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Age differences in infants' attention to stimuli varying in complexity Brennan, Wendy Margaret 1965

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L A S S DIFFERENCES IN INFANTS INATTENTION TO STIMULI yARYING IN COMPLEXITY by WENDY MARGARET BRENNAN B.A. Hons., Manchester U n i v e r s i t y , I96J4. A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n t h e Department o f P s y c h o l o g y We a c c e p t t h i s t h e s i s a s c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA June, 1965 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r -m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my Department o r by h i s r e p r e s e n t a t i v e s , , I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i -c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada ABSTRACT i i The research presented in this thesis was designed to investigate the effects of age on infant preferences for stimuli of different complexity levels. The hypothesis was that the older the infant, the more complex the pattern he prefers. Hershenson (196i|.) presented three checkerboard designs containing 2 x 2 , Ij. x if, and 12 x 12 black and white squares to newborn infants. He found that the infants preferred the stimuli in decreasing order of their complexity. The purpose of the f i r s t experiment of the present research was to com-pare the responses of older Infants towards these stimuli with those of Hershenson's newborns. In Experiment I, 10 and 20 week old infants were presented with the three checker-boards in a single stimulus presentation procedure. The length of time during which each stimulus was fixated by an infant was recorded. It was found that the Infants of both age groups preferred the stimuli in increasing order of their e complexity. These results complemented those of Hershenson (I96I4.} In supporting the hypothesis that older infants prefer stimuli of greater complexity than do younger infants. The fact that no difference was found i n the preferences of the 10 and 20 week olds was attributed to the fact that the set of stimuli used did not encompass a wide enough range of com-plexity. Further support of the hypothesis was sought on Experi-ment II. Using the same single stimulus presentation i l l procedure as that used i n Experiment I, three, eight and ll]. week old infants were presented with three black and white checkerboards containing 2 x 2 , 8 x 8 , and 2l\. x 2ij. squares. In terms of t o t a l f i x a t i o n time for each stimulus, three week olds preferred the least complex stimulus, eight week olds preferred the stimulus of intermediate complexity, and li). week olds preferred the most complex stimulus. These r e -sults support the hypothesis that the older the i n f a n t , the more complex the pattern her prefers. However, three week olds did not look s i g n i f i c a n t l y longer at the c% x 2J4. checkerboard than at a p l a i n gray square with which they were also presented. This suggests the p o s s i b i l i t y that they could not perceive the pattern o f this stimulus.A control study seems warranted. One subsidiary purpose of the research was to compare various response measures, namely t o t a l f i x a t i o n time, length of f i r s t f i x a t i o n , and rate of habituation. The l a t -ter response measure was of no value i n detecting the pre-ferences of the infants f o r the s t i m u l i . The t o t a l f i x a t i o n time and length o f f i r s t f i x a t i o n measures gave the same patterns of preference with each age group. With both mea-sures an increasing preference for complexity with age was found. However, i t was f e l t that t o t a l f i x a t i o n time was the more sensitive and r e l i a b l e of the two measures. Another purpose of the research was to compare two ex-perimental procedures i n the study of infant attention -; i v s i n g l e s t i m u l u s and p a i r comparisons* I n Experiment I I I , 8 and IIL week o l d i n f a n t s were p r e s e n t e d w i t h t h e 2 x 2 , 8 x 8 , and 2 i i x 2li c h e c k e r b o a r d s i n a m o d i f i e d p a i r c o m p a r i -sons p r o c e d u r e . The r e s u l t s o b t a i n e d were consonant w i t h t h o s e o b t a i n e d i n Experiment I I and s u p p o r t i v e o f the h y -p o t h e s i s . The e i g h t week o l d group p r e f e r r e d t h e s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y o v e r t h e o t h e r two, w h i l e t h e I i i week o l d group p r e f e r r e d t h e most complex, s t i m u l u s o ver th e o t h e r s . The r e s u l t s o f the e x p e r i m e n t s p r e s e n t e d i n t h i s t h e s i s were c o n g r u e n t , and were s u p p o r t i v e o f t h e h y p o t h e s i s t h a t i n c r e a s e d p r e f e r e n c e f o r c o m p l e x i t y comes w i t h age. V TABLE OP CONTENTS Page Chapter 1. Introduction • 1 Chapter 2. Experiment I...... • ILO Chapter 3 . Experiment I I . . . . £2 Chapter i i . Comparison of Response Measures obtained i n Experiment I I . . . . . 6 8 Chapter 5« Experiment I I I . 78 Chapter 6 . Summary and Conclusions... 91 Bibliography 96 v i LIST OP TABLES Page T a b l e 1 T o t a l t i m e spent l o o k i n g a t each o f t h e t h r e e s t i m u l u s p a t t e r n s by 1 0 and 2 0 week o l d I n f a n t s , a v e r a g e d over s u b j e c t s . (Experiment I ) .1+.6 T a b l e 2 Summary t a b l e o f a n a l y s i s o f v a r i a n c e o f t o t a l l o o k i n g t i m e spent l o o k i n g at each o f t h e t h r e e s t i m u l i by 1 0 week o l d group. (Experiment I ) kl T a b l e 3 Summary t a b l e o f a n a l y s i s o f v a r i a n c e o f t o t a l l o o k i n g t i m e spent l o o k i n g at each o f t h e t h r e e s t i m u l u s p a t t e r n s by 2 0 week o l d group. (Experiment I ) . . • kl T a b l e k Summary t a b l e o f two-way a n a l y s i s o f v a r -i a n c e o f t o t a l l o o k i n g t ime spent l o o k i n g at e a ch o f t h e t h r e e s t i m u l i by 1 0 and 2 0 week o l d groups (Experiment I ) . . . . . . I4.9 T a b l e 5 T o t a l l o o k i n g t i m e i n seconds spent l o o k i n g a t each o f t h e s t i m u l i by 3, 8 , and U4. week o l d i n f a n t s , a v e r a g e d over s u b j e c t s . (Experiment I I ) . . . . £6 T a b l e 6 Summary t a b l e o f two-way a n a l y s i s o f v a r -i a n c e o f t o t a l l o o k i n g t i m e spent l o o k i n g at each o f t h r e e s t i m u l i ( E x c l u d i n g g r a y ) by 3» 8 , and l k week o l d g r o u p s . (Experiment I I J . . . . 5 6 T a b l e 7 Summary t a b l e o f a n a l y s i s o f v a r i a n c e of t o t a l l o o k i n g t i m e spent l o o k i n g at each o f t h e s t i m u l u s p a t t e r n s ( i n c l u d i n g g r a y ) by t h r e e week o l d group. (Experiment I I ) 5*9 T a b l e 8 Summary t a b l e o f a n a l y s i s o f v a r i a n c e o f t o t a l l o o k i n g time spent l o o k i n g a t each o f t h e s t i m u l u s p a t t e r n s ( e x c l u d i n g g r a y ) by t h r e e week o l d group. (Experiment I I ) £9 T a b l e 9 Summary t a b l e o f a n a l y s i s - o f v a r i a n c e o f t o t a l l o o k i n g t i m e spent l o o k i n g at each o f t h r e e s t i m u l u s p a t t e r n s by e i g h t week o l d group. (Experiment I I ) 6 0 v i i Page T a b l e 10 Summary t a b l e o f a n a l y s i s o f v a r i a n c e o f t o t a l l o o k i n g t ime spent l o o k i n g at each, o f t h r e e s t i m u l u s p a t t e r n s by f o u r t e e n week o l d group. (Experiment I I ) . 60 T a b l e 11 L o o k i n g time i n seeonds o f f i r s t f i x a -t i o n s o f the t h r e e s t i m u l i by 3, 8, and L i i week o l d i n f a n t s , a v e r a g e d over sub-j e c t s . (Experiment I I ) . 69 T a b l e 12 Summary t a b l e o f two-way a n a l y s i s o f v a r i a n c e o f l e n g t h o f f i r s t f i x a t i o n f o r e a c h o f t h r e e s t i m u l i by 3, 8* and I i i week o l d gro u p s . (Experiment I I ) 69 T a b l e 13 Summary t a b l e o f a n a l y s i s o f v a r i a n c e o f l e n g t h o f f i r s t f i x a t i o n o f each o f t h r e e s t i m u l i by 3 week o l d group (Experiment I I ) • 72 T a b l e U4. Summary t a b l e o f a n a l y s i s of v a r i a n c e o f l e n g t h o f f i r s t f i x a t i o n of each o f t h r e e s t i m u l i by 8 week o l d grou p . (Experiment I I ) . .... 72 T a b l e 15 Summary t a b l e of a n a l y s i s of v a r i a n c e o f l e n g t h o f f i r s t f i x a t i o n o f each o f t h r e e s t i m u l i by LLj. week o l d group. (Experiment I I ) 72 T a b l e 16 T o t a l f i x a t i o n t i m e ( i n seconds) f o r each h a l f o f t h e 1 2 - t r i a l s e r i e s 75 T a b l e 17 R e s u l t s o b t a i n e d f r o m t h e response mea-s u r e s s t u d i e d i n Experiment I I . . . . . . . 76 T a b l e 18 R e s u l t s o f s i g n t e s t performed on p a i r comparisons d a t a (Experiment I I I ) . . . . 83 T a b l e 19 I n d i v i d u a l p r e f e r e n c e s i i i the p a i r com-p a r i s o n s experiment (Experiment I I I ) . . . . . . . 85 v i i i LIST OF FIGURES Page F i g u r e 1 . The s t i m u l i u s e d by B e r l y n e (195*8 b) 15 F i g u r e 2 . T o t a l l o o k i n g t ime i n seconds spent l o o k i n g a t each o f the t h r e e s t i m u l i by 10 and 20 week o l d i n f a n t s , a v e r -aged over s u b j e c t s . (Experiment I ) i i8 F i g u r e 3» T o t a l l o o k i n g t i m e i n seconds spent l o o k i n g a t each o f the s t i m u l i by 3# 8 , and 11L week o l d I n f a n t s , a v e r a g e d over s u b j e c t s . (Experiment I I ) • 57 F i g u r e 11. T o t a l l o o k i n g t i m e i n seconds spent l o o k i n g a t each o f t h e s t i m u l i by 3 , 5 , 8 , 1 0 , II4. and 20 week o l d i n f a n t s , a v e r a g e d over s u b j e c t s (Experiment I I ) . . . . . 63 F i g u r e 5» The l o o k i n g t i m e I n seconds of f i r s t f i x a t i o n s o f t h e t h r e e c h e c k e r b o a r d s by t h e 3 , 8 , and l i i week o l d groups, averaged over s u b j e c t s . (Experiment I I ) . . . . 70 I x ACKNOWLEDGEMENTS The a u t h o r w i s h e s t o express h e r s i n c e r e g r a t i t u d e t o D r . E. W. Ames f o r h e r generous a s s i s t a n c e and guidance throughout a l l phases o f t h e r e s e a r c h . Thanks a r e a l s o due t o Dr. R.Knox f o r h i s h e l p f u l c r i t i c i s m s i n the p r e p a r a t i o n o f t h e t h e s i s , t o Mr. Ron Moore f o r h i s a s s i s t a n c e i n the t e s t i n g o f s u b j e c t s , and t o M i s s V a l e r i e Peden f o r h e r c l e r i c a l a s s i s t a n c e . The r e s e a r c h i n t h i s t h e s i s was s u p p o r t e d by a g r a n t -i n - a i d o f t h e A s s o c i a t e Committee on E x p e r i m e n t a l P s y c h o l o g y , N a t i o n a l R e s e a r c h C o u n c i l , Canada ( g r a n t APA-121). CHAPTER ONE INTRODUCTION T h i a t h e s i s i s c o n c e r n e d w i t h t h e a t t e n t i o n p a i d by i n f a n t s t o s t i m u l i o f d i f f e r e n t c o m p l e x i t i e s : More s p e c i -f i c a l l y , i t i n v e s t i g a t e s t h e v i s u a l f i x a t i o n r e s p o n s e s o f i n f a n t s o f v a r i o u s ages t o s t i m u l u s p a t t e r n s o f v a r y i n g c o m p l e x i t y l e v e l s . T h i s c h a p t e r s e r v e s as a r e v i e w o f t h e l i t e r a t u r e r e l e v a n t t o t h i s t o p i c . I DEFINITIONS OF STIMULUS COMPLEXITY A major p r o b l e m e n c o u n t e r e d i n s t u d y i n g any d i m e n s i o n i n p s y c h o l o g y i s f i n d i n g a c o n c i s e d e f i n i t i o n o f t h a t dimen-s i o n w h i c h I s t h e o r e t i c a l l y u s e f u l and o p e r a t i o n a l l y mana-g e a b l e . S i n c e t h i s t h e s i s i s concerned w i t h age d i f f e r e n c e s i n t h e l e v e l o f s t i m u l u s c o m p l e x i t y p r e f e r r e d by i n f a n t s , i t i s f r u i t f u l t o l o o k a t t h e v a r i o u s d e f i n i t i o n s o f c o m p l e x i t y w h i c h have r e c e n t l y appeared I n t h e l i t e r a t u r e . 1. A b s t r a c t D e f i n i t i o n s B e r l y n e (I960) a t t e m p t s t o d e f i n e t h e co n c e p t s o f n o v e l t y , u n c e r t a i n t y , c o n f l i c t , and c o m p l e x i t y w h i c h he f e e l s " a r e among our most v a l u a b l e t o o l s f o r r e s e a r c h i n t o s t i m u l u s s e -l e c t i o n " ( B e r l y n e , i 9 6 0 , p. 1 8 ) . He admits t h a t o f t h e s e s t i m u l u s v a r i a b l e s , c o m p l e x i t y p r e s e n t s t h e s e v e r e s t d e f i n i -t i o n a l p r o b l e m s . I n g e n e r a l , c o m p l e x i t y r e f e r s t o t h e amount o f v a r i e t y or d i v e r s i t y i n a s t i m u l u s p a t t e r n . C o m p l e x i t y 2 . I n c r e a s e s w i t h the number o f d i s t i n g u i s h a b l e elements i n a s t i m u l u s , and w i t h t h e d i s s i m i l a r i t y between t h e e l e m e n t s . I t v a r i e s i n v e r s e l y w i t h t h e degree t o w h i c h s e v e r a l e l e -ments a r e responded t o as a u n i t , B e r l y n e c o n c l u d e s h i s d e f i n i t i o n by c l a i m i n g t h a t " c o m p l e x i t y depends on t h e num-ber o f p s y c h o l o g i c a l p a r t s r a t h e r t h a n t h e number o f p h y s i -c a l p a r t s " ( B e r l y n e , I 9 6 0 , p. 3 9 ) . A c c o r d i n g t o Dember ( I 9 6 0 ) "the more complex s t i m u l u s i s t h e one t h e i n d i v i d u a l c a n do more w i t h : i t a f f o r d s more p o t e n t i a l o p p o r t u n i t i e s f o r r e s p o n d i n g t h a n does t h e l e s s complex" (Dember, i 9 6 0 , pp. 3 5 2 - 3 5 3 ) . The few c h a r a c t e r i s -t i c s o f c o m p l e x i t y w h i c h he su g g e s t s a r e movement, s p a t i a l h e t e r o g e n e i t y , I n c o n g r u i t y , and change. Walker ( 196k) s u g g e s t s t h a t s t i m u l u s c o m p l e x i t y I s a f u n c t i o n o f t h e number o f s t i m u l u s elements i n an a r r a y and o f t h e p a t t e r n i n g o f t h e s e e l e m e n t s . P a t t e r n i s r e g a r d e d i n terms o f t h e r e l a t i o n s between t h e e l e m e n t s . He p o i n t s out t h a t a p o s s i b l e a p p r o a c h t o a c o m b i n a t i o n o f t h e number o f elements and t h e p a t t e r n i n a s t i m u l u s i s o f f e r e d by any s i -t u a t i o n i n w h i c h an i n d e x o f u n c e r t a i n t y can be o b t a i n e d f r o m i n f o r m a t i o n t h e o r y . The g r e a t e r t h e i n d e x o f u n c e r t a i n t y , t h e g r e a t e r t h e s t i m u l u s c o m p l e x i t y . These a b s t r a c t d e f i n i t i o n s o f s t i m u l u s c o m p l e x i t y have s e v e r a l p o i n t s o f c o n c o r d a n c e . B o t h B e r l y n e ( i 9 6 0 ) and Walker ( 1 9 6 k ) agree t h a t t h e number o f elements i n a s t i m u l u s 3. contributes to i t s complexity, Dember's (I960) "heteroge-n e i t y " i s probably much l i k e Berlyne's (I960) " d i s s i m i l a r i t y between the elements"• Probably the area of greatest s i m i l a r i t y among these d e f i n i t i o n s , however, l i e s i n the fact that they are a l l unsatisfactory from an operational standpoint. The d e f i n i -tions of Berlyne and Dember both lack the p r e c i s i o n needed to convert them into workable bases of measurement• Walker suggests the use of information theory as a basis for con-st r u c t i n g s t i m u l i of varying complexity l e v e l s , but, as w i l l be seen i n the next section t h i s has not proven to be as use-f u l to the problem of stimulus complexity as he suggested i t might be. By means of ge n e r a l i t i e s , each author i s presenting hi s own i n t u i t i v e idea of stimulus complexity. Understanding of the d e f i n i t i o n s can, therefore, only be i n t u i t i v e as well, and very l i t t l e advance i s made i n the search f o r a d e f i n i -t i o n of stimulus complexity which makes the indices of com-pl e x i t y e x p l i c i t and amenable to measurement. Some experimenters working on the effects of complexity on learning and memory i n adults have attempted to define complexity and vary i t systematically. Their experiments are presented in the next section. 2. Definitions of Complexity i n Experiments on Human Adult Learning and Memory ' Moffett (1963) has reviewed the various studies concerned with the influence of complexity on adult learning and memory, and t h i s s e c t i o n w i l l s e r v e m e r e l y t o p o i n t out t h e v a r i o u s s t i m u l u s c h a r a c t e r i s t i c s w h i c h were m a n i p u l a t e d under the e x p e r i m e n t a l a s s u m p t i o n t h a t t h e s e c h a r a c t e r i s t i c s a f f e c t e d s t i m u l u s c o m p l e x i t y . Many e x p e r i m e n t e r s agree t h a t c o m p l e x i t y v a r i e s w i t h t h e number of p a r t s t h a t make up a f i g u r e . F o r i n s t a n c e , Deese's (1956) d e f i n i t i o n o f "number o f changes i n c o n t o u r " i s e q u i v a l e n t t o t h e number o f p a r t s i n d e x used by F e h r e r (1935), F r e n c h (195k), and A t t n e a v e (1955K T h i s i s a s t i -mulus c h a r a c t e r i s t i c w h i c h , i n whatever manner one w i s h e s t o d e f i n e i t , i s r e a d i l y q u a n t i f i a b l e . A n o t h e r s t i m u l u s c h a r a c -t e r i s t i c w h i c h many f e e l can be u s e d as an i n d e x o f complex-i t y i s symmetry ( A t t n e a v e , 1955; F e h r e r , 1935)* or r e g u l a r i -t y (Deese, 1956), w h i c h concerns t h e c o m p l e x i t y o f a r r a n g e -ment o f t h e elements i n a f i g u r e . However, t h i s i n d e x i s not as r e a d i l y amenable t o measurement as i s t h e number o f p a r t s i n d e x . S e v e r a l r e s e a r c h e r s c l a i m t h a t one measure o f s t i m u l u s c o m p l e x i t y I s t h e amount o f i n f o r m a t i o n c o n t a i n e d i n a f i g u r e ( e . g . , W e i n s t e i n , 1955). However, A t t n e a v e (1957) f o u n d t h a t t h e r e was no d i r e c t r e l a t i o n s h i p between the amount o f i n f o r -m a t i o n c o n t a i n e d I n a s t i m u l u s and the c o m p l e x i t y o f t h e s t i -mulus as judged by a d u l t s . I n g e n e r a l , I t was f o u n d i n t h e s e s t u d i e s o f human a d u l t l e a r n i n g and memory t h a t t h e o n l y d e f i n i t i o n s o f c o m p l e x i t y 5". w h i c h y i e l d e d c o n s i s t e n t p o s i t i v e f i n d i n g s were tho s e i n w h i c h t h e number o f elements making up t h e s t i m u l u s was c o n -s i d e r e d . A t t e m p t s a t f i n d i n g more s o p h i s t i c a t e d d e f i n i t i o n s o f c o m p l e x i t y i n terms o f I n f o r m a t i o n t h e o r y ( e . g . , A t t n e a v e , 1955 and 1957) were u n s u c c e s s f u l . T h i s suggests t h a t i n f o r -m a t ion t h e o r y does not p r o v i d e t h e easy s o l u t i o n t o t h e p r o -blems o f s t i m u l u s c o m p l e x i t y t h a t was a n t i c i p a t e d by many workers ( e . g . , W a l k e r , 1 9 6 k ) . S t i l l , i t seems r e a s o n a b l e t o suppose t h a t t h e r e a r e many more ways t o c r e a t e complex s t i m u l i t h a n were used i n t h e e x p e r i m e n t s d i s c u s s e d i n t h i s s e c t i o n . T h e r e f o r e , the next s e c t i o n r e v i e w s s t u d i e s i n v e s t i g a t i n g t h e amount o f v i s u a l a t t e n t i o n p a i d t o s t i m u l i v a r y i n g i n c o m p l e x i t y i n o r -der t o d i s c o v e r t h e d e f i n i t i o n s o f c o m p l e x i t y used t h e r e i n . The v i s u a l a t t e n t i o n response measure i s more r e l e v a n t t o the work u n d e r t a k e n i n t h i s t h e s i s . 3. D e f i n i t i o n s o f C o m p l e x i t y i n R e s e a r c h on V i s u a l A t t e n t i o n i n A d u l t s . ' I n an experiment by B e r l y n e (1958 a ) , p a i r s o f s t i m u l u s f i g u r e s were p r e s e n t e d s i m u l t a n e o u s l y t o a d u l t s u b j e c t s . Re-c o r d was made o f the l e n g t h o f t i m e i n w h i c h each member o f t h e p a i r was f i x a t e d , and o f w h i c h member was f i x a t e d f i r s t . The s t i m u l i were grouped i n t o s i x c a t e g o r i e s , w i t h f o u r p a i r s o f s t i m u l i i n e a ch o f f i v e c a t e g o r i e s and two p a i r s i n t h e s i x t h . Each c a t e g o r y was meant t o r e p r e s e n t a d i f f e r e n t a s -p e c t o f c o m p l e x i t y . For each p a i r w i t h i n a c a t e g o r y , one 6 s t i m u l u s was "more complex" t h a n t h e o t h e r * The s i x a s p e c t s o f c o m p l e x i t y u s e d were: (1) Amount o f m a t e r i a l - b o t h f i g u r e s i n a p a i r c o n s i s t e d o f t h e same t y p e o f m a t e r i a l , but one c o n s i s t e d o f more o f t h a t m a t e r i a l t h a n t h e o t h e r s * (2) I r r e g u l a r i t y o f shape - each p a i r c o n t a i n e d one r e g u l a r g e o m e t r i c a l shape s y m m e t r i c a l a l o n g two or more a x e s , and one i r r e g u l a r n o n - s y m m e t r i c a l shape. (3) I r r e g u l a r i t y o f arrangement - b o t h members o f a p a i r c o n t a i n e d t h e same number o f I d e n t i c a l elements but i n one f i g u r e t h e y were a r r a n g e d i n a r e g u l a r g e o m e t r i c a l p a t t e r n and i n t h e o t h e r t h e y were i r r e g u l a r l y s c a t t e r e d . (k) H e t e r o g e n e i t y o f elements - one f i g u r e i n e a c h p a i r c o n s i s t e d o f a number o f i d e n t i c a l e l e m e n t s , whereas t h e o t h e r f i g u r e c o n s i s t e d o f t h e same number o f heterogeneous elements i n a s i m i l a r s p a t i a l arrangement. (5) I n c o n g r u i t y - e x e m p l i f i e d by such f i g u r e s as an e l e -phant's massive head on a v e r y f r a g i l e body. (6) Incongruous j u x t a p o s i t i o n - e x e m p l i f i e d by a r a b b i t ' s head f o r m i n g t h e f r o n t p a r t o f an a u t o m o b i l e . S e v e r a l o f t h e s e I n d i c e s were e n c o u n t e r e d i n t h e p r e v i o u s s e e t i o n : amount o f m a t e r i a l i s e q u i v a l e n t t o the number o f p a r t s i n d e x i n t h e experiments on l e a r n i n g and memory; i r r e -g u l a r i t y o f shape e q u a l s symmetry as us e d by F e h r e r (1935) and r e g u l a r i t y as u s e d by Deese (1956). H e t e r o g e n e i t y o f elements and d i s s i m i l a r i t y between elements were mentioned by Dember ( I 9 6 0 ) and B e r l y n e ( i 9 6 0 ) r e s p e c t i v e l y I n t h e i r ab-s t r a c t d e f i n i t i o n s , and a r e e q u i v a l e n t t o the h e t e r o g e n e i t y o f elements e n c o u n t e r e d i n t h i s s t u d y . The o t h e r a s p e c t s o f c o m p l e x i t y a re new t o t h i s d i s c u s s i o n . The l a s t two c h a r a c t e r i s t i c s , i n c o n g r u i t y and incongruous j u x t a p o s i t i o n , seem t o be t h e unique c r e a t i o n o f B e r l y n e . B o t h o f t h e s e v a r i a b l e s a r e h e a v i l y dependent upon p a s t e x p e r i e n c e . How-e v e r , i n t h i s experiment B e r l y n e (195>8 a) was a b l e t o o p e r a -t i o n a l i z e h i s d e f i n i t i o n s and t h i s marks a s i g n i f i c a n t a d -vance i n t h e s e a r c h f o r an adequate o p e r a t i o n a l d e f i n i t i o n o f c o m p l e x i t y . k. D e f i n i t i o n s o f C o m p l e x i t y i n Expe r i m e n t s on V i s u a l a t t e n t i o n i n C h i l d r e n Cantor ( I 9 6 3 ) has r e v i e w e d s e v e r a l s t u d i e s on t h e v i s -u a l a t t e n t i o n of c h i l d r e n t o complex s t i m u l i . T h i s s e c t i o n p r e s e n t s a b r i e f d i s c u s s i o n of t h e v a r i o u s d e f i n i t i o n s o f c o m p l e x i t y u s e d i n t h e s e e x p e r i m e n t s . I n s t u d y i n g t h e p r e f e r e n c e s f o r s t i m u l u s c o m p l e x i t y I n r e t a r d a t e s and i n no r m a l c h i l d r e n , S p i t z and Hoats ( 1 9 6 l ) used p a i r s o f s t i m u l i d i f f e r i n g i n c o m p l e x i t y as d e f i n e d by B e r l y n e (19S>8 a) I n h i s experiment w i t h a d u l t s . The i n d i c e s o f c o m p l e x i t y u s e d were i r r e g u l a r i t y o f arrangement o f t h e elements i n a s t i m u l u s , t h e amount o f m a t e r i a l c o n t a i n e d i n a s t i m u l u s , h e t e r o g e n e i t y o f the e l e m e n t s , i r r e g u l a r i t y o f shape o f t h e f i g u r e s , and i n c o n g r u i t y and i n c o n g r o u s j u x t a -p o s i t i o n . The p a i r s o f s t i m u l i used i n t h e l a t t e r two 8. c a t e g o r i e s "appear t o c o n t a i n s t i m u l i d i f f e r i n g more i n n o v e l t y t h a n I n c o m p l e x i t y " ( C a n t o r , 1963, p. 13)• I n an experiment I n v o l v i n g p r e s c h o o l age c h i l d r e n , May (1962) i d e n t i f i e d c o m p l e x i t y l e v e l w i t h t h e number o f d i f f e r e n t l y c o l o u r e d r e c t a n g l e s a p p e a r i n g on 5" x 8" c a r d s * Here c o m p l e x i t y was d e f i n e d s o l e l y l n terms o f t h e amount o f m a t e r i a l i n v o l v e d i n t h e s t i m u l i . C a n t o r , C a n t o r , and D I t r i c h s (1963) c o n d u c t e d an ex-periment i n w h i c h no attempt was made t o q u a n t i f y t h e com-p l e x i t y v a r i a b l e o r i d e n t i f y i t s i n d i c e s . However, i n s p e c -t i o n o f t h e i r s i x s t i m u l u s t r i a d s r e v e a l s t h a t s t i m u l u s com-p l e x i t y seems t o have been i n t u i t i v e l y d e f i n e d i n terms o f number of elements, degree o f p a t t e r n i n g , i r r e g u l a r i t y o f shape, amount o f c o n t o u r , and number o f l i g h t - d a r k t r a n s i -t i o n s . I n t h e f i r s t two o f t h e t h r e e s t u d i e s i n t h i s s e c t i o n , t h e i n v e s t i g a t o r s were a b l e t o o p e r a t i o n a l i z e t h e i r d e f i n i -t i o n s o f s t i m u l u s c o m p l e x i t y . S p i t z and Hoats (1961) t o o k t h e i r d e f i n i t i o n s and most of t h e i r s t i m u l i d i r e c t l y f r o m B e r l y n e (1958 a ) . May (1962), w o r k i n g w i t h a u n i d i m e n s i o n a l d e f i n i t i o n o f c o m p l e x i t y , was a b l e t o q u a n t i f y h i s s t i m u l i a l o n g t h i s d i m e n s i o n and t h e r e b y d i s c o v e r e x a c t l y what l e v e l o f c o m p l e x i t y h i s s u b j e c t s p r e f e r r e d most. D e s p i t e t h e vague and i n t u i t i v e d e f i n i t i o n s o f c o m p l e x i t y u s e d i n h i s own s t u d y Cantor seems t o g i v e h i s a p p r o v a l t o May's a p p r o a c h i n s t u d y -i n g s t i m u l u s c o m p l e x i t y when he says: "With, regard t o 9 s t i m u l u s m a t e r i a l s , t h e r e appears t o be a s e r i o u s need f o r i n t e n s i v e s t u d y o f a few relafc i v e l y s i m p l e and r i g o r o u s l y d e l i m i t e d s t i m u l u s p r o p e r t i e s w h i c h h o p e f u l l y w i l l s u p p l a n t t h e vague n o t i o n s o f ' c o m p l e x i t y ' w h i c h a re c u r r e n t l y p r e -v a l e n t " ( C a n t o r , 1963, p. 21). 5>» D e f i n i t i o n s o f C o m p l e x i t y I n Ex p e r i m e n t s on V i s u a l A t t e n t i o n of I n f a n t P r i m a t e s  T h i s s e c t i o n r e v i e w s s t u d i e s on a t t e n t i o n o f t h e i n f a n t p r i m a t e t o v i s u a l s t i m u l i v a r y i n g i n c o m p l e x i t y i n o r d e r t o see what d e f i n i t i o n s o f c o m p l e x i t y a r e u s e d I n them. One o f t h e s t u d i e s ( S a c k e t t , 196k) u s e d monkeys as s u b j e c t s . The o t h e r s a l l u s e d human i n f a n t s under a year o l d . I n gen-e r a l , a s u b j e c t was shown a s e t o f s t i m u l i , t h e s t i m u l i b e i n g p r e s e n t e d e i t h e r one at a t i m e o r i n p a i r s , w h i l e t h e i n f a n t was l y i n g on h i s b a c k o r was propped up i n some way. H i s r e s p o n s e s t o each s t i m u l u s were r e c o r d e d . U s u a l l y t h e responses r e c o r d e d were v i s u a l - f o r i n s t a n c e , t h e l e n g t h o f time he f i x a t e d e a c h s t i m u l u s , or t h e member o f a p a i r f i x -a t e d f i r s t - b u t i n some cases o t h e r measures such as arm movement o r h e a r t r a t e were a l s o r e c o r d e d . These e x p e r i m e n t s on i n f a n t a t t e n t i o n t o complex s t i m u -l i f a l l i n t o a n a t u r a l o r d e r a c c o r d i n g t o t h e degree o f con -s c i o u s m a n i p u l a t i o n o f v a r i o u s a s p e c t s o f c o m p l e x i t y e x h i b i -t e d on t h e p a r t o f t h e r e s e a r c h e r . They range f r o m e x p e r i -ments i n wh i c h a c o n g l o m e r a t i o n o f p a t t e r n s were p r e s e n t e d t o 10 t h e s u b j e c t s w i t h l i t t l e o r no a t t e n t i o n p a i d t o t h e i r r e -l a t i v e c o m p l e x i t i e s , t o s t u d i e s i n w h i c h a s p e c t s o f s t i m u l u s c o m p l e x i t y were not o n l y d e f i n e d and d i s c u s s e d but were a l s o p r e c i s e l y measured. The s t u d i e s a r e d e a l t w i t h i n i n -c r e a s i n g o r d e r o f t h e i r s o p h i s t i c a t i o n w i t h r e s p e c t t o t h e c o m p l e x i t y v a r i a b l e . (a) Post Hoc E x p l a n a t i o n s o f E x p e r i m e n t a l R e s u l t s i n terms - o f S t i m u l u s C o m p l e x i t y . I n s t u d y i n g t h e e f f e c t o f m e d i c a t i o n d u r i n g l a b o u r on a t t e n t i o n i n newborn i n f a n t s , S t e c h l e r (I96I4.) p r e s e n t e d each o f t h r e e s t i m u l i , a p i c t u r e o f a f a c e , a d i e w i t h t h r e e d o t s , and a b l a n k c a r d , t h r e e t i m e s f o r one minute i n a s i n g l e s t i m u l u s p r o c e d u r e . I n terms o f t h e average t o t a l f i x a t i o n t i m e f o r each s t i m u l u s t h e o r d e r of d e c r e a s i n g p r e f e r e n c e f o r t h e t h r e e s t i m u l i were f a c e , d i e , and b l a n k . S t e c h l e r c l a i m e d t h a t t h e s e r e s u l t s c o u l d be e x p l a i n e d by t h e d i f f e r -ences i n s t i m u l u s c o m p l e x i t y a l o n e and c o n c l u d e d t h a t t h e newborn i n f a n t o r i e n t s l o n g e r t oward s o u r c e s o f g r e a t e r r e -t i n a l s t i m u l a t i o n . I n t h i s study no a p r i o r i d e s i g n a t i o n o f t h e c o m p l e x i t y l e v e l s o f the s t i m u l i was made. I t w o u l d appear t h a t i n s e a r c h i n g f o r an e x p l a n a t i o n of t h e r e s u l t s o b t a i n e d , t h e i n v e s t i g a t o r examined h i s s t i m u l i and d e c i d e d t h a t t h e y d i f -f e r e d i n c o m p l e x i t y , t h e f a c e b e i n g more complex t h a n t h e d i e , and t h e d i e more complex t h a n t h e b l a n k . He t h e n gave a 11. post hoc e x p l a n a t i o n o f t h e r e s u l t s o f h i s experiment i n terms o f t h e c o m p l e x i t y o f t h e s t i m u l i u s e d . U n f o r t u n a t e l y , t h e s e s t i m u l i do not v a r y m e r e l y I n c o m p l e x i t y . F o r I n s t a n c e , t h e y d i f f e r i n a l b e d o as w e l l , and t h e i n f a n t s c o u l d have been r e s p o n d i n g t o t h i s b r i g h t n e s s d i m e n s i o n . F a n t z (1958) a l s o p r e s e n t e d i n f a n t s w i t h s t i m u l i w h i c h were not chosen on t h e b a s i s o f t h e i r c o m p l e x i t y . As a p i o n e e r i n t h e f i e l d o f v i s u a l a t t e n t i o n i n i n f a n t s , F a n t z was m a i n l y concerned w i t h showing t h a t c o n s i s t e n t v i s u a l p r e -f e r e n c e s f o r c e r t a i n s t i m u l i were p r e s e n t as e a r l y as two months o f age. He opposed t h e p s y c h o l o g i c a l t h e o r y t h a t t h e human i n f a n t ' s v i s u a l w o r l d c o n s i s t e d t o t a l l y o f vague f i -g u res w i t h b l u r r e d o u t l i n e s . Thus, t h e pr o b l e m o f c o m p l e x i t y d i d not c o n c e r n h i m d i r e c t l y i n d e s i g n i n g h i s i n i t i a l e x p e r i -ments ( e . g . , 1958). What he was m a i n l y i n t e r e s t e d i n was t h e presence o r absence o f p a t t e r n i n a s t i m u l u s . However, h i s r e s u l t s c a n be and have been i n t e r p r e t e d i n terms o f complex-i t y and so f o r p r e s e n t purposes he may be c a t e g o r i z e d w i t h S t e c h l e r i n t h i s f i r s t c a t e g o r y . I n one s t u d y F a n t z (1958) p r e s e n t e d p a i r s o f s t i m u l i t o t h e i n f a n t s a n d r e c o r d e d t h e i r f i x a t i o n t i m e s f o r each one. The s t i m u l u s p a i r s were h o r i z o n t a l s t r i p e s and a b u l l ' s - e y e , a c h e c k e r b o a r d a nd two s i z e s o f p l a i n s q u a r e , a c r o s s and a c i r c l e , and two i d e n t i c a l t r i a n g l e s . I n a n o t h e r s t u d y F a n t z (I96I) u s e d s u c h s t i m u l i as a f a c e , n e w s p r i n t , a b u l l ' s - e y e , and s e v e r a l c i r c l e s o f a l l one 12 c o l o u r . P a n t z r a n k e d t h e s e s t i m u l i as t o t h e amount o f f o r m or p a t t e r n t h e y p o s s e s s . However, t o t h i s i n v e s t i g a t o r , i t seems l i k e l y t h a t he r a n k e d the s t i m u l i , e s p e c i a l l y t h e f a c e , n e w s p r i n t , and b u l l ' s - e y e , a f t e r he had d i s c o v e r e d t h e amount of a t t e n t i o n t h e y were p a i d by 2 and 3 month o l d i n f a n t s . So f a r t h r e e s t u d i e s on i n f a n t a t t e n t i o n have been d i s -c u s s e d . I n t h e f i r s t ( S t e c h l e r , I96I1), no d e f i n i t i o n o f com-p l e x i t y was o f f e r e d . I n t h e o t h e r two ( P a n t z , 1958 and I96I) , a p p a r e n t l y on t h e b a s i s o f t h e r e s u l t s o b t a i n e d , t h e e x p e r i -menter proposed t h a t s t i m u l u s p a t t e r n was a b a s i s f o r v i s u a l p r e f e r e n c e s I n i n f a n t s . The degree o f p a t t e r n i n g i n a s t i -mulus i s c o n s i d e r e d by some workers i n t h e f i e l d ( e . g . W a l k e r , 1961L) t o be a c h a r a c t e r i s t i c o f c o m p l e x i t y . Thus, P a n t z ' s work has a p l a c e i n t h e d i s c u s s i o n o f the d e f i n i t i o n o f s t i m u l u s c o m p l e x i t y . (b) I n t u i t i v e a p r i o r i O r d e r i n g o f S t i m u l i i n t e r m s o f C o m p l e x i t y S e v e r a l s t u d i e s have made i n t u i t i v e a p r i o r i d e s i g n a t i o n s o f t h e r a n k o r d e r o f t h e c o m p l e x i t y i n h e r e n t i n t h e s t i m u l i u s ed "depending upon p i c t o r i a l r e p r e s e n t a t i o n s o f t h e s t i m u l i so chosen t o communicate t h e a u t h o r ' s meaning o f c o m p l e x i t y 1 ' ( C a n t o r , 1963> p« k-) • Qn.e example o f t h i s i s a s t u d y by S a c k e t t (I96I1) i n w h i c h he i n v e s t i g a t e d the p r e f e r e n c e f o r v i s u a l c o m p l e x i t y i n monkeys r e a r e d under s e v e r a l l e v e l s o f e a r l y o v e r a l l v i s u a l i n p u t r a n g i n g f r o m s e v e r e l y d e p r i v e d t o 1 3 . normal j u n g l e u p b r i n g i n g . The s t i m u l i " i n i n c r e a s i n g o r d e r o f c o m p l e x i t y " were a w h i t e or b l a c k s q u a r e , s t r i p e s , a c h e c k e r b o a r d c o n t a i n i n g k x k r e c t a n g l e s , a b u l l ' s - e y e , and a c h e c k e r b o a r d c o n t a i n i n g l k x 17 s q u a r e s . He f o u n d t h a t a n i m a l s r e a r e d i n more complex v i s u a l environments p r e f e r r e d v i s u a l p a t t e r n s o f g r e a t e r c o m p l e x i t y . I t i s o b v i o u s t h a t the a u t h o r was w o r k i n g on some i n t u i t i v e d e f i n i t i o n o f com-p l e x i t y , but t h e e x a c t c o n t e n t s o f the d e f i n i t i o n a r e not made e x p l i c i t . A n o t h e r example o f a p r i o r i o r d e r i n g o f s t i m u l i i n terms o f an i n t u i t i v e d e f i n i t i o n o f c o m p l e x i t y i s a study by L e w i s , Meyers, and Kagan (1963K They p r e s e n t e d 2 k week o l d i n f a n t s w i t h t h r e e s t i m u l i - a s i n g l e b l i n k i n g l i g h t , a h o r i z o n t a l moving l i g h t , and a b l i n k i n g l i g h t w h i c h d e s c r i b e d a s quare h e l i x . E a c h s t i m u l u s was p r e s e n t e d f o r f o u r 3 0-second t r i a l s . These s t i m u l i c o u l d be i n t e r p r e t e d as p o s s e s s i n g i n c r e a s i n g degrees o f p a t t e r n , number o f e l e m e n t s , and movement, a l l o f w h i c h c o u l d be c o n c e i v e d o f as c o n t r i b u t i n g t o c o m p l e x i t y . However, t h e e x p e r i m e n t e r s do not g i v e t h e i r r e a s o n s f o r assuming t h a t t h e s t i m u l i d i f f e r i n c o m p l e x i t y and t h e i r o r d e r i n g must t h e r e f o r e be c l a s s i f i e d as i n t u i t i v e , B e r l y n e (1958 b) performed an experiment t o t e s t t h e e f f e c t s o f two v a r i a b l e s , a l b e d o and c o m p l e x i t y , on v i s u a l f i x a t i o n i n t h e human i n f a n t . He p r e s e n t e d t h e s t i m u l i t o i n f a n t s f r o m t h r e e t o n i n e months o l d i n a p a i r c omparison p r o c e d u r e and r e c o r d e d w h i c h p a t t e r n was f i x a t e d f i r s t . He used t w e l v e s t i m u l u s p a t t e r n s , f o u r s e r i e s o f t h r e e each. S e r i e s A, t h e a l b e d o s e r i e s , c o n s i s t e d o f a b l a c k , g r e y , and w h i t e r e c t a n g l e . S e r i e s B,C and D e a c h c o n t a i n e d t h r e e f i g u r e s w i t h d i f f e r e n t degrees o f c o m p l e x i t y but a l l made up of e q u a l a r e a s o f b l a c k and w h i t e . These s t i m u l i a r e r e p r o d u c e d i n F i g u r e 1. B e r l y n e f o u n d t h a t o n l y p a t t e r n s B3 and a t t r a c t e d f i r s t f i x a t i o n s s i g n i f i c a n t l y more o f t e n t h a n t h e o t h e r p a t t e r n s l n t h e i r r e s p e c t i v e s e r i e s . B e r l y n e ' s p o s t hoc e x -p l a n a t i o n f o r t h e s e r e s u l t s was t h a t t h e s e two s t i m u l i had much more c o n t o u r t h a n t h e o t h e r s i n t h e i r s e r i e s and t h i s a c c o u n t e d f o r t h e i r h i g h e ye-drawing power. But contour i s not the o n l y a t t r i b u t e on w h i c h t h e s e s t i m u l i d i f f e r . They a l s o v a r y as t o t h e number o f p a r t s t h e y p o s s e s s , t h e number o f b l a c k - w h i t e a l t e r n a t i o n s i n them, and the number o f i n -dependent a n g l e s c o n t a i n e d i n them. The r e s u l t s o f t h i s e x -periment e o u l d be e x p l a i n e d i n terms o f any one or a l l o f t h e s e a t t r i b u t e s . I n B e r l y n e ' s s t i m u l i a l l t h e s e a t t r i b u t e s appear t o c o - v a r y , a l t h o u g h i t i s p o s s i b l e f o r them t o be m a n i p u l a t e d i n d e p e n d e n t l y . I n t h e s t u d i e s d i s c u s s e d i n t h i s s e c t i o n , t h e i n v e s t i -g a t o r s were s p e c i f i c a l l y i n t e r e s t e d i n t h e i n f l u e n c e o f com-p l e x i t y on i n f a n t p e r c e p t i o n , and i t i s o b v i o u s t h a t t h e y chose t h e i r s t i m u l i on t h e b a s i s o f some i n t u i t i v e and i m p l i -c i t d e f i n i t i o n o f c o m p l e x i t y . However, t h e y n e v e r made 1 5 . F i g u r e 1 . The s t i m u l i u s e d by B e r l y n e (1958 b) 16 e x p l i c i t t h e c o n t e n t s o f t h e i r d e f i n i t i o n s . B e r l y n e (1958 &) s p e c i f i e d a q u a l i t y o f t h e s t i m u l i , c o n t o u r , w h i c h he thought a c c o u n t e d f o r h i s r e s u l t s . However, i n s p e c t i o n o f t h e s t i m u l i r e v e a l s t h a t many o t h e r v a r i a b l e s b e s i d e s t h i s one c o u l d have i n f l u e n c e d t h e s u b j e c t s ' r e s p o n s e s . Thus, any d e f i n i t i o n s o f c o m p l e x i t y d e r i v e d f r o m t h e e x p e r i m e n t s i n t h i s s e c t i o n do not emerge e a s i l y f r o m a r e a d i n g o f t h e p a p e r s c i t e d . The s t i m u l i u s e d must be i n -s p e c t e d t o see t h e p o s s i b l e i n d i c e s o f c o m p l e x i t y w h i c h t h e e x p e r i m e n t e r s , a c t i n g i n t u i t i v e l y , f e l t were c o n t r i b u t i n g t o t h e c o m p l e x i t y o f t h e i r s t i m u l i . Upon i n s p e c t i o n o f t h e s t i -m u l i s u c h i n d i c e s o f c o m p l e x i t y as p a t t e r n , number of e l e -ments, and movement (Lewis et a l . , 1 9 6 3 ) $ c o n t o u r , number o f b l a c k - w h i t e a l t e r n a t i o n s , and number o f independent a n g l e s ( B e r l y n e , 1958 b) may be n o t e d . ( c ) O r d e r i n g t h e S t i m u l i i n terms o f C o m p l e x i t y by Means , o f A d u l t R a t i n g s  Thomas ( i n p r e s s ) d e s i g n a t e d t h e r a n k o r d e r o f h i s s t i -m u l i i n terms o f c o m p l e x i t y by means o f t h e r a t i n g s g i v e n t h e s t i m u l i by c o l l e g e s t u d e n t s . I n o r d e r o f i n c r e a s i n g c o m p l e x i t y t h e o v a l shaped a c h r o m a t i c s t i m u l i were two b r o a d h o r i z o n t a l s t r i p e s , a c h e c k e r b o a r d , a f a c e , and a c l o t h e d female f i g u r e . However, t h e i n d i c e s w h i c h t h e a d u l t s u s e d as bases f o r t h e i r judgements a r e not s p e c i f i e d , nor i s i t l i k e -l y t h a t t h e y were even a s c e r t a i n e d . T h e r e f o r e , t h i s s t u d y 1 7 o f f e r s l i t t l e h e l p i n t h e s e a r c h f o r adequate d e f i n i t i o n s o f c o m p l e x i t y . (d) A p r i o r i O r d e r i n g o f S t i m u l i i n Terms o f C o m p l e x i t y , U s i n g E x p l i c i t D e f i n i t i o n s and Measurements  A few e x p e r i m e n t e r s have not o n l y g i v e n t h e i r s t i m u l i an a p r i o r i o r d e r i n terms o f t h e i r c o m p l e x i t y but have done so w i t h t h e a i d o f e x p l i c i t d e f i n i t i o n s o f c o m p l e x i t y . H e rshenson, Munsinger, and Kessen (I96I1) compared t h e p r e f e r e n c e s o f 17 newborn i n f a n t s f o r t h r e e s t i m u l i v a r y i n g i n t h e number of a n g l e s t h e y c o n t a i n e d . The s t i m u l i had 5>» 10, and 20 a n g l e s r e s p e c t i v e l y . The i n v e s t i g a t o r s c l a i m e d t h a t t h e d i m e n s i o n o p e r a t i n g i n t h e s t i m u l i was t h e number o f t u r n s i n t h e s t i m u l i , "a d i m e n s i o n a p p r o x i m a t i n g i n f o r m a -t i o n v a l u e " (Hershenson et a l . , 1961i, p. 631) • However, t h e y n o t e d t h a t i f one d e f i n e s c o m p l e x i t y a s t h e number o f l i g h t - d a r k t r a n s i t i o n s i n a s t i m u l u s , t h e c o m p l e x i t y l e v e l I n c r e a s e s as t h e number of a n g l e s I n c r e a s e s . T h e r e f o r e , number o f a n g l e s i s a l s o an a t t r i b u t e o f c o m p l e x i t y and one w h i c h i n t h i s case c o r r e l a t e s t h e number o f l i g h t - d a r k t r a n -s i t i o n s i n t h e s t i m u l i . M o f f e t t (1963), u s i n g as s t i m u l i c r o s s - h a t c h e d b l a c k l i n e s on a w h i t e square background, s y s t e m a t i c a l l y v a r i e d t h e c o m p l e x i t y o f h e r s t i m u l i u s i n g as c r i t e r i a t h e number o f p a r t s c o n t a i n e d i n the s t i m u l i , t h e r e g u l a r i t y o f arrangement o f t h e p a r t s , and t h e number o f r i g h t a n g l e d c r o s s i n g s t h e y c o n t a i n e d . She was a b l e t o r a n k o r d e r h e r s t i m u l i a c c o r d i n g 18 t o each o f t h e s e v a r i a b l e s and t h u s d e s i g n a t e t h e i r r e l a -t i v e c o m p l e x i t y l e v e l s . An experiment by Spears (196k) was one o f t h e most s u c c e s s f u l a t t e m p t s i n a p p r o a c h i n g e x p l i c i t d e f i n i t i o n s o f c o m p l e x i t y . He u s e d 5 s e r i e s o f k s t i m u l i each w h i c h he p r e -s e n t e d i n a p a i r comparison p r o c e d u r e t o f o u r month o l d i n -f a n t s . U s i n g a p r i o r i d e f i n i t i o n s o f c o m p l e x i t y he q u a n t i -f i e d p r e c i s e l y each o f t h e s t i m u l i a l o n g t h r e e c o m p l e x i t y d i m e n s i o n s : amount o f c o n t o u r a l o n g t h e t r a n s i t i o n boundar-i e s o f c o l o u r e d and w h i t e a r e a s , number o f independent a n g l e s or c u r v e s i n t h e c o n t o u r o f t h e f i g u r e , and t h e degree o f symmetry p o s s e s s e d by t h e p a t t e r n s . The p a t t e r n s used were such t h i n g s as two r e d or gr e y diamonds on a w h i t e back-ground, r e d , b l u e , or gr e y b u l l ' s - e y e s , a k x k r e d and w h i t e c h e c k e r b o a r d , random r e d shapes on a w h i t e b a ckground, and y e l l o w o r b l u e hexagonal-shaped b u l l ' s - e y e s . Spears f o u n d t h a t c o n t o u r seemed t o be the most i m p o r t a n t v a r i a b l e i n d e t e r m i n i n g i n f a n t s ' s t i m u l u s s e l e c t i o n b e h a v i o r w h i l e sym-metry p l a y e d no r o l e at a l l l n t h i s b e h a v i o r . The r a n k o r d e r i n g s o f t h e s t i m u l i I n terms o f t h e t h r e e c o m p l e x i t y a t t r i b u t e s w h i c h Spears employed were not t h e same. Fo r I n s t a n c e , t h e b u l l ' s - e y e had t h e h i g h e s t rank f o r t h e amount o f c o n t o u r I t c o n t a i n e d but was deemed t h e l e a s t com-p l e x o f t h e s t i m u l i i n terms o f t h e number o f independent a n g l e s and. t h e degree o f symmetry i t p o s s e s s e d . 1 9 . Spear's s t u d y p r o v i d e s e v i d e n c e o f t h e d i v e r s i t y o f a t t r i b u t e s w h i c h can be c o n s i d e r e d t o c o n t r i b u t e t o t h e c o m p l e x i t y o f a p a t t e r n . I n u s i n g many d i f f e r e n t p a t t e r n s i n h i s e x p e r i m e n t , and i n q u a n t i f y i n g t h e amounts o f t h e v a r i o u s c o m p l e x i t y a t t r i b u t e s w h i c h t h e y p o s s e s s , Spears has demonstrated j u s t how complex t h e concept o f c o m p l e x i t y i s , and how d i f f i c u l t i t i s t o o b t a i n neat o r d e r i n g s o f s t i m u l i a l o n g t h i s d i m e n s i o n . H e rshenson (I96I4.) a l s o a t t e m p t e d t o o r d e r s t i m u l i a l o n g a c o m p l e x i t y d i m e n s i o n . He used t h r e e b l a c k and w h i t e c h e c k e r b o a r d s q u a r e s as s t i m u l i . The l e a s t complex c o n t a i n e d 2 x 2 s q u a r e s , t h e i n t e r m e d i a t e p a t t e r n i i x 11 s q u a r e s , and th e most complex 12 x 12 s q u a r e s . Hershenson d i d n o t spe-c i f y j u s t what I n d i c e s o f s t i m u l u s c o m p l e x i t y were o p e r a t i n g i n t h e c h e c k e r b o a r d d e s i g n s , b u t i t i s o b v i o u s t h a t he has q u a n t i f i e d t h e c o m p l e x i t y l e v e l o f each d e s i g n a t l e a s t i n terms o f t h e number o f p a r t s c o m p r i s i n g i t . The e x p e r i m e n t s i n t h i s s e c t i o n a r e more s a t i s f a c t o r y t h a n t h o s e p r e v i o u s l y d i s c u s s e d f o r s e v e r a l r e a s o n s . I n two o f them (Hershenson et a l . , I96I4., and Hershenson, 1961+) o n l y one t y p e of p a t t e r n was u s e d . T h i s meant t h a t any i n d i c e s o f c o m p l e x i t y w h i c h were o p e r a t i n g i n a p a t t e r n were c o r r e -l a t e d so t h a t as one Index I n c r e a s e d the o t h e r s i n c r e a s e d as w e l l . F o r example, as t h e number o f a n g l e s i n t h e s t i m u l i u s e d by Hershenson et a l . i n c r e a s e d , so d i d the number o f 20. light-dark t r a n s i t i o n s . Thus, there could be l i t t l e doubt as to whether one stimulus was more complex than another. In Moffett's (1963) study, where the s t i m u l i were a l l com-posed of the same elements, black l i n e s on a white back-ground, the experimenter was able to manipulate one index of complexity, f o r instance number of right angled crossings, while keeping another index constant, f o r instance number of l i n e s . By so doing she was able to determine exactly which index of complexity the subjects were responding to, that i s , number of parts. By the use of many di f f e r e n t patterns, Spears ( 196k) was also able to ascertain exactly which i n -dex of complexity, i n t h i s case contour, seemed to be the most important attention getter for i n f a n t s . It would be premature at t h i s stage to make judgements as to which kind of study i s better i n determining the bases of v i s u a l attention i n in f a n t s , those employing only one pattern whose complexity i s e a s i l y manipulated, or those employing many di f f e r e n t patterns a l l of which can be mea-sured on various indices of complexity. Both kinds of stu-dies w i l l probably be needed for a long time yet, and d i f f e r -ent r e s u l t s may be expected from each. In either case, however, i t i s clear that stimuli must be chosen according to e x p l i c i t d e f i n i t i o n s of complexity. Results obtained from studies employing i n t u i t i v e l y chosen st i m u l i are d i f f i -cult to interpret and off e r l i t t l e help towards the discovery 2 1 . o f t h e bases of i n f a n t a t t e n t i o n t o s t i m u l i v a r y i n g i n com-p l e x i t y . As Walker p u t s i t , "making do w i t h i n t u i t i v e l y o r d e r e d s t i m u l u s elements i s a m i s t a k e " (Walker, 1961L, p. 7 2 ) . Now t h a t the g e n e r a l l a c k o f e x p l i c i t d e f i n i t i o n i n s t u d i e s i n v e s t i g a t i n g v a r i o u s a s p e c t s o f s t i m u l u s c o m p l e x i -t y has been i n d i c a t e d , t h e r e s u l t s o b t a i n e d i n the e x p e r i -ments c o n c e r n e d w i t h i n f a n t a t t e n t i o n t o s t i m u l i v a r y i n g i n c o m p l e x i t y w i l l be d i s c u s s e d and compared i n t h e n e x t s e c t i o n . I I RESULTS OP EXPERIMENTS ON INFANT ATTENTION TO STIMULI VARYING IN GOMPLEXITY The e x p e r i m e n t e r s c i t e d i n t h i s s e c t i o n have g e n e r a l l y i n f e r r e d t h a t p r e f e r e n c e has been shown f o r s t i m u l u s A over s t i m u l u s B i f the v i s u a l a t t e n t i o n p a i d by an i n f a n t t o A was g r e a t e r t h a n t h e a t t e n t i o n p a i d t o B. S e v e r a l r e s p o n s e mea-sur e s have been u s e d t o a s s e s s v i s u a l a t t e n t i o n and t h e s e w i l l be d i s c u s s e d f u l l y i n t h e next s e c t i o n . L e w i s , et a l . , ( 1 9 6 3 ) p r e s e n t e d t h r e e s t i m u l i t o 6 month o l d i n f a n t s as d e s c r i b e d above. I n o r d e r o f i n c r e a s i n g com-p l e x i t y the s t i m u l i were a s i n g l e b l i n k i n g l i g h t , a h o r i z o n t a l moving l i g h t , and a b l i n k i n g l i g h t w h i c h d e s c r i b e d a square h e l i x . I n terms o f b o t h t o t a l f i x a t i o n t ime and r a t e of h a b i t u a t i o n t h e d e c r e a s i n g o r d e r o f p r e f e r e n c e f o r the s t i m u -l i were t h e square h e l i x , t h e l i n e , and the s i n g l e l i g h t . The i n v e s t i g a t o r s c l a i m e d t h a t r a t e o f h a b i t u a t i o n was a f u n c t i o n o f t h e c o m p l e x i t y o f t h e p a t t e r n . For t h e l e a s t 22. complex s t i m u l u s , t h e s i n g l e b l i n k i n g l i g h t , t h e g r e a t e s t decrease i n f i x a t i o n t i m e o c c u r r e d a f t e r t r i a l one; f o r t h e row p a t t e r n t h e g r e a t e s t d e c r e a s e o c c u r r e d a f t e r t r i a l two; and f o r t h e square h e l i x , t h e most complex p a t t e r n o f t h e t h r e e , t h e g r e a t e s t d e c r e a s e i n f i x a t i o n t i m e o c c u r r e d a f t e r t r i a l t h r e e . These r e s u l t s l e d t h e a u t h o r s t o con-c l u d e t h a t " c o m p l e x i t y i s an i m p o r t a n t parameter i n main-t a i n i n g t h e i n f a n t ' s i n t e r e s t " (Lewis et a l . , 1963* p. 1 0 ) . B e r l y n e (1958 h) p r e s e n t e d t h e f o u r s t i m u l u s t r i a d s r e p r e s e n t e d i n F i g u r e 1 t o i n f a n t s r a n g i n g f rom t h r e e t o n i n e months o f age. F i n d i n g t h a t t h e o n l y s i g n i f i c a n t p r e -f e r e n c e s w i t h i n e a ch row were shown f o r s t i m u l i B^ and D^, B e r l y n e r e a s o n e d t h a t t h e s e s t i m u l i c o n t a i n e d more c o n t o u r t h a n t h e o t h e r and t h a t t h i s was t h e r e a s o n f o r t h e i r h i g h a t t r a c t i o n . As we have seen, c o n t o u r may be c o n s i d e r e d t o be an i n d e x o f c o m p l e x i t y . T h e r e f o r e , t h e t h r e e t o n i n e month o l d s t e s t e d e x h i b i t e d a p r e f e r e n c e f o r t h e p a t t e r n s o f g r e a t e s t c o m p l e x i t y . Spears (1961).) p r e s e n t e d f o u r month o l d i n f a n t s w i t h p a t -t e r n s w h i c h c o m p r i s e d s u c h t h i n g s as b u l l ' s - e y e s , diamonds, random shapes, and c h e c k e r b o a r d s . He measured e a c h s t i m u l u s i n terms o f t h r e e c o m p l e x i t y i n d i c e s — amount of c o n t o u r , number o f t u r n s , and degree of symmetry. He t h e n r a n k o r -d e r e d t h e s t i m u l i s e p a r a t e l y on each o f t h e s e a t t r i b u t e s . He f o u n d t h a t I n terms of t h e number o f i n f a n t s showing s i g n i f i -cant p r e f e r e n c e s f o r one s t i m u l u s over a n o t h e r , t h e b u l l ' s - e y e 23 d e s i g n was t h e most p r e f e r r e d s t i m u l u s * T h i s l e d S p e a r s t o conelude t h a t c o n t o u r was an i m p o r t a n t v a r i a b l e i n de-t e r m i n i n g i n f a n t s 1 s t i m u l u s s e l e c t i o n b e h a v i o r . These r e -s u l t s c oncur w i t h t h o s e o f B e r l y n e (195"8 b) j u s t d i s c u s s e d . I n h e r e x p e r i m e n t s w i t h two t o f o u r month o l d s , M o f f e t t (1963) u s e d s t i m u l i composed o f b l a c k l i n e s v a r i o u s l y a r r a n g e d on w h i t e b a c k g r o u n d s . She found t h a t the number o f p a r t s i n t o w h i c h t h e b l a c k l i n e s d i v i d e d the w h i t e a r e a was a more i m p o r t a n t d e t e r m i n a n t o f v i s u a l f i x a t i o n t h a n t h e num-be r o f l i n e s t h e m s e l v e s . That i s , two t o f o u r month o l d i n f a n t s e x h i b i t e d t h e l o n g e s t f i x a t i o n t i m e s f o r the s t i m u l i c o n t a i n i n g t h e g r e a t e s t number o f p a r t s . I n t e r p r e t i n g t h e number o f p a r t s i n a s t i m u l u s as an i n d e x o f c o m p l e x i t y , she t h u s found t h a t i n f a n t s p r e f e r r e d t h e most complex s t i m u l i o f t h e s e r i e s p r e s e n t e d . I n t h e f o u r s t u d i e s j u s t c i t e d t h e i n f a n t s r anged i n age f r o m j u s t o v e r two months t o n i n e months. I n e v e r y case p r e f e r e n c e was shown f o r t h e most complex s t i m u l i o f t h e r e -s p e c t i v e s e r i e s p r e s e n t e d . S t e c h l e r (19614.) p r e s e n t e d a s e r i e s of s t i m u l i — a f a c e , a d i e , and a b l a n k — t o new-borns and f o u n d t h a t t h e y a l s o showed a p r e f e r e n c e f o r t h e most complex s t i m u l u s , t h a t i s , f o r t h e f a c e . I f one c o n s i -d e r e d o n l y t h e r e s u l t s o f t h e s e s t u d i e s , he would p r o b a b l y c o n s i d e r i t r e a s o n a b l e t o c o n c l u d e t h a t a l l i n f a n t s p r e f e r more complex s t i m u l i . However, t h e r e i s some e v i d e n c e t o show t h a t t h i s i s n o t t h e c a s e . 2k. I n t h e e xperiment by Hershenson et a l . (196k) i n w h i c h t h r e e s t i m u l i , c o n t a i n i n g 10, and 20 a n g l e s r e s p e c t i v e l y were p r e s e n t e d t o newborns, g r e a t e s t a t t e n t i o n was p a i d t o the s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y , t h a t i s , t h e one w i t h 10 a n g l e s . The most complex s t i m u l u s , t h e one w i t h 20 a n g l e s , was p r e f e r r e d second t o t h e 10 a n g l e d s t i m u l u s . T h i s s t u d y p r o v i d e s e v i d e n c e t h a t t h e most complex s t i m u l u s o f a s e r i e s i s not always the most p r e f e r r e d by i n f a n t s . F u r t h e r e v i d e n c e i s o f f e r e d i n a n o t h e r s t u d y by H e r -shenson (196k). The s t i m u l i u s e d were t h r e e b l a c k and w h i t e c h e c k e r b o a r d s q u a r e s , c o n t a i n i n g 2 x 2 , k x k, and 12 x 12 s q u a r e s r e s p e c t i v e l y . Hershenson p r e s e n t e d the s t i m u l i i n p a i r s t o newborn i n f a n t s and photographed t h e i r eyes as t h e y l o o k e d a t the s t i m u l i . He found t h a t t h e l e a s t complex s t i -mulus was t h e most p r e f e r r e d . F u r t h e r m o r e , t h e o r d e r o f p r e -f e r e n c e e x h i b i t e d f o r the s t i m u l i was i n d e c r e a s i n g o r d e r o f t h e i r c o m p l e x i t y — t h a t i s , t h e s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y was t h e next most p r e f e r r e d , w h i l e t h e most complex s t i m u l u s was t h e l e a s t p r e f e r r e d . I t seems s i g n i f i c a n t t h a t t h e s t u d y i n w h i c h most p r e -f e r e n c e was shown f o r t h e l e a s t complex s t i m u l u s o f a s e r i e s employed newborn i n f a n t s as s u b j e c t s . None o f t h e s t u d i e s d i s c u s s e d so f a r has s p e c i f i c a l l y i n v e s t i g a t e d t h e i n f l u e n c e o f age on t h e p r e f e r e n c e s shown f o r s t i m u l i o f d i f f e r e n t com-p l e x i t y l e v e l s . However, two w o r kers i n t h e f i e l d have f o u n d changes i n p r e f e r e n c e w i t h age, t h u s p r o v i d i n g f u r t h e r e v i d e n c e 2 5 . t h a t t h e age o f the baby may i n f l u e n c e h i s p r e f e r e n c e f o r c o m p l e x i t y , F a n t z (1958 and 1961) p r e s e n t e d p a i r s o f s t i m u l i t o i n f a n t s v a r y i n g i n age f r o m 2 t o 15 weeks. One o f the p a i r s c o n s i s t e d o f a s t r i p e d d e s i g n and a b u l l ' s - e y e . F a n t z f o u n d t h a t i n f a n t s o f l e s s t h a n e i g h t weeks p r e f e r r e d t h e s t r i p e s t o t h e b u l l ' s - e y e , w h i l e t h o s e o f e i g h t weeks and o l d e r con-s i s t e n t l y p r e f e r r e d the b u l l ' s - e y e t o the s t r i p e s . I n terms o f s e w e r a l i n d i c e s o f c o m p l e x i t y , F a n t z ' s b u l l ' s - e y e d e s i g n c o u l d be c o n s i d e r e d t o be more complex t h a n h i s s t r i p e d s t i -mulus. F o r i n s t a n c e , t h e b u l l ' s - e y e p o s s e s s e s more p a r t s , c o n t o u r , and l i g h t - d a r k t r a n s i t i o n s t h a n t h e s t r i p e s . Thus, the r e s u l t s o f t h i s experiment can be i n t e r p r e t e d as p r o v i -d i n g e v i d e n c e t h a t o l d e r i n f a n t s p r e f e r s t i m u l i o f g r e a t e r c o m p l e x i t y . An experiment b y Thomas ( i n p r e s s ) i s t h e o n l y one d i s -c u s s e d h e r e w h i c h d e l i b e r a t e l y t r i e d t o t e s t age d i f f e r e n c e s i n the l e v e l o f s t i m u l u s c o m p l e x i t y p r e f e r r e d by i n f a n t s . Thomas d e s i g n a t e d t h e r a n k o r d e r o f h i s s t i m u l i i n terms o f complex-i t y be means o f t h e r a t i n g s g i v e n t h e s t i m u l i by c o l l e g e s t u d e n t s . I n o r d e r o f i n c r e a s i n g c o m p l e x i t y , the o v a l shaped a c h r o m a t i c s t i m u l i were two b r o a d h o r i z o n t a l s t r i p e s , a c h e c k e r b o a r d - l i k e p a t t e r n , a f a c e , and a c l o t h e d f e m a l e f i -g u r e . I n terms o f f i x a t i o n t i m e , i n f a n t s 2 t o LLL weeks o l d most p r e f e r r e d t h e c h e c k e r b o a r d , t h e n t h e f i g u r e , t h e f a c e , and t h e s t r i p e s l e a s t . A l l d i f f e r e n c e s were s i g n i f i c a n t 26. except t h e d i f f e r e n c e between th e f i g u r e and t h e f a c e . The o r d e r o f p r e f e r e n c e f o r i n f a n t a 15 t o 26 weeks was t h e f a c e , f i g u r e , c h e c k e r b o a r d , and t h e s t r i p e s . The o n l y change i n p r e f e r e n c e w i t h age was f r o m t h e c h e c k e r b o a r d t o t h e f a c e -t h a t i s , a p r e f e r e n c e f o r i n c r e a s e d c o m p l e x i t y w i t h age. The r e s u l t s o f t h e s e r e c e n t s t u d i e s on v e r y young i n -f a n t s seem t o demand a more s o p h i s t i c a t e d a t t i t u d e t h a n t h a t w h i c h a r o s e out o f e x p e r i m e n t s i n w h i c h t h e samples were com-p r i s e d o n l y o f i n f a n t s over two months o l d and where t h o s e i n f a n t s were t r e a t e d as homogeneous g r o u p s . I t seems t h a t t h e r e I s some p r e l i m i n a r y e v i d e n c e f o r b e l i e v i n g t h a t as a n I n f a n t grows o l d e r he shows an i n c r e a s i n g p r e f e r e n c e f o r more complex v i s u a l s t i m u l i . T h i s b e l i e f i s f u r t h e r b o l s -t e r e d by a t h e o r y p r o p o s e d by Dember and E a r l ( 195?) i n terms o f w h i c h an e x p l a n a t i o n can be f o u n d f o r t h e s e r e s u l t s . T h i s t h e o r y i s d e s c r i b e d b elow. I l l A THEORY ABOUT COMPLEXITY I n t h e i r attempt t o account f o r t h e a t t e n t i o n - g e t t i n g p r o p e r t i e s o f s t i m u l i , Dember and E a r l (1957) p o i n t out t h a t a s t i m u l u s may have a d i f f e r e n t measure of c o m p l e x i t y on each o f i t s a t t r i b u t e s . Presumably t h e n , u s i n g , f o r exam-p l e , t h e d e f i n i t i o n o f c o m p l e x i t y p r oposed by B e r l y n e (I960), one c o u l d i n c r e a s e t h e c o m p l e x i t y o f a s t i m u l u s a l o n g i t s "number o f e l e m e n t s " a t t r i b u t e w h i l e k e e p i n g i t s " d i s s i m i -l a r i t y between e l e m e n t s " a t t r i b u t e c o n s t a n t . Dember and 2? E a r l c l a i m f u r t h e r t h a t an i n d i v i d u a l haa an i d e a l com-p l e x i t y v a l u e on each a t t r i b u t e , c o r r e s p o n d i n g i n a g e n e r a l -i z e d sense t o h i s " a b i l i t y " on t h a t a t t r i b u t e . On i n d e -pendent a t t r i b u t e s t h e s e v a l u e s may change I n d e p e n d e n t l y . For i n s t a n c e , an I n d i v i d u a l ^ i d e a l c o m p l e x i t y v a l u e f o r music may i n c r e a s e w h i l e h i s c o m p l e x i t y v a l u e f o r l i t e r a -t u r e remains t h e same. T h i s i d e a l p s y c h o l o g i c a l c o m p l e x i t y l e v e l i s char act e r i s t i c o f t h e i n d i v i d u a l a t a g i v e n moment i n t i m e and w i t h r e s p e c t t o s p e c i f i c s t i m u l u s a t t r i b u t e s . I n d i v i d u a l s come t o have d i f f e r e n t i d e a l s t h r o u g h e x p e r i e n c e . A c c o r d i n g t o t h i s t h e o r y , e x p e r i e n c e w i t h c e r t a i n s t i -m u l i i n c r e a s e s t h e p s y c h o l o g i c a l c o m p l e x i t y l e v e l o f t h e i n d i v i d u a l . Only s t i m u l i t h a t a r e g r e a t e r , but not t o o much g r e a t e r , t h a n t h e p r e s e n t i d e a l c o m p l e x i t y l e v e l o f t h e i n d i v i d u a l a r e a b l e t o i n c r e a s e t h e p s y c h o l o g i c a l com-p l e x i t y o f t h e i n d i v i d u a l . Such s t i m u l i a r e c a l l e d p a c e r s . An i n d i v i d u a l a t t e n d s t o a set o f s t i m u l i i f t h a t s e t con-t a i n s a s t i m u l u s t h a t i s a p a c e r f o r h i m . The i n d i v i d u a l a t t e n d s t o s t i m u l i i n p r o p o r t i o n t o t h e i r s i m i l a r i t y t o t h e p a c e r , w i t h t h e most a t t e n t i o n b e i n g g i v e n t o the paeer i t -s e l f . As t h e I n d i v i d u a l g a i n s e x p e r i e n c e w i t h t h e s e t , h i s I d e a l c o m p l e x i t y l e v e l i n c r e a s e s u n t i l e v e n t u a l l y t h e s e t no l o n g e r c o n t a i n s a p a c e r . At t h a t time t h e s e t has l o s t i t s a b i l i t y t o change t h e p s y c h o l o g i c a l c o m p l e x i t y l e v e l o f t h e i n d i v i d u a l a i d t h u s i t a l s o has l o s t i t s a t t e n t i o n -a r o u s i n g p r o p e r t y f o r h i m . 2 8 . Thus, t h r o u g h c o n t a c t w i t h a pacer an I n d i v i d u a l ' s i d e a l c o m p l e x i t y v a l u e on a g i v e n a t t r i b u t e i s moved t o -ward t h e v a l u e of the p a c e r . "As l o n g as t h e r e a r e s u i t a b l e p a c e r s a v a i l a b l e , and as l o n g as t h e I n d i v i d u a l can r e -spond f r e e l y t o a l l a v a i l a b l e s t i m u l i , h i s i d e a l c o m p l e x i t y l e v e l w i l l c o n t i n u e t o i n c r e a s e " (Dember, i 9 6 0 , p. 3 6 0 ) . The e x t e n t o f t h i s i n c r e a s e i s l i m i t e d o n l y by t h e I n d i v i -d u a l ' s h e r e d i t a r y endowment. I n n o r mal development t h e i n -d i v i d u a l paces h i m s e l f by c h o o s i n g t o i n t e r a c t w i t h s t i m u l i t h a t a r e somewhat more complex t h a n t h o s e he I s used t o . I n o t h e r words, an i n d i v i d u a l ' s p r e f e r e n c e s f o r s o c i a l and n o n s o c i a l s t i m u l a t i o n a r e paced by g r a d u a l i n c r e a s e s i n s t i m u l u s c o m p l e x i t y . Thomas ( i n p r e s s ) e x p l a i n e d h i s r e s u l t s I n terms o f Dember and E a r l ' s t h e o r y o f l e v e l s o f c o m p l e x i t y o f both s t i m u l u s and o r g a n i s m . R e c a l l t h a t i n o r d e r o f i n c r e a s i n g c o m p l e x i t y , h i s s t i m u l i were s t r i p e s , a c h e c k e r b o a r d , a f a c e , and a f i g u r e . He found t h a t 2 t o l k week o l d s p r e -f e r r e d t h e c h e c k e r b o a r d most, w h i l e 15 t o 26 week o l d s p r e -f e r r e d t h e f a c e most. He h y p o t h e s i z e d t h a t an even o l d e r group would p r e f e r t h e f e m a l e f i g u r e most as i t would be a pacer f o r them. Thomas i s t h e o n l y one o f the p r e v i o u s l y mentioned i n -v e s t i g a t o r s who r e c o g n i z e d t h e p o s s i b i l i t y o f age d i f f e r e n c e s i n t h e l e v e l o f c o m p l e x i t y p r e f e r r e d and who s p e c i f i c a l l y t e s t e d f o r them. However, t h e r e a r e two drawbacks t o h i s 2 9 . e x p e r i m e n t . F i r s t , t h e s t i m u l i he u sed v a r i e d a l o n g s e v e r a l d i m e n s i o n s s i m u l t a n e o u s l y : f o r i n s t a n c e , they v a r i e d i n t h e amount o f m e a n i n g f u l n e s s t h e y might have f o r an i n f a n t . T h e r e f o r e , c o n c l u s i o n s about the r e s u l t s cannot be made s o l e l y I n terms o f d i f f e r e n c e s i n c o m p l e x i t y among t h e s t i m u l i . S e c o n d l y , he u s e d a d u l t judgments t o o r d e r h i s s t i m u l i i n c o m p l e x i t y . T h i s may not always be a w i s e p r o -c e d u r e , as M o f f e t t (1963) f o u n d l i t t l e r e l a t i o n between a d u l t s 1 judgements o f c o m p l e x i t y and i n f a n t s ' l o o k i n g t i m e s , even t h o u g h she f o u n d s i g n i f i c a n t agreement among a d u l t s and s i g n i f i c a n t agreement among i n f a n t s . I t seems t h e n , t h a t a d u l t s ' judgements o f c o m p l e x i t y a r e not n e c e s s a r i l y t h e bases f o r i n f a n t s ' l o o k i n g t i m e s , nor a r e t h e y n e c e s s a r -i l y i n l i n e w i t h t h e p h y s i c a l o r d e r i n g o f s t i m u l i a l o n g a c o m p l e x i t y d i m e n s i o n . However, i n terms o f t h e s t i m u l u s o r d e r i n g he u s e d , Thomas d i d demonstrate i n c r e a s i n g p r e f e r -ence f o r more complex s t i m u l i w i t h age. The r e s u l t s o f t h e o t h e r e x p e r i m e n t s can be I n t e r p r e t e d i n terms o f Dember and E a r l ' s t h e o r y a l s o . I n t h e s t u d i e s d e a l i n g w i t h i n f a n t s over two months ( B e r l y n e , 1958 h j Lewis et a l . 1963J M o f f e t t , 1963; and S p e a r s , 196IL), t h e s t i m u l i t h a t were p r e f e r r e d were t h o s e t h a t were the most s i m i l a r o f any i n t h e i r s e t s t o t h e p a c e r s t i m u l u s f o r t h o s e I n f a n t s . Thus, t h e y a t t r a c t e d more a t t e n t i o n t h a n any o f t h e o t h e r s t i -m u l i . Because o f t h e p a r t i c u l a r range o f s t i m u l i u s e d , t h e most p r e f e r r e d s t i m u l i I n t h e s e s e t s were a l s o t h e most 30. complex. I f s t i m u l i o f even g r e a t e r c o m p l e x i t y had been added t o t h e s e t s , however, I t might have been f o u n d t h a t i n f a n t s w o u l d not have p a i d most a t t e n t i o n t o t h e most complex o f t h e s e t , but i n s t e a d would have p a i d most a t t e n -t i o n t o t h a t s t i m u l u s w h i c h most resem b l e d t h e p a c e r f o r them. I t w o u l d seem, t h e n , t h a t t h e s e t s o f s t i m u l i used i n t h e s e e x p e r i m e n t s d i d not c o n t a i n s t i m u l i complex enough t o be above t h e l e v e l o f c o m p l e x i t y o f the p a c e r f o r t h e i n f a n t s t e s t e d . However, t h e s e t s o f s t i m u l i w h i c h Hershenson et a l . ( I 9 6 i i ) and Hershenson (I96I4.) p r e s e n t e d t o newborns d i d ex-t e n d above t h e c o m p l e x i t y l e v e l o f the p a c e r s f o r t h e s e s u b -j e c t s . F o r newborns t h e l e a s t complex c h e c k e r b o a r d most re s e m b l e d t h e pacer s t i m u l u s f o r t h e a t t r i b u t e s r e p r e s e n t e d i n a c h e c k e r b o a r d p a t t e r n , w h i l e t h e p a t t e r n w i t h t h e I n t e r -m ediate number o f a n g l e s most resem b l e d t h e pacer s t i m u l u s f o r the a t t r i b u t e s r e p r e s e n t e d i n t h a t t y p e o f d e s i g n . H a v i n g f o u n d a t h e o r y w h i c h seems r e l e v a n t t o t h e s t u d y o f i n f a n t a t t e n t i o n t o s t i m u l i v a r y i n g i n c o m p l e x i t y , I t w ould seem a p p r o p r i a t e n e x t t o d e s i g n e x p e r i m e n t s t o t e s t t h i s t h e o r y . However, f i r s t a v a l i d and r e l i a b l e method o f a s s e s s i n g i n f a n t a t t e n t i o n and a p r o c e d u r a l d e s i g n w h i c h i s s u i t e d t o t h e c a p a b i l i t i e s o f the o r g a n i s m t e s t e d must be f o u n d . These problems a r e d i s c u s s e d i n t h e f o l l o w i n g s e c t i o n . 3 1 . IV METHODOLOGICAL PROBLEMS IN THE STUDY OP INFANT ATTENTION TO STIMULI VARYING. IN COMPLEXITY. 1 . Response Measures Many d i f f e r e n t methods have been used t o a s s e s s I n f a n t a t t e n t i o n t o y i s u a l s t i m u l i . Most o f t h e measures i n v o l v e o b s e r v i n g the i n f a n t f s eyes and somehow r e c o r d i n g h i s r e -sponses t o the s t i m u l i p r e s e n t e d . The responses r e c o r d e d have been s e v e r a l , as have been t h e ways i n w h i c h t h e s e r e -sponses have been a n a l y z e d , (a) T o t a l F i x a t i o n Time The t o t a l t i m e d u r i n g w h i c h t h e s u b j e c t s f i x a t e the s t i m u l i has been used by many e x p e r i m e n t e r s . An i n f a n t i s c o n s i d e r e d t o be f i x a t i n g a s t i m u l u s i f t h e s t i m u l u s i s r e f l e c t e d o v e r t h e p u p i l s of h i s e y e s . On each t r i a l i n w h i c h a s t i m u l u s I s p r e s e n t e d t h e e x p e r i m e n t e r s r e c o r d the l e n g t h o f t i m e d u r i n g w h i c h the s t i m u l u s i s so r e f l e c t e d t o d e r i v e d a t o t a l f i x a t i o n t i m e f o r t h a t s t i m u l u s . M o f f e t t (1963) made use o f a l l t h e t o t a l f i x a t i o n d a t a she o b t a i n e d i n an a n a l y s i s of v a r i a n c e d e s i g n f o r a s c e r t a i n i n g s i g n i f i -cant p r e f e r e n c e s . Hersenson ( 1 9 6 k ) , Hershenson et a l . ( 1 9 6 k ) and S p e a r s ( 196k) measured t o t a l l o o k i n g t i m e but c o n v e r t e d t h i s i n f o r m a t i o n i n t o f r e q u e n c y d a t a on t h e number o f sub-j e c t s showing s i g n i f i c a n t p r e f e r e n c e s ( S p e a r s , 1 9 6 k ) , or t h e number o f frames o f f i l m i n w h i c h the v a r i o u s s t i m u l i were f i x a t e d (Hershenson, 1 9 6 k , and Hershenson et a l . , 1 9 6 k ) . 3 2 . (b) L e ngth o f F i r s t F i x a t i o n F a n t z (1963) and L e w i s et a l . (1965) r e c o r d e d o n l y t h e l e n g t h o f t h e f i r s t f i x a t i o n on a s t i m u l u s and o l a i m e d t h a t t h i s was as r e l i a b l e a measure as l e n g t h o f t o t a l f i x a t i o n . I n f a c t , Lewis et a l . suggest t h a t l e n g t h o f t h e f i r s t f i x -a t i o n i s a more s e n s i t i v e measure t h a n t o t a l f i x a t i o n t i m e i n s t u d y i n g i n d i v i d u a l d i f f e r e n c e s and t h e a t t r a c t i v e n e s s o f s t i m u l i . However, they d i d f i n d t h a t t h e r e l a t i o n s h i p between t h e s e two measures was a f u n c t i o n o f the s t i m u l u s f i x a t e d and the s u b j e c t f i x a t i n g . (c) Rate o f H a b i t u a t i o n Lewis et a l . (1963) a l s o a n a l y z e d t h e r a t e o f h a b i t u a -t i o n to s t i m u l i d i f f e r i n g i n c o m p l e x i t y i n terms o f the de-c r e a s e i n t o t a l f i x a t i o n t i m e m a n i f e s t e d t o s t i m u l i p r e s e n t e d over f o u r t r i a l s e a c h . (d) C a r d i a c D e c e l e r a t i o n Rate L e w i s et a l . (1963) and Kagan and Lewis ( i n p r e s s ) r e -corde d i n f a n t s ' h e a r t d e c e l e r a t i o n r a t e i n r e s p o n s e t o the s t i m u l i shown. They c l a i m t h a t o b s e r v i n g t h e o r i e n t a t i o n o f i n f a n t s ' eyes i s an i m p e r f e c t method o f a s s e s s i n g a t t e n -t i o n i n t h e young n o n v e r b a l o r g a n i s m . "The c h i l d ' s eyes may f o c u s on t h e s t i m u l u s but he may not n e c e s s a r i l y a t t e n d t o i t o r a c t i v e l y s can i t " ( L e wis et a l . , 1 9 6 3 , P« 2 ) . At t h e F e l s R e s e a r c h I n s t i t u t e t h e s e same i n v e s t i g a t o r s f o u n d t h a t a c h a r a c t e r i s t i c c o r r e l a t e o f a t t e n t i o n t o v i s u a l and a u d i t o r y s t i m u l i i n f i v e y e a r o l d s and a d u l t s was d e c e l e r a t i o n o f h e a r t 33. r a t e . They t h e n t r i e d t h i s method on i n f a n t s : They f o u n d t h a t t h e r e was a tendency f o r c a r d i a c d e c e l e r a t i o n t o o c c u r when t h e i n f a n t f i x a t e d on a p a t t e r n but t h a t t h i s r e l a t i o n -s h i p was not o r d e r l y . I t seemed t h a t f o r h i g h l y a t t e n t i v e I n f a n t s , t h a t i s I n f a n t s who had r e l a t i v e l y l o n g t o t a l f i x -a t i o n t i m e s t o a l l the p a t t e r n s shown, t h e r e was a p o s i t i v e r e l a t i o n s h i p between f i x a t i o n t i m e and c a r d i a c d e c e l e r a t i o n . However, f o r m i n i m a l l y a t t e n t i v e s u b j e c t s no s u c h r e l a t i o n -s h i p was f o u n d . N e v e r t h e l e s s , t h e r e s e a r c h e r s f e l t t h a t a s s e s s i n g f i x a t i o n t i m e and c a r d i a c change t o g e t h e r gave a more f a i t h f u l i n d e x o f a t t e n t i o n t h a n f i x a t i o n a l o n e , (e) Movement and V o c a l i z a t i o n Lewis et a l . (1963) a l s o o b s e r v e d t h e amount o f arm movement and v o c a l i z a t i o n e m i t t e d i n response t o t h e p a t t e r n s , but t h e s e two measures d i d not show o r d e r l y r e l a t i o n s h i p s e i t h e r t o f i x a t i o n t i m e or t o c a r d i a c d e c e l e r a t i o n r a t e . 2. E x p e r i m e n t a l P r o c edures Used i n A s s e s s i n g I n f a n t A t t e n t i o n . ; . Two e x p e r i m e n t a l p r o c e d u r e s have been used i n s t u d i e s o f i n f a n t a t t e n t i o n t o s t i m u l i v a r y i n g i n c o m p l e x i t y — t h e s t i m u l i have e i t h e r been p r e s e n t e d s i n g l y or i n p a i r s . F o r i n s t a n c e , F a n t z (1963), Lewis et a l . ( 1 9 6 5 ) , Kagan and L e w i s ( i n p r e s s ) , and S t e c h l e r (196k) a l l p r e s e n t e d t h e i r s t i m u l i one a t a t i m e and r e c o r d e d the r e a c t i o n s o f t h e i n f a n t s t o t h e s t i m u l u s so p r e s e n t e d . On t h e o t h e r hand, B e r l y n e (1958 b ) , F a n t z (1958, 1959, and 1962), Hershenson (196k), 34. Hershenson et a l , (196i|.), Spears (1961L), and Thomas ( i n p r e s s ) p r e s e n t e d t h e i r s t i m u l i two a t a t i m e i n a p a i r comparison p r o c e d u r e and n o t e d t h e p r e f e r e n c e s o f t h e i n f a n t s f o r t h e v a r i o u s s t i m u l i , M o f f e t t (1963) p a i r e d each o f h e r s t i m u l i w i t h a b l a n k c a r d and compac ed t h e p r o p o r t i o n s o f t o t a l l o o k i n g t i m e spent l o o k i n g a t each s t i m u l u s . Some r e s u l t s o f two r e c e n t s t u d i e s u n d e r t a k e n at McMaster u n i v e r s i t y and at the U n i v e r s i t y o f B r i t i s h Colum-b i a (Ames and S i l f e n , 1965) throw some doubt on t h e v a l i d i t y o f t he p a i r c o mparison method w i t h young i n f a n t s . B o t h ex-p e r i m e n t s employed t h e p a i r c o mparison p r o c e d u r e , one d e a l -i n g w i t h moving s t i m u l i , t h e o t h e r w i t h s t a t i o n a r y p a t t e r n s . I n comparing t h e percentage o f t r i a l s i n w h i c h i n f a n t s o f d i f f e r e n t ages l o o k e d a t b o t h s t i m u l i o f a p a i r i t i s c l e a r t h a t e i g h t week o l d s a r e much l e s s l i k e l y t h a n o l d e r b a b i e s t o l o o k at b o t h s t i m u l i . I n t h e movement s t u d y e i g h t week o l d s l o o k e d a t b o t h s t i m u l i o n l y Ii9 p e r c e n t o f t h e t i m e , and f o r non-moving p a t t e r n s o f c r o s s - h a t c h e d b l a c k l i n e s on a w h i t e background t h e y l o o k e d a t b o t h o n l y 17 p e r c e n t o f the t i m e . I n t h e movement experiment 16 and 21L week o l d s f i x a t e d b o t h members o f a p a i r on 78 and 76 p e r c e n t of t h e t r i a l s r e s p e c t i v e l y . F o r t h e s t a t i o n a r y p a t t e r n s t h e c o r r e s p o n d i n g p e r c e n t a g e s were 60 and 63 p e r c e n t r e s p e c t i v e l y . K essen and Hershenson (1963) have a r g u e d t h a t j u s t b e -cause t h e s u b j e c t f i x a t e s l o n g e r on s t i m u l u s A t h a n on s t i m u -35. l u s B i t cannot be c o n c l u d e d t h a t he has d i s c r i m i n a t e d t h e two s t i m u l i o r t h a t he has responded t o t h e d i m e n s i o n on w h i c h t h e two s t i m u l i a r e p o i n t s . 411 t h a t has been demon-s t r a t e d i s t h a t t h e s u b j e c t a t t e n d s t o one o f the s t i m u l i more t h a n t h e o t h e r . Even i f s t i m u l u s A i s p r e f e r r e d t o a l a r g e number o f o t h e r s t i m u l i , t h i s does n o t e s t a b l i s h a d i m e n s i o n . Kessen and Hershenson c l a i m t h a t o n l y when t r a n s i t i v i t y has been e s t a b l i s h e d among at l e a s t t h r e e s t i -m u l i i s i t j u s t i f i a b l e t o c o n c l u d e t h a t t h e i n f a n t i s r e -s p o n d i n g t o a d i m e n s i o n o f s t i m u l u s v a r i a t i o n . " I f we want t o go beyond t h e d e m o n s t r a t i o n o f something l i k e a t t e n t i o n t r o p i s m s I n i n f a n t s , we w i l l have t o use m u l t i p l e - s t i m u l u s p a i r e d c o m p a r i s o n d e s i g n s " (Kessen and Hershenson, 1963, p. 13). However, on v e r y p r a c t i c a l grounds i t would seem t h a t t h e r e s u l t s o f a " p a i r c o m p a r i s o n " s t u d y I n w h i c h b o t h members of a p a i r a r e not f i x a t e d a r e open t o q u e s t i o n . And s i n c e i t has been demonstrated t h a t d i f f e r e n t age groups a r e r e s p o n d i n g t o t h i s method t o d i f f e r e n t degrees I t would be q u e s t i o n a b l e t o compare t h e i r r e s u l t s . F or t h e s e r e a s o n s i t seems more f r u i t f u l t o use a s i n g l e s t i m u l u s p r o c e d u r e w i t h a l l age g r o u p s . C o n c e p t u a l l y t h i s method may not be as s a -t i s f a c t o r y as p a i r c o m p a r i s o n s . But o p e r a t i o n a l l y i t i s b e t t e r t o r u n a l l s u b j e c t s on a common method f o r w h i c h t h e y a r e a l l s u i t e d r a t h e r t h a n t o r u n o l d e r b a b i e s under a p a i r c omparison p r o c e d u r e and younger b a b i e s under what amounts t o a r a t h e r i n a d e q u a t e s i n g l e s t i m u l u s p r o c e d u r e . 36. V SETTING- FOR THE PRESENT RESEARCH I t has been shown t h a t I n the m a j o r i t y o f s t u d i e s con-c e r n e d w i t h s t i m u l u s c o m p l e x i t y , no e x p l i c i t d e f i n i t i o n s o f c o m p l e x i t y were employed as bases f o r s t i m u l u s s e l e c t i o n and o r d e r i n g . One i s l e d t o agree w i t h Walker t h a t "making do w i t h i n t u i t i v e l y o r d e r e d s t i m u l u s elements i s a m i s t a k e " (Walker, 196ii, p. ?2). I t i s o b v i o u s t h a t t h i s method s h o u l d be d i s c o n t i n u e d . F u r t h e r , t h e m u l t i d i m e n s i o n a l i t y o f t h e c o m p l e x i t y has been p o i n t e d o u t . Many i n d i c e s of c o m p l e x i t y have been d e s -c r i b e d and e v i d e n c e has been g i v e n t h a t r a n k o r d e r i n g s o f s t i m u l i In:terms o f s e v e r a l I n d i c e s o f c o m p l e x i t y can c o n -f l i c t . One must agree w i t h C antor t h a t " t h e r e a p p e a r s t o be a s e r i o u s need f o r i n t e n s i v e s t u d y o f a few r e l a t i v e l y s i m p l e and r i g o r o u s l y d e l i m i t e d s t i m u l u s p r o p e r t i e s w h i c h h o p e f u l l y w i l l s u p p l a n t t h e vague n o t i o n s o f " c o m p l e x i t y " w h i c h a r e c u r r e n t l y p r e v a l e n t " ( C a n t o r , 1963, P» 21). T h e r e -f o r e , i n t h e e x p e r i m e n t s d e s c r i b e d I n t h i s t h e s i s , o n l y one s t i m u l u s p a t t e r n was u s e d - t h e c h e c k e r b o a r d . The advantages o f t h i s p a t t e r n i n s t u d y i n g i n f a n t p e r -c e p t i o n , and e s p e c i a l l y I n t h e s t u d y o f age changes i n p r e -f e r e n c e s f o r s t i m u l i v a r y i n g I n c o m p l e x i t y , a r e s e v e r a l . "Not o n l y have c h e c k e r b o a r d s been u s e d w i d e l y i n i n f a n t f i x -a t i o n s t u d i e s , but t h e y a l l o w t h e easy c o n t r o l o f k e e p i n g b l a c k and w h i t e a r e a s e q u a l w h i l e b r e a k i n g t h e t o t a l a r e a i n t o more and more p a r t s . . A d u l t judgements o f complex-37. i t y are v e r y c l e a r , and agree w i t h t h e s e p h y s i c a l d e f i n i t i o n s i n c a l l i n g most complex t h a t c h e c k e r b o a r d w i t h the l a r g e s t number o f s q u a r e s i n i t " (Ames and S i l f e n , 1 9 6 5 , P« 3>). I n a d d i t i o n , d e f i n i t i o n s o f c o m p l e x i t y i n terms o f number o f t u r n s , p a r t s , r i g h t a n g l e d c r o s s i n g s , o r l i g h t - d a r k t r a n -s i t i o n s c o n t a i n e d i n s t i m u l i , o r t h e amount o f c o n t o u r t h e y p o s s e s s do not c o n t r a d i c t each o t h e r . F i n a l l y , I t i s r e a -s o n a b l e t o assume t h a t c h e c k e r b o a r d s have no meaning f o r a n i n f a n t and a r e t h e r e f o r e b e i n g responded t o s o l e l y because o f t h e i r p h y s i c a l a t t r i b u t e s and not i n terms o f any l e a r n e d a s s o c i a t i o n s o r p r e v i o u s e x p e r i e n c e s on t h e p a r t o f t h e sub-j e c t . The v a r i o u s r e s p o n s e measures o f i n f a n t a t t e n t i o n have been d e s c r i b e d and i t seems p r o f i t a b l e t o a n a l y z e s e v e r a l o f t h e s e f u r t h e r t o a s s e s s t h e i r r e l i a b i l i t y and v a l i d i t y . The c o n t r o v e r s y o ver w h i c h p r o c e d u r a l method, p a i r comparison o r s i n g l e s t i m u l u s , i s b e t t e r i n I n f a n t s t u d i e s has never been s a t i s f a c t o r i l y s e t t l e d . I n many r e s p e c t s , t h e p a i r c o m p a r i -son p r o c e d u r e seems t h e o r e t i c a l l y s u p e r i o r , but as n o t e d , t h e r e a r e many problems e n c o u n t e r e d i n u s i n g t h i s p r o c e d u r e w i t h young i n f a n t s . T h e r e f o r e , i n t h e r e s e a r c h r e p o r t e d i n t h i s t h e s i s , t h e s i n g l e s t i m u l u s p r o c e d u r e was p r e d o m i n a n t l y employed. However, r e s u l t s o b t a i n e d by t h i s method were a l -so compared w i t h t h o s e f o u n d i n an experiment u s i n g a modi-f i e d p a i r c o m parison procedure, i n w h i c h t h o s e t r i a l s on w h i c h o n l y one member o f a p a i r was f i x a t e d were r e p e a t e d u n t i l 38. both s t i m u l i had been f i x a t e d , up to a maximum of four t r i a l s for each p a i r . There has been a general lack of experimentation on age differences i n infant attention to s t i m u l i varying i n complexity. It has been noted that i n most of the experi-ments c i t e d infant subjects preferred the most complex of the s t i m u l i with which they were presented. However, Her-shenson, et a l . ( 1 9 6 I L ) , and Hershenson (I96I1) found that t h i s was not the case with newborn i n f a n t s . Only the ex-periment by Thomas ( i n press) s p e c i f i c a l l y showed an/ i n -creased preference with age f o r stimuli of greater complex-i t y , and t h i s study can be c r i t i c i z e d f o r the lack of u n i -dimensionality of the s t i m u l i employed. The experiments described i n t h i s thesis were s p e c i f i -c a l l y designed to test the hypothesis that older Infants pay more attention to s t i m u l i of greater complexity. In the de-sign of these experiments an attempt has been made to avoid the various p i t f a l l s discussed above. VI PURPOSES OF THE PRESENT RESEARCH The purposes of the present research are t h r e e f o l d : 1 . To test the hypothesis that older infants prefer s t i m u l i of greater complexity than do younger infants* 2. To compare various response measures, namely t o t a l f i x a t i o n time, length of f i r s t f i x a t i o n , and rate of habitu-a t i o n . 39. 3. To compare two e x p e r i m e n t a l p r o c e d u r e s i n t h e s t u d y o f i n f a n t a t t e n t i o n -- s i n g l e s t i m u l u s and p a i r c o mparison. To f u l f i l l t h e s e purposes t h r e e e x p e r i m e n t s were p e r -formed. Experiment I used c h e c k e r b o a r d s t i m u l i o f t h e same c o m p l e x i t y as Hershenson's (196k) w i t h i n f a n t s o f o l d e r ages, namely 10 and 20 weeks. I n Experiment I I t h e c o m p l e x i t y o f t h e s e s t i m u l i was extended upward and i n f a n t s o f 3, 8, and l k weeks were t e s t e d w i t h them. B o t h Experiments I and I I were r u n w i t h a s i n g l e s t i m u l u s p r o c e d u r e . I n Experiment I I I , 8 and l k week o l d i n f a n t s were p r e s e n t e d w i t h the s t i m u l i o f Experiment I I i n a p a i r com-p a r i s o n p r o c e d u r e , and t h e s e r e s u l t s were compared w i t h t h o s e f o r t h e 8 and l k week o l d groups i n Experiment I I . The next t h r e e c h a p t e r s d e a l w i t h each o f t h e s e ex-p e r i m e n t s s e p a r a t e l y . ho CHAPTER TWO EXPERIMENT I Purpose Hershenson (1961L) presented three black and white checkerboards containing 2 x 2 , l i x l i , and 12 x 12 squares to newborn i n f a n t s . He found that the infants looked most at the least complex pattern. Experiment I was designed to compare the v i s u a l responses of older Infants, s p e c i f i -c a l l y 10 and 20 week olds, with those of Hershenson's newborns . Hypotheses 1. Ten and 20 week old infants prefer stimuli of greater complexity than the 2 x 2 checkerboard preferred by newborns. 2. Twenty week olds prefer more complex s t i m u l i than 10 week olds. METHOD Subjects Infant subjects were obtained for the experiment from three sources. Notices were sent out to a l l parents i n the Vancouver area who announced the b i r t h of t h e i r baby i n the l o c a l evening newspaper. Notices were also sent out to parents of a l l f u l l term, healthy babies who were born i n Grace Maternity Hospital. Further notices were plaeed i n the U.B.C. Child Health Program C l i n i c , and i n several Van-couver City Health Program C l i n i c s . In response to the k l . n o t i c e s p a r e n t s phoned t o v o l u n t e e r t h e i r b a b i e s f o r t h e e x p e r i m e n t . Each s u b j e c t who came t o t h e l a b o r a t o r y was g i v e n $2 whether o r not he completed t h e e x p e r i m e n t a l p r o -c e d u r e . Data were d i s c a r d e d f rom i n f a n t s who f a i l e d t o complete t h e e x p e r i m e n t a l s e r i e s due- t o c r y i n g or f a l l i n g a s l e e p . The bases o f s u b j e c t s e l e c t i o n were age, f u l l t e r m b i r t h , and p r e f e r e n c e f o r l y i n g i n t h e supine, p o s i t i o n . T h i s p r e f e r e n c e was a s c e r t a i n e d f r o m t h e mother o v e r t h e t e l e p h o n e and any baby who had a s t r o n g p r e f e r e n c e f o r l y -i n g i n t h e prone p o s i t i o n d i d not come t o the l a b o r a t o r y as i t h a d been found t h a t such b a b i e s were not s u i t e d t o t h e a p p a r a t u s employed. No premature b a b i e s were i n c l u d e d i n t h e sample. The i n f a n t s used i n t h i s experiment were e i g h t 10-week o l d s and e i g h t 20-week o l d s . The t e n week o l d s ranged i n age f r o m n i n e weeks, two d a y s , t o 10 weeks, f i v e days. The 20 week o l d s ranged from 19 weeks, two d a y s , t o 20 weeks, f i v e d a y s . A p p a r a t u s The a p p a r a t u s c o n s i s t e d o f a wooden chamber 3 l " h i g h , 30" w i d e , and 2k" deep, w h i c h housed a m o b i l e c r a d l e 30" l o n g by 16" w i d e . The base o f t h e c r a d l e was u n i f o r m l y con-cave a l o n g i t s l e n g t h and p r e v e n t e d g r o s s body movements. A p i l l o w s e r v e d as a m a t t r e s s and f o r t h e younger i n f a n t s sponges a t t h e s i d e s o f the head p r e v e n t e d t h e head f r o m 42. t u r n i n g t o extreme a i d e p o s i t i o n s from w h i c h t h e i n f a n t c o u l d not r e c o v e r . The sponges b o t h e r e d i n f a n t s o l d e r t h a n 10 weeks and s i n c e t h e y were found t o be u n n e c e s s a r y i n c o n t r o l l i n g t h e head movements o f o l d e r b a b i e s t h e y were not u s e d w i t h t h e 20 week group. One s i d e o f t h e chamber was open so t h a t t h e c r a d l e , c o n t a i n i n g t h e s u p i n e i n f a n t , c o u l d be s l i d i n t o i t . The c h i l d ' s f i e l d o f v i s i o n was r e s t r i c t e d t o t h e i n s i d e o f t h e chamber, w h i e h was c o v e r e d w i t h navy b l u e f e l t , and t o the f a r y e l l o w w a l l exposed by the open end o f t h e box. On t h e c e i l i n g o f t h e chamber was h i n g e d a door 28" l o n g by 12" wide w h i c h opened toward the back o f t h e box. T h i s door c o n t a i n e d one s t i m u l u s s l o t 12" l o n g by 9" w i d e i n i t s c e n t r e . There were two o b s e r v a t i o n h o l e s 9s" a p a r t on e i t h e r s i d e o f and a d j a c e n t t o the s t i -mulus h o l d e r . Each o b s e r v a t i o n h o l e was 5 " i n d i a m e t e r and was a n g l e d t o w a r d t h e l o c u s o f t h e s u b j e c t ' s eyes as he l a y i n t h e c r a d l e u n d e r n e a t h . Cardboard s t i m u l u s c a r d s 11^" b y 8 3/V' s l i d i n t o t h e h o l d e r . When t h e i n f a n t was r o l l e d i n t o t h e chamber h i s eyes were 18" below t h e c e n t r e o f t h e c e i l i n g . I l l u m i n a t i o n was p r o v i d e d f r o m below t h e i n f a n t ' s f i e l d o f v i s i o n by two I4.O watt b u l b s , j u s t b e h i n d and t o t h e r i g h t and l e f t o f h i s h e a d . A navy b l u e f e l t b l i n d a t t a c h e d 2 £ n below th e c e i l i n g o f t h e chamber c o u l d be drawn h o r i z o n t a l l y a c r o s s t h e chamber f r o m bottom t o t o p o f t h e i n f a n t ' s f i e l d ^ 3 . o f v i s i o n . Responses were r e c o r d e d on a R u s t r a k model 92 k - c h a n n e l event r e c o r d e r moving at a speed o f 12 mm. p e r second. The f o u r c h a n n e l s o f t h e r e c o r d e r were a c t i v a t e d i n d e p e n d e n t l y by f o u r b u t t o n s a t t a c h e d t o t h e o u t s i d e o f t h e a p p a r a t u s . Two b u t t o n s were t o t h e r i g h t o f t h e box t o p and two were t o t h e l e f t . S t i m u l i The s t i m u l i were t h r e e b l a c k and w h i t e 6" square c h e c k e r b o a r d s . I n s t i m u l u s A t h e square was d i v i d e d i n t o q u a d r a n t s , t h e f i r s t and t h i r d q uadrents b e i n g b l a c k , t h e second and f o u r t h w h i t e . T h i s i s d e s i g n a t e d as a 2 x 2 c h e c k e r b o a r d . S t i m u l u s B was a k x k c h e c k e r b o a r d c o n s i s -t i n g o f s i x t e e n l ^ " s q u a r e s , h a l f o f them w h i t e and h a l f o f them b l a c k . S t i m u l u s C was a 12 x 12 c h e c k e r b o a r d c o n s i s -t i n g o f l k k b l a c k and w h i t e s q u a r e s . The s t i m u l i were p r e s e n t e d one a t a time f o r f o u r 30 second t r i a l s e ach. F o r t h e f i r s t s i x t r i a l s o f t h e 1 2 - t r i a l s e r i e s f o r each sub-j e c t t h e s t i m u l i were p r e s e n t e d i n random o r d e r . F or t h e second s i x t r i a l s t h i s o r d e r was r e v e r s e d . Thus each s t i -mulus was p r e s e n t e d t w i c e i n t h e f i r s t h a l f o f t h e t r i a l s and t w i c e i n t h e second h a l f . P r o c e d u r e A l l i n f a n t s were brought t o t h e l a b o r a t o r y by one o r b o t h o f t h e i r p a r e n t s . When t h e c h i l d was awake and i n a good humour he was p l a c e d i n t h e c r a d l e by h i s mother ( o r i n s e v e r a l cases by h i s f a t h e r ) , who remained i n t h e room iA. but out o f t h e i n f a n t ' s f i e l d o f v i s i o n . The c r a d l e was t h e n pushed i n t o t h e chamber t o a p o s i t i o n i n w h i c h t h e i n f a n t ' s head was d i r e c t l y below t h e p o i n t a t w h i c h t h e s t i m u l i were t o a p p e a r . The b l i n d was a l r e a d y drawn and th e s t i m u l u s p a t t e r n s were not v i s i b l e t o t h e i n f a n t . The e x p e r i m e n t e r s t o o d b e h i n d t h e a p p a r a t u s a t t h e head o f t h e i n f a n t . He r e l e a s e d t h e b l i n d h a l f way so t h a t t h e i n f a n t c o u l d be seen t h r o u g h the o b s e r v a t i o n h o l e . When t h e i n f a n t was l o o k i n g up at t h e c e n t r e o f t h e c e i l i n g t h e b l i n d was r e l e a s e d t h e r e s t o f t h e way, a c t i v a t i n g t h e t i m e r and t h e r e c o r d e r . The s t i m u l u s p a t t e r n s were r e f l e c -t e d on t h e corneas of t h e i n f a n t ' s e y e s . When the eyes were d i r e c t e d towards a s t i m u l u s p a t t e r n t h e image o f t h e p a t -t e r n o v e r l a p p e d t h e p u p i l as viewed t h r o u g h t h e o b s e r v a t i o n h o l e . T h i s o v e r l a p o f r e f l e c t e d image and p u p i l was the c r i t e r i o n o f f i x a t i o n . W h i l e o b s e r v i n g t h e s u b j e c t t h r o u g h t h e o b s e r v a t i o n h o l e t h e e x p e r i m e n t e r r e c o r d e d t h e l e n g t h o f tim e o f each f i x a t i o n on each s t i m u l u s by p r e s s i n g one o f th e b u t t o n s t o t h e r i g h t o f the door i n t h e chamber c e i l i n g . At t h e end o f 30 seconds a b u z z e r on t h e t i m e r sounded and t h e e x p e r i m e n t e r drew t h e b l i n d , w h i c h s t o p p e d t h e t i m e r and r e c o r d e r . The s t i m u l i were t h e n changed and t h e i n f a n t q u i e t e d or r o u s e d i f t h i s was n e c e s s a r y . The i n t e r v a l b e -tween t r i a l s was a p p r o x i m a t e l y 10 seconds a l t h o u g h t h i s v a r i e d depending on t h e d i s p o s i t i o n o f t h e i n f a n t . 45. RESULTS T a b l e 1 shows the t o t a l l o o k i n g t i m e spent" l o o k i n g at each o f t h e t h r e e s t i m u l u s p a t t e r n s , averaged o v e r sub j e c t s • T a b l e s 2 and 3 p r e s e n t the r e s u l t s o f two one-way a n a l y s e s o f v a r i a n c e p e r f o r m e d s e p a r a t e l y on the t o t a l l o o k i n g t i m e s o f t h e 10 and 20 week g r o u p s . Newman-Keuls t e s t s p e r f ormed on t h e d i f f e r e n c e s between p a i r s o f t o t a l l o o k i n g t i m e s f o r each s t i m u l u s r e v e a l t h a t f o r b o t h groups a l l d i f f e r e n c e s between p a i r s were s i g n i f i c a n t (p l e s s t h a n .01). F o r b o t h g r o u p s , I n terms o f t o t a l f i x a t i o n t i m e , t h e o r d e r o f p r e f e r e n c e f o r t h e s t i m u l i was i n i n c r e a s i n g o r d e r o f t h e i r c o m p l e x i t y . B o t h age groups p r e f e r r e d t h e most complex s t i m u l u s t h e most, t h e s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y n e x t , and t h e l e a s t complex s t i m u l u s l e a s t . F i g u r e 2 p r e s e n t s a gr a p h on w h i c h a r e p l o t t e d t h e t o t a l l o o k i n g t i m e s averaged over s u b j e c t s , f o r each s t i m u l u s f o r b o t h t h e 10 and 20 week o l d g r o u p s . T a b l e Ii p r e s e n t s t h e r e s u l t s o f a two-way a n a l y s i s o f v a r i a n c e o f t h e t o t a l l o o k i n g t i m e f o r e a c h s t i m u l u s f o r b o t h age g r o u p s . The s i g n i f i c a n c e o f t h e Age f a c t o r i n d i c a t e s t h a t 10 week o l d s l o o k e d s i g n i f i c a n t l y l o n g e r at a l l t h r e e s t i m u l i t a k e n t o g e t h e r t h a n d i d t h e 20 week o l d s . The s i g n i f i c a n c e o f t h e s t i m u l i f a c t o r was e x p e c t e d f r o m t h e r e s u l t s o f t h e 46. TABLE 1 T o t a l L o o k i n g Time Spent L o o k i n g at Each o f t h e Three S t i m u l u s P a t t e r n s , by 10 and 20 week O l d I n f a n t s Averaged Over S u b j e c t s (Experiment I) A B C Mean t o t a l l o o k i n g 2 x 2 li x 4 12 x 12 t i m e f o r each age 10 weeks 34.875 64.375 90.125 63.125 20 weeks 20.750 33.750 68.125 40.875 Mean t o t a l l o o k i n g t i m e f o r each 27.812 k.9.062 79.125 s t i m u l u s _____ . TABLE 2 Summary Ta b l e o f A n a l y s i s o f V a r i a n c e o f T o t a l ^ L o o k i n g .Time Spent L o o k i n g at Each o f t h e Three S t i m u l i by Source SS d f MS F P Between i n f a n t s 5553.96 7 W i t h i n i n f a n t a 13661*.. 67 16 S t i m u l i 12229.00 2 6114.50 59.62 Less t h a n . .005 R e s I d u a l 1435.67 4 102.55 T o t a l 19218.63 23 TABLE 3 Summary"table o f A n a l y s i s o f V a r i a n c e o f T o t a l L o o k i n g Time Spent L o o k i n g at Each o f t h e Three S t i m u l u s P a t t e r n s by 20 Week O l d Group (Experiment I ) Source SS df MS P P Between i n f a n t s 4629.96 7 W i t h i n i n f a n t s 10422.67 16 S t i m u l i 9586.75 2 4793.38 81.11L Less t h a n . .005 R e s i d u a l T o t a l 15052.63 835.92 14 23 59.71 1*8. V » io weeks ; i ! 1 •• ~ i — A B C 2 X 2 4 X 4 12 X 1 2 i -STIMULI , Figure 2. T o t a l looking time i n seconds spent looking at each of the three s t i m u l i by 10 and 20 week "old i n f a n t s , averaged over sub-j e c t s . (Experiment I) 49. TABLE l i Summary T a b l e o f Two-way A n a l y s i s o f V a r i a n c e o f T o t a l L o o k i n g Time Spent L o o k i n g a t Each, o f t h e Three S t i m u l i by 10 and 20 week O l d Groups (Experiment I )  Source SS d f MS Between I n f a n t s Age S u b j e c t s w i t h i n groups 16124.67 5940.75 10183.92 15 1 14 5940.75 727.42 8.17 L e s s t h a n .025 W i t h i n i n f a n t s S t i m u l i Age X S t i m u l i S t i m u l i X sub-j e c t s w i t h i n gr oup 21i087.33 32 21270.88 2 544.87 2 2271.58 28 10635.44 272.44 81.13 131.09 L e s s t h a n - .005 3.36 Less t h a n .05 50. two one-way analyses of variance. The significance of the i n t e r a c t i o n f a c t o r indicates that the differences between the t o t a l f i x a t i o n times for the s t i m u l i were not i d e n t i c a l for the two age groups. DISCUSSION The f i r s t hypothesis, that 10 and 20 week o l d infants prefer s t i m u l i of greater complexity than the 2 x 2 checker-board preferred by newborns, was confirmed i n t h i s experi-ment. Hershenson found that newborns looked at the 2 x 2 pattern the most, the k x k next, and the 12 x 12 the l e a s t . In the present experiment both 10 and 20 week olds looked most at the 12 x 12 checkerboard, next at the k x k, and least at the 2 x 2 . However, the second hypothesis, that 20 week olds prefer more complex s t i m u l i than 10 week olds, was not confirmed i n the experiment. The lack of support f o r the second hypothesis could have occurred because the range of complexity represented i n the s t i m u l i was too small. I f the set of s t i m u l i presented had contained more complex patterns than those used here t h i s hypothesis might have been confirmed. Therefore, i t seems premature to, conclude from these r e s u l t s that beyond 10 weeks of age there is no change i n preference for s t i m u l i of vary-ing complexity l e v e l s . The results of t h i s experiment may d i f f e r from Hershen-son's (196k) for several reasons. F i r s t , the methods of i n -v e s t i g a t i o n used i n the two s t u d i e s were v e r y d i f f e r e n t . Hershenson photographed h i s s u b j e c t s ' eyes at a r a t e o f one frame per second and scored the number of frames i n which a stimulus was f i x a t e d . Here, the i n f a n t ' s eyes were observed and h i s f i x a t i o n s r e c o r d e d as he was r e s p o n d i n g . Hershenson used a p a i r comparison procedure; a s i n g l e s t i -mulus procedure was employed i n the present experiment. Hershenson used a chi-square technique o f a n a l y s i s ; a n a l y -ses of v a r i a n c e were used h e r e . Secondly, t h e r e may be genuine d i f f e r e n c e s i n the p o p u l a t i o n s from which the two samples were s e l e c t e d . T h i r d l y , t h e r e may be a c t u a l d i f f e r -ences i n the l e v e l o f v i s u a l complexity p r e f e r r e d by i n f a n t s o f d i f f e r e n t ages. To I n v e s t i g a t e f u r t h e r the p o s s i b l e e x i s t e n c e of age d i f f e r e n c e s i n the l e v e l o f v i s u a l complexity p r e f e r r e d , Experiment I I was performed. 52. CHAPTER THREE EXPERIMENT I I Purpose Experiment I I was d e s i g n e d t o i n v e s t i g a t e f u r t h e r the v i s u a l r e s p o n s e s o f i n f a n t s o f d i f f e r e n t ages t o s t i m u l i v a r y i n g i n c o m p l e x i t y . The d e m o n s t r a t i o n o f or g a n i s m -s t i m u l u s concordance i n l e v e l s o f c o m p l e x i t y was s p e c i f i -c a l l y d e s i r e d . That i s , t h e aim was t o f i n d t h r e e age groups s u c h t h a t t h e youngest group s i g n i f i c a n t l y p r e f e r r e d t h e l e a s t complex s t i m u l u s over t h e o t h e r s , the o l d e s t p r e -f e r r e d t h e most complex s t i m u l u s , and. the m i d d l e group p r e -f e r r e d t h e s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y . I n o r d e r t o do t h i s t h e s t i m u l i used encompassed a w i d e r range o f c o m p l e x i t y t h a n t h o s e used i n Experiment I , and I n f a n t s o f s e v e r a l d i f f e r e n t ages were t e s t e d . H y p o t h e s i s The o l d e r t h e i n f a n t , t h e more complex t h e p a t t e r n he p r e f e r s . METHOD The method o f Experiment I I was t h e same as t h a t o f Experiment I except f o r t h e f o l l o w i n g m o d i f i c a t i o n s : S u b j e c t s The s t i m u l i were p r e s e n t e d t o i n f a n t s o f t h r e e age gr o u p s . They were t e n t h r e e week o l d s r a n g i n g i n age from e x a c t l y t h r e e weeks t o t h r e e weeks, f o u r days, t e n e i g h t week 5 3 . o l d s r a n g i n g i n age from, seven weeks, two days t o e i g h t weeks, f i v e d a y s , and t e n 11L week o l d s r a n g i n g i n age frau 13 weeks, two days, t o H L weeks, f i v e d a y s . S t i m u l i The s t i m u l i u sed were t h r e e 6" s q u a r e , b l a c k and w h i t e c h e c k e r b o a r d d e s i g n s . The l e a s t complex s t i m u l u s (A) c o n -t a i n e d 2 x 2 b l a c k and w h i t e 3 M s q u a r e s . The s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y (B) c o n t a i n e d 8 x 8 b l a c k and w h i t e 3/V s q u a r e s . The most complex s t i m u l u s (G) c o n t a i n e d 2 i i x 21L b l a c k and w h i t e l A " s q u a r e s . P a n t z , Ordy, and TJdelf ( 1962) f o u n d t h a t t h e minimum s e p a r a b l e v i s u a l a n g l e f o r one and two month o l d I n f a n t s was I4.0 minutes o f a r c . T h i s was a p a t t e r n of l / l j - " b l a c k s t r i p e s on a w h i t e back-ground shown at a d i s t a n c e o f 20 i n c h e s . Three and f o u r month o l d s c o u l d see 1/8" s t r i p e s a t a d i s t a n c e of 20 i n -c h e s . A c c o r d i n g t o t h e s e d a t a , t h e o l d e r s u b j e c t s i n t h e p r e s e n t experiment were a b l e t o p e r c e i v e t h e t h r e e s t i m u l i u s e d . However, t h e p o s s i b i l i t y e x i s t e d t h a t t h r e e week o l d s , b e i n g near t h e youngest age t e s t e d f o r a c u i t y by P a n t z et a l . ( 1 9 6 2 ) , were not a b l e t o p e r c e i v e c l e a r l y t h e most complex s t i m u l u s . T h e r e f o r e , f o r the t h r e e week o l d group a f o u r t h s t i m u l u s was i n t r o d u c e d - a p l a i n g r a y square o f t h e same s i z e and a l b e d o as the c h e c k e r b o a r d s . I t was h y p o t h e s i z e d t h a t i f a c h e c k e r b o a r d were f i x a t e d s i g n i f i c a n t l y l o n g e r t h a n t h e gray s q u a r e , i t was p e r c e p t i b l e t o t h e t h r e e week o l d s • As i n Experiment I each, s t i m u l u s p a t t e r n was p r e s e n t e d f o r f o u r 30 second t r i a l s . Each appeared t w i c e i n t h e f i r s t h a l f o f the s e r i e s o f t r i a l s , and t w i c e i n t h e s e c o n d h a l f . Thus t h e 8 and l k week o l d s had t w e l v e t r i a l s , and t h e t h r e e week o l d s had s i x t e e n t r i a l s because o f the I n -c l u s i o n o f t h e p l a i n gray s t i m u l u s . I n t e r - O b s e r v e r Agreement I n t h e t e s t i n g o f t h r e e o f t h e three-week o l d s u b j e c t s and s i x o f the l k week o l d s u b j e c t s , two o b s e r v e r s were u s e d . One o b s e r v e d t h e i n f a n t ' s eyes t h r o u g h t h e o b s e r v a -t i o n h o l e t o t h e l e f t o f the s t i m u l u s h o l d e r i n t h e chamber c e i l i n g d o o r , and t h e o t h e r o b s e r v e d t h r o u g h t h e h o l e t o t h e r i g h t o f the h o l d e r . Each o b s e r v e r o p e r a t e d a r e c o r d i n g b u t t o n on h i s r e s p e c t i v e s i d e o f t h e a p p a r a t u s t o p . The o p e r a t i o n o f the b u t t o n s was r e n d e r e d p r a c t i c a l l y i n a u d i b l e by e n c l o s i n g t h e event r e c o r d e r i n a padded box. Thus each o b s e r v e r r e c o r d e d the f i x a t i o n s o f t h e i n f a n t i n d e p e n d e n t l y o f the o t h e r . Whenever a n o b s e r v e r pushed a b u t t o n , a pen on one o f t h e c h a n n e l s o f the event r e c o r d e r was d e f l e c t e d , making a r e c o r d o f t h e l e n g t h o f e a ch f i x a t i o n . The r e c o r d s made by t h e two o b s e r v e r s appeared on a d j a c e n t c h a n n e l s o f the r e -c o r d i n g t a p e . Had agreement been p e r f e c t t h e y would have been i d e n t i c a l . F o r each s u b j e c t an i n t e r - o b s e r v e r a g r e e -ment s c o r e was c a l c u l a t e d by c o u n t i n g the number o f seconds 55. per 30 second t r i a l d u r i n g w h i c h t h e o b s e r v e r s a g r e e d , i . e . , a l l t i m e except t h a t d u r i n g w h i c h one o b s e r v e r r e c o r d e d a f i x a t i o n w h i l e t h e o t h e r o b s e r v e r d i d n o t . The s c o r e s were t o t a l l e d o v e r t h e number o f t r i a l s f o r each s u b j e c t (16 f o r t h r e e week o l d s , 12 f o r l k week o l d s ) , and c o n v e r t e d t o a pe r c e n t a g e o f t o t a l s t i m u l u s p r e s e n t a t i o n t i m e . I n t e r - o b s e r v e r agreement ranged from 90% t o 96%, t h e average agreement over t h e n i n e s u b j e c t s b e i n g 93$. RESULTS T a b l e 5 p r e s e n t s the t o t a l l o o k i n g t i m e , a v e r a g e d o v e r s u b j e c t s , spent l o o k i n g at each o f t h e s t i m u l i by t h e 3, 8, and l k week o l d groups. These d a t a a r e p l o t t e d i n F i g u r e 3.. T a b l e 6 p r e s e n t s a summary o f a two-way a n a l y s i s o f v a r i a n c e of t h e t o t a l l o o k i n g t i m e o f each age group f o r each s t i m u l u s e x c l u d i n g g r a y . The two main e f f e c t s and t h e i n t e r a c t i o n e f f e c t were a l l s i g n i f i c a n t ( a l l p*s l e s s t h a n .005). The s i g n i f i c a n c e of t h e Age f a c t o r i n d i c a t e s t h a t t h e t o t a l l o o k i n g t i m e s f o r t h e t h r e e age groups were not the same. A Newman-Keuls t e s t p e r f o r m e d on t h e d i f f e r e n c e s b e -tween t h e t o t a l s r e v e a l s t h a t e i g h t week o l d s l o o k e d l o n g e r a t t h e t h r e e s t i m u l i t a k e n t o g e t h e r t h a n d i d t h r e e week o l d s (p l e s s t h a n .01), t h a t l k week o l d s a l s o l o o k e d l o n g e r t h a n t h r e e week o l d s (p l e s s t h a n .05, )» and t h a t e i g h t week o l d s l o o k e d l o n g e r t h a n l k week o l d s , but t o an i n s i g n i f i c a n t d e g r e e . 56 TABLE 5 T o t a l L o o k i n g Time i n Seconds Spent L o o k i n g a t Each o f t h e S t i m u l i by 3, 8 , and I k Week O l d I n f a n t s , A v e r a g e d over s u b j e c t s . (Experiment I I ) A B C Grey Mean t o t a l l o o k i n g 2 x 2 8 x 8 2k x 2k t i m e f o r each age 3 weeks 8 0 . 3 5 1 . 8 2 3 . 6 1 5 . 7 5 1 . 9 ( w i t h o u t g r a y ) 8 weeks 5 4 . 2 111.3 7 4 . 1 7 9 . 8 7 l k weeks 4 3 . 1 6 8 . 8 91.1 6 7 . 6 6 Mean t o t a l l o o k i n g t i m e f o r each s t i - 59.2 77.3 62.93 mulus TABLE 6 Summary T a b l e o f Two-way A n a l y s i s o f V a r i a n c e o f T o t a l L o o k i n g Time Spent L o o k i n g at Each o f Three S t i -m u l i ( e x c l u d i n g Gray) by 3 , 8 , and l k week o l d Groups. (Experiment I I ) Source SS d f MS P P Between i n f a n t s 2 8 1 3 2 . 4 6 29 Age 1 1 7 9 5 . 6 3 2 5 8 9 7 . 8 1 5 9 . 7 4 7 l e s s t h a n S u b j e c t s w i t h i n . 0 0 5 groups 1 6 3 3 6 . 8 3 27 6 0 5 . 0 6 8 W i t h i n i n f a n t s 5 8 8 7 0 . 0 0 60 St i m u l i 5 4 7 9 . 4 9 2 2 7 3 9 . 7 4 5 1 0 . 2 3 4 l e s s t h a n . 0 0 5 Age X S t i m u l i 3 8 9 3 5 . 2 4 4 9 7 3 3 . 8 1 3 6 . 3 6 2 l e s s t h a n . 0 0 5 S t i m u l i X sub-j e c t s w i t h i n 14455.27 54 2 6 7 . 6 9 groups 57. c o Q z o u LU CO LU 3 z o !< x Z < LU 120 I 10 100 90 80 70 60 50 40 30 20 10 As - A — A 3 weeks * — • 8 weeks 14 weeks / \ A 2 X 2 B 8 X 8 C G r e y 2 4 X 2 4 ST IMULI Figure 3. Tot a l looking time i n seconds spent looking at each of the st i m u l i by 3* 8, and l k week old i n f a n t s , averaged over subjects (Experiment II) £8. The significance of the Stimuli factor indicates that the total looking times for the three checkerboards were different. A Newman-Keuls test performed on the differences between these totals reveals that stimulus B was fixated significantly longer than either A or C (both p's less than .01). Stimulus 0 was fixated longer than A to an insigni-ficant degree. The significance of the interaction between Age and Stimuli indicates that the patterns of preference of the three groups were significantly different. In order to i n -vestigate the preferences of each group, one-way analysis of variance were performed separately on the total looking times of each group. analyses were performed on the three week group, one including the looking time for the plain gray stimulus and one excluding i t . The summaries of these four analyses of variance are presented in Tables 7 through 10. The stimuli effect was highly significant in a l l four analyses ( a l l p's less than .00f>). For each of these analy-ses a Newman-Keuls test was performed on the differences be-tween the total looking times for each pair of stimuli. For the three week old group a l l differences were sig-nificant ( a l l p's less than .01) except the difference be-tween stimulus C, the most complex pattern, and the gray square. Thus the three week old group preferred the least TABLE 7 Summary Table of Analysis of Variance of Total Looking Time Spent Looking at Each of the Stimulus Pat-terns (including Gray) by three week old Group (Experiment II) Source Between Infants Within infants Stimuli Residual T o t a l SS df k 8 9 0 . 1 3kO9k.0 2 5 9 0 2 . 9 9 30 8191.1 38.98k.l 39 3 27 MS 863k.3 303.37 28.k6 less than . 0 0 5 TABLE 8 Summary Table of Analysis of Variance of"Total Looking .Time Spent Looking at Each of the Stimulus Patf terns„(excluding Gray) by~three week old Group (Experiment II)  Source SS df MS P p Between infants 5916 .03 9 -Within infants 21978.67 20 Stimuli I607k.60 2 8037.30 2 k . 5 0 k less than 18 3 2 8 . 0 0 . 0 0 5 Residual 590k.07 T o t a l 2789k.70 29 TABLE 9 Summary Ta b l e o f A n a l y s i s o f V a r i a n c e o f T o t a l L o o k i n g Time Spent. L o o k i n g at Each o f Three S t i m u l u s P a t t e r n s Source SS d f MS P P Between i n f a n t s 1477.^7 9 -W i t h i n i n f a n t s 19850.00 20 8400.435 49.59 S t i r a u l i 16800.87 2 l e s s t h a n .005 R e s i d u a l 3049.13 18 169.396 T o t a l 21327.47 29 TABLE 10 Summary "Table o f A n a l y s i s of V a r i a n c e o f T o t a l L o o k i n g Time Spent. L o o k i n g at Each o f Three S t i m u l u s P a t t e r n s Source ... . _ . SS d f MS P P Between i n f a n t s 8943.34 9 W i t h i n i n f a n t s 17041.33 20 -S t i m u l i 11539.27 2 5769.635 18.87 l e s s t h a n - .005 R e s i d u a l 5502.06 18 305.67 T o t a l 25984.67 29 o 6 1 . c o m p l e x s t i m u l u s m o a t , t h e s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y n e x t , a n d t h e most c o m p l e x s t i m u l u s l e a s t . N i n e o u t o f t h e t e n i n f a n t s I n t h e t h r e e w e e k o l d s a m p l e a h o w e d t h e same p r e -f e r e n c e p a t t e r n a s t h e o v e r a l l g r o u p p r e f e r e n c e p a t t e r n . One i n f a n t s h o w e d a a l i g h t p r e f e r e n c e f o r s t i m u l u s B o v e r s t i m u l u s A . F o r t h e e i g h t w e e k o l d g r o u p t h e d i f f e r e n c e s i n t h e t o t a l l o o k i n g t i m e s f o r a l l p a i r s o f s t i m u l i w e r e a l s o s i g n i f i c a n t ( a l l p ' a l e a s t h a n .01). E i g h t w e e k o l d s p r e f e r r e d t h e s t i -m u l u s o f i n t e r m e d i a t e c o m p l e x i t y m o s t , t h e m o s t c o m p l e x s t i m u -l u s n e x t , a n d t h e l e a s t . c o m p l e x s t i m u l u s l e a s t . A l l t e n o f t h e e i g h t w e e k o l d s m o s t p r e f e r r e d s t i m u l u s B . E i g h t o f t h e m p r e f e r r e d s t i m u l u s C n e x t , w h i l e t w o s h o w e d s l i g h t p r e f e r e n c e s f o r s t i m u l u s A o v e r s t i m u l u s C . F o r t h e l k w e e k o l d g r o u p a l l d i f f e r e n c e s b e t w e e n t h e t o -t a l l o o k i n g t i m e s f o r a l l p a i r s o f s t i m u l i w e r e s i g n i f i c a n t ( p l e s s t h a n .02 f o r t h e CB p a i r ; b o t h p ' s l e a s t h a n .01 f o r t h e o t h e r t w o p a i r s ) . T h u s , l k w e e k o l d s p r e f e r r e d t h e s t i m u -l i i n i n c r e a s i n g o r d e r o f t h e i r c o m p l e x i t y , p r e f e r r i n g t h e m o s t c o m p l e x p a t t e r n m o s t , a n d t h e l e a s t c o m p l e x l e a s t . E i g h t o f t h e t e n l k w e e k o l d s h a d p r e f e r e n c e s i n t h e same d i r e c t i o n a s t h e o v e r a l l g r o u p p r e f e r e n c e . One i n f a n t h a d a s l i g h t p r e f e r -e n c e f o r a t i m u l u a B o v e r G , a n d a n o t h e r p r e f e r r e d a t i m u l u a A n e x t a f t e r s t i m u l u s C . 62, DISCUSSION The h y p o t h e s i s , t h a t the o l d e r t h e I n f a n t t h e more complex the p a t t e r n he p r e f e r s , was c o n f i r m e d i n t h i s e x p e r i -ment. Three week o l d s p r e f e r r e d t h e 1 e a s t complex c h e c k e r -b o a r d , e i g h t week o l d s p r e f e r r e d t h e c h e c k e r b o a r d o f I n t e r -mediate c o m p l e x i t y , and l k week o l d s p r e f e r r e d the most com-p l e x c h e c k e r b o a r d . F u r t h e r Support f o r t h e H y p o t h e s i s F u r t h e r support f o r the h y p o t h e s i s was g i v e n by o t h e r age groups w h i c h were p r e s e n t e d w i t h the same s t i m u l i . These o t h e r groups were 10 twenty week o l d s , 10 t e n week o l d s , and two f i v e week o l d s . The t o t a l l o o k i n g t i m e s o f t h e s e groups ar e p l o t t e d a l o n g w i t h t h o s e o f t h e 3 , 8 , and l k week o l d groups i n F i g u r e k. I n t h e 20 week o l d group ev e r y i n f a n t showed a p r e f e r -ence f o r t h e s t i m u l i i n I n c r e a s i n g o r d e r o f t h e i r c o m p l e x i t y . However, t e s t i n g o f younger I n f a n t s r e v e a l e d t h a t t h i s p r e -f e r e n c e emerged as e a r l y as 12 and 13 weeks and was w e l l e s -t a b l i s h e d by l k weeks as has been see n . T h e r e f o r e i t was f e l t t h a t t h e 20 week o l d s were r e a l l y t o o o l d f o r the s t i m u l i used here and t h a t i f an even more complex p a t t e r n had been I n c l u d e d i n t h e s e r i e s , 20 week o l d i n f a n t s would have shown a p r e f e r e n c e f o r i t over t h e o t h e r t h r e e . The p r e f e r e n c e s o f t h e 10 week o l d group are between t h o s e o f t h e 8 and l k week o l d s . B o t h s t i m u l i B and C were s i g n i f i -c a n t l y p r e f e r r e d t o A, but s t i m u l u s B was o n l y s l i g h t l y 6 3 . I20 i t o 110-Q Z O I O O -u LU CO 90-Z —* 80H LU - § 70H O < x 2 O i — z < LU 3 60 50 40 30 20 10 A — A — ^ 5 weeks o — o - o I O weeks •—••--a 2 0 weeks _ A „ - 3 weeks • 8 weeks 1 4 weeks 1 — A 2 X 2 B 8 X 8 S T I M U L I G G r e y 2 4 X 24 Figure k. T o t a l looking time i n seconds spent looking.at each of the s t i m u l i by 3*5*8 , 1©, l k , and 20 week old i n f a n t s , averaged over subjects. (Experiment 11} 6k. p r e f e r r e d t o a t i m u l u a C. Seven o f t h e 10 i n f a n t s i n t h i a age group showed p r e f e r e n c e s f o r B over C, whereas t h r e e p r e f e r r e d C t o B. Of t h e two f i v e week o l d s one showed a p r e f e r e n c e f o r s t i m u l u s B over A w h i l e t h e o t h e r p r e f e r r e d b o t h t h e s e s t i m u l i to t h e same degree. Thus i t would appear t h a t t h e p r e f e r e n c e s o f f i v e week o l d s l i e s between t h o s e o f t h r e e and e i g h t week o l d s . T h i s experiment r e p r e s e n t s t h e f i r s t n e c e s s a r y s t e p i n s t u d y i n g t h e e f f e c t s o f i n f a n t s ' e x p e r i e n c e ^ w i t h s t i m u l i above, a t , and below t h e i r pacer l e v e l , t h a t i s , the l e v e l o f c o m p l e x i t y most p r e f e r r e d by i n f a n t s o f a g i v e n age (Dember and E a r l , 1 9 5 7 ) * P e r t h i a purpose i t was n e c e s s a r y t o f i n d t h e ages a t w h i c h p a t t e r n o f reaponae were b o t h a i g n i f i c a n t and u n i f o r m . The e x a c t pacer s t i m u l u s f o r each o f t h e 3» 8* and l k week o l d groups may n o t have been r e p r e -s e n t e d i n t h e s e t o f s t i m u l i u s e d . However, t h e s i g n i f i c a n e o f t h e gr o u p s ' r e s p e c t i v e p r e f e r e n c e s f o r one of t h e p a t t e r n a i n t h e set i n d i c a t e d t h a t t h e s e p a t t e r n s were, at t h e l e a s t , v e r y c l o s e t o t h e pace r s t i m u l u s f o r eaeh age. F i n e r g r a d a -t i o n s o f c o m p l e x i t y among t h e s t i m u l i would be needed i n o r -der t o I d e n t i f y t h e e x a c t p a c e r s t i m u l u s f o r each age g r o u p s . Accommodation and A c u i t y Haynes, W h i t e , and H e l d (196f>) s t u d i e d t h e v i s u a l accommodation o f 22 human i n f a n t s r a n g i n g i n age f r o m s i x days t o f o u r months by means o f t h e t e c h n i q u e o f dynamie r e t i n o s -6 5 . copy. They found t h a t " p r i o r t o one month of age, t h e i n f a n t ' s accommodative r e s p o n s e d i d not a d j u s t t o changes i n t a r g e t d i s t a n c e s . The s y s t e m appeared t o be l o c k e d a t one f o c a l d i s t a n c e whose median v a l u e f o r t h e group was 19 cm." (Haynes et a l . , 1965* p . 5 3 0 ) . T h i s d i s t a n c e i s e q u a l t o a p p r o x i m a t e l y 7f-# or l e s s t h a n h a l f t h e d i s t a n c e a t w h i c h the s t i m u l i I n t h e p r e s e n t experiment were shown. Thus, i t I s p o s s i b l e t h a t the t h r e e week o l d s i n the p r e s e n t e x p e r i -ment c o u l d . n o t f o c u s on t h e s t i m u l i at t h e 18" d i s t a n c e a t w h i c h t h e y were p r e s e n t e d . On t h e o t h e r hand, P a n t z , et a l . ( 1962) f o u n d t h a t one month o l d s c o u l d p e r c e i v e -^" b l a c k s t r i p e s on a w h i t e back-ground a t a d i s t a n c e o f 20 I n c h e s . That i s , t h e i n f a n t s l o o k e d a t t h i s p a t t e r n s i g n i f i c a n t l y more t h a n a t a g r e y square w i t h w h i c h i t was p a i r e d . However, i t i s w e l l docu-mented t h a t d i f f e r e n t v i s u a l a o u i t y t h r e s h o l d s a r e o b t a i n e d w i t h d i f f e r e n t t a r g e t s ( B a r t l e y , 1 9 5 8 ) , and as i t i s q u i t e p o s s i b l e t h a t v i s u a l a c u i t y f o r c h e c k e r b o a r d i s not as good as t h a t f o r s t r i p e s . I n t h e p r e s e n t experiment t h r e e week o l d s d i d n o t l o o k s i g n i f i c a n t l y l o n g e r a t the c h e c k e r b o a r d c o n t a i n i n g 2k x 2 k ^" squares t h a n a t t h e g r a y s q uare when each was p r e s e n t e d s i n g l y . T h i s would t e n d t o i n d i c a t e e i t h e r t h a t t h e y p r e -f e r r e d e a c h t o t h e same low degree, or t h a t t h e y c o u l d not d i s t i n g u i s h t h e c h e c k e r b o a r d f r o m a u n i f o r m l y gray s q u a r e . On t h e e v i d e n c e o f Haynes et a l . ( 1 9 6 5 ) , and o f B a r t l e y 6 6 . ( 1 9 5 8 ) , i t w o u l d appear p o s s i b l e t h a t n e i t h e r the accommo-d a t i v e a b i l i t y n o r t h e v i s u a l a c u i t y o f t h e t h r e e week o l d s was d e v e l o p e d enough to e n a b l e them t o p e r c e i v e c l e a r l y the most complex s t i m u l u s w i t h w h i c h t h e y were p r e s e n t e d . The c l a r i f i c a t i o n o f t h i s p o i n t r e q u i r e s a c o n t r o l s t u d y i n w h i c h the s t i m u l i a r e p r e s e n t e d a t a d i s t a n c e o f about 7^"« However, the t h r e e week o l d s d i d l o o k at b o t h s t i m u l i A and B s i g n i f i c a n t l y l o n g e r than at the g r a y square and showed a s i g n i f i c a n t p r e f e r e n c e f o r s t i m u l u s A over B, T h i s i n d i c a t e s t h a t t h e y p e r c e i v e d b o t h of t h e s e p a t t e r n s at l e a s t c l e a r l y enough t o d i s t i n g u i s h them f r o m t h e gray and f r o m eaeh o t h e r , and t h a t t h e y p r e f e r r e d t h e l e s s complex of the two s t i m u l i , Haynes et a l , ( 1965) a l s o f o u n d t h a t f l e x i b i l i t y o f t h e accommodative r e s p o n s e "began at about th e m i d d l e of the 2nd month and performance comparable to t h a t o f the n o r m a l a d u l t was a t t a i n e d by t h e k t h month" ( p . 5 3 0 ) . The f a c t t h a t t h e e i g h t week o l d s i n t h e p r e s e n t experiment p r e f e r r e d t h e moat complex s t i m u l u s s i g n i f i c a n t l y t o the l e a s t complex one i n d i c a t e s t h a t t h e y p e r c e i v e d a l l t h r e e s t i m u l i w i t h w h i c h t h e y were p r e s e n t e d . T h e i r f o c u s on the s t i m u l i at 18" may not have been p e r f e c t , but i t was s u f f i c i e n t f o r them t o make d i s t i n c t i o n s between t h e t h r e e s t i m u l i . A n o t h e r P o s s i b l e I n t e r p r e t a t i o n o f the R e s u l t s There i s a p o s s i b l e I n t e r p r e t a t i o n o f t h e r e s u l t s i n terms o t h e r t h a n t h a t o f the d i f f e r e n c e i n c o m p l e x i t y o f t h e 67. t h r e e c h e c k e r b o a r d p a t t e r n s . T h i s i n t e r p r e t a t i o n w o u l d t a k e i n t o account t h e s i z e o f the b r i g h t n e s s p a t c h e s i n t h e p a t t e r n s . The h y p o t h e s i s i n t h i s case would be t h a t t h e younger t h e i n f a n t , the l o n g e r he l o o k s a t l a r g e p a t c h e s o f b r i g h t n e s s . As t h e s t i m u l i u s e d h e r e I n c r e a s e d i n complex-i t y , the w h i t e squares c o n t a i n e d i n them beeame s m a l l e r . W i t h the method o f o b s e r v a t i o n employed i n t h i s experiment t h e r e was no way o f d e t e c t i n g t h e e x a c t a r e a s of t h e s t i m u l i w h i c h t h e i n f a n t s were f i x a t i n g . I t i s p o s s i b l e t h a t t h e t h r e e week o l d s , f o r i n s t a n c e , were f i x a t i n g m a i n l y on t h e l a r g e w h i t e a r e a s o f the l e a s t complex s t i m u l u s . I n o r d e r t o f i n d out whether i n f a n t s f i x a t e one a r e a o f a s t i m u l u s o n l y o r whether t h e y scan t h e whole p a t t e r n , a more s o p h i s t i -c a t e d method o f o b s e r v a t i o n i s needed. A c i n e m a t o g r a p h i c t e c h n i q u e such as t h a t u s e d by S a l a p a t e k and Kessen (1965) might be u s e f u l l y a p p l i e d t o t h e p r e s e n t p r o b l e m . CHAPTER POUR 68. COMPARISON OP RESPONSE MEASURES OBTAINED IN EXPERIMENT I I . Two o t h e r r e s p o n s e measures b e s i d e s t o t a l l o o k i n g t i m e were s t u d i e d i n Experiment I I . These were l e n g t h o f f i r s t f i x a t i o n and r a t e o f h a b i t u a t i o n . I n t h i s ehapter the r e -s u l t s o b t a i n e d w i t h t h e s e measures a r e d e s c r i b e d and t h e n comparisons between l e n g t h o f f i r s t f i x a t i o n and t o t a l l o o k -i n g t i m e a r e d i s c u s s e d , a) L e n g t h o f F i r s t F i x a t i o n T a b l e 11 p r e s e n t s t h e l o o k i n g t i m e i n seconds o f f i r s t f i x a t i o n s o f t h e t h r e e c h e c k e r b o a r d s by t h e 3» 8, and l k week o l d g r o u p s , a v e r a g e d a c r o s s s u b j e c t s . These d a t a a r e p l o t t e d i n F i g u r e 5". T a b l e 12 p r e s e n t s a summary t a b l e o f a two-way a n a l y s i s o f v a r i a n c e o f the l e n g t h o f f i r s t f i x a t i o n f o r the t h r e e s t i m u l i by t h e t h r e e age g r o u p s . The two main e f f e c t s and the I n t e r a c t i o n e f f e c t were a l l s i g n i f i c a n t . The s i g n i f i c a n c e o f the Age e f f e c t i n d i c a t e s t h a t t h e o v e r a l l l e n g t h o f f i r s t f i x a t i o n s f o r t h e age groups were not t h e same. A Newman-Keuls t e s t p e r f ormed on the d i f f e r e n c e s between the l e n g t h o f f i r s t f i x a t i o n s among t h e t h r e e groups i n d i c a t e s t h a t t h e l e n g t h o f f i r s t f i x a t i o n s o f t h e e i g h t week o l d s was s i g n i f i c a n t l y g r e a t e r t h a n t h a t o f t h e f o u r t e e n week o l d s (p l e s s t h a n . 0 5 ) • The f i r s t f i x -69. TABLE 11 L o o k i n g Time i n Seconds o f F i r s t F i x a t i o n s o f t h e Three S t i m u l i by 3 , 8 , and l k Week O l d I n f a n t s , Averaged Over S u b j e c t s (Experiment I I ) A B G Mean l e n g t h o f f i r s t 2 x 2 8 x 8 2k x 2 k f i x a t i o n s f o r each age 3 weeks 4 9 . 1 25.9 1 5 . 0 3 0 . 0 8 weeks 9 . 5 76.9 3 6 . 8 41.06 l k weeks 1 1 . 3 19 .7 35.6 2 2 . 2 Mean l e n g t h o f f i r s t f i x a t i o n s 2 3 . 3 4 0 . 8 3 2 9 . 1 3 f o r e a c h s t i m u -l u s TABLE 12 Summary T a b l e o f Two-way A n a l y s i s o f V a r i a n c e o f L e n g t h o f F i r s t F i x a t i o n f o r each o f t h r e e - a t 1 -. m u l l by 3» 8 , and l i j . week o l d groups ( E x p e r i -m e n t l l ) Source SS d f MS P Between i n f a n t s • Age 2 2798.62 5392.62 S u b j e c t s w i t h i n 1 7 4 0 6 . 0 0 groups W i t h i n i n f a n t s .. S t i m u l i Age X s t i m u l i S t i m u l i X sub-j e c t s w i t h i n groups 5 0 2 3 k . 6 7 4 7 8 3 . 3 6 2 7 3 1 5 . 9 1 1 8 1 3 5 . 4 0 29 2 27 60 2 4 54 2692.31 4«18 l e s s t h a n . 0 5 6 k k . 6 7 2391.68 7.12 l e s s t h a n . 0 0 5 6828 .98 20.33 l e s s t h a n . 0 0 5 335.84 70. < LU 2 x 2 8 x 8 2 4 x 2 4 S T I M U L I Figure 5• The looking time i n seconds of f i r s t f i x a t i o n s of the three checkerboards by the 3,8, and l k week old groups, average" over subjects. (Experiment I I ) . 7 1 . a t i o n a o f e i g h t week o l d a were not s i g n i f i c a n t l y l o n g e r t h a n t h o s e o f t h r e e week o l d s , nor were the f i r s t f i x a t i o n s o f the t h r e e week o l d s s i g n i f i c a n t l y l o n g e r t h a n t h o s e o f the f o u r t e e n week o l d s * A Newman-Keuls t e s t p e r f ormed on the s i g n i f i c a n t s t i m u l i e f f e c t r e v e a l s t h a t the f i r s t f i x a t i o n s o f s t i m u l u s B were s i g n i f i c a n t l y l o n g e r than t h o s e o f A (p l e s s t h a n .01) and o f C (p l e s s t h a n *05>). The f i r s t f i x a t i o n s o f s t i m u l u s C were not s i g n i f i c a n t l y l o n g e r t h a n t h o s e o f A. The s i g n i f i c a n c e o f the i n t e r a c t i o n between Age and S t i m u l i i n d i c a t e s t h a t the p a t t e r n s o f p r e f e r e n c e d e r i v e d from l e n g t h s o f f i r s t f i x a t i o n o f t h e t h r e e age groups were s i g n i f i c a n t l y d i f f e r e n t . To i n v e s t i g a t e f u r t h e r the p a t t e r n o f p r e f e r e n c e of each age group, t h r e e one-way a n a l y s e s o f v a r i a n c e were performed s e p a r a t e l y on t h e l e n g t h o f f i r s t f i x a t i o n o f t h e t h r e e age gr o u p s . Summaries o f t h e s e a n a l y -ses a r e p r e s e n t e d i n T a b l e s 13 t h r o u g h 1£>. Newman-Keuls t e s t s were p e r f o r m e d s e p a r a t e l y f o r each group on t h e d i f f e r e n c e s i n l e n g t h o f f i r s t f i x a t i o n s be-tween p a i r s o f s t i m u l i . - For the t h r e e week o l d s f i r s t f i x -a t i o n s of s t i m u l u s A were s i g n i f i c a n t l y l o n g e r t h a n t h o s e o f b o t h s t i m u l i B and G ( b o t h p's l e s s t h a n .01). The f i r s t f i x a t i o n s o f s t i m u l u s B were not s i g n i f i c a n t l y l o n g e r t h a n t h o s e of s t i m u l u s C. Thus, i n terms of t h e l e n g t h o f f i r s t f i x a t i o n s , t h e t h r e e week o l d s p r e f e r r e d the s t i m u l i i n de-c r e a s i n g o r d e r o f t h e i r c o m p l e x i t y . TABLE 13 Source Summary T a b l e o f A n a l y s i s o f V a r i a n c e o f L e n g t h o f F i r s t F i x a t i o n o f . e a c h of ""three S t i m u l i by 3 Week o l d group (Experiment I I ) SS d f MS Between i n f a n t s W i t h i n i n f a n t s S t l m u l i Res i d u a l T o t a l 6 6 8 9 . 3 3 1 2 5 9 2 . 6 7 19282.GO 6 0 6 6 . 2 6526.k? 9 20 29 2 18 3 0 3 3 . 1 3 6 2 . 5 8 8 . 3 6 5 l e s s t h a n . 0 0 5 TABLE l k Summary Ta b l e o f " A n a l y s i s o f V a r i a n c e " o f L e n g t h o f F i r s t F i x a t i o n o f each of ""Three .St i m u l i by 8 Week o l d Group (Experiment I I ) Source SS d f MS F P Between p e o p l e W i t h i n p e o p l e S t i m u l i R e s i d u a l T o t a l k 9 8 l . 2 0 9 3 1 0 7 6 . 6 7 20 2 2 9 8 6 . 8 7 2 8 0 8 9 . 8 0 18 3 6 0 5 7 . 8 7 . 29. 1 1 4 9 3 . 4 3 5 4 4 9 . 4 3 0 2 5 . 5 7 l e s s t h a n . 0 0 5 TABLE 15 Summary T a b l e o f A n a l y s i s o f V a r i a n c e o f Length o f F i r s t F i x a t i o n o f each o f Three S t i m u l i by l i j . Week o l d Group (Experiment I I ) Source SS df . ..MS F P Between i n f a n t s W i t h i n i n f a n t s S t i m u l i Res i d u a l T o t a l 5 7 3 5 . 4 7 9 6565.33 20 3 0 4 6 . 2 0 2 3519.13 18 1 2 3 0 0 . 8 0 29 1 5 2 3 . 1 1 9 5 . 5 1 7 .79 l e s s t h a n . 0 0 5 73. For t h e e i g h t week o l d group a l l d i f f e r e n c e s between p a i r s o f f i r s t f i x a t i o n times o f the s t i m u l i were s i g n i f i c a n t ( a l l p's l e s s t h a n . 0 1 }• The f i r s t f i x a t i o n s o f s t i m u l u s B were s i g n i f i c a n t l y l o n g e r t h a n t h o s e o f b o t h A and G, and t h e f i r s t f i x a t i o n s o f s t i m u l u s C were s i g n i f i c a n t l y l o n g e r t h a n t h o s e o f A. A c c o r d i n g t o t h i s r e s p o n s e measure e i g h t week o l d s p r e f e r r e d t h e s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y most, the most complex p a t t e r n n e x t , and the l e a s t complex l e a s t . For t h e l k week o l d group the f i r s t f i x a t i o n s o f s t i m u l u s C were s i g n i f i c a n t l y l o n g e r t h a n t h o s e of b o t h A and B (P's l e s s t h a n . 0 1 and . 0 5 r e s p e c t i v e l y ) . The f i r s t f i x a t i o n s o f B were not s i g n i f i c a n t l y l o n g e r t h a n t h o s e o f A. Thus, i n terms o f t h e l e n g t h o f f i r s t f i x a t i o n , t h e l k week o l d s p r e -f e r r e d the s t i m u l i i n i n c r e a s i n g o r d e r o f t h e i r c o m p l e x i t y . The p a t t e r n o f p r e f e r e n c e f o r each o f t h e t h r e e age groups i n terms o f t h e i r t o t a l l o o k i n g t i m e was t h e same as t h e p r e f e r e n c e s d e r i v e d f r o m t h e l e n g t h s o f f i r s t f i x a t i o n s o f each g r o u p . A few o f the s i g n i f i c a n c e l e v e l s a t t a i n e d by th e d i f f e r e n c e s between t h e f i r s t f i x a t i o n s of t h e s t i m u l i were not as h i g h as t h o s e r e a c h e d by t h e d i f f e r e n c e s i n t o t a l f i x a t i o n t i m e s . I n t e r - O b s e r v e r R e l i a b i l i t y o f L e n g t h o f F i r s t F i x a t i o n : I n t e r - o b s e r v e r r e l i a b i l i t y f o r t h i s measure was a s s e s s e d on t h e same n i n e s u b j e c t s on whom i n t e r - o b s e r v e r agreement was c a l c u l a t e d i n Chapter T h r e e . A P e a r s o n product-moment 7k. c o r r e l a t i o n between the length of f i r s t f i x a t i o n s recorded by each observer i n each t r i a l was +.79. b) Rate of Habituation For each subject the series of 12 t r i a l s was divided into two halves of s i x t r i a l s each. For each age group the t o t a l looking time for each stimulus was calculated for each h a l f of the s e r i e s . These t o t a l are presented i n Table 16 along with the proportion of the t o t a l looking time of the whole series that each h a l f - t o t a l represents. Inspection of t h i s table reveals that there was no con-sistent pattern of change In f i x a t i o n time over t r i a l s . DISCUSSION OF THE RESPONSE MEASURES STUDIED IN EXPERIMENT II Contrary to the findings of Lewis et a l . (1963)* rate of habituation was not a function of the complexity of the patterns i n the present experiment. There was no habituation i n any age group to any of the s t i m u l i over the four t r i a l s i n which each was presented. Therefore, i n the rest of the chapter discussion w i l l be concerned with the other two r e -sponses measures analyzed — t o t a l looking time, and length of f i r s t f i x a t i o n . Table 17 presents the results obtained from both of these response measures. Part A presents a comparison between the re s u l t s of Newman-Keuls tests performed with each group. Within each group the patterns of preference derived from both response 7 5 . TABLE 16 T o t a l F i x a t i o n Time ( i n seconds) f o r Each, ' - H a l f of t h e 1 2 - T r i a l S e r i e s  " STIMULUS A STIMULUS B STIMULUS C 1 s t h a l f 2nd h a l f 1 s t h a l f 2nd, h a l f 1s t h a l f 2 n d h a l f 3 weeks k l 7 387 239 279 136 100 p r o p o r t i o n o f t o t a l . 5 2 . k 8 . k 6 . 5 4 . 5 8 . k 2 l o o k i n g t i m e 8 weeks 282 260 531 580 366 380 p r o p o r t i o n o f t o t a l . 5 2 . 4 8 , k 8 . 5 2 . 4 9 . 5 1 l o o k i n g t ime l k weeks 239 192 365 323 4 7 8 k 3 3 p r o p o r t i o n o f t o t a l . 5 5 . 4 5 . 5 3 . 4 7 . 5 2 . 4 8 l o o k i n g t i m e 7 6 . TABLE 17 Results Obtained from the Response MeasureB Studied i n Experiment II A. INDIVIDUAL ANALYSES OP EACH AGE GROUP Length of Total F i x a t i o n Length of F i r s t - ' Fi x a t i o n Results P Results P 3 WEEKS 1> 2 < .01 1> 2 <.01 1>3 < .01 1> 3 <.01 2 > 3 < .01 2> 3 NS 8 WEEKS 2 > 3 < .01 2> 3 <.01 2>1 < .01 2 > 1 c.01 3>1 <• .01 3>1 < .01 l k WEEKS 3>1 < .01 3>1 <.01 3> 2 < .©2 3 > 2 <.o5 2> 1 < .01 2>1 NS B. OVERALL ANALYSES OP THE AGE GROUPS AND STIMULI TAKEN . .. . TOGETHER Length of T o t a l F i x a t i o n .Length of F i r s t - .. Fi x a t i o n Results P Results P AGE 8>lk NS 8> l k <.05 8 > 3 < .01 8> 3 NS lk>3 < .05 3> l k NS STIMULI B > C < .01 B> C <.©5 B > A < .01 B > A <.01 G > A NS Q> A NS C. PEARSON PRODUCT-MOMENT CORRELATION BETWEEN THE TWO OBSERVERS RECORDS. Length of To t a l F i x a t i o n Length of F i r s t F i x a t i o n + .9k + . 7 9 7 7 * measures were i d e n t i c a l . Only t h e l e v e l s o f s i g n i f i c a n c e v a r i e d . On the whole the r e s u l t s o b t a i n e d w i t h t h e l e n g t h of t o t a l f i x a t i o n were more s i g n i f i c a n t t h a n t h o s e o b t a i n e d from t h e l e n g t h o f f i r s t f i x a t i o n . T h i s suggests t h a t l e n g t h of t o t a l f i x a t i o n was a more s e n s i t i v e measure i n d e t e c t i n g d i f f e r e n c e s i n t h e g r o u p s 1 p r e f e r e n c e s among the s t i m u l i . P a r t B o f T a b l e 16 p r e s e n t s t h e r e s u l t s o f the Newman-K e u l s t e s t s f o l l o w i n g the two-way a n a l y s e s of v a r i a n c e f o r b o t h r e s p o n s e measures. The r e s u l t s o b t a i n e d f r o m b o t h r e s p o n s e measures were i n t h e same d i r e c t i o n s f o r b o t h e f f e c t s exeept f o r a n o n - s i g n i f i c a n t r e v e r s a l I n the Age e f f e c t . I n terms o f t o t a l f i x a t i o n , l k week o l d s l o o k e d s i g -n i f i c a n t l y l o n g e r at the s t i m u l i t a k e n t o g e t h e r t h a n d i d t h r e e week o l d s , whereas t h e f i r s t f i x a t i o n s o f t h r e e week o l d s were l o n g e r t h a n t h o s e of l k week o l d s t o an i n s i g n i -f i c a n t d e g ree. The product-moment c o r r e l a t i o n between the two o b s e r -v e r s ' r e c o r d s f o r t h e n i n e i n f a n t s i n the r e l i a b i l i t y study r e v e a l e d t h a t l e n g t h o f t o t a l f i x a t i o n was the more r e l i a b l e r e s p o n s e measure o f the two. I n c o n c l u s i o n , b o t h l e n g t h o f t o t a l f i x a t i o n and l e n g t h o f f i r s t f i x a t i o n were good response measures wh i c h gave s i m i l a r r e s u l t s . However, l e n g t h o f t o t a l f i x a t i o n was the more r e l i a b l e and more s e n s i t i v e measure o f the two. CHAPTER FIVE 78 EXPERIMENT I I I Purpose Experiment I I I was d e s i g n e d to compare r e s u l t s ob-t a i n e d w i t h a p a i r comparisons p r o c e d u r e w i t h t h o s e ob-t a i n e d i n Experiment I I , w h i c h employed a s i n g l e s t i m u l u s p r o c e d u r e . METHOD The method o f Experiment I I I was t h e same as t h a t f o r Experiment I I except f o r the f o l l o w i n g m o d i f i c a t i o n s : S u b j e c t s The s u b j e c t s were 10 e i g h t week o l d s , r a n g i n g i n age f r o m seven weeks, t h r e e d a y s , t o e i g h t weeks, f i v e d a y s , and t e n l k week o l d s , r a n g i n g i n age f r o m 13 weeks, two days, t o l k weeks, f i v e d a y s . Apparat us F o r t h e p a i r comparisons p r o c e d u r e a d i f f e r e n t door was h i n g e d i n t o the a p p a r a t u s c e i l i n g . T h i s door c o n t a i n e d two s t i m u l u s h o l d e r s , each 12" by 9", t h e i r i n n e r edges b e i n g 10j-" a p a r t . One o b s e r v a t i o n h o l e o f i | " i n di a m e t e r was l o -c a t e d midway between t h e two s t i m u l u s h o l d e r s . Two o t h e r s were l o c a t e d j u s t t o the i n s i d e o f t h e h o l d e r s , 9tru a p a r t . P r o c e d u r e Each o f the t h r e e c h e c k e r b o a r d s was combined w i t h e a ch o f t h e o t h e r s t w i c e , a p p e a r i n g once i n each o f the two l e f t -r i g h t s p a t i a l a rrangements. I n t h e d e s c r i p t i o n t o f o l l o w , 79. a c o m b i n a t i o n r e f e r s t o two s t i m u l i o c c u r r i n g t o g e t h e r no matter what t h e i r s p a c i a l arrangement ( e . g . A w i t h B i n any o r d e r ) . A p a i r r e f e r s t o a s p e c i f i c c o m b i n a t i o n o f t h e two s t i m u l i t a k i n g s p a t i a l arrangement i n t o a c c o u n t , so t h a t f o r each c o m b i n a t i o n o f s t i m u l i t h e r e a r e two p a i r s ( e . g . AB and B A ) . Each o f t h e t h r e e c o m b i n a t i o n s (A w i t h B, A w i t h C, and B w i t h C) was p r e s e n t e d i n random o r d e r f o r t h e f i r s t t h r e e t r i a l s , and t h e n t h i s o r d e r was r e v e r s e d w i t h t h e s t i m u l i on o p p o s i t e s i d e s f o r t h e l a s t t h r e e t r i a l s . A f t e r t h e s e s i x t r i a l s any t r i a l on w h i c h b o t h members o f t h e p a i r had n o t been f i x a t e d by t h e s u b j e c t was r e p e a t e d u n t i l b o t h members had been f i x a t e d , up t o a maximum of t h r e e more t r i a l s f o r any one p a i r . I n t e r - O b s e r v e r Agreement I n t h e t e s t i n g o f t h r e e o f t h e e i g h t week o l d s and s i x o f t h e l k week o l d s two o b s e r v e r s were u s e d . One o b s e r v e d t h e I n f a n t ' s eyes t h r o u g h t h e o b s e r v a t i o n h o l e a d j a c e n t t o t h e r i g h t s t i m u l u s h o l d e r , and t h e o t h e r o b s e r v e d t h r o u g h t h e h o l e a d j a c e n t t o t h e l e f t s t i m u l u s h o l d e r . Each o b s e r v e r o p e r a t e d t h e r e c o r d i n g b u t t o n s on h i s r e s p e c t i v e s i d e o f the ap p a r a t u s t o p . The o p e r a t i o n o f t h e b u t t o n s was r e n d e r e d n e a r l y I n a u d i b l e by e n c l o s i n g t h e event r e c o r d e r i n a padded box. Thus, each o b s e r v e r r e c o r d e d t h e f i x a t i o n s o f the i n f a n t i n d e p e n d e n t l y o f t h e o t h e r . I n t h e p a i r c o mparison p r o c e d u r e each o b s e r v e r o p e r a t e d two b u t t o n s , one f o r each s t i m u l u s , and t h u s a l l f o u r c h a n n e l s 8 0 . o f t h e event r e c o r d e r were u s e d . An i n t e r - o b s e r v e r a g r e e -ment s c o r e was c a l c u l a t e d f o r each s u b j e c t by c o u n t i n g t h e number o f seconds per 30 second t r i a l d u r i n g w h i c h the ob-s e r v e r s a g r e e d , t h a t i s , a l l t i m e except t h a t d u r i n g w h i c h one o b s e r v e r r e c o r d e d a f i x a t i o n on one s t i m u l u s w h i l e t h e o t h e r o b s e r v e r e i t h e r r e c o r d e d a f i x a t i o n on t h e o t h e r s t i -mulus o r r e c o r d e d no f i x a t i o n a t a l l . The s c o r e s were t o t a l l e d over t h e number o f t r i a l s f o r each s u b j e c t and con-v e r t e d t o a percentage o f t o t a l s t i m u l u s p r e s e n t a t i o n t i m e . I n t e r - o b s e r v e r agreement ranged f r o m Q0% t o 97% t t h e average agreement o v e r t h e n i n e s u b j e c t s b e i n g 89%. RESULTS I n n e i t h e r age group d i d any I n f a n t l o o k at b o t h members o f a p a i r o f s t i m u l i i n a l l o f t h e f i r s t s i x t r i a l s . At l e a s t one t r i a l had t o be r e p e a t e d f o r each s u b j e c t . F o r t h e l k week o l d group t h e t o t a l number o f t r i a l s r a nged f r o m 7 t o 1 3 . The mean number f o r t h e 10 i n f a n t s was n i n e . F o r e i g h t i n f a n t s , s i x t r i a l s were f i n a l l y o b t a i n e d i n w h i c h b o t h members o f a p a i r were f i n a l l y f i x a t e d . B o t h s t i m u l i were f i x a t e d i n 6 k $ o f t h e t o t a l number o f t r i a l s r u n on t h e group.. F o r t h e e i g h t week o l d group t h e number o f t r i a l s p r e s e n t e d ranged f r o m 8 t o 2 3 . The mean number o f t r i a l s f o r t h e 10 i n f a n t s was l k . For o n l y f i v e i n f a n t s were s i x t r i a l s f i n a l l y o b t a i n e d i n w h i c h b o t h members o f a p a i r were f i x a t e d . B o t h s t i m u l i were f i x a t e d i n 3 3 $ o f t h e t o t a l number o f t r i a l s r u n on t h e grou p . 81. Pour s e t s o f s i x t r i a l s each were a n a l y z e d f o r each s u b j e c t . T h i s was done so t h a t t h e r e s u l t s o b t a i n e d w i t h each set c o u l d be compared t o see i f d i f f e r e n t p r e f e r e n c e s emerged when u n s u c c e s s f u l t r i a l s were r e p l a c e d or when c o r r e c t i o n s f o r s i d e p r e f e r e n c e were made. These f o u r s e t s were: 1. O r i g i n a l t r i a l s . One o f t h e s e t s was merely t h e f i r s t s i x t r i a l s w i t h w h i e h t h e i n f a n t was p r e s e n t e d . 2. O r i g i n a l t r i a l s c o r r e c t e d f o r s i d e p r e f e r e n c e . I n t h e s e f i r s t s i x t r i a l s c o r r e c t i o n s f o r s i d e p r e f e r e n c e were made. The t o t a l l o o k i n g t i m e f o r the r i g h t s t i m u l i and t h e t o t a l l o o k i n g t i m e f o r t h e l e f t s t i m u l i were c a l c u l a t e d over t h e s i x t r i a l s and t h e d i f f e r e n c e between them f o u n d . T h i s d i f -f e r e n c e was t h e n d i v i d e d by t h e number o f t r i a l s (6) t o ob-t a i n t h e average amount o f s i d e p r e f e r e n c e per t r i a l . T h i s f i g u r e was t h e n added t o t h e l o o k i n g t i m e f o r each s t i m u l u s on t h e n o n - p r e f e r r e d s i d e on each o f t h e s i x t r i a l s , r e s u l t -i n g i n t h e c o r r e c t e d l o o k i n g t i m e s f o r each s t i m u l u s . 3. T r i a l s w i t h r e p l a c e m e n t . I n the t h i r d s e t o f t r i a l s any o f t h e f i r s t s i x t r i a l s I n w h i c h b o t h s t i m u l i had not been f i x a t e d was r e p l a c e d by a r e p e a t e d t r i a l i n w h i c h b o t h s t i m u -l i had been f i x a t e d , i f such a t r i a l e x i s t e d . As n o t e d , w i t h s e v e r a l i n f a n t s even a f t e r t h r e e r e p e t i t i o n s o f a p a i r o f s t i m u l i b o t h s t i m u l i had not been f i x a t e d . I n s u c h a ease, t h e t r i a l f o r t h i s p a i r i n t h e f i r s t s i x t r i a l s was not r e -p l a c e d . 82. k» T r i a l s w i t h replacement c o r r e c t e d f o r s i d e p r e f e r e n c e . For t h e t h i r d s et o f t r i a l s c o r r e c t i o n s f o r s i d e p r e f e r e n c e were a l s o made. I n terms o f l o o k i n g t i m e f o r each s t i m u l u s o f a p a i r , an i n f a n t ' s p r e f e r e n c e on each t r i a l was n o t e d . F o r each o f the f o u r s e t s o f t r i a l s , t h r e e s i g n t e s t s were performed s e p a r a t e l y f o r each c o m b i n a t i o n o f s t i m u l i f o r the 1© sub-j e c t s i n each a g e 1 g r o u p . The r e s u l t s o f t h e s e t e s t s a r e p r e s e n t e d i n T a b l e 18. F o r t h e e i g h t week o l d group s t i m u l u s B, t h e p a t t e r n o f i n t e r m e d i a t e c o m p l e x i t y , was s i g n i f i c a n t l y p r e f e r r e d t o b o t h s t i m u l u s A, t h e l e a s t complex p a t t e r n , and s t i m u l u s C, the most complex p a t t e r n . S t i m u l u s A was o n l y s l i g h t l y p r e -f e r r e d t o s t i m u l u s G. F o r t h e BA s t i m u l u s c o m b i n a t i o n , r e -p l a c i n g t h e t r i a l s on w h i c h o n l y one s t i m u l u s was f i x a t e d w i t h r e p e a t e d t r i a l s on w h i c h b o t h were f i x a t e d i n c r e a s e d t h e s i g n i f i c a n c e l e v e l o f p r e f e r e n c e f o r B over A. T h i s was not so w i t h the replacement t r i a l s f o r the o t h e r two c o m b i n a t i o n s . C o r r e c t i n g f o r s i d e p r e f e r e n c e i n c r e a s e d t h e s i g n i f i c a n c e o f t h e group p r e f e r e n c e f o r B over G w i t h b o t h t h e o r i g i n a l t r i a l s s e t and t h e t r i a l s w i t h replacement s e t . Thus, f o r the e i g h t week o l d grou p , t h e most s i g n i f i c a n t p r e f e r e n c e s were o b t a i n e d w i t h t h e t r i a l s w i t h replacement s e t i n w h i c h c o r r e c t i o n s f o r s i d e p r e f e r e n c e s were made. For t h e l k week o l d group, b o t h s t i m u l i B and C were s i g -n i f i c a n t l y p r e f e r r e d t o s t i m u l u s A I n a l l f o u r s e t s o f t r i a l s . 83 TABLE 18 R e s u l t s o f S i g n Test Performed on P a i r Com-p a r i s p n s Data (Experiment i l l ) STIMDXUS PREFERENCES OF THE GROUPS 8 WEEKS B; A A> C B> G 1. O r i g i n a l t r i a l s <.©5* NS C.10 2. O r i g i n a l t r i a l s c o r r e c t e d <.05 NS < ,©5 3 . T r i a l s w i t h replacement <.01 NS < .10 k. T r i a l s w i t h r e p l a c e m e n t c o r r e c t e d <.01 NS <.©5 l k WEEKS B> A O A O B 1. O r i g i n a l t r i a l s <.01 <.01 G = I 2. O r i g i n a l t r i a l s c o r r e c t e d <.01 <.01 G = I 3 . T r i a l s w i t h replacement <.01 < .01 <.05* k- T r i a l s w i t h r e p l a c e m e n t c o r r e c t e d < .01 ^ .01 < .05 * F i g u r e s i n t h e m a t r i x r e p r e s e n t t h e l e v e l s o f s i g n i f i c a n c e a t t a i n e d i n eaeh t e s t . 8k. However, C was s i g n i f i c a n t l y p r e f e r r e d t o B o n l y i n the r e -placement t r i a l s : i n t h e o r i g i n a l t r i a l s s t i m u l i C and B were p r e f e r r e d e q u a l l y . C o r r e c t i n g f o r s i d e p r e f e r e n c e s d i d not change the magnitude o f t h e p r e f e r e n c e s on any o f t h e s t i m u l u s c o m b i n a t i o n s . T h i s was p r o b a b l y because l e s s s i d e p r e f e r e n c e was shown by l k week o l d s t h a n by e i g h t week o l d s ; t h e r e f o r e , c o r r e c t i o n s were s l i g h t and not l a r g e enough t o change t h e d i r e c t i o n o f any p r e f e r e n c e s . There were many I n d i v i d u a l p r e f e r e n c e s w h i c h d i f f e r e d f r o m t h e o v e r a l l group p r e f e r e n c e s , e s p e c i a l l y i n t h e e i g h t week o l d group. T a b l e 19 p r e s e n t s t h e i n d i v i d u a l p r e f e r e n -ces shown f o r t h e s t i m u l u s c o m b i n a t i o n s i n terms o f t h e t o t a l l o o k i n g t i m e f o r e a c h s t i m u l u s c o m b i n a t i o n f o r t h e t r i a l s w i t h replacement c o r r e c t e d f o r s i d e p r e f e r e n c e s . I n t h e e i g h t week o l d group e i g h t s u b j e c t s showed t r a n -s i t i v e p r e f e r e n c e s a l t h o u g h o n l y two o f t h e s e were t h e same as t h e o v e r a l l group p r e f e r e n c e . A l l 10 o f t h e l k week o l d s had t r a n s i t i v e p r e f e r e n c e s , s i x of t h e s e b e i n g t h e same as t h e o v e r a l l group p r e f e r e n c e . I n summary, f o r b o t h g r o u p s , p r e f e r e n c e s of g r e a t e r s i g n i f i c a n c e were o b t a i n e d w i t h t h e t r i a l s w i t h replacement t h a n w i t h t h e o r i g i n a l t r i a l s . C o r r e c t i n g f o r s i d e p r e f e r -ences i n c r e a s e d t h e s i g n i f i c a n c e l e v e l o f one p r e f e r e n c e f o r t h e e i g h t week o l d group o n l y . T h e r e f o r e , t a k i n g b o t h groups t o g e t h e r , t h e most s i g n i f i c a n t r e s u l t s were o b t a i n e d w i t h t h e t r i a l s w i t h replacement c o r r e c t e d f o r s i d e p r e f e r e n c e s . 85*. TABLE 19 I n d i v i d u a l p r e f e r e n c e s i n t h e P a i r Comparisons E x p e r i -ment i n Terms o f Total L o o k i n g Time f o r T r i a l s w i t h Re-placement c o r r e c t e d f o r s i d e p r e f e r e n c e s . (Experiment I I I )  INDIVIDUAL PREFERENCES SHOWN NUMBER OF RELATION TO . TRANSITIVE INFANTS SHOWING OVERALL GROUP OR PREFERENCE PREFERENCE INTRANSITIVE 8 WEEKS B > A B> G A > C same t r a n s i t i v e B ? A B > C O A d i f f e r e n t t r a n s i t i v e B >A G > B C >A d i f f e r e n t t r a n s i t i v e A > B B > C A ? G d i f f e r e n t t r a n s i t i v e B > A C > B A > C d i f f e r e n t i n t r a n s i t i v e l k WEEKS A > B B > C O A G > B B > A G ^ A d i f f e r e n t i n t r a n s i t i v e same t r a n s i t i v e B > G B ?k O A d i f f e r e n t t r a n s i t i v e 86.. DISCUSSION I . Comparison o f R e s u l t s o f P a i r Comparisons and S i n g l e S t i m u l u s P r o c e d u r e s . " W i t h the p a i r comparisons p r o c e d u r e t h e most s i g n i f i c a n t r e s u l t s were o b t a i n e d w i t h t h e t r i a l s w i t h replacement c o r r e c -t e d f o r s i d e p r e f e r e n c e . The p r e f e r e n c e s of b o t h groups were t r a n s i t i v e and consonant w i t h t h e h y p o t h e s i s t h a t t h e o l d e r the i n f a n t , t h e more complex t h e p a t t e r n he p r e f e r s . For t h e l k week o l d group t h e same o r d e r o f p r e f e r e n c e was o b t a i n e d w i t h b o t h p r o c e d u r e s : the most complex s t i m u l u s was p r e f e r r e d t o b o t h the o t h e r s , and t h e s t i m u l u s of i n t e r -mediate c o m p l e x i t y was p r e f e r r e d t o t h e l e a s t complex p a t t e r n . For the e i g h t week o l d group t h e s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y was s i g n i f i c a n t l y p r e f e r r e d t o t h e o t h e r two w i t h b o t h p r o c e d u r e s . Under the s i n g l e s t i m u l u s p r o c e d u r e t h e most complex s t i m u l u s was s i g n i f i c a n t l y p r e f e r r e d t o t h e l e a s t com-p l e x s t i m u l u s . Under the p a i r comparisons p r o c e d u r e about h a l f o f t h e i n f a n t s p r e f e r r e d A t o C, and t h e o t h e r h a l f p r e f e r r e d C t o A. T h i s c r e a t e s no p r o blem o f i n t r a n s i t i v i t y - e i t h e r a B-A-C o r d e r or a B-C-A o r d e r i s p o s s i b l e . I I . Problems w i t h t h e P a i r Comparisons D e s i g n 1. Methods o f A n a l y z i n g t h e Data M e a s u r i n g l o o k i n g time and c o n v e r t i n g t h i s I n t o p r e f e r e n c e s , f o r i n s t a n c e , i n the use o f t h e s i g n t e s t , or l n p a i r comparison s c a l i n g methods, wastes d a t a . The magnitude of t h e p r e f e r e n c e s i n t e rms o f l o o k i n g t i m e a r e not t a k e n i n t o a c c o u n t . On t h e o t h e r hand, s u i t a b l e methods o f u s i n g l o o k i n g t i m e d a t a have not 8 7 . y e t been found f o r t h i a p r o c e d u r e . Keasen and Hershenson (1963) used a c h i - s q u a r e t e c h n i q u e i n a n a l y z i n g t h e number o f frames of f i l m i n w h i c h an i n f a n t ' s eyes were f i x a t i n g each s t i m u l u s , but t h e t e c h n i q u e was i n a p p r o p r i a t e l y a p p l i e d i n t h e i r e x p e r i m e n t . 1 S c h e f f e ( 1952) has d e v i s e d an a n a l y s i s o f v a r i a n c e f o r p a i r comparisons d e s i g n s but h i s d e s i g n w o u l d need c o n s i d e r a b l e m o d i f i c a t i o n b e f o r e i t c o u l d be a p p l i e d t o s t u d i e a on i n f a n t p e r c e p t i o n . I n t h e experiments by Hershenson ( 1 9 6 k ) , Hershenson, et a l . ( 1 9 6 k ) , and Kessen and Hershenson (1963), p i c t u r e s o f the eyes o f t h e i n f a n t s u b j e c t s were t a k e n a t an.average r a t e o f one frame per s e c o n d . The number of frames i n w h i c h t h e eyes were f i x a t i n g one s t i m u l u s o f a p a i r was r e c o r d e d and compared w i t h the number of frames I n w h i c h I t was e x p e c t e d t h a t t h e eyes would f i x a t e t h a t s t i m u l u s , t a k i n g the i n f a n t ' s s i d e p r e f e r e n c e i n t o a c c o u n t . T h i s was done by means of a c h i -square t e c h n i q u e . Suppose t h a t i n t h e p r e s e n t a t i o n o f s t i m u -l u s p a i r AB, a t i m u l u a A was f i x a t e d i n f o u r frames as gppoaed t o an e x p e c t e d two f r a m e s . U s i n g t h e formulaJ^^'ZJ 3^- a c h i - s q u a r e v a l u e o f 2 would be o b t a i n e d i n t h i s c a s e . However, I f on t h i s t r i a l t h e p i c t u r e a o f the I n f a n t ' a eyea had been t a k e n a t a r a t e of two frames per aecond, i t I a l i k e l y t h a t he would have been f i x a t i n g t h e s t i m u l u s i n 8 frames as opposed t o a n e x p e c t e d k f r a m e s . The c h i - a q u a r e v a l u e o b t a i n e d i n t h i s case w o u l d be ^ ( 8-k ) 2 , t w i c e a s l a r g e as t h e previous v a l u e . Thus, had t h e 11 experiment era photographed t h e i r a u b j e c t a ' eyea at any r a t e o t h e r t h a n at one frame per aecond, t h e y w o u l d have o b t a i n e d c h i - a q u a r e v a l u e s d i f f e r e n t f r o m t h e ones t h e y d i d o b t a i n . Kessen and Hershenson (1963) c l a i m e d t h a t t h e c h i - s q u a r e was used not as a t e s t o f s i g n i f i c a n c e but as a m e t r i c from w h i c h s i g n e d Z s c o r e s were d e r i v e d t o get s c a l e v a l u e s f o r each o f t h e s t i m u l i . However, t e s t s o f s i g n i f i c a n c e were p e r f o r m e d on t h e s e s c a l e v a l u e s and the l a t t e r were com-p l e t e l y dependent upon t h e I n i t i a l c h i - s q u a r e v a l u e s o b t a i n e d . T h i s i s a good example o f t h e misuse o f t h e c h i - s q u a r e t e c h -n i q u e by a p p l y i n g i t t o d a t a w h i c h a r e based on t h e a r b i t r a r y b r e a k i n g i n t o u n i t s o f a c o n t i n u o u s v a r i a b l e , I n t h i s case t i m e . The c h i - s q u a r e v a l u e so o b t a i n e d i s c o m p l e t e l y dependent upon t h e s i z e o f t h e u n i t s i n t o w h i c h t i m e i s d i v i d e d . 88, 2. F i n d i n g C o n t r o l s f o r S i d e P r e f e r e n c e s a. E x p e r i m e n t a l C o n t r o l s B e f o r e p a i r comparisons can be u s e d w i d e l y i n s t u d i e s o f i n f a n t p e r c e p t i o n adequate e x p e r i m e n t a l methods o f c o n -t r o l l i n g head movements o f i n f a n t s must be f o u n d . Young i n f a n t s show s t r o n g s i d e p r e f e r e n c e s i n t h e n a t u r a l r e s t i n g p o s i t i o n s o f t h e i r h e a ds. Perhaps something l i k e t h e s u r g i -c a l sandbags p l a c e d on eaeh s i d e o f t h e i n f a n t ' s head i n a s t u d y by Watson (1965) w o u l d r e s t r a i n g r o s s head movements t o e i t h e r t h e l e f t o r t h e r i g h t . However, even i f t h e s e s i d e p r e f e r e n c e s a r e e x p e r i m e n t a l l y c o n t r o l l e d and t h e i n f a n t ' s head i s w e l l c e n t e r e d , young I n f a n t s do not s c a n t h e i r v i s u a l f i e l d s as much as o l d e r i n f a n t s . T h e i r eyes t e n d t o r e s t on t h e f i r s t s t i m u l u s t h e y see and not t o move t o the o t h e r s t i -mulus o f a p a i r . T h i s can be overcome t o some degree by r e -p e a t i n g t r i a l s u n t i l b o t h members o f a p a i r have been f i x a t e d . But t h e r e i s a drawback i n t h i s a p p r o a c h i n t h a t an experimen-t e r can o n l y r e p e a t a t r i a l so many t i m e s b e f o r e t h e i n f a n t s t a r t s t o f u s s . By t h e n t h e i n f a n t may s t i l l not have l o o k e d at b o t h s t i m u l i . T h i s i s a s e r i o u s p r oblem w i t h v e r y young s u b j e c t s. b. S t a t i s t i c a l C o n t r o l S i d e p r e f e r e n c e can be c o n t r o l l e d somewhat by s t a t i s t i c a l methods. A s i m p l e method i s t h e one employed I n t h e p r e s e n t experiment i n w h i c h t h e average s i d e p r e f e r e n c e per t r i a l was added t o t h e l o o k i n g t i m e f o r t h e s t i m u l u s on t h e n o n - p r e f e r r e d 8 9 . a i d e . A n o t h e r method i s t h e c h i - s q u a r e t e c h n i q u e u s e d by Kessen and Hershenson ( 1 9 6 3 ) i n wh i c h t h e e x p e c t e d f r e q u e n -c i e s t a k e s i d e p r e f e r e n c e i n t o a c c o u n t . As n o t e d , t h o u g h , t h i s t e c h n i q u e i s not a p p r o p r i a t e when " t i m e " i s t h e v a r i a b l e t o be a n a l y z e d . The c h i - s q u a r e t e c h n i q u e would be a p p r o p r i a t e -l y a p p l i e d t o a "number o f f i x a t i o n s " v a r i a b l e , but t h i s r esponse measure i s not as good as f i x a t i o n t i m e f o r d i s -c o v e r i n g i n f a n t p r e f e r e n c e s f o r d i f f e r e n t s t i m u l i . I I I . E v a l u a t i o n o f Procedures and Recommendationa B o t h t h e s i n g l e s t i m u l u s a n d . p a i r comparisons p r o c e d u r e s were r e l i a b l e . The s i n g l e s t i m u l u s p r o c e d u r e was e a s i e r t o r u n t h a n t h e p a i r c o m p a r i s o n s , e s p e c i a l l y w i t h i n f a n t s younger t h a n l k weeks, s i n c e s i d e p r e f e r e n c e was not a pr o b l e m i n t h i s method. However, i f i n t h e p a i r comparisons procedure t h e r e were adequate e x p e r i m e n t a l c o n t r o l s f o r s i d e p r e f e r -ences so t h a t i t was e q u a l l y p r o b a b l e t h a t t h e I n f a n t w o u l d l o o k t o e i t h e r a i d e , t h i a w o u l d r e p r e a e n t an i m p o r t a n t i m -provement f o r t h e p a i r comparisons p r o c e d u r e . I t may be a r -gued t h a t as t h e i n f a n t f i x a t e s one s t i m u l u s he may be p e r -c e i v i n g t h e o t h e r s t i m u l u s p e r i p h e r a l l y , i f not c e n t r a l l y , and t h e r e f o r e may s t i l l be making a c h o i c e between t h e two. However, i t i s as y e t unknown j u s t how much a young i n f a n t can p e r c e i v e p e r i p h e r a l l y , and t h e f a c t t h a t i n t h i s e x p e r i -ment b e t t e r r e s u l t s were o b t a i n e d f r o m t h e replacement t r i a l s t h a n f r o m t h e o r i g i n a l t r i a l s s u g g e s t s t h a t r e l i a n c e s h o u l d not be p l a c e d upon p e r i p h e r a l v i s i o n . 9 0 . I f one had excellent experimental controls f o r side preferences neither r e p e t i t i o n of t r i a l s where the two s t i -muli had not been f i x a t e d nor s t a t i s t i c a l methods of correc-t i o n , which i n any case are always a second best would be necessary. Fair comparisons would then be a v i a b l e method of studying infant attention to various s t i m u l i . It would be experimentally manageable for infants, and s t a t i s t i c a l l y analyzable. Most Important, i t Is t h e o r e t i c a l l y adequate to discover whether infants are responding to the dimension r e -presented in a set of s t i m u l i . However, In experiments where the establishment of dimensionality i s not a prime aim, the single stimulus procedure would probably be more e f f i c i e n t . 91. CHAPTER SIX SUMMARY AND CONCLUSIONS The r e s e a r c h d i s c u s s e d i n t h i s t h e s i s was d e s i g n e d t o i n v e s t i g a t e t h e e f f e c t s o f age on i n f a n t p r e f e r e n c e s f o r s t i m u l i o f d i f f e r e n t c o m p l e x i t y l e v e l s . The h y p o t h e s i s under t e s t was t h a t t h e o l d e r t h e i n f a n t , t h e more complex t h e p a t -t e r n he p r e f e r s . Three e x p e r i m e n t s were p e r f o r m e d , t o t e s t t h i s h y p o t h e s i s . Hershenson ( 196k) p r e s e n t e d t h r e e c h e c k e r b o a r d d e s i g n s c o n t a i n i n g 2 x 2, k x k, and 12 x 12 b l a c k and w h i t e squares t o newborn i n f a n t s . He found t h a t t h e i n f a n t s p r e f e r r e d the s t i m u l i i n . . d e c r e a s i n g o r d e r o f t h e i r c o m p l e x i t y . The purpose o f t h e f i r s t e x p eriment o f t h e p r e s e n t r e s e a r c h was t o compare t h e r e s p o n s e s o f o l d e r i n f a n t s t o w a r d s these s t i m u l i w i t h t h o s e o f Hershenson's newborns. I n Experiment I , 10 and 20 week o l d i n f a n t s were p r e s e n t e d w i t h t h e t h r e e c h e c k e r b o a r d s i n a s i n g l e s t i m u l u s p r e s e n t a t i o n p r o c e d u r e . The l e n g t h o f t i m e d u r i n g w h i c h each s t i m u l u s was f i x a t e d by an i n f a n t was r e c o r d e d . I t was found t h a t t h e i n f a n t s o f b o t h age groups p r e f e r r e d t h e s t i m u l i i n i n c r e a s i n g o r d e r of c o m p l e x i t y . These r e s u l t s complimented t h o s e o f Hershenson (196k) I n s u p p o r t i n g t h e h y p o t h e s i s t h a t o l d e r i n f a n t s p r e f e r s t i m u l i o f g r e a t e r c o m p l e x i t y t h a n do younger i n f a n t s . The f a c t t h a t no d i f f e r e n c e was found i n t h e p r e f e r e n c e s o f t h e 10 and 20 week o l d s was a t t r i b u t e d t o the f a c t t h a t t h e s e t o f s t i m u l i u s e d d i d not encompass a wide enough range o f c o m p l e x i t y . 92. F u r t h e r support o f the h y p o t h e s i s was sought i n E x p e r i -ment I I . U s i n g the same s i n g l e s t i m u l u s p r e s e n t a t i o n p r o c e -dure as t h a t used i n Experiment I , t h r e e , e i g h t , and l k week o l d i n f a n t s were p r e s e n t e d w i t h t h r e e b l a c k and w h i t e c h e c k e r -b oards c o n t a i n i n g 2 x 2 , 8 x 8 , and 2k x 2k s q u a r e s . I n terms of t o t a l f i x a t i o n t i me f o r eack i s t i m u l u s , t h r e e week o l d s p r e f e r r e d t h e l e a s t complex s t i m u l u s most, e i g h t week o l d s p r e f e r r e d t h e s t i m u l u s o f i n t e r m e d i a t e c o m p l e x i t y most, and l k week o l d s p r e f e r r e d t h e most complex s t i m u l u s most. These r e s u l t s s u p p o r t t h e h y p o t h e s i s t h a t the o l d e r t h e i n -f a n t , the more complex the p a t t e r n he: p r e f e r s . S i n c e t h e most complex s t i m u l u s was v e r y n e a r th e t h r e s h -o l d of v i s u a l a c u i t y f o r one month o l d s as measured by F a n t z et a l . ( 1 9 6 2 ) , i n Experiment I I t h e t h r e e week o l d s u b j e c t s were a l s o p r e s e n t e d w i t h a p l a i n g r a y square o f the same s i z e and a l b e d o as t h e c h e c k e r b o a r d s . The t h r e e week o l d s d i d not l o o k s i g n i f i c a n t l y l o n g e r at t h e most complex c h e c k e r b o a r d t h a n a t t h e g r a y s q u a r e . T h i s r e s u l t s s u g g e s t e d t h e p o s s i b i -l i t y t h a t t h e y c o u l d not d i s t i n g u i s h t h e most complex c h e c k e r b o a r d from a u n i f o r m l y gray s q u a r e . T h i s p o s s i b i l i t y was f u r t h e r s u p p o r t e d by Haynes et a l . (1965) who f o u n d t h a t t h e accommodation o f i n f a n t s o f l e s s t h a n one month was l o c k e d a t a d i s t a n c e o f 7 i M . . ' To t e s t t h i s p o s s i b i l i t y a c o n t r o l s t u d y l n w h i c h t h e s t i m u l i a r e p r e s e n t e d a t a d i s t a n c e o f 7jgn i s w a r r a n t e d . At t h i s d i s t a n c e t h r e e week o l d s s h o u l d be a b l e t o f o c u s t h e s t i m u l i c l e a r l y . A f a i l u r e o f t h e t h r e e week o l d s t o f i x a t e t h e 2k x 2k c h e c k e r b o a r d l o n g e r t h a n the g r a y square 93. p r e s e n t e d at t h i s d i s t a n c e would i n d i c a t e t h a t t h e i r v i s u a l a c u i t y i s not d e v e l o p e d enough f o r them t o p e r c e i v e t h i s p a t t e r n . One s u b s i d i a r y purpose o f t h e r e s e a r c h was t o compare v a r i o u s r e s p o n s e measures, namely t o t a l f i x a t i o n t i m e , l e n g t h o f f i r s t f i x a t i o n , and r a t e o f h a b i t u a t i o n . The l a t t e r r e -sponse measure was o f no v a l u e i n d e t e c t i n g t h e p r e f e r e n c e s o f t h e I n f a n t s f o r the s t i m u l i . The t o t a l f i x a t i o n t i m e and l e n g t h o f f i r s t f i x a t i o n measures gave t h e same p a t t e r n s o f p r e f e r e n c e w i t h each age grou p . W i t h b o t h measures an i n -c r e a s i n g p r e f e r e n c e f o r c o m p l e x i t y w i t h age was f o u n d . How-e v e r , i t was f e l t t h a t t o t a l f i x a t i o n t i m e was t h e more s e n -s i t i v e and r e l i a b l e o f the two measures. A n o t h e r purpose o f t h i s r e s e a r c h was t o compare two ex-p e r i m e n t a l p r o c e d u r e s i n t h e study o f i n f a n t a t t e n t i o n — s i n g l e s t i m u l u s and p a i r c o m p a r i s o n s . Kessen and Hershenson (1963) have a r g u e d t h a t the s i n g l e s t i m u l u s p r o c e d u r e may be i n a d e q u a t e i n i n f a n t s t u d i e s . They c l a i m t h a t o n l y i f t r a n -s i t i v i t y i s demonstrated t h r o u g h a p a i r comparisons d e s i g n can th e e x p e r i m e n t e r be s u r e t h a t t h e i n f a n t i s r e s p o n d i n g t o a s t i m u l u s d i m e n s i o n . However, t h e e x i s t e n c e o f s t r o n g s i d e p r e f e r e n c e s i n young i n f a n t s , and t h e f a c t t h a t t h e y do not r e a d i l y s can t h e i r v i s u a l f i e l d make p a i r comparisons a d i f f i -c u l t p r o c e d u r e t o r u n w i t h young i n f a n t s . I n Experiment I I I an attempt was made t o o b t a i n d a t a on t r a n s i t i v i t y w h i l e 9k. a v o i d i n g t h e s e p r a c t i c a l d i f f i c u l t i e s . The study employed a m o d i f i e d p a i r comparisons d e s i g n i n w h i c h t r i a l s on •which b o t h s t i m u l i of a p a i r had not been f i x a t e d were r e p e a t e d , and i n w h i c h a s i m p l e s t a t i s t i c a l c o r r e c t i o n f o r s i d e p r e -f e r e n c e was employed i n t h e a n a l y s i s o f the d a t a . E i g h t and l k week o l d s were p r e s e n t e d w i t h the same 2 x 2 , 8 x 8 , and 2k x 2k c h e c k e r b o a r d s used I n Experiment I I . The r e s u l t s ob-t a i n e d were oonsonant w i t h t h o s e o b t a i n e d i n Experiment I I and s u p p o r t i v e o f t h e h y p o t h e s i s . The e i g h t week o l d group p r e f e r r e d t h e s t i m u l u s of i n t e r m e d i a t e c o m p l e x i t y over the o t h e r two, w h i l e t h e l k week o l d group p r e f e r r e d t h e most complex s t i m u l u s o v e r t h e o t h e r s . The o v e r a l l p r e f e r e n c e s o f b o t h groups were c o m p l e t e l y t r a n s i t i v e . However, b e f o r e u s i n g t h e p a i r comparisons p r o c e d u r e e x t e n s i v e l y i n s t u d i e s o f a t t e n -t i o n i n young i n f a n t s , adequate e x p e r i m e n t a l c o n t r o l s f o r s i d e p r e f e r e n c e s need t o be f o u n d , and b e t t e r methods o f a n a l y z i n g t h e d a t a d e v e l o p e d . The r e s u l t s o f t h e e x p e r i m e n t s p r e s e n t e d i n t h i s t h e s i s were c o n g r u e n t , and were s u p p o r t i v e o f t h e h y p o t h e s i s t h a t i n c r e a s e d p r e f e r e n c e f o r c o m p l e x i t y comes w i t h age. The r e -s u l t s can be p a r t i a l l y e x p l a i n e d i n terms o f Dember and E a r l ' s t h e o r y (1957) o f t h e c o m p l e x i t y o f b o t h t h e s t i m u l u s and t h e o r g a n i s m . I n terms o f t h i s t h e o r y , i n t h e p r e s e n t experiment t h e s t i m u l u s most p r e f e r r e d by an age group was t h e one o f t h e se t w h i c h was most s i m i l a r t o t h e pacer s t i m u l u s f o r i n f a n t s o f t h a t a g e. S t i m u l u s - o r g a n i s m concordance i n l e v e l s o f com-p l e x i t y was o b t a i n e d , and t h u s some o f t h e ground work f o r t h e v 95". t e s t i n g of the relevance of Dember and Earl's theory to the area of infant perception has been l a i d . This done, inves-tigations of environmental effects on an infant's i d e a l com-ple x i t y l e v e l can begin. 9 6 . BIBLIOGRAPHY Ames, E l i n o r W., & S i l f e n , C a r o l e K. M e t h o d o l o g i c a l i s s u e s i n t h e s t u d y o f age d i f f e r e n c e s i n i n f a n t s 1 a t t e n t i o n t o s t i m u l i v a r y i n g i n movement and c o m p l e x i t y . Paper p r e -s e n t e d a t t h e b i e n n i a l m e e t i n g o f t h e S o c i e t y f o r Re-s e a r c h i n C h i l d Development, M i n n e a p o l i s , March, 1965* A t t n e a v e , P. Symmetry, I n f o r m a t i o n , and memory f o r p a t t e r n s . Amer. J . P s y c h o l . , 1 9 5 5 , 6j3» 2 0 9 - 2 2 2 . A t t n e a v e , P. P h y s i c a l d e t e r m i n a n t s o f t h e judged c o m p l e x i t y o f shapes. J . exp. P s y c h o l . , 1 9 5 7 , 5__, 2 2 1 - 2 2 7 . B a r t l e y , S.H. P r i n c i p l e s of P e r c e p t i o n . Hew Y o r k : Harper & B r o s . , 195BT B e r l y n e , D.E. The i n f l u e n c e o f c o m p l e x i t y and n o v e l t y in v i s u a l f i g u r e s on o r i e n t i n g r e s p o n s e s . J . exp. P s y c h o l . , 1 9 5 8 , 5j_, 2 8 9 - 2 9 6 . (a) B e r l y n e , D.E. The i n f l u e n c e o f a l b e d o and c o m p l e x i t y o f s t i -m u l i i n v i s u a l f i x a t i o n s i n t h e human i n f a n t . B r i t . J . P s y c h o l . , 1 9 5 8 , _ t _ , 3 1 5 - 3 1 8 . (b) ' " B e r l y n e , D.E. C o n f l i c t , A r o u s a l , and C u r i o s i t y . New Y o r k : M c G r a w - H i l l , i 9 6 0 . C a n t o r , G.N, Responses o f i n f a n t s and c h i l d r e n t o complex and n o v e l ' s t i m u l a t i o n . I n L . P . L I p s e t t , & C.C. S p i k e r , Advances i n C h i l d Development and B e h a v i o r , V o l . 1, New Y o r k : Academic P r e s s , 1963. C a n t o r , G.N., C a n t o r , J.H., & D i t r i c h s , R. O b s e r v i n g b e h a v i o r i n p r e s c h o o l c h i l d r e n as a f u n c t i o n o f s t i m u l u s c o m p l e x i -t y . C h i l d Develpm., 1 9 6 3 , _ J _ , 6 8 3 - 6 8 9 . Deese, J . 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M a t u r a t i o n o f p a t t e r n v i s i o n i n i n f a n t s d u r i n g t h e f i r s t s i x months. J . Comp. p h y s i o l . P a y e h o l . . 1 9 6 2 , 5 5 , 907-917. P e h r e r , E.V. An i n v e s t i g a t i o n o f t h e l e a r n i n g o f v i s u a l l y p e r c e i v e d f o r m s . Amer. J . P s y c h o l . , 1935* k l * 1 8 7 - 2 2 1 . F r e n c h , R.S. I d e n t i f i c a t i o n o f dot p a t t e r n s f r o m memory as a f u n c t i o n o f c o m p l e x i t y . J . exp. P s y c h o l . , 1954» kZ> 2 2 - 3 1 . " Haynes, H., W h i t e , B.L., & H e l d , Rv V i s u a l accommodation i n human i n f a n t s . S c i e n c e , 1 9 6 5 , l k 8 , 5 2 8 - 5 3 0 . Hershenson, M. V i a u a l d i s c r i m i n a t i o n I n t h e human newborn. J . comp. p h y s i o l . P s y c h o l . , 1 9 6 k , j_ 8 , 2 7 0 - 2 7 6 . 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