Relevant Degree Programs
Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - May 2019)
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.
Master's Student Supervision (2010 - 2018)
Autism Spectrum Disorder (ASD) is a developmental disorder characterized by deficits in social-communication and interaction in addition to restricted and repetitive behaviours and interests (American Psychiatric Association, 2013). Despite these deficits, a few studies have reported superior performance in various detail-oriented visual tasks, such as visual search (O'Riordan, Plaisted, Driver, & Baron-Cohen, 2001) and embedded figures (Shah & Frith, 1983). It has been suggested that these atypicalities can be attributed to enhanced perceptual functioning (EPF) in the ASD population (Mottron, Dawson, Soulières, Hubert, & Burack, 2006). In the present study we examined basic visual processing of spatial frequency (SF) as a potential source for EPF. We employed three experiments to assess three distinct aspects of SF perception: sensitivity, precision, and accuracy. In Experiment 1, using a 2-interval forced choice (2-IFC) detection paradigm, we measured contrast sensitivity at eight SFs. In Experiment 2, we assessed precision as a function of spatial frequency via a 2-IFC discrimination paradigm. In Experiment 3, we examined accuracy of SF perception (i.e., veridical perception) via a method-of-adjustment paradigm. Finally, in Experiment 4 we implemented a visual search paradigm that has previously demonstrated superior performance in people with ASD (Kemner, van Ewijk, van Engeland, & Hooge, 2007; O'Riordan et al., 2001). No evidence for enhanced perceptual functioning was found in any of our three experiments examining sensitivity, precision, or accuracy of SF perception in ASD (N = 20) compared to age-, gender-, non-verbal IQ-matched controls (N = 20). In addition, in the visual search task we found faster reaction times in our control group, the opposite of previous studies that found superior performance in ASD. These findings are consistent with previous research on visual orientation perception (Shafai, Armstrong, Iarocci, & Oruc, 2015) suggesting that enhanced low-level visual processing is not a source of EPF in ASD, as well as meta-analyses suggesting that EPF is not a characteristic of the overall population with ASD (Muth, Hönekopp, & Falter, 2014; Van der Hallen, Evers, Brewaeys, Van den Noortgate, & Wagemans, 2015).