Intersensory Processing and Social Orienting in Children with Autism Spectrum Disorders: Integrating Typical and Atypical Development

Background: Children with autism spectrum disorders (ASD) show altered intersensory processing and impairments in social orienting (Bebko et al., 2006; Dawson et al., 2004; Newell et al., 2007).  Compared to nonsocial events, social events are more variable, complex, and provide an extraordinary amount of intersensory redundancy (e.g., synchrony, rhythm, and intensity changes invariant across the senses).  Further, intersensory redundancy is highly salient and organizes the typical development of attention and perception in infancy (Bahrick & Lickliter, 2002).  We hypothesize that the salience of intersensory redundancy plays a fundamental role in the emergence of social orienting across infancy and that an early disturbance of intersensory processing may lead to reduced social attention in ASD.

Objectives: Little is known about how social orienting emerges in typical development.  Our aims are to investigate the emergence of social attention in typically developing (TD) infants, characterize atypical social attention in children with ASD, and evaluate the role of intersensory information.  Our goal is to begin to bridge the gap between knowledge of typical and atypical development of social attention.   

Methods: First, to examine the typical emergence of social orienting and the role of intersensory redundancy, we evaluated cross-sectional data from 703 TD 2- to 8- month-old infants.  We assessed attention maintenance and disengagement to films of social vs. nonsocial events providing intersensory redundancy (audiovisual synchrony) or no redundancy (unimodal visual, silent).

Second, to assess intersensory processing and attention in ASD, data from 2 to 5 year old children with ASD, developmental delays (DD), and TD were collected using our Behavioral Attention Assessment Protocol (BAAP; Newell et al., 2007).  Children received trials of a central stimulus followed by two side-by-side peripheral events in blocks of social neutral, social positive, and nonsocial events.  One peripheral event was synchronous with the natural soundtrack and the other was out of synchrony.  Intersensory audiovisual matching, attention maintenance and disengagement were evaluated.

Results:   TD infants showed a gradual emergence of enhanced attention to social events across infancy as a function of intersensory redundancy.  Attention to audiovisual social events was maintained across age, while attention to all other events decreased with age.   

Children with ASD showed impaired intersensory processing with no audiovisual matching for social or nonsocial events.  In contrast, TD and DD children showed significant audiovisual matching for social events and TD children also matched nonsocial events. Further, children with ASD showed reduced attention maintenance and impaired disengagement to look to social events, but no difference for nonsocial events. 

Conclusions:   Collectively, these findings confirm growing reports of intersensory processing deficits and greater attention impairments for social than nonsocial events in ASD.  Our findings also reveal new information indicating that social orienting emerges gradually across infancy as a function of intersensory redundancy.  Together, these findings are consistent with the view that an intersensory processing disturbance in early infancy could lead to a failure of social events to become selectively salient and in turn to cascading effects across development including decreased social attention, impaired joint attention, language, and communication, consistent with impairments in ASD.