UBC Theses and Dissertations
Low- and high-level visual perception in adults with autism spectrum disorder Shafai, Fakhri
Descriptions of atypical visual processing have been associated with Autism Spectrum Disorder (ASD). Pinpointing the source of altered perception has been challenging. It is possible that the divergence occurs early in visual processing. There have been reports of higher prevalence of refractive errors for children with ASD, but few studies assessing refractive error status of adults on the spectrum. We contribute to this gap by providing complete optometric eye exams to assess refractive status in a group of adults with ASD and Controls. We find no significant differences between our ASD and Control groups for presence or severity of refractive errors, but higher rates of myopia for both groups compared to prevalence in the general population. Results from behavioural studies suggest altered visual functioning may occur further downstream, possibly in the earliest cortical visual areas. The Enhanced Perceptual Functioning (EPF) model proposes that behavioural results can be explained as a consequence of superior perception for “simple visual material”. This model suggests that low-level properties of images may be processed differently in ASD. We examine this assertion for aspects of orientation processing, which is associated with low-level perception. In three behavioural psychophysical tasks, we examine the status of orientation discrimination, veridical perception, and orientation detection in adults with and without ASD. We find no significant differences between our ASD and Control groups for any aspect of orientation perception tested. As social difficulties are a criterion for diagnosis of ASD, various aspects of face processing have been studied in this population, with mixed results. The social motivation hypothesis and amygdala dysfunction hypothesis both suggest face processing abilities may be associated with social competency difficulties in ASD. We examine two different aspects of face processing: identification and recognition of expression, and compare performance to measures of ASD symptom severity and social competence. We find impaired identity and expression perception across all tasks for our ASD group, but only expression processing was associated with social competence. These results have implications for our understanding of visual perception differences in ASD and offer recommendations for future research directions and intervention tools.
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