The Unique Impact of Autism on the Detection of Temporal Synchrony in Intermodal Processing: What Are the Roles of Intellectual and Language Variables?

Background: Intermodal perception (IMP) plays an integral role in early perceptual development. Individuals with autism often exhibit ineffective sensory processing, and integration of information across auditory and visual modes appears impaired (Iarocci & McDonald, 2006). Deficits in this sensory processing may be related to some of the communication impairments that characterize autism (Bebko et al. 2006). Furthermore, there is limited research investigating the added effects of background noise on the processing of speech in persons with an Autism Spectrum Disorder (ASD).

Despite the high rates of intellectual disabilities and the specific linguistic-related IMP difficulties observed in children with autism, identifying the roles of intellectual functioning and language ability in the IMP skills of children with autism has not been well researched. Appropriate comparison groups are needed to fully understand the degree to which IMP difficulties are limited to autism or are more broadly associated with intellectual disabilities.

Objectives: The present study's objectives were to compare performance on linguistic and non-linguistic IMP tasks: (1) between children with Asperger Syndrome (AS), who diagnostically have no significant language delay, children with autism, and children with typical development (TD) and; (2) between children with an intellectual disability (ID) with no evidence of a PDD, children with autism, and children with TD.

Methods: Participant groups were matched on chronological age, verbal mental age and nonverbal mental age. Groups of participants with AS (n=10), Autism without an Intellectual Disability (ASD without ID; n=11), and TD (n=11) were matched with each other; similarly, the ID (n=10) and Autism with an Intellectual Disability (ASD with ID; n=11) groups were matched with each other.

The present study used eye-tracking with a modified preferential looking design, which involved displaying four identical videos, offset in time, with an auditory track synchronous to only one of the videos. Videos contained either linguistic (person telling a story) or non-linguistic (hand playing a piano) stimuli.  Background noise was added to a portion of trials and the signal to noise ratio (SNR) was manipulated. 

Results:   For the conditions with no background noise, Autism with or without ID differentially predicted performance for the linguistic trials only. The TD, AS, and ID participants were more likely to show a preference for the synchronous screen compared to the Autism with and without ID groups. Group membership did not predict performance in the non-linguistic trials. 

When background noise was added, rates of preferential looking decreased as the SNR increased for the Linguistic condition only. There was no trend found for the Non-linguistic condition.

Conclusions:

The current study was the first to explore IMP in AS and ID populations through the use of a 4-screen modified preferential looking paradigm and has extended our understanding of the impact of autism on IMP. These findings suggest a unique interaction of autism with the ability to detect intermodal temporal synchrony in linguistic contexts, which is not found among children with other forms of intellectual disability or in Asperger Syndrome. Implications of these findings are discussed.