l r o l e (s en e e y t n e m elop v in de a in br t n e m ron vi nd en es a n es r p e r e v ot ha es n do at th ry eo th e n e a caus e b ons ( i t a t of bot h g a in l l a or t e r 5 o f El ma n e t a l., 1996; Chap t e r 5 o f vi esponds to a beha r r o c t a h t y t i r la u g e r l i c e esp a ly Chap n r e t re c s). t n u o c y t i r ula g h f t h is infor ma t i on is in- o T helen & Sm i t h, 1994). Mu b le wi t h s t ron g na t vis t t h e o r ies (wh ic h emp ha- co i mpa t i o ghly ze a r i g i d for m o f bi o l si g ica l de t e r m in ism), a nd h i i Dy m ge. n d Cha n re a u t c u r St f ce o r u o a S s a s c a n dyna b mpa co le wi t h t he k i nd o f t m ic ap p roa c h to de v e l- i l a e w r o e: h m i ut t ld be abo u o sh y r o e h t l a t n e m elop v De us i a por or us inc o i r e he s l, t il t e. S t espo e w t n a h t t n e m op o ti c ev en ts li t erall y m a k e ( c re at e ) c h an g e . Dyna m i me m e n t in to n adv of a i n g k n c o w le dg e abo ut n e u r a l de v elop m sy em s, as a t h e o r y o f de v elop st e n t , r e p r es en t s a n ef- l t h d. o r ies has n ot y e t hap p e e ge n eral n d e v elop m e n t a e for t to imp lem en t insi gh t s f r o m dyna m ic s y s t em s t h e o r y t Th em t s y l s ica m on on dyna i t a s as i m i l t n a t impor n is is a h s, a c i t hema t s, ma sic y h in p e o r y abo ut gy to a t l o nd bi o . d e elop v t de ye he v . t r p r i s e ch a n ge o v e he en r t i m e. T h is is t e e r y c o t f o e r Be n- h c t e i t en w t e t a la l e s t s is i em t s y ic s m e dyna caus e f Se ori m o t or Ba s e s o f H ns gher C o g n i t i o n . Pi- i ot su r p r isin g t h t t hes e i deas had a tu ry mo ve me nt , i t is n or otor b im ens he s hasis on t t’s emp e ag a s es o f h i ghe r c o g- m e le inf h t l a tt t n e o elop v classic de r u he fo e on t uenc li l - d as e w y be vie nd ma , a y r o e h is t h f hpin o inc he l on is t ti ni y Gib , e v r u e k i ns l a i n o s y n-da r ode m , r e v e w o ies. H r T he sa h is m o s e m on. T i ibut r t n o c t n a t nd impor a e v i t ea r t c y a , h w nd S ( K els o, 1995; T u r v e y , 1977; T u r v e K els o, a m poin p l ic i t ly d isa v o w e d b y Ch o m sk y (wh o is c o x - t is e v Sh , R e e d , & Ma c e, 1981) ha aw e be en pi on e e r s in usin g t he r e s t o f mi tte d to a g r a m ma r t h a t is auton o m o us f r o m s o l x s to e em t s y ic s dyna a in asp e c t p f p e r c ep t u a l a n d m i c i t in Gib- m ind , mu c h less t he body i t s e l f ). It is imp l i t otor f u nc i on in g in adul t h uma ns. S m m i la r l y , c onn e c - helen a nd B a t es, n ot be caus e o f so h e o ’s t r y , but for T n ti on is t m odels as n onl in ea r n e u r a l n e t w or ks a r e n onl in- g c i g), win o l l fo e e ism (s l a t n e m f ue o iq t r ron t ’s s n o s Gib e l., t n e ma ly El l a i c e esp a e s (s em t s y l s ica m r dyna ea d. V g y o e elop v ly de l u r f e v e s n a dea w he i t e v a g o s l a y k s t e- h t nd p les a ip r 4); t 1996, Chap e h e y em body t he p r inc g t e fa tor s l i t t le ro le onc e la n hes ua g e lea r n in g a nd s o - c def u e dyna m ic s y s t gh s t h e o r em y . A l t h o no m ena t h a t in - ali zat i o n c a me i n to p l a y . Cu r ci en t c onn e c t i o n i s t t h e o r h e t f o e r a w a e r a m s ni o i ect n n o c f o s r e n o i it ract p all ot n r ies l i k e m o s t c o g n i t i vis t t h e o r ies g i v e l i t t le a t t e n t i on to nd n t t e n t to wh ic h t h is is t he cas e, a ex ot a l l c onn e c t i o n i s or y - m otor s y s t em. Dyna m ic s y s t em s ens t f le o he s he ro t e y o p r e t he in ut t y abo to sa h c mu e v odels ha m f r a l-t im la e elop- otor de l-m a u t ep c r e v s emp t i h t , wi ry eo th hasis on p y a it iv act w he slo nd t l- e v nd de g a in n r lea f o s c i m r dyna e ad me , s t a nds s t ron gly in t he t r nt i t i on o f Pia g e t in es- t on- c t a ude t oncl es c h a nd B helen a e, T g n a h c l a t n e m op u ind. ie bod ly em l d m he f g t usin po e, t n ect io n ism a nd dyna m ic s y s t em s sha r t b a s e, a he v e r y i sa e i deas abo ut t he n onl in ea r dyna m m c s o f c h a n g e, s e n- n Me n o i t a esent pr . e R l s a t In th ei r d iscussi on, to in i t ia l c ond i t i o ns, a nd t he sudden ca t a s t rop h i c si t i vi t y es l e o r e t ica l on to a i t a t en h r p e r e v i es g t a nd B l t helen a T incl ud in g U-shap e d beha vi or s) t h a ons ( ran t i t ma for s t t pe rs p ect iv es but Gib s on, n o t i n g t h a wh ile s o e dy- m n c f m t e r g r adua l inc r e m e e a t s a lon g s o a l p e k a n t ca e em t s y ic s m na h t i on (Sm i t a t en es r p e w r he s esc t s i r o e h s t he ma t an ti ta ti ve pa r a m e t e r f o s c i t hema . H o t , r e v e w qu l., 1999; T et t e i c a br a s r he h, 1994), ot t i helen & Sm em udyin t s f y o a des a w i v o r s p em t s y ic s m dyna , g ibin r desc , g e c o n e r , 2003). H o w e v h r , wha t on e c on- & S r e enc p (S p a nd e x l a i n i n g c d e t o n e g as w in ud l, incl a r e n e in g e g n h a e cl udes dep ends on wha t on e t a k es r p r es en t a t i on to a nd pa k i r-l e g g ea i r t , r ie l r r e a m e t e r-s e t t i n g p r o c ess es en t a l s ona i t i ad r g t ron t he s t n n. I a me t i e, r on ens e p r es su h . y sk m o Ch y d b e s ropo e p s o as t h c , a me sica phy ) ’s (1957 n o m i nd S l w a h l, S l e w e s N an es mb sy e em: in st sy ol ons r n a l ly r e p r t en t e d p ropo si t i m Mat m a t i c a l F o r m a l i s he s a n d Si m u lat i o n s . Fo r - a th n- nd a s ax a ema t n y a s h t ls (wi o mb y s s a e at r e p o t v ma ly sp e c i f i e d t h e o r ies ha l e p l a y e d a n impor t a n t ro le c s) wi t es ti r p e is is r h em. T t s y l s ona i t a mput o a c hin en- r r t s o f Pi- o e h ’s t n o ies, pa Gib . J . nd J ’s a y sk m o in Ch s

50 307 P PM 03 : 12 age 12/22/05 d .qx 06 _c 1 am d Co u s io n : W h y D yna mi c s ? 3 0 7 ncl ica ua s t em s. l ly l i n k e d a nd mut ua l ly in t e r a c t i v e in t he ind i v i dua l y l s nd dyna ism, a n o i t c e onn , c y r o e h t’s t e ag m sin Fo i- t n o t. C n e m ron vi he en nd t l a dua i v i he ind en t e w t nd be a gly a e r inc e m o c be l l ies wi r o e h l t ica t hema t ma al rm e y m it nu h e o r ies, wh ic h gy lo impor t a n t in de v elop m . T n t a l p s y c h o nd cu- a e m i mless in t a e e s r es a ess c o r p t a h ns t a e t v i t mula d on es a t e; m e n t a l a e m nd phy sica l a c t e in l-def l en i t f ds (o r o w f gs o n i r ar ely s r e i vi t y a r e a s s e m b le d in he m s- o m e n t a nd a l w a y s as a f u nc t i on o f t he s y s t em ’s h i th at ), ca n lead to deb a t es abo ut “ wha t is r e a l ly m e a n t ” t t t do or do n t a h ons t i t ic d e r he p ut t ons abo usi onf nd to c a r u , in t o n e m o is m h e in t ons don i t c A . y tor e t t he s t a g e n, s f w o l l fo , m i n u t e, w e ek , a nd y e a r . t x e he n or in t vi for beha s e c ond f on o i t ica f i c e l sp ica t hema t im. Ma e cla m o s m o r th l cla re t ica s a nd p r e d ic t i ons de r i v e d f r o m simula- Wit h t h is for mula t i on, i t ma k es n o s ens e to a sk wha t eo im r t o f beha vi or c o m es f r o m s t a g es, m e n t a l s t r u c f ies o t o e h t l a r n e m elop v e for de r u t u he f ly t r e clea r ons a ti t u r es, pa e p all m ons. suasi sy mb ol sy st em s, k n o w l e d g e r odules, or g e n es be caus e t e d c e onn t hes e c ons t r u c t s do n ot e x is t in t i m eless, d isc a o h e r e is n o t i m e m. T nd n for le v el when t he s y s t em c ce as . es to be dyna i m M R A SUM Y s d m i c s is t he la n g ua e o f Dyna t abil i t y a nd c h a n g e, a n g v es de m a r f h c roa p ic ap m a dyna ons i t ues q l a t n e m elop t a e s erci x ’s e s e t nd B helen a T f o t he poin T a s t e at u o i s w abo d wha n e, a g n a h le or c t t e s r s a em t s y ut when s ab ic s g r he la s in t em t s dyna y elop- v de f e o ndscap la r e m e t t a h is t s c i m dyna f r o e w he po e. T g n a h hem c hes k ma es t me al th eo r ies. As sh o uld be e nt i den t , dyna m ic s y s- v e h les. T esca m i nd t els a v le y n ma t d a e s n be po issues ca o i ms i s a p o w e r f u l f ram e w te r k i n w h c h m a n y di f fere n t m ic a l l t he w a em is dyna y do w n a nd a l l t he w a y up! sy st c deas— f ro m t r i g g e r s to ass o i i a t i v e lea i- bod to em g n i n r n g f ul de v elop m e n t a l q ues t i ons a t t h e We ca n ask m e a n i me l to s o c i a l i z a t i on— ma y be r e a i z e d. Dyna m ic s y s- nt l beha a i c o l or s dua i v i el, or ind v e l v- a c i g o l o i phys l, ra u ne l i on to t hes e ot he r te m s is n ot s o mu c h in op po si t e el. B or le v e caus e dyna m i c s s i eks to be c ons t r u c t f r e e , w w a y o f u n if yin g t he ma n pe ect iv y p es but a n e rs th er e is a r e a l pot en t i a l for in t e g r a t in g le v els o f a n a l y sis. p a t dy- e. Wha g n a h c l a t n e m elop v e de is r m o c t h eads t r th v k e wis e, w e ca n p r o e be t he s y s t em as i t c h a n g es o Li e r t h h na ic s y s t em s adds to t m is cu r r en t la ndscap e is bot h a n p e r i m e n t a l s essi on, m o r e e x - a sin ti gle e of me v en t , a n e x elop emp nde r s t a nd in g de v hasis on u m e n t as a c o m p l e x he m v e l o p en ta l t ende d t r a i n i n g , or wha t w e c onsi de r t de sy st em o f n e s t e d dyna m i c s, a nd a c o m p l e x s y s t em o f t w m ti e eks or m o n t hs. T h a esca dyna m i c s is a f r a m e- le o f z i n g in t eract i ons a t ma n y le v els o f a n a l n y sis, i a g f-or l se t y h t f o r o e h ic t f i c a sp n a h e r e h t a r e g ua g n nd a la a k r wo e in a a he br en t e w t e be s o h g t in ud incl d n , a he body nd t som ons, vi- i t la e r r e e de v elop m e n t o f e, p e t hin g — la n g ua g t ld. r o nd w he body a en t e w be en sua l d n a , t en m t adjus t p lesc ado on, i t ep c r e k he s on— is bot h a s t r e n g t h a nd a w ess. T n so a e t r e n g t h ad t n g ma win for vie l a i t en he pot is t y i t i ona l ly s epa r a t e r H N: W LUSIO NC CO d nde r t he sa m e dyna m i c e sum ins as sub ma do ? S C I M A N Y Y D u pr i m t. A dyna n e r pa ly ap l c ess is eq n k a e he w es. T ess oc ua t i es l do h c roa p ap f T he maj or c o n y o r ibut i on o f a dyna m ic ap p roa c h to de v e l- a a w s t es g g . It su k r o w l a e he r t f le o t t m op k e to enc r ohe l c ica th in t i n g , a s t r a t e gy for c o l l e c t i n g de v elop m e n t a l da t a , e r o e h g t in to br l a i t en he pot is t t n e t s: N c i t c e l a i d y b t e en bes has be t a h ield t ues q i n h c e g t in odel nd m sis a y l a n e a m o s , y l l u f e p o nd h a a a f u r e v e r sus y t o on, c i t a r u t sus ma r e g v in n r e, lea ur rt nu in ui t n v he ap- r sus th at ha v e broad g e n eralit y . ( T h a t’s n o t too b ad!) T e on isc d r he ha e for t ut t i t s ot a sub is n h c roa p r- u f o t r t pa des r- e v l a u t ep c r nde ess, p c o r sus p r e e v r u t c u r t s , y t i u n i t e st n g on. o nd s a , c i l bo ym es r sus p r e ic v l o b m y l, s a u t ep onc sus c nd usin a a t ood da g g n i t c e l l o t: C e m elop v de ng di an e a T n g e r o f su c h e i t h e r-or t h in k i n g is n ot t h a t g ood e r he da r e h ods. T h t e m l a t n e m i r e p x nd e e a v i t p i r h desc bot l o ica t e r e h r t ut clea o h t wi a t da g n i t c e l l o ls in c l a f t e pi av gr st ud ies ha v e n ot be en don e, or ca nn ot be don e, but t h a t r e g n ly da l ua is eq t ons, but i i t assump t nd in g c h a a n g e, ca n be ies, r o e h us to spin t o t he poin t o f t he en t e r p r i s e, u nde r s t l ue g o a i d t n a t ns o ut a c o h t l, wi ica t hema or ma al rb ve for g o t t en. Only t he f r a m e w o r k a nd la n g ua g e o f dyna m- a. F hes as r n e s ca ic e dua l i t ies a nd sh if t t he fo cus to ho w d e w lo l ly a l ica m dyna g n i k in h le, t mp a x or e e t t da h t wi r e r o em w t s y g s elopin v he de t us to r in t e r p ks. e t t he A-n ot-B e r ror a nd g e n erat e n e w p r e - u gh t is r a s c i m dyna f he as- e o is m o r he p T e l i z e d t h r o di ct i ons, but only t r udg in g b a ck to t he labor a tor y g a v e m e a ld o s h i t n e m i r s n sump t ons o f c o u p l nd c o n t in ui t y . C o up l g a i n g sub s t a n c e to t he t h e o r i z i n g. T hes e e x p e in th al l c o mpon en t pr om is e for n e w t h e o r e t ica l insi gh t at nd s o for t h . s o f t he de v elopin g s y s t em a r e c o n t in- s, a

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