Auditory-visual integration of temporal relations in infants.

Three experiments examined a u d i t o r y v i s u a l i n t e g r a t i o n o f t e m p o r a l r e l a t i o n s by i n f a n t s . I n t h e f i r s t experiment i n f a n t s o f 3, 6 and 10 months o f age were p l a c e d midway between two f l a s h i n g v i s u a l d i s p l a y s . Tones, t e m p o r a l l y s y n c h r o n i z e d t o one o f the v i s u a l d i s p l a y s , emanated from c o n c e a l e d speakers p l a c e d midway between the v i s u a l d i s p l a y s d i r e c t l y i n f r o n t o f the i n f a n t s . The v i s u a l d i s p l a y s , and c o r r e s p o n d i n g t ones d i f f e r e d i n t e m p o r a l r a t e by a f a c t o r o f f o u r . No e v i d e n c e was found f o r d i f f e r e n t i a l l o o k i n g t o the s o u n d s p e c i f i e d v i s u a l p a t t e r n i n any o f t h e t h r e e age l e v e l s t e s t e d . The 3-month-olds showed a s t r o n g r i g h t l o o k i n g b i a s r e g a r d l e s s o f v i s u a l p a t t e r n o r t e m p o r a l r a t e o f the t o n e , w h i l e t h e 10-month-olds p r e f e r r e d t o l o o k a t the f a s t v i s u a l p a t t e r n r e g a r d l e s s o f p o s i t i o n o r tone r a t e . Both o f t h e s e b i a s e s i m p a i r e d t h e e f f e c t i v e n e s s o f t h e s i m u l t a n e o u s p r e s e n t a t i o n paradigm t o d e t e c t d i f f e r e n t i a l l o o k i n g r e l a t e d t o a u d i t o r y v v i s u a l synchrony. Experiments I I and I I I used an h a b i t u a t i o n methodology which e l i m i n a t e d any e f f e c t s o f p o s i t i o n and r a t e b i a s . O nly 4-month-old i n f a n t s were t e s t e d . I n each experiment, one group o f i n f a n t s was f i r s t p r e s e n t e d w i t h t e m p o r a l l y synchronous a u d i t o r y and v i s u a l s i g n a l s d u r i n g h a b i t u a t i o n t r i a l s and t h e n nonsynchronous s i g n a l s d u r i n g r e c o v e r y t r i a l s . Two o t h e r groups o f i n f a n t s , one i n each experiment, r e c e i v e d t h e o p p o s i t e sequence. I n Experiment I I the a u d i t o r y and v i s u a l s i g n a l s were s p a t i a l l y congruous, but t h e y were s e p a r a t e d by 90° i n Experiment I I I . S i n c e t h e p u l s e r a t e o f t h e v i s u a l s t i m u l i was changed f o r t h e nonsynchronous t r i a l s , a c o n t r o l group.was t e s t e d which r e c e i v e d o n l y the l i g h t d u r i n g h a b i t u a t i o n and r e c o v e r y t r i a l s . B oth groups i n i t i a l l y presented with synchronous signals showed habituation and recovery. Neither group presented with nonsynchronous s t i m u l i during habituation t r i a l s demonstrated recovery and only the group with the s p a t i a l l y separated sources habituated. The results suggest that 4-month-old infants are able to coordinate the temporal relations between auditory and v i s u a l signals.