Visual and Auditory Sensitivity In Autism Spectrum Disorders

Background: The Enhanced Perceptual Functioning theory posits that individuals with ASD have enhanced auditory and visual perceptual abilities (Mottron et al., 2006). Previous studies in support of this theory found that individuals with ASD have demonstrated an enhanced ability to detect differences in pitch, discriminate changes in visual stimuli and detect novel targets in visual arrays. The response type and task demands differed greatly among these studies, making it difficult to draw firm conclusions. Furthermore, no studies have compared visual and auditory perception directly. 

Objectives: The current study sought to fill these gaps in the literature by examining visual and auditory perception in the same participants.  A simple same/different discrimination task was used. It was predicted that individuals with ASD would show increased sensitivity in both auditory and visual domains.

Methods: 13 children with ASD and 11 children with typical development were included in this study (data collection is ongoing). All participants were 8-12 years old and had an IQ above 70. Groups were matched on verbal and nonverbal ability (raw scores on the WASI). Participants completed two same/different discrimination tasks, a brief IQ test, and hearing and vision screening. In the auditory task, participants discriminated tones with three levels of difficulty for pitch and volume. In the visual task, participants discriminated shapes with three levels of difficulty for hue and luminance.

Results: Using a signal detection analysis comparing hits and false alarm rates (d-prime), children with ASD showed enhanced perception in the auditory domain but not the visual domain. For the auditory task, there was a significant two-way interaction between dimension (pitch vs. volume) and diagnosis, F(1,22)=8.68, p<.01. Follow-up analyses revealed that the ASD group demonstrated higher auditory sensitivity than the group of children with typical development in pitch but not volume. For the visual task, there was a significant two-way interaction between dimension (hue vs. luminance) and difficulty, F(1, 22)=86.98, p<.001, which indicates that both groups were more sensitive to differences in luminance than hue, particularly for more difficult discriminations. In the visual task, there was no main effect of diagnosis, F(1,22)=0.22, p=.65. 

Conclusions: Results supported the Enhanced Perceptual Functioning theory for auditory perception. Specifically, children with ASD showed enhanced perception of pitch.  The Enhanced Perceptual Functioning theory was not supported for visual perception.  The lack of significant group differences in the visual domain suggest that the enhanced featural discrimination that has been reported previously may be due to other visual aspects than luminance or color saturation. These results have clinical significance for understanding children with ASD. While in some cases, auditory sensitivity may be adaptive (e.g., for a person with musical interests), hyper-sensitivity may be experienced as painful. It is possible that auditory hyper-sensitivity may underlie the development of some difficulties with social-communication and lead to sensory or repetitive behaviors in an effort to manage the environment.