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Spatial frequency processing in autism spectrum disorder Kamensek, Todd
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).
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