Papers and Reports on Child Language Development, Vol. 10, 1978

UYCERSTMJDING SENTENCES I N CONTEXTS: SOME DEVZLOPMENTAL STUDIES

I Lo r ra ine K. T y l e r and Wil l iam D. Marslen-Wilson

Max-Planck-Gesellschaft, Projecktgruppe f i i r P s y c h o l i n g u i s t i k

The s u c c e s s f u l i n t e r p r e t a t i o n of a spoken u t t e r a n c e , h e s r d i n a n o r c a l c o n t e x t , r e q u i r e s t h e l i s t e n e r t o i n t e g r a t e t o g e t h e r t h e s e ~ a g t i c and s y n t a c t i c i n f o r n a t i o n c a r r i e d by t h e u t t e r a n c e i t s e l f , 235 s i c u l t a n e o u s l y t o r e l a t e t h i s p roces s t o t h e preceding d i s c o u r s e CO.- L.bt...t. t M' Thc r e s e a r c h clt.scribeci hctre i u v c s t i g a t e s some clevelo~!!~ent::l a s p & c t s o f t h e s e p r o c e s s e s , and it d i f f e r s f r ~ n n!3st e a r l i e r devcl- cymcntal r e s e a r c h i n i t s emphnsis on tile inmedia te p r o c c s ~ i r i ~ ; procedures involved . A s R c h i l d l i ! ; t cns t o a connec-ted d i s c o u r s ? , 1;ow does h e , c lause-by-clause, i n t e r p r e t what he h e e r s , an3 what . - 1r ln2s of i n t e r m e d i a t e rcprcsen-Lat ions does he con2truc.t n.2 p.rt of t h i s p roces s of i n t e r p r e t a t i o n ? I n p a r t i c u l a r , what i s t h e r e l a t i v e ix>a r t ance a t d i f f e r e n t ages of t h e s y n t a c t i c , semantic an& d i s c o u r s e s t r a c t u r e o f t h e c ia tc r i -a l he hea r s?

Our er i r l iu l - rc:;earch i n -tohi:: nre:i foc~lss t td OR syn:;actic and ::;,n:l.nti c s: .~-~:ct;~lr:~.l . v n r i :~l)l.i':i w3.l.h i TI n sell tcrlcc, zn:l ::howpi1 iicvel- o_r.nt.ntel c l i f fe rences i n t h e dorrir.~:lce o f s e n z n t i c r a t h e r t h a n ,synt- ; a c t i c f a c t o r s i n t h e inmedia te r e c a l l o f a s en tence h e a d in a s t o r y con tex t ( ~ y l e r and Narslen-Wilson, 1978). . C h i l d r e n aged f i v e , seven and 1 1 y e a r s l i s t e n e d t o a s t o r y , and a t u n p r e j i c t a b l e i n t e r v a l s t h e s t o r y was s topped and t h e c h i l d r e n were asked t o r e ~ s a t back ver ' sa t ix t h e l a s t seriterlce t h e y ha& >.eard. Tiie f i v e y e a r o l d c h i l d r e n d i f f e r e d from o l d e r c h i l d r e n and z d u l t s ( c f . , .7?-l-vella, 1371 ; Marslen-Wilson and T y l e r , 1976) i n t h e e x t e n t t o which t h e i r r e c a l l was dominsted by t h e s y n t a c 5 i c s t r u c t u r e o f t h e two-clause t e s t s e n t e n c e s . I n p a r t i c u l a r , t h e i r r e c a l l 2.i.d not skcw t h e double bow-shaped s e r i a l p o s i t i o n curves (one f o r each, c l z u s e ) t h a t a r e t y p i c a l of adu1.t performance and t h a t were prod- uced by t h e seven and 1 1 y e a r o l d s . Ins te r td , t h e p a t t e r n of t!i;.ir responses w a s b e s t desc r ibed by a s i n g l e bow-shaped s e r i a l p o s i t i o n curve cover ing t h e e n t i r e s en tence .

Th i s lack o f cl.au:;:i.1 s t r u c t u r i n e o f r e c a l l , t o g e t h e r wi th t h e f i n d l n g t h e t t h e meaning of t h e o r i g i n a l s en tence F;as preserved suggested t h a t t h e f i v e y e a r o l d s were responding on t h e b a s i s of a u n i f i e d semantic r e p r e s e n t a t i o n o f t h e sen tence a s a whole. This c la im was suppor ted by t h e f l i r t h e r f i ~ d i n g t h a t when t h e f i v e y e a - o l d s heard a s y n t a c t i c p rose s t o r y - which r e t a i n e d t h e syrltnc t i c s t r u c t u r e 01- t!ie o r i g i n a l b u t was s e n a n t i c a l l y un i l l t e r - ? r e t a b l e - t h e n c l e a r c l a u s a l segmentet ion was observed. Thus it .., wtj.r, not t h e c a s e t h a t t5e f i v e y c a r o i d s co :~ ld not u s e syntac t ; ic

- s t r u c t u r e t o o r g a n i s e t h e i r r e c s l l , b a t r a t h e r t h a t a ryn t,zcticnl.ly- based clausc-by-clause r e p r e s e n t a t i o n was r a p i d l y supcrceded by a s t ? n t c n t i a l ~c rnz r i t~ i c r c p r e s c n t a t i o n w h e n such a l e v e l o f ' rcprenc2nt- t ~ t i o n was a v a i l a b l e . Tllc :';c:ven and 1 1 year o l d s , a l though c l e a r l y a l s o seman t i ca l ly i n t e r p r e t i n g and unders tanding t h e t e s t -ocn tences ,

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d i d n o t show t h i s r a p i d l o s s o f t h e c l a u s a l s y n t a c t i c s t r u c t u r e o f t h e m a t e r i a l .

The f u r t h e r r e s e a r c h we r e p o r t h e r e w i l l exp lo re some of t h e i m p l i c a t i o n s of t h e s e r e s u l t s . The f i r s t experiment e x m i n e s i n more d e t a i l t h e wi th in-sentence semantic f a c t o r s c o n t r o l l i n g ycung c h i l d r e n ' s immediate r e c a l l , wh i l e t h e second e x p e r i ~ ~ i e r ~ t goes on t o e x a i n e t h e r o l e o f t h e in fo rma t iona l r e l a t i o n s h i p between t h e sen tence and t h e d i s c o u r s e con tex t i n which it occurs .

E f f e c t s of Within-Sentence Sem,%ntic Cohesion We Lrew t h e conclus ion from t h e e a r l i e r experiment t h a t what

p r i m a r i l y determined t h e o r g n n i s a ~ i o n of t h e f i v e year o l d s ' irnm- e d i a t e r e p r e s e n t a t i o n o f a sen tence was i t s semantic r a t h e r t h a n its s y n t a c t i c p r o p e r t i e s . This irrip1if.s t h n t thc extcr i t t o which s tvo-c lause sen tence i s r e c a l l e d as tT*-o s e p a r a t e u n i t s o r as a s i n g l e u n i t w i l l depend on t h e d e g r r c t o which t h e two c l a u s e s o f t h e sen tence can b e s e n z ~ t i c a l l y i n t e g r a t e d i n t o a s i n g l e u n i t . I n ozher words, t h e s t r u c t u r e of r e c a l l should r e f l e c t t h e semantic cohes iveness between d i f f e r e n t p a r t s o f t h e sen tence .

Thus f o r t h e f i r s t experiment we c o n s t r u c t e d a s e t o f 23 two- clnast. :~~:: t -s~.: l !~r lccs, c~?.b~~.i,!c~i i:l 3 si:~rt st.ory, t k 3 t var ied ir, t l i e i 1- i t i t v r ~ i * ~ l . ~ C ! Y L I I ! i ~ . C * ' I I I C * . . i V C , I ~ C * . ; : . '~'CUII is l 1 1 , . : : ~ ~ t i t , t ~ t ~ ~ t ~ : ; (!l i k * ! ~

C c ' n c s i ~ n s e n t e n c e s ) were ones i n w5ich t h e agent znd p a t i e n t were tfll- c v : ~ i n both c l n ~ l n c s , :tntl whcrc t ,hc nct.ionr, i n cnch c l x ~ l s c were c lds t l ly rclatcd and u s u a l l y p a r t of' tkic stu~ic g e n e r a l evelit . For e x m o l e : 1 ) 'Sarah went running up t o P e t e r and gave him a b i g hug The o t h e r t e n t e s t - s e n t e n c e s were Low Cohesion s e n t e n c e s , i n which t h e a g e n t s , p a t i e n t s and a c t i o n s i n each c l a u s e were d i f f e r e n t and, as f a r as p o s s i b l e , d i f f e r e n t even t s were involved . For exmaple: 2 FThcn t h e c h i l d r e n were a t school Sarnh nnd P e t e r v i s i t e d t h e i r f r i e n d s .

Note t h a t t h e s e sen tences occurred i n t h e con tex t o f a s t o r y , s o t h a t t h e e x t e n t t o which t h e c l a u s e s w i t h i n a sen tence were r e l a t e d w a s a l s o p a r t l y a f u n c t i o n of t h e s t o r y s t r u c t u r e which was a v a i l a b l e when t h e c h i l d heard t h a t s en tence . A f u r t h e r cons- equence of t h e f a c t t h n t t h e s e c t c n c c s were not p re sen ted i n i s o l a t i o n w a s t h a t it w a s no t p o s s i b l e t o c o n s t r u c t , f o r e x a ~ p l e , LCIW Colicsion scn tencos i n wl i i c l i C , : L C ~ c l n u s c tlc:;cribed t o t a l l y u n r e l a t e d e v e n t s , f o r t h e n t h e sen tence would have been anomalous i n i t s con tex t . Thus ou r a b i l i t y t c c o n s t r u c t s en tences which were c l e a r l y Eigh o r Low Cohesion was c o n s t r a i n e d by t h e f a c t t h a t each scn tence had t o be c o n s i s t e n t wi th t h e p r i o r d i s c o u r s e . Xe were, t h e r e f o r e , n a n i p u l a t i n g r e l a t i v e deg rees of cohes iveness , r a t h e r t han c o n s t r u c t i n g all-or-none c o n t r a s t s .

A s i n t h e p rev ious experiment t h e s t o r y was p re sen ted over hezdphones and t h e c h i l d was asked t o r e p e a t back t h e l a s t s en t ence heard . Tw?nty Dutch c h i l d r e n served a s s u b j e c t s , o f wb.om 10 were f i v e yea r o l d s and 10 were scvcn y e a r 0 1 d s . ~ Both age-groups heard s h i l a r m a t e r i a l s , t h e o n l y d i f f e r e n c e be ing t h a t t h e seven y e a r

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o l d s heard 14-word r a t h e r than 12-word sentences. Each word of t h e c h i l d r e n ' s responses was scored a s e i t h e r c o r r e c t o r i n c o r r e c t depending on whether o r not it was an exact reproduction of t h e word i n t h e o r i g i n a l sentence. The combined scores f o r a l l s u b j e c t s i n each age-group were then p l o t t e d a s a funct ion of word-position.

Our major hypothesis was t h a t t h e f i v e year o l d s ' s e r i a l p o s i t i o n curves should show more evidence o f c l a u s a l o rgan i sa t ion f o r t h e Low Cohesion sentences than f o r t h e Eigh Cohesion sentences. Whereas t h e seven year o l d s should show t h e same c l a u s a l l y organised p a t t e r n f o r both types of sentences , s i n c e t h e i r immediate r e c a l l i s l e s s dependent on semantic f a c t o r s alone. This means t h a t f o r t h e f i v e year o l d s a second-order ( q u a d r a t i c ) curve spanning t h e e n t i r e sentence should provide a b e t t e r d e s c r i p t i o n of t h e High Cohesion r e c a l l scores than should a fourth-order curve made up of two second-order curves ( t h a t i s , one separa te quadra t ic curve f o r each c l a u s e ) . I n c o n t r a s t , f o r t h e Low Cohesion sentences , we p red ic ted t h a t t h e fourth-ordcr curve would provide t h e b e s t descr- i p t i o n o f t h e f i v e year o l d d a t a .

Figure 1 shows t h e f i v e year o l d High Cohesion d a t a wi th 95% confidecce l i n i t s p l o t t e d f o r each d a t a p o i n t . Remaining wi th in &'-a b.-L2e - confidence l i m i t s z seconli-order qua<rz-r;ic curvs czn be

drah-n across t h e e n t i r e sentence , with only minor r e s i d u a l s . Although a fourth-order curve can be f i t t e d t o t h e s e d a t a , t h e second-order clcrve accounts f o r four t imes more of t h e va r iance than does t h e fourth-order curve.

Figure 2 shows t h e f i v e year o l d Low Cohesion d a t a with 95% confidence l i m i t s s i m i l a r l y p l o t t e d f o r each d a t a point . Here a s i n g l e second-order curve does not f a l l wi th in t h e 95% confidence l i m i t s f o r a l l t h e d a t a po in t s . Furthermore, t h e l a r g e r e s i a u a l s a r e c l e a r l y d i s t r i b u t e d i n such a way t h a t t h e y i n d i c a t e t h a t a fourth-ortlcr f i t is rcqlii r r d . A st ,ni , iat , icnl nnnlysin zhowr~t t h : ~ t t h e Sourth-order f i t i s indeed s i g n i f i c a n t l y b e t t e r than t h e second- order f i t . These d i f f e r e n c e s i n t h e curves a r e not simply due t o t h e case of r e c a l l of t h e two types of sentences , f o r t h e o v e r a l l percent c o r r e c t l y r e c a l l e d was s i m i l a r f o r High Cohesion (64%) and Low Cohesion (80%) sentences .

I n c o n t r a s t , t h e two s e t s of r e c a l l curves f o r t h e seven year o l d s were almost i d e n t i c a l . The form of both t h e High and Low Cohesion curves was dominated by t h e c l a u s a l syr i tac t ic s t r u c t u r e of t h e sentences , and i n both cases a fourth-order curve provided t h e only s t a t i s t i c a l l y s i g n i f i c a n t f i t t o t h e d a t a (Fig. 3 ) .

This d i f f e r e n c e between t h e f i v e and seven year o l d r e c a l l curves was e x a c t l y what we cxpected t o finci, giver1 our o r i g i n a l hypothesis . Semzntic f a c t o r s a r e primary i n determining t h e f i v e yea r o lds ' performance i n t h i s t a s k , and do not seem t o a f f e c t t h e seven year o lds . Rut t h i s coriclusion i s , in i t s e l f , somewhat u n s s ~ i s f a c t o r y . I n p a r t i c u l a r , we do not want t o have t o claim t h a t seven year o l d s a r e doing l e s s semantic processing than f i v e yea r o lds . The shape of t h c seven year o l d s ' r e c a l l curves shows thaz they a r e r e t a i n i n g s y n t a c t i c information about both t h e High

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m d Low Cohesion sentences , bu t t h a t does not n e c e s s a r i l y mean t h a t they a r e i n s e n s i t i v e t o semantic v a r i a b l e s .

But j u s t looking a t t h e shape of t h e r e c a l l curves i s not going t o reso1;e t h i s kind of ques t ion , n o r , i n genera l , i s it going t o t e l l u s about t h e q u a l i t a t i v e s i m i l a r i t i e s and d i s s i m i l n r i t i e s i n semantic process ing a t d i f f e r e n t ages . To g e t a t t h i s kind o f information we need t o look a t c h i l d r e n ' s performance i n t h i s type of t a s k i n a way which can t e l l u s more d i r e c t l y about how sentences a r e being semant ica l ly i n t e r p r e t e d as t h e y a r e heard i n a s t o r y con tex t . This l e a d s us not only t o a d i f f e r e n t kind of a n a l y s i s o f t h e c h i l d r e n ' s responses i n t h e t a s k , but a l s o r e q u i r e s t h a t we t a k e a c l o s e r look a t t h e r e l a t i o n s h i p between t h e t e s t - sen tences arLd t h e i r d i scourse con tex t s .

E'ffects of Textual Cohesion on Sentence I n t e r p r e t a t i o n - This p a r t of t h e r e s e a r c h f o c ~ s e s on t h e poss ib le developnental

d i f f e rences i n t h e ways i n which a c h i l d ' s i n t e r p r e t a t i o n of a Sentence i s a f f e c t e d by t h e kind of t e x t u a l r e l a t i o n s h i p t h a t holcis between t h e sentence and i t s d i scourse con tex t . We have shcrm t h a t t h e f i v e y c m o l d s 2-rc more a f f e c t e d than seven year olds by st?m.uitic cohesion w i t h i n a sentcns? . The qu.?::tions r.cw :trc., f i r s t l y , whether f i v e nncl seven yc:tr o ld c h i l d r e n a r c also , L L [ . ~ ' t - t - ~ . t i ~ i t t 1 . L ~ S C * I I . I i L i v e L o t,lic ~ ~ ~ C Q U I - S ~ ~ 1 . a ~ LOL*:: ~ l c t ~ ~ r ~ t ~ i ~ i i ~ ~ g Lkle

tc.xt~l:-il CJ!~~'.? i011 3:' n sc~i t t ' t !~ t \ , :ui~I, s c c o n ~ l l y , wiiethcr by looking t t t t 1 1 ; .l :1: :1wt.L C)!' t 1 1 e i r [ ~ ~ - I * ~ ' C I ~ * ~ I I ! ~ I I ~ , ~ ~ ! . C > C * ~ L I I : t i 11 :L L. l L - : U - C ~ ~ * p i , - t 1 1 r ~ E.SOU~ semantic i n t e g r a t i o n processes i n seven y e a r o l d s .

We found t h a t we could o b t a i n r e l a t i v e l y d i r e c t access t o t h e processes involved i n t e x t u a l i r i tcgrat icr ; by analysirlg t h e e r r o r s ~ a d e i n t h e c l ause memory t a s k i n terms o f t h e i n t e g r a t i v e processes t h a t we needed t o p o s t u l a t e i n o rde r t o expla in t h e e r r o r s . But t o do t h i s we f i r s t had t o c l a s s i f y t h e t e s t - sen tences accor5ing t o t h e i r t e x t u a l cohes iveness , while s t i l l c o n t r o l l i n g t h e i r i n t e r n a l cohesiveness ( ~ i g h and Low cohes ion) .

Af te r some t r i a l and e r r o r , and s tudy of t h e previous t e s t m a t e r i a l s , we c l a s s i f i e d a group of t e s t sentences , clause-by- c l a u s e , along two t e x t u a l dimensions. F i r s t , according t o whether t h e c l a u s e c a r r i e d information about an cvcnt a l r eady i n progress i n t h e p r i o r t e x t (i.e."Same event" ca tegory) o r whether it i n t r o - duced a new event . Secondly, whether t h e c l ause c a r r i e d new o r o l d information about t h e event t o which it belonged. This gave us t h r e e c a t e g o r i e s , l a b e l l e d a s fo l lows:

1 ) Sane event/Old information = Redundant 2 ) Same event/New i n f o r n a t i o n = Non3edundant 3 ) New event/New information = New

The f o u r t h p o s s i b i l i t y - of New event and Old information - d i d not occur.

We then app l i ed t h e s e c a t e g o r i e s t o a group of 20 t e s t sentences embedded i n a s t o r y con tex t , which a l s o v a r i e d i n t h e i r i n t e r n a l cohesiveness i n t h e way p rev ious ly descr ibed. 40 English c h i l d r e n (20 f i v e yea r o l d s , and 20 seven y e a r o l d s ) were t e s t e d on t h i s n a t e r i a l , again us ing t h e c l a u s e memory t a s k . We w i l l r e p o r t here

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only t h e r e s u l t s of t h e e r r o r a n a l y s i s . These analyses showed t h a t t h e f i v e and seven year o l d s were

o v e r a l l i n s i m i l a r ways, and were s e n s i t i v e t o t h e same v a r i a b l e s dur ing sentence process ing and r e c a l l . ~ o w e v e r , it was a l s o c l e a r t h a t t h e f i v e y e a r o l d s were more s e n s i t i v e t o c e r t a i n aspec t s of t h e input . I n p a r t i c u l a r , i t seemed t h a t f o r t h e f i v e year o l d s t o r a p i d l y semant ica l ly i n t e g r a t e t h e input - both wi th in a sentecce and wi th t h e p r i o r context - they were dependent upon a articular order of information. That i s , semantic i n t e g r a t i o n was g r e a t l y f a c i l i t a t e d when t h e f i rz j t c l ause of t h e t e s t sentence contained o l d information and d e s c r i l ~ e d t h e sane event a s . i n t h e p r i o r con tex t , and when t h e second cl,.ause contained new information about t h a t sane e v e n t ( i . e . Redundant/'~onRedundar,t). I n c o n t r a s t , t h e seven year o l d s could r a p i d l y sen ,ant ica l ly i n t k g r a t e sentences v i t h a v a r i e t y of information s t r u c t ~ r e s . The ana::yscs of t h r e e d i f f e r e n t types of e r r o r s l e a d t o t h i s e conclusion:.;.

I r i t e g r ~ t i o n e r r o r s . Both age-gr-Gups mace a s i m i l a r number of i n t e g r a t i o n e r r o r s . These included both e r r o r s of f u s i o n , where p z r t of the p r i o r d iscourse was i n t e i r a t e d i n t o t h e sentence being r e c d l e d , and e r r o r s based on inference . I n t h e in fe rence e r r o r s , a c k ~ ? g e uss ~ a d e i n t h e o r i g i n a l vhich ~ 0 7 ~ 1 2 only be i n t e r p r e t e d a!: t !lr rcsli'l t. e f nn infcrct i r~. r i t.11c.r ft'orn t . 11~ m<-ntli r ~ g of t . i~c t,wo c lauses taken toge the r o r from an i n t e g r a t i o n between t h e sentence arld t h e p r i o r d iscourse . These, t h e n , a r e e r r o r s of over- i l l togrr t ion , :L:: i t, V C ? ~ ' ! , wli~>rc LI l c cliilclt-c>ri r :~i l L a r c c ! : ~ l l t l i c : I,L\:; L - S P I I ~ C I I L ? ~ : . with verbatim accuracy because, apparen t ly , t h e process of in teg- r a t i n g t h e t e s t - sen tence with t h e preceding t e x t has been taken so fzr t i x t tilt' origil::ll fornlat of t l l u input enn no longer be recon- . s t r u c t e d . A s such, t h e s e e r r o r s d i r e c t l y r e f l e c t t h e r a p i d i t y with which sentences and c lauses of d i f f e r e n t types a r e i n t e g r a t e d i n t o t h e preceding discourse . And it i s he re t h a t we f i n d t h e c l e a r e s t d i f f e r e n c e s between age-groups.

When t h e i n t e g r a t i v e e r r o r s were broken down according t o whether t h e e r r o r occurred i n a c lause c l a s s i f i e d a s ~ e d u n d a n t , NonRedundant o r !Jew, j.t was c l e a r t h a t a l e r g e propor t ion of tlie f i v e yeal. o l t i s l c r r a r s were loca ted i n t h e Reduridant c l auses ( 6 5 % ) , whereas hardly any occurred i n New c lauses (3%) . However, t h e i n t e g r a t i v e e r r o r s i n t h e seven year o l d s ' r e c s l l were much more evenly d i s t r i b u t e d a m n g s t t h e t h r e e c a t e g o r i e s - with 45% i n Redundant c lauses , 33% i n NonRedundant c lauses and 21% i n New c lauses .

The i n t e g r a t i v e e r r o r s were a l s o analysed a s a funct ion of t h e "event s t r u c t u r e " of t h e e n t i r e sentence , and t h e s e r e s u l t s a r e shown i n Table 1 .

There a r e c l e a r assymetries between t h e f i v e and seven year o l d s , wi th t h e f i v e year o l d s making a much l a r g e r percentage of t h e i r e r r o r s i n t h e Sane event/Sa?e event sentences thzn i n any other category. Also, most of t h e e r r o r s wi th in t h i s ca tegory ' (67%) were l o c a t e d i n Redundant/NonRedundant sentences . Although t h e seven year 016s a l s o made nzny e r r o r s i n t h e Same event/Same event sentences , t h e propor t ion was smal ler than f o r t h e f i v e year o lds . 'Furthermore,

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u n l i k e t h e f i v e yea r o l d s , t h e y make a l a r g e percentage of e r r o r s i n t h e Bew event sentences.

. .

Table 1 : I n t e g r a t i o n e r r o r s and event s t r u c t u r e . . .

Event s t r u c t u r e Age Clause 1 Clause 2 . 5 years '7 yea rs

Same event Same event 73% 52%

Same event New event 19% 158

Xew event New o r Same event

-

Thus, anelyses of t h e i n t e g r a t i v e e r r o r s , both a s a func t ion of t h e p r o p e r t i e s of t h e c lause involved, and a s a func t ion of t h e event s t r u c t u r e of t h e sentence i n which t h e e r r o r occ,urred, showed t h a t t h e f i v e ytzr o l d s were r a p i d l y semant ica l ly i n t e g r a t i n g t h e input when they c o d d - but t h z t they were more l i m i t e d than t h e seven year o l d s i n t h e kind of information.which was s u f f i c i e n t l y r s p i d l y i n t e g r a t e d t o a l low f o r t h e apyearance of over- in tegra t ion e r r o r s . That i s , t h e y required R p a r t i c u l a r kind of input where t h e event which was cur ren t i n t h e t e x t was maintained i n t h e t e s t sentence ( i n p a r t i c u l a r , t h e Redundact/NonRedundant c a s e ) . This r e s t r i c t i o n , however, d i d not apply as s t r o n g l y t o t h e seven year o lds .

A breakdown of t h e i n t e g r a t i v e e r r o r s according t o t h e i n t e r n a l cohesion of t h e sentence involved ( ~ i g h v s Low Cohesion) i s a l s o cons i s t en t wi th t h i s kind of i n t e r p r e t a t i o n . A s Table 2 shows, 3 0 t h age-groups made more i n t e g r a t i o n e r l o r s i n Iiigh than' i n Low Cohesion sentences , but t h e d i f f e r e n c e was more marked f o r t h e f i v e year o lds .

Table 2: I n t e g r a t i o n e r r o r s a s a func t ion of i n t e r n a l cohesion

I n t e r n a l Cohesion Age

5 y e a r s 7 yea rs

High Cohesion

Low Cohesion

Fur thernore , of t h e Low Cohesion i n t e g r a t i v e e r r o r s made by t h e f i v e yea r o l d s occurred i n Redundant/'NonRedundant (same event) sent - ences - 2s i f t h e cohesiveness of t h e sentence with t h e t e x t was over r id ing t h e l a c k of cohesiveness of t h e two c lauses wi th each o t h e r . The seven year o l d s , on t h e o t h e r hand, were just a s l i k e l y t o make Low cohesion i n t e g r a t i o n e r r o r s i n New event ses tences as i n S m e event sentences.

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F i r s t c l ause omissions. The i n t e r p r e t a t i o n s o f a r i s a l s o supported by t h e a n a l y s i s o f a d i f f e r e n t kind of e r r o r -- cases i n which t h e c h i l d r e n omit ted t h e f i r s t c l a u s e cumpletely, and began t h e i r r e c a l l a t t h e beginning of t h e second c lause . Table 3 shows .

t h e a n a l y s i s of t h e d i s t r i b u t i o n of f i r s t c l a u s e omissions a s a f ~ ~ c t i o n of t h e l o c a t i o n of what can be c a l l e d "event boundaries" i n t h e t e s t sentences . That i s , whether t h e t e s t sentence included a s h i f t from one event t o another.

.Tab le 3: F i r s t c l a u s e omissions and event boundaries.

Location o f event Age boundary i n sentecce 5 yeaxs 7 y e a r s Chance

No boundary 13% ' 19% 45% Beginning 18% 19% 40%

Flid&l.e 69% 62% 15%

Ovcrnll, fiive nrld seven year o l d s show e x a c t l y t h e :;tune p a t t e r n . WO- th i rds of t h e f i r s t c l a u s e omissions occur i n cases where t h e r e i s an event boundary i n t h e ' m i d d l e of t h e s e n t e n c e , ' s o t h a t t h e rirst; c1:ruse 7jcl.ongs t o n s,.?pnr-nLct cvcnt; rrorn the second c lnusc . If. t h e s e e r r o r s ?rere d i s t r i b u t s d according t o chance, we would expect many more omih;:sions i n s e n t znces con ta in ing no event boundaries o r beginning w i t l i an event boundary, and many fewer i n t h o s e wi th a mid-sent encs t\vent boundary.

If, there: 'ore, we i n t e r p r e t f i r s t c l a u s e omissions a s r e f l e c t i n g t h e c,onple$e : ,ntegrat ion of t h e f i r s t c l a u s e i n t o t h e r e p r e s e n t a t i o n o f t h e preced:lng d i scourse , s o t h a t it i s no longer a v a i l a b l e a s a s e p a r a t e u n i t ' f o r r e c a l l , t pen it i s i n s t r u c t i v e t o look a t t h e d i scourse s t r u c t u r e of t h e t e s t sentences involved. Table 4 shows t h i s breekdown f o r t h e mid-sentence event-bounaary cases . Here we

Table 4: F i r s t c l ause omissions and .d i scourse s t r u c t u r e

Textual p r o p e r t i e s Age of t e s t sentences 5 yea r s 7 y e a r s

~ ~ o n ~ e d u n d a n t /New 19% 39%

New/New 22% 26%

Redundant/New . .

59% 35%

s e e t h e same kind o f d i f f e r e n c e between t h e f i v e and seven year o l d s as i n t h e i n t e g r a t i v e ' e r r o r s . Seven y e a r o l d omissions a r e evenly d i s t r i b u t e d over t h e t h r e e types of sentence wi th an event boundary

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i n t h e middle, while t h e f i v e yea r o l d ' s omissions occur twice as o f t c n i n the Rcdundnnt/New sequences as i n e i t h e r of t h e of t h e o t h e r two cases .

I n o the r words, f i v e year o lds a r e most l i k e l y t o "lose" a c lause when it i s not only a "s.lvne event" c l a u s e , but a l s o when it con ta ins o l d information -- and t h e r e f o r e i s maximally i n t e g r a t a b l e with t h e preceding discourse . The seven year o l d s , however, "lose" f i r s t c lauses j u s t as o f t e n when t h e y a r e "same event/new inform- a t ion" c l ~ u s e s o r even "new event" c lauses .

Meaning-changing e r r o r s . The t h i r d kind of e r r o r t h a t was analysed cons i s t ed of cases i n which t h e c h i l d r e n made meaning- changing e r r o r s , so t h a t t h e i r r e c a l l s e r i o u s l y diverged from t h e neaning of t h e o r i g i n a l .

Here we f i n d t h e smal les t d i f fe rvnces between age-groups. Overa l l t h e y zzke t h e same number of meaning-,-changing e r r o r s , and they show a s i m i l a r breakdown according t o in t i : rnal cohesive:iess -- with many fewer e r r o r s occurr ing i n t h e High Cohesion sentences. A s Table 5

Table 5: Meaning changing e r r o r s and i n t e r n a l cohesion.

Age I n t e r n a l Cohesion 5 years 7 y e a r s

Low Cohesion 96% 7 8%

shows, t h e r e i s a s l i g h t tendency f o r t h e 5 yea r o lds t o be more s e n s i t i v e t o t h e Low Cohesion/High Cohesion d i s t i n c t i o n . They make p r a c t i c a l l y no e r r o r s a t a l l i n High Cohesion sentences .

Table 6: Meaning-changing e r r o r s as a func t ion of c lause type .

Textual p r o p e r t i e s of Age c lause conta in ing e r r o r 5 years 7 years

Redundant 23% . 22%

NonRedundant 15% 17%

New 62% 61 %

Table 6 shows t h e i n t e r a c t i o n between meaning-changing e r r o r s and t h e t e x t u a l p r o p e r t i e s of t h e c lauses i n which t h e y occur. This type o f e r r o r occurs predominantly i n New event c lauses , and much l e s s f requen t ly i n Same event c lauses ( i r r e s p e c t i v e of whether they conta in new o r o ld informat ion) . Eoth age groups show exac t ly t h e sa!e p a t t e r n , which r e i n f o r c e s t h e claim t h a t t h e f i v e and seven year o l d s a r e performing o v e r a l l i n t h e same way. The d i f fe rences we see a r e d i f f e r e n c e s i n degree only , and they a r e not d i f f e r e n c e s

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i n t h e ex ten t t o which t h e two groups can c o r r e c t l y understand t h e rnntcr is l they hear. Where, f o r both groups, t h e i r understanding does tend t o break down i s , p red ic tab ly , a t t h e po in t s o f g r e a t e s t d i s c o n t i n u i t y i n t h e t e x t . That i s , when a new event i s being introduced, so t h a t what i s known about t h e s t o r y up t o t h a t po in t provides t h e weakest gu ide l ines f o r t h e i n t e r p r e t a t i o n o f t h e sentence being heard.

Thus, t h e e a r l i e r evidence, from t h e a n a l y s i s of t h e i n t e g r a t i o n and omission e r r o r s , showed t h a t t h e seven year o l d s ' i n t e r p r e t a t i o n o f t h e input was l e s s impeded than t h e f i v e year o l d s ' by t h e in t roduc t ion of new events o r new information about o l d events. The zvidence from t h e meaning-changing e r r o r s shows t h a t t h e s e d i scaurse v a r i a b l e s were, nonetheless , a s i g n i f i c a c t f a c t o r i n t h e seven ycar o l d s ' performance. For when they d id malrc e r r o r s of i n t e r p r e t a t i o n , t h e d i s t r i b u t i o n o f t h e s e e r r o r s w a s determined i n t h e same way a s f o r t h e f i v e year o l d s by t h e t e x t u a l r e l a t i o n s h i p between t h e context and t h e c l a u s e conta in ing t h e e r r o r .

Conclusions We need t o consider f i r s t i h e r e l a t i o n s h i p between t h e second

experiment r epor ted he re and t h e age d i f f e r e n c e s i n t h e e f f e c t s of sentence- in ternal semantic cohesion descr ibed e a r l i e r . It now s'eens p l a u s i b l e t h a t t h e d i f fe rences i n t h e t e x t u a l cohesiveness o f t h e High and Low Cohesion sentences could be s u f f i c i e n t t o account f o r t h e d i f fe rences i n t h e degree t o which t h e f i v e year o l d s c l a u s a l l y s t r u c t u r e d t h e i r r e c a l l of t h c s c two t-ypcs of mntcr in l .

For Low Cohesion sentences a r e much more l i k e l y t o contain N c w c l a u s e s , e s p e c i a l l y i n t h e second c lause pos i t ion . kid, a s t h e second expt'rime~it sllows, i L i s prcciuely t11t.st. k i r ~ d s ol' cluuscs Lllcit; L i l t .

f i v e year o lds do not r a p i d l y i n t e g r a t e , e i t h e r wi th in t h e sentence o r between t h e sentence and t h e d iscourse . High Cohesion sentences , on t h e o the r hand, a r e predominantly "same-event" sentences , which f i v e year o l d s can and do r a p i d l y t e x t u a l l y i n t e g r a t e . I n t h e second experiment, t e x t u a l d i f f c r c n c e s of t h i s type n f fcc ted t h e d i s t r i b u t i o n of i n t e g r a t i o n and.clause-omission e r r o r s . I n t h e f i r s t experiment, such d i f f e r e n c e s would l ead t o a g r e a t e r c l a u s n l s t r u c t u r i n g of Low r a t h e r than High Cohesion sentences , as r e f l e c t e d i n t h e shape of t h e f i v e year o l d s ' s e r i a l p o s i t i o n curves.

The seven year o l d s , i n c o n t r a s t , were shown i n t h e second experiment t o be l e s s slowed down i n t h e i r processing by v a r i a t i o n s i n t h e t e x t u a l p r o p e r t i e s of t h e tes t -sentences . Thus, i f we j u s t consider t h e t e x t u a l cohesiveness of t h e High and Low cohesion sentences , we would not expect t o f i n d d i f f e r e n c e s i n t h e way i n which t h e o l d e r ch i ld ren s t r u c t u r e t h e i r r e c a l l of e i t h e r type o f sentence.

This r e - i n t e r p r e t a t i o n of t h e i n t e r n a l cohesion e f f e c t s i n terms of t e x t u a l cohesion v a r i a b l e s does not by i t s e l f , however, expla in t h e age-differences we f i n d i n both experiments he re , and' i n t h e e a r l i e r s tudy ( ~ ~ l e r and Marslen-Wilson, 1978). I n t h i s e a r ? i e r s tudy, we had suggested t h a t t h e age-differences we found in t h e J a r v e l l a t a s k were u l t i m a t e l y due t o d i f f e r e n c e s i n "processing capacity". The f i v e year o l d s , we proposed, were more l i m i t e d i n

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this respect, and therefore were under greater pressure to recode the input into a higher level of representation. This would mean, compared with older children, that they would more rapidly lose information about the lower-level properties of the input. In interpreting the present studies we need to invoke a similar basic explanation of how the five and seven year olds differ. But what we can now add to this explanation is a more specific account of where these processing difficulties have their effect.

Taking these three studies together, it becomes clear that the developmental sequence we have been dealing with is one in which the developmentally basic skill is the interpretation of' utterances in their contexts. What we see developing is apparently both an increase in processing "capacity" and in processing,"skills" (we leave aside here the issue of how far "capacity" and "skill" are in fact functionally distinguishable). The effect of this dual developnent is to allow the older children both to rapidly process textually more demanding inputs, and to maintain for longer in maory some information about the intermediate stages of the interpretation process. The younger children are not performing in a qualitatively different manner, but they are forced by their less developed capacities to move as rapidly as possible to the functionally basic ~ o n l of normal listening -- to interpret the utterance in its contcxt. It is likely that if we were to move still further back in the developmectsl sequence we would find increasing dominance of these context-based interpretative functions, and still less control over the putative syntactic and semantic subcomponents of these processes.

Footnotes 1. LKT is now at: Interfacultaire Werkgroep Taal- en Spraakgedrag, Katholieke Universiteit, Berg en Dalseweg 79, Nijmegen, The Eetherlands. This research was supported in part by a grant to LKT from Nederlsndse Organisatie voor zuiver-wetenschappelijk onderzoek. 2. This research was carried out in collaboration with Leo Rooijackers and Xans van der K m e n of the Katholieke Universiteit, Nijnegen. 3. We wish to thank Mrs Rozycki, the staff and children of Grange First School, Ealing, London for their generous cooperation.

References Jsrvella, R.J. (1971). Syntactic processing of connected speech.

JVLVB 10. 409-16. Marslen-Wilson,W.D. and Tyler, L.K. (1976). Memory and levels of

processing in a psycholinguistic context. J Exp Psych: HLM 2. 112-19.

Tyler L.K. and Marslen-Wilson, W.D. (1978). Some developmental aspects of sentence processing and memory. J Child Lang 5. 113-129.

,

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F I G 1: 5 YEAR OLD HIGH CONSTRAINT DATA WITH 9 5 O I o CONFIDENCE LIMITS '

i i 3 i 5 6 i B 1 0 1 i 1 2 WORD POSITION

FIG 2: 5 YEAR OLD LOW CONSTRAINT DATA WITH 95"/0 CONFIDENCE LIMITS

WORD POSITION

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FIG 3: 7 YEAR OLD HIGH AND LOW CONSTRAINT DATA

WORD POSITION

High constraint - - - Low constraint -

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