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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 I N INFANTS INATTENTION TO S T I M U L I yARYING I N COMPLEXITY  by WENDY MARGARET BRENNAN B.A. H o n s . , M a n c h e s t e r U n i v e r s i t y , I96J4.  A T H E S I S SUBMITTED I N P A R T I A L FULFILMENT THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS  i n t h e Department of Psychology  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 to the required  standard  THE U N I V E R S I T Y OF B R I T I S H June,  1965  COLUMBIA  OF  In p r e s e n t i n g the  r e q u i r e m e n t s f o r an  British  Columbia,  available for mission  representatives,,  cation  of  w i t h o u t my  this  study.  by  the  Department The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, C a n a d a  Columbia  of  University  of  s h a l l make i t  thesis  Head o f my  permission.  fulfilment  I f u r t h e r agree that  this  for financial  the  Library  It i s understood  thesis  written  the  copying of  granted  in p a r t i a l  advanced degree at  r e f e r e n c e and  be  thesis  I agree that  for extensive  p u r p o s e s may his  this  copying or  shall  not  per-  scholarly  Department or  that  gain  for  freely  be  by publi-  allowed  ii  ABSTRACT  The research presented i n t h i s thesis was designed to investigate the e f f e c t s of age on infant preferences for s t i m u l i of d i f f e r e n t complexity l e v e l s .  The hypothesis was  that the older the infant, the more complex the pattern he prefers. Hershenson (196i|.) presented three checkerboard containing 2 x 2 ,  designs  Ij. x if, and 12 x 12 black and white  to newborn i n f a n t s .  squares  He found that the infants preferred the  s t i m u l i i n decreasing order of their complexity. of the f i r s t experiment  The purpose  of the present research was to com-  pare the responses of older Infants towards these s t i m u l i with those of Hershenson's newborns.  In Experiment  I, 10  and 20 week o l d infants were presented with the three checkerboards i n 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 s t i m u l i i n increasing order of t h e i r e complexity.  These results complemented those of Hershenson  (I96I4.} In supporting the hypothesis that older infants prefer stimuli of greater complexity than do younger i n f a n t s .  The  fact that no difference was found i n the preferences of the 10 and 20 week olds was a t t r i b u t e d to the fact that the set of s t i m u l i used did not encompass a wide enough range of complexity. Further support of the hypothesis was sought on Experiment I I .  Using the same single stimulus presentation  ill procedure as t h a t used i n Experiment I , t h r e e , e i g h t and ll]. 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 three b l a c k and w h i t e checkerboards c o n t a i n i n g 2 x 2 ,  and 2l\. x 2ij. squares.  8x8,  In terms of t o t a l f i x a t i o n time f o r each s t i m u l u s , week o l d s p r e f e r r e d the l e a s t  three  complex s t i m u l u s , e i g h t week  o l d s p r e f e r r e d the s t i m u l u s of i n t e r m e d i a t e  complexity,  li). week olds p r e f e r r e d the most complex s t i m u l u s . sults  support  the hypothesis  and  These r e -  t h a t the o l d e r the i n f a n t , the  more complex the p a t t e r n her p r e f e r s . However, t h r e e week olds did not longer  look  significantly  at the c% x 2J4. checkerboard than at a p l a i n  square w i t h which they were a l s o p r e s e n t e d . the p o s s i b i l i t y that they this  stimulus.A One  This  gray suggests  c o u l d not p e r c e i v e the p a t t e r n o f  c o n t r o l study seems warranted.  s u b s i d i a r y purpose of the r e s e a r c h was  to compare  v a r i o u s response measures, namely t o t a l f i x a t i o n time, l e n g t h of f i r s t  f i x a t i o n , and  t e r response measure was  rate of habituation.  o f no value i n d e t e c t i n g the  f e r e n c e s of the i n f a n t s f o r the s t i m u l i . time and l e n g t h o f f i r s t patterns  of p r e f e r e n c e w i t h each age  However, i t was  felt  group.  f o r complexity  total  pre-  fixation  W i t h both meaw i t h age  was  t h a t t o t a l f i x a t i o n time was  more s e n s i t i v e and r e l i a b l e o f the two  procedures i n the study  the  measures.  Another purpose o f the r e s e a r c h was perimental  The  lat-  f i x a t i o n measures gave the same  sures an i n c r e a s i n g p r e f e r e n c e found.  The  to compare two  of i n f a n t a t t e n t i o n -  ex-  ; iv 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 a n d IIL week o l d i n f a n t s w e r e p r e s e n t e d 8x8,  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  sons p r o c e d u r e . those  with the 2 x 2 ,  obtained  pothesis.  compari-  The r e s u l t s o b t a i n e d w e r e c o n s o n a n t i n Experiment  I I and s u p p o r t i v e  o f the h y -  The e i g h t week o l d g r o u p p r e f e r r e d t h e s t i m u l u s  of intermediate  complexity  over the other two, w h i l e the  I i i week o l d g r o u p p r e f e r r e d t h e most c o m p l e x , s t i m u l u s the  with  over  others. 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 nthis  were congruent, 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 increased preference  f o r complexity  comes w i t h a g e .  thesis that  V  TABLE OP CONTENTS Page Chapter 1.  Introduction  •  Chapter 2.  Experiment  I......  Chapter 3 .  Experiment  II....  Chapter i i .  Comparison o f Response Measures o b t a i n e d i n Experiment  1 •  ILO £2  II.....  Chapter 5«  Experiment  Chapter 6 .  Summary and C o n c l u s i o n s . . . Bibliography  III.  68 78 91 96  vi L I S T OP TABLES Table 1  Table 2  Table 3  Table k  Table 5  Table 6  Table 7  Table 8  Table 9  Page  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 10 and 20 week o l d I n f a n t s , a v e r a g e d o v e r s u b j e c t s . (Experiment I )  .1+.6  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 a t each o f t h e t h r e e s t i m u l i b y 1 0 week o l d g r o u p . (Experiment I )  kl  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 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 b y 2 0 week o l d group. (Experiment I ) . . •  kl  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 a t e a c h o f t h e t h r e e s t i m u l i by 1 0 a n d 2 0 week o l d g r o u p s ( E x p e r i m e n t I ) . . . . . .  I4.9  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 e a c h o f t h e s t i m u l i b y 3, 8 , a n d U4. week o l d i n f a n t s , a v e r a g e d o v e r s u b j e c t s . (Experiment I I ) . . . .  £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 , a n d l k week o l d g r o u p s . (Experiment I I J.  ...56  Summary t a b l e o f a n a l y s i s t o t a l l o o k i n g t i m e spent of t h e stimulus patterns b y t h r e e week o l d g r o u p .  of variance of l o o k i n g at each ( i n c l u d i n g gray) (Experiment I I )  5*9  Summary t a b l e o f a n a l y s i s t o t a l l o o k i n g time spent of t h e stimulus patterns by t h r e e week o l d g r o u p .  o f variance of l o o k i n g at each (excluding gray) (Experiment I I )  £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 time 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 b y e i g h t week o l d group. (Experiment I I )  60  T a b l e 10  T a b l e 11  T a b l e 12  T a b l e 13  T a b l e U4.  vii Page  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 r e e s t i m u l u s p a t t e r n s b y f o u r t e e n week o l d g r o u p . ( E x p e r i m e n t II).  60  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 t h e t h r e e s t i m u l i b y 3, 8, a n d L i i week o l d i n f a n t s , a v e r a g e d o v e r s u b j e c t s . (Experiment I I ) .  69  Summary t a b l e o f two-way a n a l y s i s o f variance o f length of 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 b y 3, 8* a n d I i i week o l d g r o u p s . (Experiment I I )  69  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 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 b y 3 week o l d g r o u p (Experiment I I )  •  72  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 of each o f t h r e e s t i m u l i by 8 week o l d g r o u p . ( E x p e r i m e n t II) . ....  72  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 b y LLj. week o l d g r o u p . ( E x p e r i m e n t II)  72  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 the 1 2 - t r i a l series  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 r e s p o n s e measures 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 data (Experiment I I I ) . . . .  83  I n d i v i d u a l p r e f e r e n c e s i i i t h e p a i r comp a r i s o n s experiment (Experiment I I I ) . . . . . . .  85  T a b l e 15  T a b l e 16  T a b l e 19  viii L I S T OF FIGURES  Page  Figure  1.  The s t i m u l i u s e d b y B e r l y n e  (195*8 b )  15  Figure  2.  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 three s t i m u l i by 10 a n d 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 )  ii8  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 e a c h o f t h e s t i m u l i b y 3# 8 , a n d 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  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. a n d 2 0 week o l d i n f a n t s , averaged over subjects (Experiment I I ) . . . . .  63  The l o o k i n g t i m e I n s e c o n d s o f f i r s t f i x a t i o n s of t h e three checkerboards by t h e 3 , 8 , a n d l i i week o l d g r o u p s , averaged over s u b j e c t s . (Experiment I I ) . . . .  70  Figure  Figure  Figure  3»  11.  5»  Ix ACKNOWLEDGEMENTS The  author wishes t o express h e r s i n c e r e  t o D r . E . W. Ames f o r h e r g e n e r o u s a s s i s t a n c e  gratitude and guidance  throughout a l l phases o f t h e r e s e a r c h . T h a n k s a r e a l s o d u e t o D r . R.Knox f o r h i s h e l p f u l criticisms  i n the preparation  Moore f o r h i s a s s i s t a n c e  o f t h e t h e s i s , t o M r . Ron  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 The in-aid  research  assistance.  i n t h i s t h e s i s was s u p p o r t e d b y a  of theAssociate  Committee o n E x p e r i m e n t a l  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).  grant-  Psychology,  CHAPTER ONE INTRODUCTION  Thia t h e s i s i s concerned w i t h t h e a t t e n t i o n p a i d by infants t o stimuli of different fically,  complexities:  i t investigates t h e v i s u a l f i x a t i o n responses 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 complexity  levels.  This  chapter  literature relevant t o this I  More s p e c i -  serves  of varying  as a r e v i e w  of the  topic.  D E F I N I T I O N S 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 psychology i s f i n d i n g a concise d e f i n i t i o n o f that  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 a n d o p e r a t i o n a l l y manageable.  S i n c e t h i s t h e s i s i s c o n c e r n e d w i t h age d i f f e r e n c e s  i n the l e v e l of stimulus is f r u i t f u l  complexity  p r e f e r r e d by i n f a n t s , i t  to look at the various definitions  of complexity  which 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 ions Berlyne  (I960) attempts t o d e f i n e t h e concepts 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 complexity  w h i c h he f e e l s " a r e  among o u r 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 lection"  (Berlyne, i960,  p. 1 8 ) .  stimulus v a r i a b l e s , complexity t i o n a l problems.  He a d m i t s t h a t o f t h e s e  presents  I n general, complexity  of v a r i e t y or d i v e r s i t y  the severest  defini-  r e f e r s t o t h e amount  i n a stimulus pattern.  Complexity  2. Increases  w i t h t h e number o f d i s t i n g u i s h a b l e e l e m e n t s 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 elements. 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 which s e v e r a l ments a r e r e s p o n d e d t o as a u n i t , d e f i n i t i o n by c l a i m i n g t h a t ber  Berlyne  "complexity  ele-  concludes his  d e p e n d s o n t h e num-  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 -  cal parts"  (Berlyne, I960, p. 3 9 ) .  According  t o Dember  (I960)  " t h e more c o m p l e x  stimulus  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 c o m p l e x " (Dember, i 9 6 0 , p p . 3 5 2 - 3 5 3 ) . tics  of complexity  heterogeneity, Walker  T h e few c h a r a c t e r i s -  w h i c h h e s u g g e s t s a r e movement,  spatial  I n c o n g r u i t y , and change.  (196k) suggests t h a t  stimulus complexity  f u n c t i o n o f t h e number o f s t i m u l u s  Is a  elements i n an a r r a y and  of the p a t t e r n i n g o f these elements.  Pattern i s regarded i n  terms o f t h e r e l a t i o n s between t h e elements.  He p o i n t s o u t  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 stimulus  i s o f f e r e d b y 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 c a n b e o b t a i n e d information theory. the  greater  The g r e a t e r  the stimulus  the index  of uncertainty,  complexity.  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 s e v e r a l points o f concordance. Walker  from  Both Berlyne  complexity  have  (i960) and  ( 1 9 6 k ) a g r e e t h a t t h e number o f e l e m e n t s i n a  stimulus  3. c o n t r i b u t e s t o i t s complexity,  Dember's (I960) "heteroge-  n e i t y " i s probably much l i k e B e r l y n e ' s  (I960) " d i s s i m i l a r i t y  between t h e elements"• Probably the a r e a o f g r e a t e s t 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 t h e f a c t that they are a l l u n s a t i s f a c t o r y from an o p e r a t i o n a l s t a n d p o i n t .  The d e f i n i -  t i o n s o f B e r l y n e and Dember b o t h l a c k the p r e c i s i o n needed t o convert them i n t o workable bases o f measurement• suggests  Walker  the use o f i n f o r m a t i o n t h e o r y as a b a s i s f o r con-  s t r u c t i n g s t i m u l i o f v a r y i n g complexity l e v e l s , b u t , as w i l l be seen i n the next  s e c t i o n t h i s has not proven t o be as use-  f u l t o t h e problem o f stimulus complexity as he suggested i t might be.  By means of g e n e r a l i t i e s , each author i s p r e s e n t i n g  h i s own i n t u i t i v e idea o f stimulus c o m p l e x i t y .  Understanding  o f the d e f i n i t i o n s can, t h e r e f o r e , only be i n t u i t i v e as w e l l , and very l i t t l e advance i s made i n t h e search f o r a d e f i n i t i o n of stimulus complexity which makes t h e i n d i c e s o f complexity explicit  and amenable t o measurement.  Some experimenters  working on the e f f e c t s o f complexity  on l e a r n i n g and memory i n a d u l t s have attempted  to define  complexity and vary i t s y s t e m a t i c a l l y . T h e i r experiments a r e p r e s e n t e d i n the next 2.  section.  D e f i n i t i o n s o f Complexity i n Experiments Adult L e a r n i n g and Memory Moffett  on Human '  (1963) has reviewed the v a r i o u s s t u d i e s concerned  w i t h the i n f l u e n c e o f complexity on a d u l t l e a r n i n g and  memory, and  this section w i l l  the various stimulus under the  c h a r a c t e r i s t i c s w h i c h were  experimental  affected stimulus  serve merely t o point  assumption that these  out  manipulated  characteristics  complexity.  Many e x p e r i m e n t e r s  agree that complexity  t h e number o f p a r t s t h a t make up  a figure.  varies with  For  instance,  D e e s e ' s (1956) d e f i n i t i o n o f "number o f c h a n g e s i n  contour"  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 u s e d by  Fehrer  (1935), F r e n c h (195k), and A t t n e a v e  (1955K  This  is a  mulus c h a r a c t e r i s t i c w h i c h , i n w h a t e v e r manner one define i t , i s readily teristic ity ty  quantifiable.  i s symmetry ( A t t n e a v e ,  1955;  Fehrer,  as r e a d i l y  elements i n a f i g u r e .  of  1935)* o r  ( D e e s e , 1956), w h i c h c o n c e r n s t h e c o m p l e x i t y  ment o f t h e  wishes  Another stimulus  w h i c h many f e e l c a n be u s e d as a n i n d e x  of  However, t h i s  stito  charac-  complexregulariarrange-  index  a m e n a b l e t o measurement a s i s t h e number o f  i s not parts  index. Several researchers complexity  no  1955).  direct  mation contained mulus as  one  measure o f  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  (e.g., Weinstein, t h e r e was  claim that  However, A t t n e a v e  relationship  j u d g e d by  the  in a  figure  (1957) f o u n d t h a t  between the  I n a s t i m u l u s and  stimulus  amount o f  complexity  infor-  of the  sti-  adults.  I n g e n e r a l , I t was  found i n these  l e a r n i n g and memory t h a t t h e  s t u d i e s o f human a d u l t  only d e f i n i t i o n s  of  complexity  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 t h o s e  in  w h i c h t h e number o f e l e m e n t s m a k i n g up t h e s t i m u l u s was sidered.  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 theory 1955  and  1957)  were u n s u c c e s s f u l .  m a t i o n t h e o r y does not  (e.g.,  This suggests  Attneave,  that  infor-  p r o v i d e the easy s o l u t i o n t o the  b l e m s 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 workers  con-  pro-  a n t i c i p a t e d by many  (e.g., Walker, 196k).  Still,  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  are  many more ways t o c r e a t e c o m p l e x s t i m u l i t h a n w e r e u s e d i n the experiments next  discussed i n this  s e c t i o n reviews  section.  Therefore,  s t u d i e s i n v e s t i g a t i n g t h e amount  the of  v i s u a l a t t e n t i o n paid to s t i m u l i varying i n complexity 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 The  v i s u a l a t t e n t i o n response  work undertaken 3.  i n this  c o r d was  The  (1958  on  Visual '  a), pairs of stimulus  simultaneously to adult subjects.  f i x a t e d , and  sixth.  i n each of f i v e  E a c h c a t e g o r y was  of complexity.  Re-  i n w h i c h e a c h member o f  o f w h i c h member was  fixated  first.  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  of s t i m u l i  pect  i n Research  made o f t h e l e n g t h o f t i m e  t h e p a i r was  the  thesis.  by B e r l y n e  f i g u r e s were p r e s e n t e d  therein.  m e a s u r e i s more r e l e v a n t t o  D e f i n i t i o n s of Complexity Attention i n Adults. I n an e x p e r i m e n t  i n or-  c a t e g o r i e s and  two  pairs  p a i r s i n the  meant t o r e p r e s e n t a d i f f e r e n t  For each p a i r w i t h i n a category,  one  as-  6 s t i m u l u s was "more c o m p l e x " t h a n t h e o t h e r * of complexity used  The s i x a s p e c t s  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 pair consisted  o f t h e same t y p e o f m a t e r i a l , b u t one c o n s i s t e d o f more o f that material than the others* (2) I r r e g u l a r i t y o f s h a p e - e a c h 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 s h a p e s y m m e t r i c a l a l o n g t w o o r more a x e s , a n d one i r r e g u l a r non-symmetrical  shape.  (3) I r r e g u l a r i t y o f a r r a n g e m e n t - b o t h members o f a 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 e l e m e n t s  pair  b u t i n one  f i g u r e t h e y were arranged 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  (k) H e t e r o g e n e i t y o f elements  scattered.  - one f i g u r e  i n each  pair  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 , w h e r e a s 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 elements  i n a similar spatial  heterogeneous  arrangement.  (5) I n c o n g r u i t y - e x e m p l i f i e d b y s u c h f i g u r e s phant's  massive  h e a d on a v e r y f r a g i l e  (6) I n c o n g r u o u s  as a n e l e -  body.  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  rabbit's  head f o r m i n g t h e f r o n t p a r t o f an automobile. S e v e r a l o f these I n d i c e s were encountered  i n the previous  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 t h e number o f parts  index i n t h e experiments  o n l e a r n i n g a n d memory;  g u l a r i t y o f s h a p e e q u a l s symmetry a s u s e d b y F e h r e r and  r e g u l a r i t y as u s e d b y D e e s e (1956).  elements  irre-  (1935)  Heterogeneity of  and d i s s i m i l a r i t y between elements  were mentioned  by  Dember ( I 9 6 0 ) a n d B e r l y n e stract  (i960) r e s p e c t i v e l y I n t h e i r ab-  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  of elements encountered  i nthis  o f c o m p l e x i t y a r e new t o t h i s  study.  The o t h e r  discussion.  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 seem t o be t h e u n i q u e c r e a t i o n o f B e r l y n e .  aspects  juxtaposition, Both o f these  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 . ever, i n t h i s  experiment  How-  (195>8 a ) was a b l e t o o p e r a -  Berlyne  t i o n a l i z e h i s d e f i n i t i o n s a n d 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 of  complexity. k.  D e f i n i t i o n s o f Complexity attention i n Children Cantor  (I963) has reviewed  i n Experiments  on V i s u a l  s e v e r a l studies 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 .  This s e c t i o n  presents a b r i e f d i s c u s s i o n of the various d e f i n i t i o n s of complexity used i n these In  experiments.  studying the preferences f o r stimulus complexity I n  r e t a r d a t e s a n d i n n o r m a l c h i l d r e n , S p i t z and Hoats  (196l)  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 a s d e f i n e d by Berlyne  (19S>8 a ) I n h i s e x p e r i m e n t  with adults.  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 e l e m e n t s 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 , heterogeneity o f the elements,  irregularity of  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 a n d i n c o n g r o u s position.  juxta-  T h e p a i r s o f s t i m u l i u s e d 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 novelty than I n complexity" I n an experiment  d i f f e r i n g more i n  ( C a n t o r , 1963, p . 13)•  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 differently  coloured rectangles appearing  H e r e c o m p l e x i t y was d e f i n e d s o l e l y  o n 5" x 8" c a r d s *  l n t e r m s o f t h e amount  of m a t e r i a l involved i n the s t i m u l i . Cantor,  C a n t o r , a n d D I t r i c h s (1963) c o n d u c t e d  periment  i n w h i c h no a t t e m p t  plexity  variable or identify  tion of their plexity  an e x -  was made t o q u a n t i f y t h e comi t s indices.  s i x stimulus t r i a d s  However, i n s p e c -  r e v e a l s t h a t s t i m u l u s com-  seems t o h a v e b e e n i n t u i t i v e l y d e f i n e d i n t e r m s o f  number o f e l e m e n t s ,  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  s h a p e , amount o f c o n t o u r , a n d number o f l i g h t - d a r k  transi-  tions. In the 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  section,  the 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 tions o f stimulus complexity. their definitions Berlyne  S p i t z and Hoats  a n d most o f t h e i r  defini-  (1961) t o o k  stimuli directly  from  (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 along t h i s dimension  and t h e r e b y  d i s c o v e r e x a c t l y what  of 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. and  intuitive definitions  Cantor  level  Despite t h e vague  o f c o m p l e x i t y u s e d i n h i s own  study  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 s a y s : "With, r e g a r d 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 delimited  s i m p l e and r i g o r o u s l y  stimulus properties which hopefully w i l l  supplant  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 valent" 5>»  ( C a n t o r , 1963, p . 2 1 ) .  D e f i n i t i o n s o f Complexity I n Experiments V i s u a l A t t e n t i o n of Infant Primates This s e c t i o n reviews  primate  pre-  on  s t u d i e s on a t t e n t i o n o f the infant  t o v i s u a l s t i m u l i v a r y i n g i n complexity i n order t o  s e e 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 t h e m .  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 a s 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 u n d e r a y e a r o l d .  I n gen-  e r a l , a s u b j e c t was s h o w n 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 a t 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 o n h i s b a c k o r was p r o p p e d up i n some way. His responses responses  t o e a c h s t i m u l u s were r e c o r d e d .  Usually the  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  t i m e h e f i x a t e d e a c h s t i m u l u s , o r t h e member o f a p a i r ated f i r s t  - b u t i n some c a s e s  o t h e r measures such a s arm  movement o r h e a r t r a t e w e r e a l s o These experiments l i  fall  recorded.  on i n f a n t a t t e n t i o n t o complex  stimu-  i n t o a n a t u r a l order a c c o r d i n g t o t h e degree o f con-  scious manipulation o f various aspects o f complexity ted  fix-  on t h e p a r t o f t h e r e s e a r c h e r .  ments i n w h i c h a c o n g l o m e r a t i o n  exhibi-  They range f r o m e x p e r i -  o f p a t t e r n s were p r e s e n t e d t o  10 the  subjects with l i t t l e  o r no  attention paid to t h e i r  l a t i v e c o m p l e x i t i e s , to studies i n which aspects complexity  were not  o n l y d e f i n e d and  a l s o p r e c i s e l y measured. creasing order  of their  The  of  d i s c u s s e d but  studies are  re-  stimulus were  dealt with i n i n -  s o p h i s t i c a t i o n with respect  to  the  complexity v a r i a b l e . ( a ) P o s t 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 - of Stimulus Complexity. In studying the e f f e c t  of medication  R e s u l t s i n terms during labour  on  a t t e n t i o n i n n e w b o r n 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  of three  dots,  and  s t i m u l i , a picture of a face, a die with three  a blank  stimulus  card, three times  procedure.  claimed  minute i n a s i n g l e  In terms of the average t o t a l  time f o r each stimulus the for the three  f o r one  order  of d e c r e a s i n g  preference  s t i m u l i were f a c e , d i e , and b l a n k .  that these  ences i n s t i m u l u s  r e s u l t s c o u l d be complexity  alone  fixation  Stechler  e x p l a i n e d by t h e and  concluded  newborn i n f a n t o r i e n t s l o n g e r toward sources  differ-  that  the  of greater  re-  tinal stimulation. In 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  l e v e l s o f t h e s t i m u l i was  made.  complexity  I t w o u l d appear t h a t  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 the r e s u l t s o b t a i n e d , i n v e s t i g a t o r e x a m i n e d h i s s t i m u l i and fered i n complexity, and  decided  in the  that they  dif-  t h e f a c e b e i n g more c o m p l e x t h a n t h e  t h e d i e more c o m p l e x t h a n t h e b l a n k .  He  t h e n gave  a  die,  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 used. t h e s e s t i m u l i do n o t v a r y m e r e l y they d i f f e r  I n complexity.  For Instance,  i n a l b e d o as w e l l , a n d 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 Fantz  Unfortunately,  dimension.  (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  were n o t c h o s e n 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 . pioneer i nthe f i e l d o f v i s u a l attention i ninfants, was m a i n l y  concerned  which  As a Fantz  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  pre-  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 w e r e p r e s e n t a s e a r l y as t w o months o f a g e .  He o p p o s e d 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 v a g u e f i gures w i t h b l u r r e d o u t l i n e s . did  Thus, t h e problem  o f complexity  not concern h i m d i r e c t l y i ndesigning h i s i n i t i a l e x p e r i -  ments ( e . g . , 1958). presence  What h e was m a i n l y i n t e r e s t e d i n was t h e  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 a n d h a v e b e e n i n t e r p r e t e d i n t e r m s o f c o m p l e x i t y and so f o r p r e s e n t purposes Stechler In  i nthis first one s t u d y F a n t z  h e may b e c a t e g o r i z e d w i t h  category. (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  the  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 times 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 n d two s i z e s o f p l a i n square, a c r o s s a n d a c i r c l e , and two i d e n t i c a l In  another  triangles.  study Fantz  (I96I) u s e d s u c h s t i m u l i a s a  f a c e , n e w s p r i n t , a b u l l ' s - e y e , a n d s e v e r a l c i r c l e s o f a l l one  12 colour.  Pantz  ranked  these  or p a t t e r n they p o s s e s s .  s t i m u l i a s t o t h e amount o f  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 t h e n e w s p r i n t , and  form  s t i m u l i , e s p e c i a l l y the face,  b u l l ' s - e y e , a f t e r he h a d  discovered  amount o f a t t e n t i o n t h e y w e r e p a i d b y 2 a n d  the  3 month o l d  infants. 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 h a v e b e e n cussed.  In the f i r s t  p l e x i t y was  offered.  ( S t e c h l e r , I96I1), no I n t h e o t h e r two  dis-  d e f i n i t i o n o f com-  ( 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 the r e s u l t s o b t a i n e d , the e x p e r i m e n t e r p r o p o s e d t h a t s t i m u l u s p a t t e r n was preferences  In infants.  The  a basis for  degree of p a t t e r n i n g i n a  m u l u s i s c o n s i d e r e d b y some w o r k e r s i n t h e f i e l d  work has  of stimulus  a p l a c e i n t h e d i s c u s s i o n o f the  sti-  (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 . Pantz's  visual  Thus,  definition  complexity.  (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 Complexity S e v e r a l s t u d i e s h a v e made i n t u i t i v e a p r i o r i  designations  of the rank order o f the complexity inherent i n the  stimuli  used "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 the so c h o s e n t o communicate t h e a u t h o r ' s ( C a n t o r , 1963> p« k-) • Sackett  Q  n.e  (I96I1) i n w h i c h h e  meaning o f  example o f t h i s  stimuli  complexity '  i s a study  1  by  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 u n d e r s e v e r a l l e v e l s e a r l y o v e r a l l v i s u a l input ranging from severely deprived  of to  13. normal jungle upbringing.  The  o f c o m p l e x i t y " were a w h i t e checkerboard  or b l a c k s q u a r e ,  c o n t a i n i n g l k x 17  squares.  a  He  found  that  r e a r e d i n more c o m p l e x v i s u a l e n v i r o n m e n t s p r e f e r r e d  v i s u a l p a t t e r n s of greater complexity. t h e a u t h o r was p l e x i t y , but made  stripes,  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 checkerboard animals  s t i m u l i " i n i n c r e a s i n g order  working  the exact  I t i s obvious  that  o n some i n t u i t i v e d e f i n i t i o n o f comcontents  o f the d e f i n i t i o n a r e  not  explicit. 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 s t u d y by M e y e r s , and K a g a n (1963K  They p r e s e n t e d  2k week o l d i n f a n t s  with three s t i m u l i - a single b l i n k i n g l i g h t ,  a horizontal  m o v i n g 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 helix.  E a c h s t i m u l u s was  These s t i m u l i  c o u l d be  c o n c e i v e d o f as  effects  (1958  o f two  do n o t  and movement, a l l  contributing to give their  complexity.  reasons  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  o r d e r i n g must t h e r e f o r e be Berlyne  trials.  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  However, t h e e x p e r i m e n t e r s assuming that the  square  p r e s e n t e d f o r f o u r 30-second  d e g r e e s o f p a t t e r n , number o f e l e m e n t s , o f w h i c h c o u l d be  Lewis,  c l a s s i f i e d as  f i x a t i o n i n t h e human i n f a n t .  He  and  their  intuitive,  b) p e r f o r m e d an e x p e r i m e n t  v a r i a b l e s , albedo  for  to test  c o m p l e x i t y , on  presented  the  visual  the s t i m u l i  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  to  comparison  procedure  a n d 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  He u s e d t w e l v e each.  stimulus patterns, four series of three  S e r i e s A, t h e a l b e d o  series,  grey, and w h i t e r e c t a n g l e .  consisted of a black,  S e r i e s B,C a n d D e a c h c o n t a i n e d  three figures with different  degrees o f c o m p l e x i t y but a l l  made u p o f e q u a l a r e a s o f b l a c k and w h i t e . are reproduced  i n Figure  Berlyne found first  first.  These  stimuli  1.  t h a t o n l y p a t t e r n s B3 a n d  attracted  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  patterns l n their respective series.  Berlyne's post hoc ex-  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 t w o s t i m u l i h a d much more c o n t o u r accounted not  than the others i n t h e i r  f o r t h e i r h i g h eye-drawing power.  the only a t t r i b u t e  on w h i c h t h e s e  a l s o v a r y a s t o t h e number  s e r i e s and  this  But contour i s  stimuli differ.  o f parts they  possess,  They  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 t h e m , a n d t h e number o f i n dependent angles periment  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  ex-  e o u l d be e x p l a i n e d i n t e r m s o f a n y one o r a l l o f  these a t t r i b u t e s .  In Berlyne's  s t i m u l i a l l these  attributes  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 manipulated In  independently.  the studies discussed i n t h i s section, the 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  interested  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 chose t h e i r cit  that  they  s t i m u l i o n t h e b a s i s o f some i n t u i t i v e a n d  d e f i n i t i o n of complexity.  H o w e v e r , t h e y n e v e r made  impli-  15.  F i g u r e 1.  The s t i m u l i u s e d b y B e r l y n e  (1958 b)  16 explicit  the contents of t h e i r  specified thought  a quality  accounted  definitions.  o f the s t i m u l i , contour, which  for his results.  (1958  Berlyne he  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 one  c o u l d have i n f l u e n c e d t h e T h u s , any  experiments  definitions  this  subjects' responses.  of complexity derived from  i n t h i s s e c t i o n do n o t  r e a d i n g of the papers  cited.  &)  The  the  emerge e a s i l y f r o m  a  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 which  the  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 the complexity of 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  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 a s p a t t e r n , number o f m e n t s , and  movement  (Lewis et a l . , 1963)$  b) may  be  ele-  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 i n d e p e n d e n t ( B e r l y n e , 1958  sti-  angles  noted.  ( c ) O r d e r i n g t h e 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 b y Means , of Adult Ratings 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 m u l i i n t e r m s o f c o m p l e x i t y b y means o f t h e r a t i n g s 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 .  In order of  c o m p l e x i t y the o v a l shaped achromatic h o r i z o n t a l s t r i p e s , a checkerboard, female  figure.  bases f o r t h e i r  sti-  given  increasing  s t i m u l i w e r e two  broad  a f a c e , and a c l o t h e d  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 judgements are not  specified,  l y t h a t t h e y were even a s c e r t a i n e d .  nor  as  is i t like-  Therefore, this  study  17  offers of  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  definitions  complexity.  (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 an a p r i o r i  have not only g i v e n t h e i r  stimuli  order 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 of complexity.  H e r s h e n s o n , M u n s i n g e r , a n d K e s s e n (I96I1) c o m p a r e d t h e p r e f e r e n c e s o f 17 n e w b o r n i n f a n t s f o r t h r e e s t i m u l i i n t h e number o f a n g l e s t h e y c o n t a i n e d . 10, a n d 20 a n g l e s r e s p e c t i v e l y . that t h e dimension  The s t i m u l i h a d 5>»  The i n v e s t i g a t o r s  claimed  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  of turns i n the s t i m u l i ,  "a d i m e n s i o n  approximating  t i o n v a l u e " ( H e r s h e n s o n e t a l . , 1961i, p . 631) • they noted  varying  informa-  However,  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  light-dark transitions  i n a stimulus, the complexity  I n c r e a s e s a s t h e number o f a n g l e s I n c r e a s e s .  level  Therefore,  number o f a n g l e s i s a l s o a n a t t r i b u t e o f c o m p l e x i t y a n d one which i n t h i s  c a s e 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  tran-  sitions i n the stimuli. Moffett  (1963), u s i n g a s s t i m u l i c r o s s - h a t c h e d  l i n e s on a white  black  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 a s 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 t h e 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 , a n d t h e number o f r i g h t contained.  angled  crossings  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  they  according  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 t i v e complexity  levels.  An experiment  by Spears  s u c c e s s f u l attempts  (196k) was one o f t h e most  i n approaching  explicit  definitions of  He u s e d 5 s e r i e s o f k s t i m u l i e a c h w h i c h h e  complexity.  sented i n a p a i r comparison procedure fants.  rela-  pre-  t o f o u r month o l d i n -  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 dimensions:  amount o f c o n t o u r  complexity  along the t r a n s i t i o n  boundar-  i e s o f c o l o u r e d a n d w h i t e a r e a s , number o f i n d e p e n d e n t or curves  i n the contour  symmetry p o s s e s s e d  angles  o f t h e f i g u r e , and t h e degree o f  by the p a t t e r n s .  The p a t t e r n s u s e d w e r e  s u c h t h i n g s as t w o r e d o r g r e y d i a m o n d s o n a w h i t e  back-  ground, r e d , b l u e , or grey b u l l ' s - e y e s , a k x k r e d and w h i t e checkerboard,  random r e d shapes on a w h i t e b a c k g r o u n d , and  yellow or b l u e hexagonal-shaped b u l l ' s - e y e s . that contour determining  seemed t o be t h e most i m p o r t a n t  Spears  found  variable i n  i n f a n t s ' stimulus s e l e c t i o n behavior while  m e t r y p l a y e d no r o l e a t a l l l n t h i s  sym-  behavior.  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 t e r m s 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 S p e a r s e m p l o y e d w e r e n o t t h e same. For 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 b u t 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 t e r m s o f t h e number o f i n d e p e n d e n t angles  and. t h e d e g r e e o f symmetry i t p o s s e s s e d .  19.  Spear's study p r o v i d e s evidence  o f the diversity of  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 complexity o f a pattern. i n h i s experiment,  I n u s i n g many d i f f e r e n t  a n d i n q u a n t i f y i n g t h e amounts o f t h e  various complexity a t t r i b u t e s which they possess, has  d e m o n s t r a t e d j u s t how c o m p l e x t h e c o n c e p t  i s , a n d how d i f f i c u l t s t i m u l i along t h i s  i t i s t o o b t a i n neat  a complexity  dimension.  checkerboard  squares  squares,  o f complexity  orderings o f  t o order  stimuli  along  He u s e d t h r e e b l a c k a n d w h i t e  as s t i m u l i .  The l e a s t  complex  contained  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 , a n d  t h e most c o m p l e x 12 x 12 s q u a r e s . cify  Spears  dimension.  H e r s h e n s o n (I96I4.) a l s o a t t e m p t e d  2 x 2  patterns  Hershenson d i d not  spe-  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 w e r e o p e r a t i n g  i n the checkerboard  designs, but i t i s obvious  t h a t he has  q u a n t i f i e d t h ecomplexity l e v e l o f each d e s i g n a t l e a s t i n t e r m s 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 than those  i n t h i s s e c t i o n a r e more  satisfactory  previously discussed f o r several reasons.  I n two  o f t h e m ( H e r s h e n s o n e t a l . , I96I4., a n d H e r s h e n s o n , 1961+) o n l y one t y p e  o f p a t t e r n was u s e d .  T h i s meant t h a t a n y 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 I n d e x I n c r e a s e d t h e o t h e r s i n c r e a s e d a s well.  F o r e x a m p l e , a s t h e number o f a n g l e s  i n the stimuli  u s e d b y H e r s h e n s o n e t a l . i n c r e a s e d , s o d i d t h e number o f  20. light-dark transitions.  Thus, t h e r e c o u l d be l i t t l e  as t o whether one s t i m u l u s was In  more complex than  doubt  another.  M o f f e t t ' s ( 1 9 6 3 ) study, where the s t i m u l i were a l l com-  posed o f the same elements, ground, t h e experimenter  was  b l a c k l i n e s on a white backa b l e t o manipulate  one index of  complexity, f o r i n s t a n c e number of r i g h t angled c r o s s i n g s , w h i l e k e e p i n g another index c o n s t a n t , f o r i n s t a n c e number o f lines.  By so doing she was  a b l e t o determine  e x a c t l y which  index o f complexity the s u b j e c t s were responding t o , t h a t i s , number of p a r t s . Spears  ( 1 9 6 k ) was  By the use o f many d i f f e r e n t p a t t e r n s ,  a l s o a b l e to a s c e r t a i n e x a c t l y which i n -  dex o f complexity, i n t h i s case contour, seemed t o be most important  the  attention getter for infants.  It would be premature at t h i s stage t o make judgements as to which k i n d o f study i s b e t t e r i n determining the bases of  v i s u a l a t t e n t i o n i n i n f a n t s , those employing  p a t t e r n whose complexity i s e a s i l y manipulated, employing many d i f f e r e n t  only  or those  p a t t e r n s a l l of which can be mea-  sured on v a r i o u s i n d i c e s o f c o m p l e x i t y .  Both k i n d s o f s t u -  d i e s w i l l probably be needed f o r a long time y e t , and ent r e s u l t s may  one  be expected from each.  In e i t h e r  differ-  case,  however, i t i s c l e a r t h a t s t i m u l i must be chosen a c c o r d i n g to  e x p l i c i t d e f i n i t i o n s of complexity.  from s t u d i e s employing  Results obtained  i n t u i t i v e l y chosen s t i m u l i are  diffi-  c u l t t o i n t e r p r e t and o f f e r l i t t l e h e l p towards the d i s c o v e r y  21.  of 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 plexity.  A s W a l k e r p u t s i t , " m a k i n g do w i t h  ordered stimulus  elements i s a m i s t a k e "  i n com-  intuitively  ( W a l k e r , 1961L, p .  72).  Now t h a t studies  the g e n e r a l l a c k o f e x p l i c i t  i n v e s t i g a t i n g various  definitioni n  aspects of stimulus  complexi-  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  infant attention to s t i m u l i varying 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 a n d c o m p a r e d i n t h e n e x t II  section.  RESULTS OP EXPERIMENTS ON INFANT ATTENTION TO S T I M U L I VARYING I N 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  inferred that stimulus greater  generally  p r e f e r e n c e h a s b e e n shown f o r s t i m u l u s  A over  B i f t h e v i s u a l a t t e n t i o n p a i d b y a n i n f a n t t o A was t h a n t h e a t t e n t i o n p a i d t o B.  Several  r e s p o n s e mea-  sures 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 be  discussed f u l l y  i n t h e next  will  section.  L e w i s , e t 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 order o f increasing  com-  p l e x i t y t h e 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 m o v i n g 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 helix.  I n terms o f b o t h t o t a l f i x a t i o n time and r a t e of  habituation l i  the decreasing order o f preference f o r the stimu-  were t h e square h e l i x , t h e l i n e , and t h e s i n g l e The  a square  i n v e s t i g a t o r s claimed that  a function  light.  rate o f habituation  of the complexity of the pattern.  was  For the 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 decrease t h e row two;  and  greatest  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; p a t t e r n the g r e a t e s t decrease  for  occurred after  trial  f o r t h e s q u a r e h e l i x , t h e most c o m p l e x p a t t e r n o f  the t h r e e , the g r e a t e s t decrease after t r i a l  three.  These r e s u l t s  clude that "complexity  i s an  represented  (1958  l e d the authors  important  occurred to  h) p r e s e n t e d  parameter i n main-  the f o u r stimulus  that these  t h a n t h e o t h e r and  to  Finding that the only s i g n i f i c a n t  f e r e n c e s w i t h i n e a c h row w e r e shown f o r s t i m u l i B^ Berlyne reasoned  10).  triads  i n F i g u r e 1 to i n f a n t s ranging from three  n i n e months o f age.  attraction.  con-  ( L e w i s e t a l . , 1963* p .  t a i n i n g the infant's i n t e r e s t " Berlyne  i n f i x a t i o n time  As we h a v e s e e n ,  be a n i n d e x o f c o m p l e x i t y .  and  s t i m u l i c o n t a i n e d more  t h a t t h i s was  the reason  contour  may  be  preD^,  contour  for their  high  considered  Therefore, the three t o  to  nine  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 greatest  complexity.  S p e a r s (1961).) p r e s e n t e d f o u r m o n t h o l d i n f a n t s w i t h terns which comprised random s h a p e s , and in  pat-  s u c h t h i n g s as b u l l ' s - e y e s , d i a m o n d s ,  checkerboards.  He  measured e a c h s t i m u l u s  terms of three complexity i n d i c e s —  number o f t u r n s , and d e g r e e o f s y m m e t r y .  amount o f  contour,  He t h e n r a n k  or-  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 e a c h o f t h e s e a t t r i b u t e s . found  of  t h a t I n t e r m s o f t h e number o f i n f a n t s s h o w i n g  c a n t p r e f e r e n c e s f o r one  stimulus over another,  He  signifi-  the 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 o conelude  t h a t c o n t o u r was  termining infants  1  T h i s l e d Spears  an i m p o r t a n t v a r i a b l e  stimulus selection behavior.  s u l t s c o n c u r w i t h t h o s e o f B e r l y n e (195"8 b ) In her experiments (1963) u s e d  w i t h two  i n de-  These r e -  just discussed.  t o f o u r month o l d s , M o f f e t t  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  on w h i t e b a c k g r o u n d s .  She  arranged  f o u n d 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 t h e w h i t e a r e a was more i m p o r t a n t  determinant  ber o f l i n e s themselves.  a  o f v i s u a l f i x a t i o n t h a n t h e numT h a t i s , two t o f o u r m o n t h 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 times f o r the 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 .  stimuli  Interpreting  the  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 , s h e t h u s f o u n d t h a t i n f a n t s p r e f e r r e d t h e most c o m p l e x of the s e r i e s  presented.  In the f o u r s t u d i e s just from  j u s t o v e r two  p r e f e r e n c e was  c i t e d the i n f a n t s ranged  months t o n i n e m o n t h s .  In every  i n age  case  shown f o r t h e most c o m p l e x s t i m u l i o f t h e r e -  spective series presented. s e r i e s of s t i m u l i — borns  stimuli  S t e c h l e r (19614.) p r e s e n t e d  a f a c e , a d i e , and a b l a n k —  a  t o new-  a n d 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 c o m p l e x s t i m u l u s , t h a t i s , f o r t h e f a c e . dered only the r e s u l t s  of these  I f one  s t u d i e s , he w o u l d p r o b a b l y  consider i t reasonable t o conclude that a l li n f a n t s more c o m p l e x s t i m u l i . that t h i s  i s not the  consi-  prefer  H o w e v e r , t h e r e i s some e v i d e n c e t o show case.  2k. I n t h e e x p e r i m e n t b y H e r s h e n s o n et a l . (196k) i n w h i c h three s t i m u l i , containing were p r e s e n t e d the  10,  angles.  a n g l e s , was  20  angles r e s p e c t i v e l y  t o n e w b o r n s , g r e a t e s t a t t e n t i o n was  stimulus of intermediate  w i t h 10  and  The  complexity,  This  study  provides  of a  s e r i e s i s not  that i s , the  most c o m p l e x s t i m u l u s , t h e  p r e f e r r e d s e c o n d t o t h e 10  paid  angled  one  The  most p r e f e r r e d by  stimulus  infants.  containing 2 x 2 ,  k x k,  squares r e s p e c t i v e l y . Hershenson presented p a i r s t o newborn i n f a n t s and He  the s t i m u l i .  m u l u s was  t h e most p r e f e r r e d .  e x h i b i t e d f o r the  t h e i r complexity complexity  was  s t i m u l u s was  —  found that the  s t i m u l i was  that i s , the  o f age plexity  the l e a s t  stimuli  in  least  complex  i n decreasing  stimulus of  they sti-  of  pre-  order  of  intermediate  preferred.  shown f o r t h e l e a s t  so f a r h a s  subjects.  pre-  of a s e r i e s  None o f t h e  i n v e s t i g a t e d the  studies influence  shown f o r s t i m u l i o f d i f f e r e n t  H o w e v e r , two  changes i n p r e f e r e n c e  i n w h i c h most  complex s t i m u l u s  specifically  on t h e p r e f e r e n c e s levels.  12  t h e n e x t most p r e f e r r e d , w h i l e t h e most c o m p l e x  e m p l o y e d n e w b o r n i n f a n t s as discussed  the  12 x  Furthermore, the order  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 f e r e n c e was  and  white  p h o t o g r a p h e d t h e i r e y e s as  looked at  ference  Her-  s t i m u l i u s e d w e r e t h r e e b l a c k and  checkerboard squares,  20  stimulus.  F u r t h e r evidence i s o f f e r e d i n another study by s h e n s o n (196k).  one  with  e v i d e n c e t h a t t h e most c o m p l e x always the  to  com-  workers i n the f i e l d have found  w i t h age,  thus p r o v i d i n g f u r t h e r evidence  25. t h a t t h e age o f t h e b a b y 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 complexity, Fantz  (1958 a n d 1961)  infants varying  presented p a i r s of s t i m u l i t o  i n age f r o m 2 t o 15 w e e k s .  consisted of a s t r i p e d design that  One o f t h e p a i r s  and a b u l l ' s - e y e .  Fantz found  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  to the bull's-eye, while  t h o s e o f e i g h t weeks a n d o l d e r  s i s t e n t l y preferred the bull's-eye t o the s t r i p e s . of seweral i n d i c e s o f complexity, c o u l d be c o n s i d e r e d mulus.  I n terms  Fantz's bull's-eye  design  t o be more c o m p l e x t h a n h i s s t r i p e d  sti-  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 . the r e s u l t s o f t h i s experiment ding  con-  evidence that  Thus,  c a n be i n t e r p r e t e d a s p r o v i -  older infants prefer  s t i m u l i of greater  complexity. A n e x p e r i m e n t b y Thomas  ( i n press) i s the only  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 stimulus  designated  complexity  the rank order  p r e f e r r e d by i n f a n t s .  Thomas  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 b y c o l l e g e students.  I n order  of increasing complexity,  the oval  shaped  a c h r o m a t i c s t i m u l i w e r e two b r o a d h o r i z o n t a l s t r i p e s , a checkerboard-like gure.  p a t t e r n , a f a c e , and a c l o t h e d female  I n terms of f i x a t i o n time,  f i -  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  the stripes l e a s t .  A l l d i f f e r e n c e s were  significant  26. except  t h e d i f f e r e n c e b e t w e e n t h e f i g u r e and i n f a n t a 15  order of preference f o r f i g u r e , checkerboard, p r e f e r e n c e w i t h age that  and  was  the f a c e .  t o 26 weeks was  the s t r i p e s .  The  the f a c e ,  o n l y change i n  from the checkerboard  t o the face  i s , a preference f o r increased complexity with The  fants  The  -  age.  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 y o u n g i n -  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  which arose out  of experiments  i n which the  p r i s e d o n l y o f i n f a n t s o v e r two  s a m p l e s w e r e com-  months o l d a n d w h e r e  i n f a n t s w e r e t r e a t e d as homogeneous g r o u p s . 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 I n f a n t grows o l d e r he  those  I t seems t h a t  f o r b e l i e v i n g t h a t as  an  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 c o m p l e x v i s u a l s t i m u l i .  This b e l i e f i s further bols-  t e r e d b y a t h e o r y p r o p o s e d b y Dember and o f w h i c h an e x p l a n a t i o n c a n be  (195?) i n terms  Earl  found f o r these  results.  This theory i s described below. Ill  A THEORY ABOUT COMPLEXITY I n t h e i r attempt  t o account  p r o p e r t i e s o f s t i m u l i , Dember and a s t i m u l u s may  f o r the a t t e n t i o n - g e t t i n g Earl  (1957) p o i n t o u t  have a d i f f e r e n t measure of c o m p l e x i t y  each of i t s a t t r i b u t e s .  on  P r e s u m a b l y t h e n , u s i n g , f o r exam-  p l e , the d e f i n i t i o n of complexity proposed by B e r l y n e one  that  (I960),  could increase the complexity of a stimulus along i t s  "number o f e l e m e n t s "  a t t r i b u t e while keeping  l a r i t y between elements"  attribute constant.  i t s "dissimiDember  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 p l e x i t y v a l u e on each a t t r i b u t e , ized  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 .  pendent a t t r i b u t e s For  corresponding  these  v a l u e s may c h a n g e  i n s t a n c e , an I n d i v i d u a l ^  i n a generalOn i n d e -  Independently.  i d e a l complexity value f o r  m u s i c 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 t u r e r e m a i n s t h e same.  com-  litera-  This ideal psychological complexity  l e v e l i s c h a r a c t 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 time and w i t h respect t o s p e c i f i c stimulus I n d i v i d u a l s come t o h a v e d i f f e r e n t  ideals  attributes.  through  experience.  According t o t h i s theory, experience w i t h c e r t a i n  sti-  muli increases the psychological complexity l e v e l o f the individual.  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 complexity 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 complexity of the individual. An 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  pacers.  attends t o a set o f s t i m u l i i f that s e t con-  t a i n s a stimulus that i s a pacer  f o r him.  attends to stimuli i n proportion t o their  The  individual  similarity to the  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 t h e p a e e r i t self.  As t h e I n d i v i d u a l g a i n s experience w i t h t h e s e t , h i s  Ideal complexity l e v e l increases u n t i l eventually the set no  longer contains a pacer.  its ability  A t t h a t time t h e s e t has l o s t  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  the i n d i v i d u a l a i d thus  i t a l s o has l o s t  arousing property f o r him.  i t s attention-  28.  Thus, through ideal complexity  contact w i t h a pacer  an I n d i v i d u a l ' s  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 value of the  pacer.  p a c e r s a v a i l a b l e , and  a s l o n g as t h e I n d i v i d u a l c a n  spond f r e e l y  "As  to a l lavailable  l o n g as t h e r e a r e  stimuli, his ideal  suitable re-  complexity  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 .  360).  The  Indivi-  extent of 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  d u a l ' s h e r e d i t a r y endowment.  I n n o r m a l 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 t h a t a r e somewhat more c o m p l e x t h a n t h o s e h e  stimuli  Is used t o .  I n o t h e r w o r d s , 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 p a c e d by g r a d u a l i n c r e a s e s i n stimulus  complexity.  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 t e r m s Dember and  E a r l ' s theory  s t i m u l u s and o r g a n i s m .  of l e v e l s of complexity of  of  both  R e c a l l that i n order of 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 checkerboard, f a c e , and  a figure.  He  f e r r e d the checkerboard f e r r e d the f a c e most.  found  m o s t , w h i l e 15  pre-  t o 26 week o l d s  pre-  He h y p o t h e s i z e d t h a t a n e v e n o l d e r  group would p r e f e r the female pacer  t h a t 2 t o l k week o l d s  a  f i g u r e most as i t w o u l d be  a  f o r them. Thomas i s t h e o n l y one  v e s t i g a t o r s who  of the p r e v i o u s l y mentioned i n -  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 a n d who t e s t e d f o r them.  H o w e v e r , t h e r e a r e two  specifically  drawbacks t o h i s  29. experiment.  F i r s t , the  s t i m u l i he  s e v e r a l dimensions simultaneously: v a r i e d i n the an  infant.  used v a r i e d for instance,  Therefore,  stimuli.  conclusions  about the  S e c o n d l y , he u s e d a d u l t  s t i m u l i i n complexity. c e d u r e , as adults  Moffett  e v e n t h o u g h she and  This  may  not  complexity  a l w a y s be  and  dimension.  r e l a t i o n between times,  I t seems t h e n ,  are not nor  necessarily  are they necessar-  However, i n terms o f the  The  r e s u l t s of the  t e r m s o f Dember and  dealing with  other  i n f a n t s o v e r two  also.  and  sets t o the pacer  Interpreted  In the  studies  months ( B e r l y n e , 1958 Spears,  stimulus  hj  196IL), t h e  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  Lewis  stimuli  most s i m i l a r o f  f o r those  T h u s , 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 muli.  stimulus  age.  e x p e r i m e n t s c a n be  E a r l ' s theory  e t a l . 1963J M o f f e t t , 1963;  in their  a  u s e d , Thomas d i d d e m o n s t r a t e i n c r e a s i n g p r e f e r -  e n c e f o r more c o m p l e x s t i m u l i w i t h  any  pro-  i n l i n e w i t h the p h y s i c a l o r d e r i n g of s t i m u l i along  o r d e r i n g he  his  f o u n d s i g n i f i c a n t a g r e e m e n t among a d u l t s  a d u l t s ' judgements o f c o m p l e x i t y  complexity  in  a wise  infants' looking  the bases f o r i n f a n t s ' l o o k i n g t i m e s , ily  among  judgments t o order  s i g n i f i c a n t a g r e e m e n t among i n f a n t s .  that  r e s u l t s cannot  i n complexity  (1963) f o u n d l i t t l e  judgements o f  1  they  amount o f m e a n i n g f u l n e s s t h e y m i g h t h a v e f o r  be made s o l e l y I n t e r m s o f d i f f e r e n c e s the  along  Infants.  of the  other  Because of the p a r t i c u l a r range o f s t i m u l i u s e d ,  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 w e r e a l s o t h e  most  stithe  30. complex.  I f s t i m u l i of even g r e a t e r c o m p l e x i t y had  added t o t h e  been  s e t s , however, I t might have been found  that  i n f a n t s w o u l d n o t h a v e p a i d most a t t e n t i o n t o t h e most complex o f the s e t , but  i n s t e a d w o u l d h a v e 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 r e s e m b l e d them.  the pacer  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  i n these  experiments  d i d not  for used  c o n t a i n s t i m u l i complex enough  t o be a b o v e t h e l e v e l o f c o m p l e x i t y o f t h e p a c e r  f o r the  infants tested. 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 . (I96ii)  and H e r s h e n s o n (I96I4.) p r e s e n t e d t o n e w b o r n s d i d  t e n d above t h e jects.  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 newborns the  resembled  t h e pacer  i n a checkerboard  least  stimulus f o r the a t t r i b u t e s  sub-  most  represented  p a t t e r n , w h i l e the p a t t e r n w i t h the the pacer  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 type of Having  f o r these  complex checkerboard  m e d i a t e number o f a n g l e s most r e s e m b l e d  ex-  Inter-  stimulus  design.  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  study  of infant a t t e n t i o n to s t i m u l i varying i n complexity, I t w o u l d seem a p p r o p r i a t e n e x t this  theory.  However, f i r s t  t o design experiments a v a l i d and  to  test  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 the c a p a b i l i t i e s o f the organism found.  t e s t e d must  These problems a r e d i s c u s s e d i n the f o l l o w i n g  be section.  31. IV  METHODOLOGICAL PROBLEMS I N THE STUDY OP INFANT ATTENTION TO S T I M U L I VARYING. I N COMPLEXITY. 1.  Response Measures Many d i f f e r e n t methods h a v e b e e n u s e d t o a s s e s s I n f a n t  attention to yisual stimuli.  Most o f t h e m e a s u r e s i n v o l v e  o b s e r v i n g t h e i n f a n t s e y e s a n d somehow r e c o r d i n g h i s r e f  sponses  t o the s t i m u l i presented.  The responses  recorded  h a v e b e e n s e v e r a l , a s h a v e b e e n 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 time d u r i n g which t h e subjects f i x a t e the  s t i m u l i h a s b e e n u s e d b y 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 e a c h t r i a l i n  which a stimulus I s presented t h e experimenters  record the  l e n g t h o f time d u r i n g which the s t i m u l u s i s so r e f l e c t e d t o derived a t o t a l f i x a t i o n time f o r that stimulus.  Moffett  ( 1 9 6 3 ) made u s e 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 s h e o b t a i n e d i n a n 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 cant p r e f e r e n c e s . and S p e a r s  signifi-  Hersenson (196k), Hershenson et a l . (196k)  (196k) measured t o t a l l o o k i n g time b u t c o n v e r t e d  t h i s information into frequency  d a t a o n t h e number o f s u b -  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 (Spears, 196k), or t h e number o f f r a m e s o f f i l m i n w h i c h t h e v a r i o u s s t i m u l i w e r e fixated  (Hershenson,  196k, and Hershenson et a l . ,  196k).  32. (b) L e n g t h o f F i r s t F i x a t i o n Fantz  (1963) and L e w i s e t a l . (1965) r e c o r d e d  length of the f i r s t  f i x a t i o n on a s t i m u l u s  and olaimed  t h i s was as r e l i a b l e a m e a s u r e a s l e n g t h o f t o t a l In f a c t , Lewis et a l . suggest t h a t  only t h e  fixation.  length of the f i r s t  a t i o n i s a more s e n s i t i v e m e a s u r e t h a n t o t a l f i x a t i o n in  that  fixtime  studying  i n d i v i d u a l d i f f e r e n c e s and the a t t r a c t i v e n e s s  of stimuli.  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  b e t w e e n t h e s e two m e a s u r e s was a f u n c t i o n o f t h e s t i m u l u s f i x a t e d and the subject  fixating.  (c) Rate o f H a b i t u a t i o n Lewis e t a l . (1963) a l s o a n a l y z e d  the rate of habitua-  t i o n to s t i m u l i d i f f e r i n g i n complexity crease  i n terms o f the de-  i n t o t a l f i x a t i o n time manifested  over f o u r t r i a l s (d) C a r d i a c  to stimuli  each.  Deceleration  Rate  L e w i s e t a l . (1963) a n d Kagan a n d L e w i s corded i n f a n t s ' heart stimuli  shown.  They c l a i m t h a t  observing  the o r i e n t a t i o n  method o f a s s e s s i n g  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 .  it  ( i n press) r e -  d e c e l e r a t i o n r a t e i n response t o the  o f i n f a n t s ' eyes i s an i m p e r f e c t  focus  presented  atten-  "The c h i l d ' s e y e s may  o n t h e s t i m u l u s b u t h e may n o t n e c e s s a r i l y a t t e n d t o  or actively  scan i t " (Lewis  e t 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 stimuli  i n f i v e y e a r o l d s a n d 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. rate. that  They t h e n t r i e d t h i s method o n i n f a n t s :  They f o u n d  t h e r e was a t e n d e n c y 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 o n a p a t t e r n b u t t h a t s h i p was n o t o r d e r l y . Infants, that  I t seemed t h a t  long t o t a l  s h i p was f o u n d . assessing  attentive subjects  Nevertheless,  deceleration.  no s u c h  the researchers  f i x a t i o n time and c a r d i a c  more f a i t h f u l  fix-  shown, t h e r e w a s 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 However, f o r m i n i m a l l y  relation-  for highly attentive  i s I n f a n t s who h a d r e l a t i v e l y  a t i o n times t o a l l the patterns  this  relation-  felt  change t o g e t h e r  index o f a t t e n t i o n than f i x a t i o n  that gave a  alone,  (e) Movement a n d V o c a l i z a t i o n L e w i s e t a l . (1963) a l s o o b s e r v e d t h e amount o f a r m movement a n d v o c a l i z a t i o n e m i t t e d but  i n response t o t h e p a t t e r n s ,  t h e s e t w o m e a s u r e s d i d n o t 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 time or t o cardiac d e c e l e r a t i o n 2.  E x p e r i m e n t a l Procedures Used i n A s s e s s i n g Attention . ; Two e x p e r i m e n t a l  rate.  Infant .  procedures have been used i n s t u d i e s  of infant a t t e n t i o n t o s t i m u l i varying  i n complexity  — the  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 instance, Fantz  (1963), L e w i s e t a l . ( 1 9 6 5 ) , K a g a n a n d 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  stimuli  one a t a t i m e a n d r e c o r d e d t h e r e a c t i o n s o f t h e i n f a n t s t o the  stimulus  so p r e s e n t e d .  On t h e o t h e r h a n d , B e r l y n e  b ) , F a n t z (1958, 1959, a n d 1962), H e r s h e n s o n  (196k),  (1958  34. H e r s h e n s o n e t a l , (196i|.), S p e a r s  (1961L), a n d 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  procedure and noted t h e preferences o f the i n f a n t s f o r t h e various  stimuli,  M o f f e t t (1963) p a i r e d e a c h 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 a n d compac e d 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 time  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 t w o r e c e n t s t u d i e s u n d e r t a k e n a t McMaster u n i v e r s i t y and a t the U n i v e r s i t y o f B r i t i s h bia of  (Ames a n d S i l f e n , the pair  periments ing In  some d o u b t o n t h e v a l i d i t y  method w i t h young i n f a n t s .  employed t h e p a i r  comparison  Both ex-  p r o c e d u r e , one d e a l -  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 . comparing  different that to  comparison  1965) t h r o w  Colum-  the percentage  of t r i a l s  i n which  infants o f  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  e i g h t w e e k o l d s a r e much l e s s  look at both s t i m u l i .  l i k e l y than older  babies  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 , a n d for  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 time.  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 t h e  I n t h e movement e x p e r i m e n t  16 a n d 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 o n 78 a n d 76 p e r c e n t o f t h e t r i a l s respectively.  For the stationary patterns the corresponding  p e r c e n t a g e s w e r e 60 a n d 63 p e r c e n t Kessen cause  respectively.  a n d H e r s h e n s o n (1963) h a v e a r g u e d t h a t j u s t b e -  t h e subject f i x a t e s longer on stimulus A than on stimu-  35. l u s B i t c a n n o t be c o n c l u d e d t h a t he h a s d i s c r i m i n a t e d two  the  s t i m u l i o r t h a t he h a s r e s p o n d e d 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 . s t r a t e d i s that the subject  411  attends  t o one o f t h e  more t h a n t h e o t h e r .  Even i f stimulus  l a r g e number o f o t h e r  stimuli, this  dimension.  K e s s e n and H e r s h e n s o n  t h a t h a s b e e n demonstimuli  A i s preferred to a  does n o t e s t a b l i s h a claim that  o n l y when  t r a n s i t i v i t y h a s b e e n e s t a b l i s h e d among a t l e a s t t h r e e muli  is i t justifiable  t o conclude that the i n f a n t i s r e -  sponding t o a dimension of stimulus t o go b e y o n d tropisms  variation.  " I f we  the demonstration o f something l i k e  I n i n f a n t s , we w i l l h a v e t o u s e  paired comparison designs" p . 13).  sti-  want  attention  multiple-stimulus  (Kessen and Hershenson,  H o w e v e r , on v e r y p r a c t i c a l g r o u n d s  1963,  i t would  seem  that the r e s u l t s o f a " p a i r comparison" study In which both members o f a p a i r a r e n o t f i x a t e d a r e o p e n t o q u e s t i o n . s i n c e i t has been demonstrated t h a t  d i f f e r e n t age  And  groups  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 d e g r e e s I t w o u l d questionable  t o compare t h e i r r e s u l t s .  Conceptually  this  t i s f a c t o r y as p a i r comparisons. better to run a l l subjects  be  For these reasons i t  seems more f r u i t f u l t o u s e a s i n g l e s t i m u l u s a l l age g r o u p s .  are  method may  procedure  with  n o t be as s a -  But o p e r a t i o n a l l y i t i s  on a common m e t h o d f o r w h i c h t h e y  are 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 o m p a r i s o n p r o c e d u r e and y o u n g e r to a rather  b a b i e s u n d e r what a m o u n t s  inadequate s i n g l e stimulus  procedure.  36. V  SETTING- FOR I t has  THE  PRESENT RESEARCH  b e e n shown t h a t I n the  cerned w i t h stimulus complexity, complexity  be  One  explicit  definitions  i s l e d t o agree w i t h Walker that  intuitively  (Walker,  no  con-  ordered  196ii, p . ?2).  stimulus  "making  elements i s a  mistake"  I t i s o b v i o u s t h a t t h i s method  should  discontinued. F u r t h e r , the m u l t i d i m e n s i o n a l i t y of the complexity  been p o i n t e d out. c r i b e d and  Many i n d i c e s o f c o m p l e x i t y  e v i d e n c e has  s t i m u l i In:terms o f flict. be  of  w e r e e m p l o y e d as b a s e s 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 . do w i t h  majority of studies  One  and  several Indices of complexity  supplant  con-  relatively  (Cantor,  used - the  "complexity"  1963,  P»  e s p e c i a l l y I n the  21).  There-  In t h i s t h e s i s , only  study  o f age  f o r s t i m u l i varying In complexity,  infant  b l a c k and w h i t e i n t o more a n d  are s e v e r a l .  they a l l o w the easy c o n t r o l of  ..Adult  judgements o f  fix-  keeping  areas equal while breaking the t o t a l  more p a r t s  per-  changes i n p r e -  o n l y have checkerboards been used w i d e l y i n i n f a n t  a t i o n s t u d i e s , but  one  checkerboard.  advantages of t h i s p a t t e r n i n studying  c e p t i o n , and  "Not  o f a few  t h e vague n o t i o n s o f  currently prevalent"  s t i m u l u s p a t t e r n was  ferences  can  r i g o r o u s l y delimited stimulus properties which  f o r e , i n the experiments described  The  of  must a g r e e w i t h C a n t o r t h a t " t h e r e a p p e a r s t o  hopefully w i l l which are  have been d e s -  been g i v e n that rank orderings  a s e r i o u s need f o r i n t e n s i v e study  simple  has  area complex-  37. i t y are very c l e a r , and agree w i t h these p h y s i c a l i n c a l l i n g most c o m p l e x t h a t  definitions  checkerboard w i t h the largest  number o f s q u a r e s i n i t " (Ames a n d S i l f e n , 1 9 6 5 , P« 3>).  In  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 t e r m s o f number o f turns, parts, right sitions  angled crossings, or l i g h t - d a r k  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  possess do not c o n t r a d i c t each o t h e r . s o n a b l e t o assume t h a t infant of  tran-  Finally,  It i s rea-  c h e c k e r b o a r d s h a v e no m e a n i n g f o r a n  and a r e t h e r e f o r e b e i n g responded  to solely  t h e i r p h y s i c a l a t t r i b u t e s a n d not i n terms  because  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 experiences on t h e p a r t o f t h e subject. The  v a r i o u s response measures o f i n f a n t a t t e n t i o n have  b e e n d e s c r i b e d a n d 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 these f u r t h e r t o assess 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 over 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 satisfactorily  settled.  I n many r e s p e c t s , t h e p a i r  s o n p r o c e d u r e seems t h e o r e t i c a l l y t h e r e a r e many p r o b l e m s w i t h young i n f a n t s .  been  compari-  s u p e r i o r , b u t as n o t e d ,  encountered i n u s i n g t h i s  procedure  Therefore, i n the research reported 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 e x p e r i m e n t  u s i n g a modi-  f i e d p a i r comparison procedure, i n which those t r i a l s  on which  o n l y one member o f a p a i r was f i x a t e d w e r e 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 t o a maximum of f o u r trials  f o r each p a i r .  There has age  been a g e n e r a l l a c k of experimentation on  differences i n infant a t t e n t i o n to s t i m u l i varying i n  complexity.  I t has been noted t h a t i n most of the  experi-  ments c i t e d i n f a n t s u b j e c t s p r e f e r r e d the most complex of the s t i m u l i w i t h which they were p r e s e n t e d . shenson, et a l . t h i s was  not  (196IL),  However, Her-  and Hershenson (I96I1) found that  the case w i t h newborn i n f a n t s .  Only the  ex-  periment by Thomas ( i n p r e s s ) s p e c i f i c a l l y showed an/ i n creased p r e f e r e n c e i t y , and  f o r s t i m u l i of greater  t h i s study can be c r i t i c i z e d f o r the  dimensionality The  w i t h age  complex-  lack of u n i -  o f the s t i m u l i employed.  experiments d e s c r i b e d  i n t h i s t h e s i s were s p e c i f i -  c a l l y designed t o t e s t the h y p o t h e s i s that o l d e r I n f a n t s  pay  more a t t e n t i o n t o s t i m u l i o f g r e a t e r  de-  complexity.  s i g n o f these experiments an attempt has the v a r i o u s p i t f a l l s d i s c u s s e d VI  PURPOSES OF THE  In the  been made t o  avoid  above.  PRESENT RESEARCH  The  purposes o f the present  1.  To t e s t the h y p o t h e s i s that 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 of greater 2.  To  complexity than do younger i n f a n t s *  compare v a r i o u s response measures, namely t o t a l  f i x a t i o n time, l e n g t h o f f i r s t ation.  r e s e a r c h are t h r e e f o l d :  f i x a t i o n , and r a t e o f  habitu-  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  study of infant a t t e n t i o n  -- s i n g l e s t i m u l u s a n d p a i r  comparison. To f u l f i l l t h e s e p u r p o s e s t h r e e e x p e r i m e n t s w e r e p e r formed.  Experiment  I u s e d 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 a s H e r s h e n s o n ' s (196k) w i t h i n f a n t s n a m e l y 10 a n d 20 w e e k s .  I n Experiment  of older  I I the complexity  o f t h e s e s t i m u l i was e x t e n d e d u p w a r d a n d i n f a n t s o f 3, a n d l k weeks w e r e t e s t e d w i t h t h e m .  ages,  Both Experiments  8, 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 . In Experiment  I I I , 8 a n d l k week o l d i n f a n t s w e r e  presented w i t h the s t i m u l i o f Experiment  I I i n a pair  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 a n d l k week o l d g r o u p s i n E x p e r i m e n t I I . The n e x t periments  three chapters d e a l w i t h each o f these ex-  separately.  ho  CHAPTER TWO EXPERIMENT I Purpose Hershenson (1961L) presented t h r e e b l a c k and white c o n t a i n i n g 2 x 2 , l i x l i , and 12 x 12 squares  checkerboards  t o newborn i n f a n t s . at the l e a s t to  He found t h a t t h e i n f a n t s l o o k e d most  complex p a t t e r n .  compare t h e v i s u a l responses  cally  Experiment I was  designed  o f older Infants, s p e c i f i -  10 and 20 week o l d s , w i t h those of Hershenson's  newborns . Hypotheses 1.  Ten and 20 week o l d 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 complexity than t h e 2 x 2  checkerboard  p r e f e r r e d by  newborns. 2.  Twenty week o l d s p r e f e r more complex s t i m u l i  than  10 week o l d s . METHOD Subjects Infant s u b j e c t s were o b t a i n e d f o r the experiment from three sources.  N o t i c e s were sent out t o a l l parents i n t h e  Vancouver area who announced the b i r t h o f t h e i r baby i n t h e l o c a l evening newspaper.  N o t i c e s were a l s o sent out t o  parents o f a l l f u l l term, h e a l t h y b a b i e s who were born i n Grace M a t e r n i t y H o s p i t a l .  F u r t h e r n o t i c e s were plaeed i n  the U.B.C. C h i l d H e a l t h Program C l i n i c , and i n s e v e r a l Vancouver  C i t y H e a l t h Program C l i n i c s .  In response  t o the  kl. 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 experiment.  E a c h 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 w h e t h e r o r n o t he c o m p l e t e d t h e e x p e r i m e n t a l p r o cedure.  D a t a w e r e d i s c a r d e d f r o m i n f a n t s who  failed to  c o m p l e t e 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 o r  falling  asleep. The b a s e s birth,  o f s u b j e c t s e l e c t i o n were age, f u l l  and p r e f e r e n c e f o r l y i n g  T h i s p r e f e r e n c e was  had a s t r o n g p r e f e r e n c e f o r l y -  p o s i t i o n d i d n o t come t o t h e  as i t h a d b e e n f o u n d t h a t the a p p a r a t u s employed. i n the  i n t h e supine, p o s i t i o n .  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 a n d any b a b y who i n g i n the prone  term  laboratory  such b a b i e s were not s u i t e d t o No p r e m a t u r e b a b i e s w e r e  included  sample.  The  i n f a n t s used i n t h i s experiment were e i g h t  o l d s a n d e i g h t 20-week o l d s .  The  t e n week o l d s r a n g e d i n  age f r o m n i n e w e e k s , two d a y s , t o 10 w e e k s , f i v e  days.  20 week o l d s r a n g e d f r o m 19 w e e k s , two d a y s , t o 20 five  10-week  The  weeks,  days. Apparatus The  30"  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 ,  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  l o n g b y 16" w i d e .  The b a s e o f t h e c r a d l e was  30"  uniformly  con-  c a v e a l o n g i t s l e n g t h a n d p r e v e n t e d g r o s s b o d y movements. pillow sponges  s e r v e d a s a m a t t r e s s and f o r t h e y o u n g e r  infants  at the sides of the head prevented the head  from  A  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 the i n f a n t c o u l d not  recover.  10 weeks a n d  The  sponges b o t h e r e d  infants older  s i n c e t h e y w e r e f o u n d t o be u n n e c e s s a r y  c o n t r o l l i n g t h e h e a d movements o f o l d e r b a b i e s n o t u s e d w i t h t h e 20 week g r o u p . was  o p e n so t h a t t h e  c o u l d be  One  they  s i d e of the  The  child's field  t h e open end hinged  o f t h e box.  a d o o r 28"  back of the box. l o n g by holes  of v i s i o n  apart  mulus h o l d e r . was  angled  8 3/V'  slid  i n t o the  wide w h i c h opened toward  T h i s door c o n t a i n e d  one  by  adjacent  t o the  stiand  s u b j e c t ' s e y e s as he  lay  When t h e  chamber h i s e y e s w e r e 18"  12"  observation  Cardboard s t i m u l u s cards  i n t o the holder.  the  5 " i n diameter  E a c h o b s e r v a t i o n h o l e was locus of the  was  stimulus slot  T h e r e w e r e two  on e i t h e r s i d e o f a n d  i n the cradle underneath.  covered  On t h e c e i l i n g o f t h e chamber  l o n g b y 12"  toward the  was  t o the f a r y e l l o w w a l l exposed  9" w i d e i n i t s c e n t r e .  9s"  were  infant,  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 c h a m b e r , w h i e h was w i t h n a v y b l u e f e l t , and  in  chamber  c r a d l e , c o n t a i n i n g the supine  slid into i t .  than  i n f a n t was  below the  11^"  by  rolled  centre of  the  ceiling. I l l u m i n a t i o n was o f v i s i o n by and  left  below the  two  provided  f r o m below the i n f a n t ' s  I4.O w a t t b u l b s , j u s t b e h i n d  of h i s head.  A navy b l u e f e l t  c e i l i n g of the  and  to the  b l i n d attached  chamber c o u l d be  field right 2£  n  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 b o t t o m t o t o p o f t h e i n f a n t ' s  field  ^3.  of  vision.  k-channel second.  R e s p o n s e s were r e c o r d e d on a R u s t r a k model 92 event  r e c o r d e r m o v i n g a t a s p e e d o f 12 mm.  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  per  activated  independently by four buttons attached t o the outside of the apparatus.  Two b u t t o n s w e r e 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 . Stimuli The s t i m u l i w e r e t h r e e b l a c k a n d w h i t e 6" checkerboards.  I n s t i m u l u s A t h e s q u a r e was d i v i d e d  quadrants, t h e f i r s t and t h i r d quadrents second  and f o u r t h w h i t e .  checkerboard.  square into  being black, the  T h i s i s d e s i g n a t e d as a 2 x 2  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  consis-  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 t h e m 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  t i n g o f l k k b l a c k and w h i t e  squares.  The s t i m u l i w e r e  p r e s e n t e d one a t a t i m e f o r f o u r 3 0 s e c o n d the f i r s t s i x t r i a l s  trials  sixtrials  each. F o r  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 . second  consis-  t h i s o r d e r was r e v e r s e d .  For the  Thus e a c h  sti-  m u l u s 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  half.  Procedure All  i n f a n t s were brought  both of t h e i r  parents.  t o t h e l a b o r a t o r y b y one o r  When t h e c h i l d was awake and i n a  good humour h e was p l a c e d i n t h e c r a d l e b y h i s m o t h e r ( o r in  s e v e r a l c a s e s b y h i s f a t h e r ) , who r e m a i n e d i n t h e room  iA. but  out o f t h e i n f a n t ' s  field of vision.  T h e c r a d l e was  t h e n p u s h e d i n t o t h e chamber t o a p o s i t i o n infant's  h e a d was d i r e c t l y b e l o w 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 stimulus The  i nwhich the  The b l i n d was a l r e a d y d r a w n a n d  p a t t e r n s were n o t v i s i b l e t o t h e i n f a n t .  experimenter stood behind  head o f t h e i n f a n t .  the apparatus a t t h e  He r e l e a s e d t h e b l i n d h a l f way so  that the infant  c o u l d be s e e n t h r o u g h t h e o b s e r v a t i o n  When t h e i n f a n t  was l o o k i n g u p a t 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 timer and t h e r e c o r d e r .  o f t h e way, a c t i v a t i n g t h e  The s t i m u l u s  t e d on t h e corneas of t h e i n f a n t ' s directed  eyes.  When t h e e y e s w e r e  This  t h e p u p i l as viewed through the  overlap  observation hole  observation  o f r e f l e c t e d image a n d p u p i l was t h e  criterion of fixation. the  p a t t e r n s were r e f l e c -  t o w a r d s 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 -  tern overlapped hole.  hole.  While observing  the subject  the experimenter recorded  through  the length o f  t i m e o f e a c h f i x a t i o n o n e a c h s t i m u l u s b y p r e s s i n g one o f the buttons At  t o t h e r i g h t o f t h e d o o r i n t h e chamber c e i l i n g .  t h e end o f 30 seconds a b u z z e r  on t h e timer  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  recorder.  The s t i m u l i w e r e t h e n c h a n g e d a n d t h e i n f a n t  quieted or roused  i f t h i s was n e c e s s a r y .  t w e e n t r i a l s was a p p r o x i m a t e l y varied  The i n t e r v a l b e -  10 s e c o n d s a l t h o u g h  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 .  this  45. RESULTS T a b l e 1 shows t h e 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 , a v e r a g e d  over  sub j e c t s • T a b l e s 2 a n d 3 p r e s e n t t h e r e s u l t s o f two one-way analyses o f variance performed  s e p a r a t e l y on t h e t o t a l  l o o k i n g t i m e s o f t h e 10 a n d 20 week g r o u p s . t e s t s performed  on t h e d i f f e r e n c e s b e t w e e n 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 all than  Newman-Keuls  stimulus r e v e a l that f o r b o t h groups  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  .01). For both groups,  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 order o f t h e i r complexity.  B o t h age g r o u p s p r e f e r r e d t h e  most c o m p l e x s t i m u l u s t h e m o s 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 , 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 graph 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 times 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 a n d 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  the  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  groups.  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 week o l d s l o o k e d s i g n i f i c a n t l y  longer at a l l three  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  10  stimuli  significance  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 a t E a c h 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 , b y 10 a n d 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)  A 2x2  B li x 4  C Mean t o t a l l o o k i n g 12 x 12 t i m e f o r e a c h a g e  10 weeks  34.875  64.375  90.125  63.125  20 weeks  20.750  33.750  68.125  40.875  27.812  k.9.062  79.125  Mean t o t a l looking time for each stimulus  _____  .  TABLE 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 .Time Spent L o o k i n g a t E a c h o f t h e T h r e e S t i m u l i b y SS  Source Between i n f a n t s Within  infanta  df  5553.96  ResIdual  P  59.62  Less  16 12229.00  2  6114.50  1435.67  4  102.55  19218.63  Total  F  7  13661*.. 67  Stimuli  MS  . .005  than  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 a t E a c h 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 b y 20 Week O l d Group ( E x p e r i m e n t I ) SS  Source Between Within  infants infants  4629.96  7  10422.67  16  Stimuli Residual Total  15052.63  MS  df  9586.75  2  4793.38  835.92  14  59.71  23  P  81.11L  P  Less  .  than  .005  1*8.  V  i  »  !  io w e e k s  ;  ••  1  A  B  2X2  4X4  ~ i —  C  12 X 1 2  i  STIMULI  -  ,  F i g u r e 2. 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 the t h r e e s t i m u l i by 10 and 20 week "old i n f a n t s , averaged over subj 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 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 i b y 10 a n d 20 week O l d G r o u p s (Experiment I ) Source Between  Infants Age  Subjects w i t h i n groups Within infants Stimuli Age X S t i m u l i S t i m u l i X subjects within g r oup  SS  df  16124.67 5940.75  15 1  5940.75  14  727.42  21i087.33 21270.88  32 2  10635.44  131.09 L e s s  than  544.87  2  272.44  3.36 L e s s  than  2271.58  28  81.13  10183.92  MS 8.17  Less  .025  than  - .005 .05  50. two  one-way analyses of v a r i a n c e .  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 f a c t o r i n d i c a t e s that the d i f f e r e n c e s between the t o t a l f i x a t i o n times f o r the s t i m u l i were not f o r the two  age  identical  groups. DISCUSSION  The f i r s t  h y p o t h e s i s , that  10 and 20 week o l d 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 complexity than the 2 x 2 board p r e f e r r e d by newborns, was ment.  confirmed i n t h i s  checkerexperi-  Hershenson found t h a t newborns l o o k e d at the  2x2  p a t t e r n the most, the k x k next, and the 12 x 12 the l e a s t . In the present experiment  b o t h 10 and 20 week olds looked  most at the 12 x 12 checkerboard, next at the k x k, least  at the 2 x 2 .  and  However, the second h y p o t h e s i s , that  20 week olds p r e f e r more complex s t i m u l i than 10 week o l d s , was  not confirmed i n the  experiment.  The l a c k o f support f o r the second hypothesis c o u l d have o c c u r r e d because s t i m u l i was  the range of complexity r e p r e s e n t e d i n the  too small.  I f the set o f s t i m u l i p r e s e n t e d had  c o n t a i n e d more complex p a t t e r n s t h a n those used here t h i s h y p o t h e s i s might  have been confirmed.  T h e r e f o r e , i t seems  premature to, conclude from these r e s u l t s that beyond 10 weeks o f age t h e r e i s no change i n p r e f e r e n c e f o r s t i m u l i o f v a r y i n g complexity  levels.  The r e s u l t s of t h i s experiment son's  (196k) f o r s e v e r a l reasons.  may  d i f f e r from  Hershen-  F i r s t , the methods of i n -  v e s t i g a t i o n u s e d i n t h e two s t u d i e s were v e r y Hershenson  p h o t o g r a p h e d h i s s u b j e c t s ' eyes a t a r a t e  frame p e r s e c o n d and s c o r e d t h e number a s t i m u l u s was  fixated.  used a p a i r  mulus p r o c e d u r e was Hershenson  eyes  o f one  i n which were  r e c o r d e d a s he was r e s p o n d i n g .  comparison procedure; a s i n g l e  sti-  employed i n t h e p r e s e n t e x p e r i m e n t .  used a chi-square technique o f a n a l y s i s ; a n a l y -  s e s o f v a r i a n c e were u s e d h e r e . genuine d i f f e r e n c e s samples  o f frames  Here, the i n f a n t ' s  observed and h i s f i x a t i o n s Hershenson  different.  be  i n t h e p o p u l a t i o n s f r o m w h i c h t h e two  were s e l e c t e d .  T h i r d l y , t h e r e may  ences i n t h e l e v e l o f v i s u a l of different  S e c o n d l y , t h e r e may  be a c t u a l  differ-  complexity preferred by  infants  ages.  To I n v e s t i g a t e  further  the possible  e x i s t e n c e o f 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  II  Purpose Experiment  I I was d e s i g n e d  v i s u a l responses  t o i n v e s t i g a t e f u r t h e r the  of infants of different  varying i n complexity.  The d e m o n s t r a t i o n  ages t o s t i m u l i of  organism-  s t i m u l u s c o n c o r d a n c e i n l e v e l s o f c o m p l e x i t y was cally desired.  specifi-  T h a t i s , t h e a i m was t o f i n d t h r e e a g e  groups such 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 the least  complex s t i m u l u s over  the others, the oldest pre-  f e r r e d t h e most c o m p l e x s t i m u l u s , and. t h e m i d d l e  group pre-  ferred the stimulus o f intermediate complexity.  In order  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 those used i n Experiment I , and I n f a n t s o f several different  ages were t e s t e d . Hypothesis  The  o l d e r t h e i n f a n t , t h e more c o m p l e x t h e p a t t e r n h e  prefers.  METHOD The  m e t h o d o f E x p e r i m e n t I I was t h e same a s t h a t o f  Experiment  I except  f o rthe following modifications: Subjects  The groups.  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  They w e r e t e n t h r e e week o l d s r a n g i n g  i n age f r o m  e x a c t l y t h r e e w e e k s t o t h r e e w e e k s , f o u r d a y s , t e n e i g h t week  53. olds ranging  i n age  from, s e v e n w e e k s , two  t e n 11L week o l d s r a n g i n g i n age  w e e k s , f i v e d a y s , and 13  w e e k s , two  days t o e i g h t  days, t o H L w e e k s , f i v e  frau  days.  Stimuli s t i m u l i u s e d w e r e t h r e e 6"  The  checkerboard  designs.  The  tained 2 x 2  b l a c k and w h i t e  intermediate complexity 3/V  squares.  The  least  (B)  3  M  square,  complex s t i m u l u s squares.  contained  lA"  squares.  The  8 x 8  most c o m p l e x s t i m u l u s  2ii x 21L b l a c k a n d w h i t e  b l a c k and (A)  a n d two m o n t h o l d I n f a n t s was  T h i s was  l/lj-"  a p a t t e r n of  b l a c k and  (G)  Pantz,  month o l d s c o u l d see ches.  According to these  present used.  1/8"  stripes  contained Ordy,  and  inches.  on a w h i t e  angle  back-  T h r e e and  four  a t a d i s t a n c e o f 20 i n -  experiment were a b l e t o p e r c e i v e the t h r e e  stimuli  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 , 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 ) , w e r e n o t 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 stimulus.  Therefore,  s t i m u l u s was s i z e and  f o r the  as t h e  i f a checkerboard square,  complex  t h r e e week o l d g r o u p a f o u r t h  i n t r o d u c e d - a p l a i n gray  albedo  than t h e gray olds •  white  d a t a , the o l d e r s u b j e c t s i n the  b e i n g n e a r t h e y o u n g e s t age  that  of  I4.0 m i n u t e s o f a r c .  black stripes  g r o u n d shown a t a d i s t a n c e o f 20  con-  stimulus  T J d e l f ( 1 9 6 2 ) 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 f o r one  white  checkerboards.  square o f the I t was  same  hypothesized  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 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  As for  i n Experiment  f o u r 30  second  f i r s t h a l f o f the half.  Thus t h e  I each, s t i m u l u s p a t t e r n was  trials.  Each appeared t w i c e i n the  s e r i e s of t r i a l s ,  8 and  and  l k week o l d s h a d  t h e t h r e e week o l d s had  presented  sixteen trials  twice i n the  second  twelve t r i a l s ,  and  b e c a u s e o f the  In-  c l u s i o n of the 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 In and  the t e s t i n g of three of the three-week o l d s u b j e c t s  s i x of the  used.  One  l k week o l d s u b j e c t s , two  observed  t i o n hole to the  left  c e i l i n g d o o r , and the right  the  o b s e r v e r s were  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 -  o f the  stimulus holder i n the  the other observed  of the h o l d e r .  through the h o l e  o p e r a t i o n o f t h e b u t t o n s was  rendered  the  top.  The  practically inaudible  r e c o r d e r i n a padded box.  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 of  to  Each observer operated 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  by e n c l o s i n g the event  chamber  of the infant  Thus e a c h  independently  other.  Whenever a n o b s e r v e r p u s h e d a b u t t o n , a p e n o n one the channels  o f the event  r e c o r d e r was  record of the l e n g t h of each f i x a t i o n . t h e two  o b s e r v e r s a p p e a r e d on a d j a c e n t  cording tape. been i d e n t i c a l . ment s c o r e was  Had  of  d e f l e c t e d , making a The  r e c o r d s made b y  channels  o f the  re-  agreement been p e r f e c t t h e y w o u l d have  For 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 c a l c u l a t e d by  c o u n t i n g t h e number o f s e c o n d s  55. per  30 s e c o n d 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 l l t i m e e x c e p t t h a t d u r i n g w h i c h one o b s e r v e r f i x a t i o n while the other observer  agreed, i . e . , recorded  d i d n o t . The s c o r e s w e r e  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 subject  t h r e e week o l d s , 12 f o r l k week o l d s ) , a n d c o n v e r t e d percentage o f t o t a l stimulus p r e s e n t a t i o n Inter-observer  a  (16 f o r to a  time.  a g r e e m e n t r a n g e d f r o m 90% t o 96%, t h e  average agreement over t h e n i n e  subjects being  93$.  RESULTS Table 5 presents  the t o t a l  l o o k i n g time, averaged  over  s u b j e c t s , s p e n t l o o k i n g a t e a c h o f t h e s t i m u l i b y t h e 3, 8, and  l k week o l d g r o u p s . Table 6 presents  variance  T h e s e d a t a a r e p l o t t e d i n F i g u r e 3..  a summary o f a two-way a n a l y s i s o f  of t h e t o t a l l o o k i n g t i m e o f e a c h age g r o u p f o r  each stimulus  excluding gray.  T h e t w o main e f f e c t s a n d 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 total  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 t h e  l o o k i n g times  same.  f o r t h e t h r e e age g r o u p s w e r e n o t t h e  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 -  t w e e n 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 at t h e three  s t i m u l i taken together  (p l e s s t h a n  .01), t h a t  t h r e e week o l d s looked degree.  t h a n d i d t h r e e week o l d s  l k week o l d s a l s o l o o k e d  (p l e s s t h a n  longer  longer  .05, )» a n d t h a t e i g h t week  l o n g e r t h a n l k week o l d s , b u t t o a n  than olds  insignificant  56 TABLE 5 T o t a l L o o k i n g Time i n S e c o n d s S p e n t L o o k i n g a t E a c h o f t h e S t i m u l i b y 3, 8 , a n d I 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 2 x 2  B 8 x 8  C Grey 2k x 2k  Mean t o t a l l o o k i n g t i m e f o r e a c h age  3 weeks  80.3  51.8  23.6  8 weeks  54.2  111.3  74.1  79.87  l k weeks  43.1  68.8  91.1  67.66  77.3  62.93  Mean t o t a l looking time f o r e a c h s t i - 59.2 mulus  15.7  51.9  (without gray)  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 S p e n t L o o k i n g a t E a c h 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 ) b y 3 , 8 , a n d l k week o l d Groups. (Experiment I I ) Source  SS  df  Between i n f a n t s 28132.46 Age 11795.63 Subjects w i t h i n groups 16336.83  29  Within infants St i m u l i  MS  2  5897.815  27  605.068  58870.00 5479.49  60 2  2739.745  Age X S t i m u l i  38935.24  4  S t i m u l i X subjects within groups  14455.27  54  9733.81 267.69  P  P  9.747 l e s s t h a n .005  10.234 l e s s t h a n .005 36.362 l e s s than .005  57.  120  As /  I 10 co  Q  z o u  LU CO  100  - A — A  3 weeks  * — •  8 weeks 14 weeks  \  90 80 70  LU  3  60  z o  50  !< x  40 30 20  Z <  10  LU  A  B  2X2  8X8  C 24 X 2 4  STIMULI F i g u r e 3. T o t a l l o o k i n g time i n seconds spent l o o k i n g at each o f t h e 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 )  Grey  £8.  The significance o f the Stimuli factor indicates that the t o t a l looking times f o r the three checkerboards were different.  A Newman-Keuls test performed on the differences  between these t o t a l s reveals that stimulus B was  fixated  s i g n i f i c a n t l y longer than either A or C (both p's less than .01).  Stimulus 0 was f i x a t e d longer than A to an i n s i g n i -  ficant  degree.  The significance of the interaction between Age and Stimuli indicates that the patterns of preference of the three groups were s i g n i f i c a n t l y d i f f e r e n t .  In order to i n -  vestigate the preferences of each group, one-way analysis of variance were performed separately on the t o t a l looking times of each group.  analyses were performed on the three  week group, one including the looking time for the p l a i n gray stimulus and one excluding i t .  The summaries of these  four analyses of variance are presented i n Tables 7 through 10. The s t i m u l i effect was highly s i g n i f i c a n t i n 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 between the t o t a l looking times for each pair of s t i m u l i . For the three week old group a l l differences were s i g 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 T a b l e o f A n a l y s i s of Variance o f T o t a l L o o k i n g Time Spent Looking at Each o f t h e Stimulus Patt e r n s ( i n c l u d i n g Gray) by t h r e e week o l d Group (Experiment I I ) SS  Source Between  Infants  Within infants Stimuli Residual Total  df  k890.1  MS  9  3kO9k.0  30 25902.9  38.98k.l  3  8191.1  39  27  863k.3  28.k6  l e s s than .005  303.37  TABLE 8 Summary T a b l e of A n a l y s i s of Variance o f " T o t a l Looking .Time Spent Looking at Each o f t h e Stimulus P a t f terns„(excluding Gray) by~three week o l d Group (Experiment I I ) Source Between i n f a n t s  SS  df  5916.03  Within infants Stimuli  21978.67  Residual Total  2789k.70  MS  9 I607k.60 590k.07  20  29  2  8037.30  18  328.00  P -  2k.50k  p  l e s s than .005  TABLE 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 a t E a c h o f T h r e e S t i m u l u s P a t t e r n s  df  SS  Source  MS  P  P  -  Between  infants  9  1477.^7  20  19850.00  Within infants Stirauli  16800.87  Residual Total  3049.13  29  21327.47  2  8400.435  18  169.396  49.59  less than .005  TABLE 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 Time Spent. L o o k i n g a t E a c h o f T h r e e S t i m u l u s P a t t e r n s ...  Between  . _.  SS  Source infants  Within infants Stimuli  MS  df  8943.34  9  17041.33  20 11539.27  2 18  5502.06 25984.67  29  P  -  5769.635  -  Residual Total  P  305.67  18.87  less than .005  o  61. complex next, ten  stimulus  and t h e  infants  moat,  most  In the  ference  pattern  infant  showed a  the  stimulus  of  complex  stimulus  least.  three  as  the  alight  week o l d  overall  intermediate  sample  group  preference  Nine  ahowed  out the  preference  complexity of  the  same  pre-  pattern.  One  for  s t i m u l u s B over  the  differences  stimulus  A. For looking (all  the  eight  times  for  p'a  mulus  leas  of  and the  the  eight  week  preferred  tal  stimulus  the  less  than  other  .02  two  most  for  pairs).  complex  pattern most,  the  ten  l k week o l d s  the  overall  next  after  group  their  B over  stimulus  C.  stimuli both  G,  Eight  slight  of  of  them  preferences  least  p's  leas  and a n o t h e r  than  least. same  had a  to-  for  .01 the  preferring  i n the  the  significant  preferred  complex  One i n f a n t  between  were  complexity,  preferences  group p r e f e r e n c e .  atimulua  of  l k week o l d s  and t h e had  showed  stimu-  A l l ten  B.  a l l differences  CB p a i r ;  Thus, of  two  sti-  complex  least.  stimulus  the  C.  a l l pairs the  most  total  significant  preferred  the  stimulus  while  stimulus  for  most,  preferred  C next,  i n increasing order  ence f o r  week o l d s  complexity  l k week o l d  looking times  the l i  olds  i n the  s t i m u l i were a l s o  least.complex  stimulus A over For  of  Eight  .01).  intermediate  next,  (p  a l l pairs  than  lus  for  week o l d group  stimu-  the  Eight  direction slight  preferred  most of as  prefer-  atimulua A  62, DISCUSSION The  hypothesis,  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  c o m p l e x t h e 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 ment.  T h r e e week o l d s p r e f e r r e d t h e 1 e a s t  i n this  complex  experi-  checker-  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 , plex  checkerboard.  Further  Support f o r t h e  Further age  support  Hypothesis  f o r the hypothesis  groups w h i c h were p r e s e n t e d  other two  a n d l k week o l d s p r e f e r r e d t h e most com-  was g i v e n b y  other  w i t h t h e same s t i m u l i .  These  g r o u p s w e r e 10 t w e n t y week o l d s , 10 t e n week o l d s , a n d  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  are p l o t t e d along w i t h those groups i n F i g u r e  o f the 3,  o f these  groups  8 , a n d l k week o l d  k.  I n t h e 2 0 week o l d g r o u p e v 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  of their  complexity.  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 ference  emerged a s e a r l y a s 12 a n d 13 weeks a n d was w e l l e s -  t a b l i s h e d by l k weeks as h a s b e e n s e e n . felt  pre-  Therefore  i t was  t h a t t h e 20 week o l d s w e r e r e a l l y t o o o l d f o r t h e s t i m u l i  u s e d h e r e a n d t h a t i f a n e v e n more c o m p l e x p a t t e r n h a d b e e n Included  i n t h e s e r i e s , 20 week o l d i n f a n t s w o u l d h a v e shown  a preference The  f o r i t over t h e other  preferences  three.  o f t h e 10 w e e k o l d g r o u p a r e b e t w e e n  o f t h e 8 a n d l k week o l d s .  Both s t i m u l i B and C were  c a n t l y p r e f e r r e d t o A, b u t s t i m u l u s B was o n l y  those  signifi-  slightly  63.  A — A — ^  I20i  t o  o—o-o  5  weeks  _ A „-  IO  weeks  •  3 weeks 8 weeks 14 w e e k s  •—••--a 2 0 w e e k s  110-  Q  Z  O u  I O O -  CO  90-  LU  Z —*  80H  -§  70H  LU  O < x  2  O i—  z < LU  3  60 50 40 30 20 10  1  A  —  2X2  B  8X8  G 2 4 X 24  STIMULI F i g u r e k. 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 of the s t i m u l i by 3 * 5 * 8 , 1 © , l k , and 20 week o l d i n f a n t s , averaged over s u b j e c t s . (Experiment 11}  Grey  6k. preferred t o atimulua age  C.  S e v e n o f t h e 10 i n f a n t s  g r o u p showed p r e f e r e n c e s  p r e f e r r e d C t o B.  f o r B over  i n thia  C, w h e r e a s  three  Of t h e t w o f i v e week o l d s one showed a  preference  f o r stimulus B over A w h i l e t h e other p r e f e r r e d  both these  stimuli  t o t h e same d e g r e e .  that the preferences  Thus i t w o u l d  o f f i v e week o l d s l i e s b e t w e e n  appear  those  o f t h r e e a n d e i g h t week o l d s . T h i s experiment  represents the f i r s t  necessary  step  in studying the effects o f infants' experience^with above, a t , and below t h e i r pacer  stimuli  l e v e l , that 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 b y i n f a n t s o f a g i v e n age (Dember a n d E a r l , 1 9 5 7 ) *  P e r t h i a p u r p o s e i t was  necessary  t o f i n d t h e a g e s a t w h i c h p a t t e r n o f r e a p o n a e were aignificant  and u n i f o r m .  The e x a c t  pacer  both  s t i m u l u s f o r each  o f t h e 3» 8* a n d l k week o l d g r o u p s may n o t h a v e b e e n r e p r e sented i n the set o f s t i m u l i used. of t h e groups'  However, t h e s i g n i f i c a n e  respective preferences  f o r one o f t h e p a t t e r n a  i n t h e s e t 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, a t t h e l e a s t , very c l o s e t o t h e pacer  s t i m u l u s f o r eaeh age.  Finer  grada-  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 w o u l d be n e e d e d i n o r der  t o I d e n t i f y the exact  pacer  s t i m u l u s f o r e a c h age  groups.  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  a c c o m m o d a t i o n 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 d a y s t o f o u r m o n t h s b y means o f t h e t e c h n i q u e  o f dynamie  retinos-  65. copy.  T h e y f o u n d t h a t " p r i o r t o one  accommodative response d i d not distances.  The  s y s t e m a p p e a r e d t o be  (Haynes e t a l . , 1 9 6 5 * p . 7f-#  530).  This  l o c k e d a t one  g r o u p was  e x p e r i m e n t w e r e shown.  t h r e e week o l d s i n the  ment c o u l d . n o t  on t h e s t i m u l i at the  which they were On t h e  cm."  distance at  I s p o s s i b l e t h a t the focus  19  focal  distance i s equal  or l e s s t h a n h a l f t h e  the s t i m u l i I n the present  the i n f a n t ' s  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 whose m e d i a n v a l u e f o r t h e  approximately  month o f age,  which Thus, i t  present 18"  experi-  distance  et a l . (1962) f o u n d t h a t  m o n t h 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 g r o u n d a t a d i s t a n c e o f 20  Inches.  That  mented t h a t d i f f e r e n t  paired.  back-  grey  However, i t i s w e l l docu-  v i s u a l aouity thresholds are  t a r g e t s ( B a r t l e y , 1 9 5 8 ) , and  as  obtained  i t i s quite  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 t h a t f o r  one  i s , the i n f a n t 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  s q u a r e w i t h w h i c h i t was  with different  at  presented.  other hand, Pantz,  looked at t h i s  to  as  good  e x p e r i m e n t t h r e e week o l d s d i d n o t  look  stripes.  In the present  s i g n i f i c a n t l y l o n g e r at 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  ^"  s q u a r e when e a c h was  squares than at the gray  singly.  presented  This would tend t o i n d i c a t e e i t h e r that they  f e r r e d each t o the  same low  degree, or t h a t they  t h e e v i d e n c e o f Haynes e t a l . ( 1 9 6 5 ) , and  pre-  could  d i s t i n g u i s h the checkerboard from a u n i f o r m l y gray On  2k  not  square.  of Bartley  66. ( 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 d a t i v e a b i l i t y nor was  accommo-  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  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  olds  clearly  most c o m p l e x s t i m u l u s w i t h w h i c h t h e y w e r e p r e s e n t e d .  the The  c l a r i f i c a t i o n of t h i s point r e q u i r e s a c o n t r o l study i n w h i c h the  s t i m u l i are  However, the A and  presented at a distance  t h r e e week o l d s d i d l o o k a t b o t h  B significantly  showed a s i g n i f i c a n t  longer  preference  indicates that they perceived least  t h a n at the  of the  two  and  A o v e r B,  b o t h of t h e s e p a t t e r n s  c l e a r l y enough to d i s t i n g u i s h them f r o m t h e  f r o m e a e h o t h e r , and  stimuli  gray square  for stimulus  t h a t they p r e f e r r e d the  7^"«  o f about  less  This  at  gray  and  complex  stimuli,  Haynes et a l , (1965) a l s o f o u n d t h a t  of  the  a c c o m m o d a t i v e r e s p o n s e " b e g a n a t about t h e m i d d l e of t h e  2nd  m o n t h and  p e r f o r m a n c e c o m p a r a b l e t o t h a t o f the t h e k t h month" ( p . 5 3 0 ) .  was  a t t a i n e d by  the  e i g h t week o l d s i n t h e p r e s e n t  moat c o m p l e x s t i m u l u s  t h e y were p r e s e n t e d .  a l l three  i t was  stimuli with  the one  which  s t i m u l i a t 18"  may  f o r them to  Results  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 of the o f the  that  stimuli.  I n t e r p r e t a t i o n of the  than that  fact  adult  l e a s t complex  sufficient  make d i s t i n c t i o n s b e t w e e n t h e t h r e e  terms other  normal  experiment p r e f e r r e d  T h e i r f o c u s o n the  have b e e n p e r f e c t , but  Another Possible  The  s i g n i f i c a n t l y t o the  indicates that they perceived  not  flexibility  results in  d i f f e r e n c e i n complexity  of  the  67. three checkerboard patterns. i n t o account patterns.  This i n t e r p r e t a t i o n would  t h e s i z e o f the b r i g h t n e s s patches  take  i n the  The h y p o t h e s i s i n t h i s case w o u l d 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 patches o f brightness.  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 c o m p l e x -  i t y , t h e w h i t e s q u a r e s c o n t a i n e d i n t h e m beeame  smaller.  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 n o 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 o f 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 possible that the  t h r e e week o l d s , f o r i n s t a n c e , w e r e f i x a t i n g m a i n l y o n t h e large white areas of the l e a s t  complex s t i m u l u s .  t o f i n d out whether i n f a n t s f i x a t e  I n order  one a r e a o f a s t i m u l u s  o n l y o r w h e t h e r t h e y s c a n t h e w h o l e p a t t e r n , a more c a t e d method o f o b s e r v a t i o n i s needed. technique might  A  cinematographic  such as t h a t used by S a l a p a t e k and Kessen  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  sophisti-  problem.  (1965)  68. CHAPTER POUR COMPARISON OP RESPONSE MEASURES OBTAINED I N EXPERIMENT I I . Two o t h e r r e s p o n s e m e a s u r e s b e s i d e s 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 rate of h a b i t u a t i o n . s u l t s obtained w i t h these  In this  ehapter  the r 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 ing  t o t a l looking time  f i x a t i o n and t o t a l  look-  time are discussed,  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 f i x a t i o n s o f the three  t h e l o o k i n g t i m e i n seconds o f f i r s t c h e c k e r b o a r d s b y t h e 3» 8, a n d 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  subjects.  These d a t a a r e  5".  plotted i n Figure  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  of variance of the l e n g t h of f i r s t s t i m u l i by t h e three  f i x a t i o n f o r the t h r e e  age g r o u p s .  The t w o m a i n e f f e c t s a n d t h e I n t e r a c t i o n e f f e c t w e r e a l l significant.  T h e s i g n i f i c a n c e o f t h e Age e f f e c t  that the o v e r a l l  length of f i r s t  w e r e n o t t h e same.  f i x a t i o n s f o r t h e age g r o u p s  A Newman-Keuls t e s t  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 three  indicates  performed on t h e f i x a t i o n s among t h 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  fixations  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 T h r e e S t i m u l i b y 3 , 8 , a n d l 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 ( E x p e r i m e n t I I ) A 2 x 2  B 8 x 8  G 2k x 2k  Mean 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 e a c h age  3 weeks  49.1  25.9  15.0  30.0  8 weeks  9.5  76.9  36.8  41.06  l k weeks  11.3  19.7  35.6  22.2  23.3  40.83  Mean l e n g t h o f first fixations for each stimulus  29.13  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 Length 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 b y 3» 8 , a n d l i j . week o l d g r o u p s ( E x p e r i mentll) -  SS  Source Between • Age  infants  Subjects within groups Within infants .. S t i m u l i Age X s t i m u l i S t i m u l i X subjects within groups  df  MS  2 2798.62 5392.62  29 2  2692.31  1  7406.00  27  6kk.67  5  023k.67 4783.36  60 2  2391.68  2  7315.91  4  1  8135.40  54  P 4«18  l e s s than .05  7.12  less than .005 less than .005  6828.98 20.33 335.84  70.  <  LU  2x2  8x8  24x24  STIMULI F i g u r e 5• The 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 t h r e e checkerboards by t h e 3,8, and l k week o l d groups, average" over s u b j e c t s . (Experiment I I ) .  71.  a t i o n a o f e i g h t week o l d a w e r e n o t s i g n i f i c a n t l y than those  o f t h r e e week o l d s , n o r w e r e t h e f i r s t  o f t h e t h r e e week o l d s s i g n i f i c a n t l y  longer  longer fixations  than those  of  t h e f o u r t e e n week o l d s * A Newman-Keuls  test  performed 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 B were s i g n i f i c a n t l y longer .01) a n d o f C ( p l e s s t h a n  than those *05>).  f i x a t i o n s of stimulus o f A (p l e s s  The f i r s t  than  fixations of  s t i m u l u s C w e r e n o t 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 t h e i n t e r a c t i o n b e t w e e n Age a n d Stimuli  i n d i c a t e s that the patterns of preference  from lengths  of f i r s t  f i x a t i o n o f t h e t h r e e age g r o u p s w e r e  significantly different. of preference  derived  To i n v e s t i g a t e f u r t h e r t h e p a t t e r n  o f e a c h age g r o u p , t h r e e one-way a n a l y s e s  of  v a r i a n c e were p e r f o r m e d 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 g r o u p s . ses a r e p r e s e n t e d Newman-Keuls  i n Tables  Summaries o f t h e s e  13 t h r o u g h  1£>.  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 tween p a i r s o f s t i m u l i . -  f i x a t i o n s be-  F o r t h e t h r e e week o l d s f i r s t  a t i o n s of s t i m u l u s A w e r e s i g n i f i c a n t l y l o n g e r t h a n o f b o t h s t i m u l i B a n d G ( b o t h p's l e s s t h a n  .01).  o f s t i m u l u s C.  fix-  those The  f i x a t i o n s o f s t i m u l u s B were n o t s i g n i f i c a n t l y l o n g e r those  analy-  first than  Thus, i n terms of t h e l e n g t h of 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 t h e s t i m u l i i n d e creasing order o f t h e i r  complexity.  TABLE 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 . e a c h o f ""three S t i m u l i b y 3 Week o l d group (Experiment I I ) Source Between i n f a n t s Within infants Stlmuli Res i d u a l Total  SS 6689.33 12592.67 19282.GO  df  6066.2 6526.k?  9 20  2 18  MS  3033.1 362.58  8.365  less than  .005  29  TABLE l k 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 o f ""Three .St i m u l i b y 8 Week o l d Group (Experiment I I ) Source Between people Within people Stimuli Residual Total  Source Between i n f a n t s Within infants Stimuli Res i d u a l Total  SS k98l.20 31076.67  22986.87 8089.80 36057.87 .  df  MS  F  P  9 20 2 18  11493.435 449.430  25.57  less  t h a n .005  29.  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 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 o f T h r e e S t i m u l i b y l i j . Week o l d Group (Experiment I I ) SS df . ..MS F 5735.47 9 6565.33 20 3046.20 2 1523.1 7.79 3519.13 18 195.51 12300.80 29  P less  than .005  73. F o r t h e e i g h t week 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 pairs  of f i r s t  ( a l l p's l e s s  f i x a t i o n times than  .01}•  o f t h e s t i m u l i were  The f i r s t  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 first  fixations  those  o f A.  fixations  significant  o f stimulus B  o f b o t h A a n d G, a n d t h e  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  A c c o r d i n g t o t h i s r e s p o n s e m e a s u r e e i g h t week  olds preferred the stimulus o f intermediate complexity t h e most c o m p l e x p a t t e r n n e x t , a n d t h e l e a s t For  t h e l k week o l d g r o u p t h e f i r s t  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 less  than  those  .01 and . 0 5 r e s p e c t i v e l y ) .  terms o f t h e l e n g t h o f f i r s t  complex  fixations  The f i r s t  least.  o f stimulus  f i x a t i o n s of  o f A.  Thus, i n  f i x a t i o n , t h e l k week o l d s  the s t i m u l i i n i n c r e a s i n g order o f t h e i r  The  most,  of both A and B (P's  B were n o t s i g n i f i c a n t l y l o n g e r t h a n those  ferred  than  pattern of preference  pre-  complexity.  f o r e a c h o f t h e t h r e e age  g r o u p s i n t e r m s 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 a s the preferences  derived from the lengths  of f i r s t  fixations  of each group.  A few o f t h e s i g n i f i c a n c e  levels  a t t a i n e d by  the d i f f e r e n c e s between t h e f i r s t  fixations  w e r e n o t as h i g h a s t h o s e  by t h e d i f f e r e n c e s i n t o t a l  fixation  reached  of the s t i m u l i  times.  Inter-Observer  R e l i a b i l i t y o f Length of F i r s t  Inter-observer r e l i a b i l i t y on t h e same n i n e was c a l c u l a t e d  Fixation:  f o r t h i s m e a s u r e was  assessed  s u b j e c t s o n whom i n t e r - o b s e r v e r a g r e e m e n t  i n Chapter Three.  A P e a r s o n product-moment  7k. c o r r e l a t i o n between the l e n g t h o f f i r s t f i x a t i o n s r e c o r d e d by each o b s e r v e r i n each t r i a l was +.79. b) Rate o f H a b i t u a t i o n For  each s u b j e c t the s e r i e s o f 12 t r i a l s was d i v i d e d  i n t o two h a l v e s o f s i x t r i a l s  each.  For each age group the  t o t a l l o o k i n g time f o r each stimulus was c a l c u l a t e d f o r each h a l f o f the s e r i e s .  These t o t a l are p r e s e n t e d i n T a b l e 16  along w i t h t h e p r o p o r t i o n o f the t o t a l l o o k i n g time o f the whole s e r i e s that each h a l f - t o t a l  represents.  I n s p e c t i o n o f t h i s t a b l e r e v e a l s t h a t there was no cons i s t e n t p a t t e r n o f 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 I I Contrary t o the f i n d i n g s o f Lewis et a l . (1963)* r a t e of h a b i t u a t i o n was not a f u n c t i o n o f t h e complexity o f the p a t t e r n s i n the present experiment.  There was no h a b i t u a t i o n  i n any age group t o any o f the s t i m u l i over the f o u r i n which each was p r e s e n t e d .  trials  T h e r e f o r e , i n the r e s t o f the  chapter d i s c u s s i o n w i l l be concerned w i t h the other two r e sponses measures a n a l y z e d — of f i r s t  t o t a l l o o k i n g time, and l e n g t h  fixation.  Table 17 p r e s e n t s the r e s u l t s o b t a i n e d from b o t h o f these response measures. Part A p r e s e n t s a comparison between t h e r e s u l t s o f Newman-Keuls t e s t s performed w i t h each group.  W i t h i n each  group 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 b o t h response  75. TABLE 16 Total  F i x a t i o n T i m e ( i n s e c o n d s ) f o r Each, ' - Half of the 1 2 - T r i a l Series  " STIMULUS A 1st h a l f 2nd h a l f  1st  STIMULUS B h a l f 2nd, h a l f  1st  STIMULUS C h a l f 2nd h a l f  3 weeks  kl7  387  239  279  136  100  proportion of t o t a l  .52  .k8  .k6  .54  .58  .k2  282  260  531  580  366  380  proportion of t o t a l .52 l o o k i n g t ime  .48  ,k8  .52  .49  .51  239  192  365  323  478  k33  proportion of t o t a l .55 looking time  .45  .53  .47  .52  .48  looking 8 weeks  l k weeks  time  76.  TABLE 17 R e s u l t s Obtained from t h e Response MeasureB S t u d i e d i n Experiment I I A.  INDIVIDUAL ANALYSES OP EACH AGE GROUP Length o f T o t a l F i x a t i o n ' P Results  3 WEEKS  8 WEEKS  l k WEEKS  B.  1> 2 1>3 2> 3 2> 3 2>1 3>1 3>1 3> 2 2> 1  < .01 < .01 < .01 < .01 < .01 <• .01 < .01 < .©2 < .01  Length o f F i r s t Fixation P Results  1> 2 1> 3 2> 3 2> 3 2> 1 3>1 3>1 3> 2 2>1  <.01 <.01 NS <.01 .01 < .01 <.01 <.o5 NS c  OVERALL ANALYSES OP THE AGE GROUPS AND STIMULI TAKEN . .. . TOGETHER Length o f T o t a l F i x a t i o n .Length o f F i r s t .. Fixation P P Results Results  8>lk  AGE  NS  8> 3  < .01 < .05 < .01 < .01 NS  lk>3 STIMULI  C.  B >C B >A G> A  8> l k 8> 3 3> l k  <.05  B> C B > A Q> A  <.©5 <.01 NS  NS NS  PEARSON PRODUCT-MOMENT CORRELATION BETWEEN THE TWO OBSERVERS RECORDS. Length o f T o t a l F i x a t i o n + .9k  Length o f F i r s t Fixation + .79  7  measures were i d e n t i c a l . varied. of  7  *  Only t h e l e v e l s o f s i g n i f i c a n c e  On t h e w h o l e t h e 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  t o t a l f i x a t i o n w e r e 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 the l e n g t h of f i r s t  fixation.  T h i s suggests  that  l e n g t h o f 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 detecting differences  i n the groups  1  p r e f e r e n c e s among t h e  stimuli. 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 t h e NewmanKeuls t e s t s  f o l l o w i n g t h e two-way a n a l y s e s o f v a r i a n c e f o r  both response measures.  The r e s u l t s o b t a i n e d f r o m  r e s p o n s e m e a s u r e s w e r e i n t h e same d i r e c t i o n s e f f e c t s exeept effect.  f o r a non-significant  both  for both  r e v e r s a l I n t h e Age  I n t e r m s 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  sig-  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 together than d i d t h r e e week o l d s , w h e r e a s t h e f i r s t o l d s were l o n g e r t h a n t h o s e ficant  f i x a t i o n s o f t h r e e week  o f l k week o l d s t o an  insigni-  degree.  The p r o d u c t - m o m e n t c o r r e l a t i o n b e t w e e n t h e t w o o b s e r vers' records f o r t h e nine infants 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 t h e more r e l i a b l e r e s p o n s e measure o f the t w o . In of  first  similar  conclusion, both length of t o t a l f i x a t i o n were good response results.  more r e l i a b l e  f i x a t i o n and l e n g t h  measures w h i c h  gave  H o w e v e r , l e n g t h o f t o t a l f i x a t i o n was t h e  a n d more s e n s i t i v e m e a s u r e o f t h e t w o .  78  CHAPTER  FIVE  EXPERIMENT I I I Purpose Experiment  I I I was d e s i g n e d t o compare r e s u l t s o b -  t a i n e d w i t h a p a i r comparisons procedure w i t h those obt a i n e d i n Experiment  I I , w h i c h employed  a single  stimulus  procedure. METHOD The m e t h o d o f E x p e r i m e n t Experiment  I I I was t h e same as t h a t f o r  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 : Subjects  The  s u b j e c t s w e r e 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 and t e n l k week o l d s , r a n g i n g t o l k weeks, f i v e  days,  i n age f r o m 13 w e e k s , t w o d a y s ,  days. Apparat us  For t h e p a i r comparisons procedure a d i f f e r e n t hinged i n t o the apparatus c e i l i n g .  T h i s door c o n t a i n e d  s t i m u l u s h o l d e r s , e a c h 12" b y 9", t h e i r 10j-" a p a r t .  One o b s e r v a t i o n h o l e  door  i n n e r edges  was two  being  o f i | " i n d i a m e t e r was l o -  c a t e d midway b e t w e e n t h e two s t i m u l u s h o l d e r s .  Two  others  w e r e l o c a t e d j u s t t o t h e i n s i d e o f t h e h o l d e r s , 9tr  apart.  u  Procedure Each o f the t h r e e  c h e c k e r b o a r d s was c o m b i n e d  with  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 e a c h o f the two right  s p a t i a l arrangements.  In  each left-  the description to follow,  79. a combination  r e f e r s t o t w o 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  m a t t e r what t h e i r s p a c i a l a r r a n g e m e n t order).  A pair refers to a specific  ( e . g . A w i t h B i n any combination  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 account, for  each combination  AB a n d B A ) .  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 .  Each o f t h e three combinations  w i t h C, a n d B w i t h C) was p r e s e n t e d first  so t h a t  (A w i t h B, A  i n random o r d e r f o r t h e  t h r e e t r i a l s , a n d 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 A f t e r these s i x t r i a l s  any t r i a l  three  trials.  o n w h i c h b o t h members o f  t h e p a i r h a d n o t b e e n f i x a t e d by t h e s u b j e c t was  repeated  u n t i l b o t h members h a d b e e n f i x a t e d , up t o a maximum o f t h r e e more t r i a l s f o r a n y o n e p a i r . I n t e r - O b s e r v e r Agreement In of  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 a n d s i x  t h e l k week o l d s two o b s e r v e r s w e r e u s 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 to  the right  to the left  operated the recording buttons  In two  independently  through  Each  observer  on h i s r e s p e c t i v e s i d e o f t h e  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  Thus, each observer  infant  adjacent  stimulus holder.  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 box.  observed  s t i m u l u s h o l d e r , and t h e other observed  the hole adjacent  apparatus  One  rendered  r e c o r d e r i n a padded  recorded t h e f i x a t i o n s o f the  of the other.  t h e p a i r comparison  procedure  each observer  operated  b u t t o n s , one f o r e a c h s t i m u l u s , a n d t h u s a l l f o u r  channels  80. of 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  agree-  ment s c o r e was c a l c u l a t e d f o r e a c h s u b j e c t b y c o u n t i n g t h e number o f s e c o n d s p e r 30 s e c o n d t r i a l servers agreed, that  d u r i n g which the ob-  i s , a l l time except that  during  which  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 o n 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  sti-  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 totalled  o v e r t h e number o f t r i a l s  f o r each subject and con-  v e r t e d t o a percentage o f t o t a l stimulus 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 a g r e e m e n t r a n g e d 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 g r o u p d i d a n y I n f a n t l o o k a t b o t h members of 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 h a d t o be r e p e a t e d f o r e a c h s u b j e c t .  For the  l k week o l d g r o u p t h e t o t a l number o f t r i a l s to 13.  ranged from 7  The mean number f o r t h e 10 i n f a n t s was n i n e .  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 b o t h members o f a p a i r w e r e f i n a l l y  For  obtained i n which  fixated.  Both  stimuli  w e r e 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 o n t h e group..  F o r t h e e i g h t week o l d g r o u p t h e number o f t r i a l s  presented ranged from 8 t o 2 3 . the  The mean number o f t r i a l s f o r  10 i n f a n t s was l k . F o r o n l y f i v e  finally  i n f a n t s were s i x t r i a l s  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 w e r e  fixated.  B o t h s t i m u l i w e r e 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 run  on t h e group.  81. Pour s e t s of s i x t r i a l s subject.  T h i s was  e a c h s e t c o u l d be  each were a n a l y z e d f o r each  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 c o m p a r e d t o see  emerged when u n s u c c e s s f u l t r i a l s  i f different  preferences  w e r e r e p l a c e d o r 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 w e r e made.  These f o u r s e t s  were: 1.  Original t r i a l s .  six  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  2.  Original trials  first The  six trials  o f t h e s e t s was  trials  merely  the  In  these  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 w e r e made.  f o r the l e f t  right  s t i m u l i and  the  total  s t i m u l i were c a l c u l a t e d over  and t h e d i f f e r e n c e b e t w e e n t h e m f o u n d .  f e r e n c e was  first  presented.  corrected f o r side preference.  t o t a l l o o k i n g t i m e f o r the  looking time six  One  t h e n d i v i d e d by  t h e number o f t r i a l s  the  This (6)  to  t a i n t h e a v e r a g e amount o f s i d e p r e f e r e n c e p e r t r i a l . f i g u r e was  s i d e on e a c h o f t h e s i x t r i a l s ,  This  result-  ing  i n the c o r r e c t e d l o o k i n g times f o r each s t i m u l u s .  3.  T r i a l s w i t h replacement.  of the f i r s t  l i  six trials  I n the t h i r d set o f 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  r e p l a c e d by a r e p e a t e d t r i a l  had been f i x a t e d , i f such a t r i a l  not  i n which both  existed.  As  s t i m u l i both s t i m u l i had  not been f i x a t e d .  the t r i a l f o r t h i s p a i r i n the f i r s t  stimu-  noted,  In such a  six trials  any  been  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 of a p a i r  placed.  ob-  t h e n added t o the l o o k i n g time 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  f i x a t e d was  dif-  was  not  with  of ease, re-  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  For t h e t h i r d  set of t r i a l s  preference.  corrections f o r side  preference  w e r e a l s o made. I n terms o f l o o k i n g time f o r each stimulus 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  o n e a c h t r i a l was n o t e d .  F o r each  o f t h e 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 p e r f o r m e d separately f o r each combination jects i n each age group. 1  presented For  i n Table  o f s t i m u l i f o r t h e 1© s u b -  The r e s u l t s o f t h e s e  tests are  18.  t h e e i g h t week o l d g r o u p s t i m u l u s B, t h e p a t t e r n  of intermediate  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  t h e most c o m p l e x p a t t e r n .  Stimulus  f e r r e d t o stimulus  G.  A was o n l y  F o r t h e BA s t i m u l u s  slightly  trials  on w h i c h b o t h were f i x a t e d  the s i g n i f i c a n c e l e v e l o f preference  combinations.  the o r i g i n a l t r i a l s  set  increased the  f o r B over G w i t h  both  s e t and t h e t r i a l s w i t h replacement s e t .  T h u s , f o r t h e e i g h t week o l d g r o u p , t h e most preferences  This  f o r the o t h e r two  Correcting f o r side preference  s i g n i f i c a n c e o f t h e group preference  fixated  increased  f o r B o v e r A.  was n o t s o w i t h t h e r e p l a c e m e n t t r i a l s  pre-  combination, r e -  p l a c i n g t h e t r i a l s o n w h i c h o n l y one s t i m u l u s was w i t h repeated  C,  significant  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  i n which corrections f o r side preferences  replacement w e r e made.  F o r t h e l k week o l d g r o u p , b o t h s t i m u l i B a n d C w e r e n i f i c a n t l y preferred t o stimulus A I n a l l four  sig-  sets of t r i a l s .  83  TABLE 18 R e s u l t s o f S i g n T e s t P e r f o r m e d o n P a i r Comp a r i s p n s Data (Experiment i l l )  8  STIMDXUS PREFERENCES OF THE GROUPS A > C B; A B> G  WEEKS  <.©5*  NS  C.10  <.05  NS  < ,©5  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  <.01  NS  <.©5  l k WEEKS  B> A  O A  O  <.01  <.01  G = I  <.01  <.01  G = I  1. O r i g i n a l  trials  2. O r i g i n a l t r i a l s 3.  Trials with  corrected  corrected  trials  B  1.  Original  2.  Original trials  3.  Trials with  replacement  <.01  < .01  <.05*  k-  Trials with corrected  replacement  < .01  ^ .01  < .05  corrected  * Figures i n the matrix represent the levels 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. H o w e v e r , 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 t h e r e placement t r i a l s :  i n the original t r i a l s  were p r e f e r r e d e q u a l l y . did  s t i m u l i C and B  Correcting f o r side  preferences  not c h a n g e t h e m a g n i t u d e o f t h e p r e f e r e n c e s  the stimulus combinations.  on a n y o f  T h i s was p r o b a b l y b e c a u s e  less  s i d e p r e f e r e n c e was shown b y l k week o l d s t h a n b y 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 w e r e s l i g h t a n d n o t 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 . T h e r e w e r e 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 from 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 week o l d g r o u p . ces  Table  19 p r e s e n t s  i n terms o f the t o t a l  looking time f o r each stimulus combination  In  f o rthe t r i a l s  corrected f o r side preferences.  t h e e i g h t week o l d g r o u p e i g h t s u b j e c t s showed  s i t i v e preferences  tran-  a l t h o u g h o n l y t w o o f t h e s e w e r e t h e same  as 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 . had  i n the eight  the individual preferen-  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  w i t h replacement  differed  A l l 10 o f t h e l k week o l d s  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 . In  summary, f o r b o t h g r o u p s ,  preferences  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 than w i t h the o r i g i n a l t r i a l s .  t o g e t h e r , t h e most s i g n i f i c a n t trials  w i t h replacement  with  replacement  Correcting f o r side prefer-  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 t h e e i g h t week o l d g r o u p o n l y .  of g r e a t e r  l e v e l o f one p r e f e r e n c e f o r Therefore, taking both  groups  r e s u l t s were o b t a i n e d w i t h t h e  corrected f o r side preferences.  85*.  TABLE 1 9 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 T i m e f o r T r i a l s w i t h R e 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 III) INDIVIDUAL PREFERENCES SHOWN 8 WEEKS  B>A  B> G  NUMBER OF INFANTS SHOWING PREFERENCE  RELATION TO . T R A N S I T I V E OVERALL GROUP OR PREFERENCE INTRANSITIVE same  transit ive  A >C  l k WEEKS  B ?A B >C O A  different  transitive  B >A G >B C >A  different  transitive  A >B B > C A ? G  different  transitive  B >A C >B A >C  different  intransitive  A >B B > C O A  different  intransitive  G>B B >A G ^A  same  B >G B ?k O A  different  transitive  transitive  86.. DISCUSSION I.  Comparison o f R e s u l t s o f P a i r Comparisons and Stimulus Procedures.  Single "  W i t h t h e p a i r c o m p a r i s o n s p r o c e d u r e t h e most r e s u l t s were o b t a i n e d  w i t h the t r i a l s w i t h replacement  ted for side preference. t r a n s i t i v e and  significant  The  preferences  of b o t h g r o u p s were  consonant w i t h the h y p o t h e s i s  i n f a n t , t h e m o r e c o m p l e x t h e p a t t e r n he  that the older  l k week o l d group t h e  same o r d e r  was  obtained  w i t h both procedures:  the most complex  was  p r e f e r r e d t o b o t h the  mediate complexity F o r the complexity  was  was  p r e f e r r e d t o the l e a s t  Under t h e  c o m p l e x s t i m u l u s was  single stimulus  significantly  Under the  B-A-C II.  This  order  c r e a t e s no  o r a B-C-A  inter-  complex p a t t e r n . intermediate  o t h e r two  with  procedure the  and  the  least  most com-  other h a l f p r e f e r r e d  problem of i n t r a n s i t i v i t y  order  M e a s u r i n g l o o k i n g t i m e and  Design  Data  converting t h i s Into  of the  s c a l i n g methods, wastes d a t a .  - either a  i s possible.  Methods o f A n a l y z i n g t h e  f o r i n s t a n c e , i n the use  of  p r e f e r r e d to the  Problems w i t h t h e P a i r Comparisons 1.  stimulus  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, C t o A.  preference  stimulus of  s i g n i f i c a n t l y p r e f e r r e d to the  both procedures.  plex stimulus.  of  the s t i m u l u s  e i g h t week o l d g r o u p t h e  the  prefers.  For t h e  o t h e r s , and  correc-  preferences,  s i g n t e s t , or l n p a i r comparison The  i n terms o f l o o k i n g time are not  m a g n i t u d e of t h e  taken into account.  preferences On  the  o t h e r h a n d , 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  87.  yet been found f o r t h i a procedure. (1963) u s e d a c h i - s q u a r e t e c h n i q u e  Keasen and  Hershenson  i n a n a l y z i n g t h e number o f  f r a m e s o f f i l m i n w h i c h an i n f a n t ' s e y e s w e r e f i x a t i n g s t i m u l u s , but their  t h e t e c h n i q u e was  experiment.  Scheffe  1  of variance f o r pair  inappropriatelyapplied i n  (1952) has  d e v i s e d an a n a l y s i s  comparisons designs but h i s d e s i g n would  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 s t u d i e a on i n f a n t  each  i t c o u l d be a p p l i e d t o  perception.  I n t h e e x p e r i m e n t s by H e r s h e n s o n ( 1 9 6 k ) , H e r s h e n s o n , e t a l . ( 1 9 6 k ) , and K e s s e n a n d H e r s h e n s o n (1963), p i c t u r e s o f t h e e y e s o f t h e i n f a n t s u b j e c t s w e r e t a k e n a t a n . a v e r a g e r a t e o f one f r a m e p e r s e c o n d . The number of f r a m e s i n w h i c h t h e e y e s w e r e 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 a n d c o m p a r e d w i t h t h e number of f r a m e s 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 preference into account. T h i s was done by means o f 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 f r a m e s as g p p o a e d t o a n 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 w o u l d 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 o f two f r a m e s p e r a e c o n d , i t I a l i k e l y t h a t h e 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 an expected k frames. 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 c a s e w o u l d be ^ (8-k)2 , t w i c e a s l a r g e as the previous v a l u e . Thus, had the 11 experiment era photographed t h e i r a u b j e c t a ' e y e a a t any r a t e o t h e r t h a n a t one f r a m e p e r a e c o n d , they would have o b t a i n e d chi-aquare values d i f f e r e n t from the ones t h e y d i d o b t a i n . K e s s e n and H e r s h e n s o n (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 u s e d n o t a s a t e s t o f s i g n i f i c a n c e b u t as a m e t r i c f r o m w h i c h s i g n e d Z s c o r e s w e r e d e r i v e d t o g e t 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 w e r e 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 a n d t h e l a t t e r w e r e comp 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 m i s u s e 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 of a continuous v a r i a b l e , In 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 d e p e n d e n t upon the s i z e o f the u n i t s i n t o w h i c h time i s d i v i d e d .  88, 2. a.  Finding Controls f o r Side  Experimental Before p a i r  Preferences  Controls c o m p a r i s o n s c a n 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 t r o l l i n g h e a d movements o f i n f a n t s must be f o u n d .  con-  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 of t h e i r heads.  Perhaps something l i k e the  surgi-  c a l s a n d b a g s p l a c e d on e a e h s i d e o f t h e i n f a n t ' s h e a d i n a s t u d y b y W a t s o n (1965) w o u l d r e s t r a i n g r o s s h e a d movements t o e i t h e r the l e f t  or the r i g h t .  However, even i f t h e s 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 h e a d i s w e l l c e n t e r e d , y o u n g I n f a n t s do n o t f i e l d s as much a s o l d e r i n f a n t s . the f i r s t  s t i m u l u s t h e y s e e and  mulus o f a p a i r .  T h i s c a n be  infant's  scan t h e i r  visual  T h e i r eyes t e n d t o r e s t not  side  t o move t o t h e o t h e r  on sti-  overcome t o some d e g r e e b y 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 h a v e b e e n 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  ter  can o n l y r e p e a t a t r i a l  starts to fuss. at both s t i m u l i .  experimen-  so many t i m e s b e f o r e t h e  By t h e n t h e i n f a n t may  still  infant  not have  looked  T h i s i s a s e r i o u s problem 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 Control S i d e p r e f e r e n c e c a n be  methods. experiment  controlled  A s i m p l e method i s t h e  one  somewhat b y  statistical  employed I n t h e  present  i n which the average s i d e preference per t r i a l  a d d e d 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  was  non-preferred  89.  aide.  Another  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 (1963)  i n which  the expected  cies take side preference i n t o account. this to  technique  frequen-  As n o t e d ,  though,  i s n o t 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  be a n a l y z e d .  T h e c h i - s q u a r e t e c h n i q u e w o u l d 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 , b u t t h i s response  measure i s n o t as good as f i x a t i o n t i m e f o r d i s -  covering infant preferences f o r different III.  E v a l u a t i o n o f Procedures Both the single  were r e l i a b l e .  and Recommendationa  s t i m u l u s and.pair comparisons  The s i n g l e  run than the p a i r  stimuli.  stimulus procedure  comparisons,  procedures  was e a s i e r t o  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 w e e k s , s i n c e s i d e p r e f e r e n c e was n o t a p r 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 e n c e s s o t h a t i t was  equally probable that the Infant would  look t o e i t h e r a i d e , t h i a would repreaent provement f o r t h e p a i r  comparisons  an i m p o r t a n t  procedure.  im-  I t may be a r -  g u e d t h a t a s 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 h e may be p e r c e i v i n g t h e other s t i m u l u s p e r i p h e r a l l y , i f not and  t h e r e f o r e may  centrally,  s t i l l be m a k i n g a c h o i c e b e t w e e n t h e t w o .  H o w e v e r , i t i s a s y e t unknown j u s t how c a n 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  much a y o u n g i n f a n t that i n t h i s  ment b e t t e r r e s u l t s w e r e o b t a i n e d f r o m t h e r e p l a c e m e n t than from the o r i g i n a l t r i a l s  suggests that r e l i a n c e  n o t be p l a c e d u p o n p e r i p h e r a l v i s i o n .  experitrials should  90.  I f one had e x c e l l e n t experimental  c o n t r o l s f o r side  p r e f e r e n c e s n e i t h e r r e p e t i t i o n of t r i a l s where the two  sti-  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 c o r r e c t i o n , which i n any necessary. of  Fair  case a r e always a second best would be  comparisons would then be a v i a b l e method  studying infant a t t e n t i o n t o various s t i m u l i .  be e x p e r i m e n t a l l y manageable f o r i n f a n t s , and analyzable.  It would  statistically  Most Important, i t Is t h e o r e t i c a l l y adequate t o  d i s c o v e r whether i n f a n t s a r e responding to the dimension presented  i n a set of s t i m u l i .  the establishment  re-  However, In experiments where  o f d i m e n s i o n a l i t y i s not a prime aim,  the  s i n g l e stimulus procedure would probably be more e f f i c i e n t .  91. CHAPTER S I X SUMMARY AND The  CONCLUSIONS  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 stimuli of different  complexity 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 c o m p l e x t h e p a t t e r n he p r e f e r s . this  Three experiments  were p e r f o r m e d , t o t e s t  hypothesis. H e r s h e n s o n (196k)  presented  three checkerboard  designs  c o n t a i n i n g 2 x 2 , k x k, a n d 1 2 x 12 b l a c k a n d w h i t e t o newborn i n f a n t s . stimuli  that t h e infants preferred the  in..decreasing order o f t h e i r  of the f i r s t the responses those  He f o u n d  experiment  squares  complexity.  The p u r p o s e  o f t h e p r e s e n t r e s e a r c h was t o compare  o f o l d e r i n f a n t s towards these  o f Hershenson's newborns.  stimuli  I n Experiment  week o l d i n f a n t s w e r e p r e s e n t e d w i t h t h e t h r e e i n a s i n g l e stimulus presentation procedure.  with  I , 10 a n d 2 0 checkerboards The l e n g t h o f  t i m e d u r i n g w h i c h e a c h s t i m u l u s was f i x a t e d b y a n i n f a n t was recorded.  I t was f o u n d  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 order These r e s u l t s complimented t h o s e  of complexity.  o f Hershenson (196k) I n  supporting the hypothesis that older infants prefer 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 . d i f f e r e n c e was f o u n d  The f a c t  t h a t no  i n t h e p r e f e r e n c e s o f t h e 10 a n d 2 0 week  o l d s was a t t r i b u t e d t o t h e f a c t  that the set of s t i m u l i  d i d n o t encompass a w i d e e n o u g h r a n g e o f c o m p l e x i t y .  used  92. Further ment I I .  support  Using  o f the h y p o t h e s i s  the  was  sought i n E x p e r i -  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  dure as t h a t used i n Experiment I , t h r e e , e i g h t , and old  i n f a n t s were p r e s e n t e d  boards c o n t a i n i n g 2 x 2 ,  procel k week  w i t h t h r e e b l a c k and w h i t e  8x8,  and  2k x 2k  checker-  squares.  In  terms of t o t a l f i x a t i o n time f o r eack i s t i m u l u s , three o l d s p r e f e r r e d the l e a s t olds preferred the and  complex s t i m u l u s most, e i g h t week  stimulus of intermediate  complexity  l k week o l d s p r e f e r r e d t h e most c o m p l e x s t i m u l u s  These r e s u l t s support  the hypothesis  t h a t the  f a n t , t h e more c o m p l e x t h e p a t t e r n he:  most,  most.  older the i n -  prefers.  S i n c e t h e most c o m p l e x s t i m u l u s was  very near the  o l d o f v i s u a l a c u i t y f o r one  month o l d s as m e a s u r e d by  et a l . (1962),  I I t h e t h r e e week o l d  i n Experiment  were a l s o p r e s e n t e d and  week  w i t h a p l a i n gray  a l b e d o as t h e c h e c k e r b o a r d s .  The  threshFantz  subjects  square of the  same s i z e  t h r e e week o l d s d i d n o t  look s i g n i f i c a n t l y longer  at the most complex c h e c k e r b o a r d  than at the gray  This  l i t y that they  square.  c o u l d not  f u r t h e r supported  suggested the  d i s t i n g u i s h t h e most  checkerboard from a uniformly was  results  gray  square.  at a d i s t a n c e o f l n which the warranted. to focus  the  7i ..' M  b y H a y n e s e t a l . ( 1 9 6 5 ) who  To  found that  m o n t h was l o c k e d  a t a d i s t a n c e o f 7jg  d i s t a n c e t h r e e week o l d s  stimuli clearly.  t o f i x a t e t h e 2k x 2k  possibility  test this possibility a control  s t i m u l i are presented At t h i s  complex  This  t h e a c c o m m o d a t i o n o f i n f a n t s o f l e s s t h a n one  possibi-  n  s h o u l d be  study  is able  A f a i l u r e o f t h e t h r e e week o l d s  checkerboard longer t h a n the gray  square  93. presented at t h i s d i s t a n c e would  indicate that their  visual  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 pattern. One s u b s i d i a r y p u r p o s e  o f t h e r e s e a r c h was t o compare  v a r i o u s response 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 of  first  fixation,  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 -  s p o n s e m e a s u r e was o f n o 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 of  the Infants f o r the s t i m u l i .  length of f i r s t  The t o t a l f i x a t i o n t i m e a n d  f i x a t i o n m e a s u r e s 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 g r o u p .  W i t h b o t h measures a n 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 a g e was f o u n d . e v e r , i t was f e l t sitive  How-  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 -  a n d r e l i a b l e o f t h e two m e a s u r e s .  Another purpose  o f t h i s r e s e a r c h was t o compare two e x -  p e r i m e n t a l procedures 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 (1963) h a v e a r g u e d t h a t inadequate i n infant sitivity the  comparisons.  Kessen and Hershenson  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 may b e  studies.  i s demonstrated  They c l a i m t h a t o n l y i f t r a n -  through a p a i r comparisons  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  stimulus dimension.  —  design can  i s responding t o a  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 y o u n g i n f a n t s , a n d t h e f a c t t h a t t h e y do n o t readily cult  scan t h e i r v i s u a l f i e l d  make p a i r  procedure t o r u n w i t h young i n f a n t s .  comparisons  a diffi-  I n Experiment I I I  a n a t t e m p t was made t o o b t a i n d a t a o n 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 these  practical difficulties.  The s t u d y  employed  a modified p a i r comparisons design i n which t r i a l s both s t i m u l i and  of a p a i r h a d n o t been f i x a t e d were  i n which a simple s t a t i s t i c a l  o n •which  repeated,  correction f o r side pre-  f e r e n c e was e m p l o y e d i n t h e a n a l y s i s o f t h e d a t a .  E i g h t and  l k week o l d s w e r e p r e s e n t e d w i t h t h e same 2 x 2 , 8 x 8 , 2k x 2 k c h e c k e r b o a r d s  used I n Experiment I I .  and  The r e s u l t s o b -  t a i n e d were o o n s o n a n t w i t h t h o s e o b t a i n e d i n E x p e r i m e n t I I and  supportive of the hypothesis.  The e i g h t week o l d g r o u p  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 complexity over the o t h e r t w o , w h i l e t h e l k w e e k o l d g r o u p p r e f e r r e d t h e most complex s t i m u l u s over  the others.  b o t h groups were c o m p l e t e l y the pair  The o v e r a l l p r e f e r e n c e s o f  transitive.  comparisons procedure  However, b e f o r e  using  extensively i n studies of atten-  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 preferences the data The  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  developed. r e s u l t s o f t h e experiments  were congruent,  presented  i nthis  and w e r e 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  increased preference f o r complexity  comes w i t h a g e .  thesis that The r e -  s u l t s c a n be p a r t i a l l y e x p l a i n e d i n t e r m s o f Dember a n d E a r l ' s theory  (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 a n d t h e  organism.  I n terms of t h i s theory, i n t h e present  experiment  t h e s t i m u l u s most p r e f e r r e d b y a n a g e g r o u p was t h e o n e o f t h e set  w h i c h was most s i m i l a r t o t h e p a c e r  of that age.  Stimulus-organism  stimulus f o r infants  c o n c o r d a n c e 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 , a n d t h u s some o f t h e g r o u n d w o r k f o r t h e  v  95". t e s t i n g o f the r e l e v a n c e o f Dember and E a r l ' s area o f i n f a n t tigations  p e r c e p t i o n has been l a i d .  o f environmental  p l e x i t y l e v e l can b e g i n .  theory t o the  T h i s done, i n v e s -  e f f e c t s on an i n f a n t ' s  i d e a l com-  96.  BIBLIOGRAPHY  Ames, E l i n o r W., & S i l f e n , C a r o l e K. Methodological issues 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 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 a n d c o m p l e x i t y . 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