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Paul Dassonville, Carrie A. Williamson; The Systemizing Trait of Autism Reflects a Shift from Reliance on Global to Local Contextual Cues. Journal of Vision 2010;10(7):458. doi: 10.1167/10.7.458.
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The theory that autism is associated with a decreased reliance on contextual cues (Frith 1989) suggested that individuals with autism might have a decreased susceptibility to visual illusions. However, direct evidence for this was mixed (e.g., Happé 1996; Ropar & Mitchell 1999). Recent work, though, has shown that illusion susceptibility is negatively correlated with the autistic trait of systemizing, when measured across the general population (Walter, Dassonville & Bochsler 2009). However, this relationship seemed to hold only for those illusions that were caused by global distortions of the observer's egocentric reference frame. In the present study, we tested this distinction, using an illusion (the Rod-and-Frame Illusion, or RFI) that is known to have two variants. When shown a large tilted frame, the observer's global perception of vertical is distorted, causing a misperception of the orientation of an enclosed rod. In contrast, a smaller tilted frame has no effect on perceived vertical, but causes a misperception of rod orientation via a local contrast effect between the rod and nearby contours of the frame. In 54 typically-developing undergraduates, we separately measured the magnitude of the global and local effects of the RFI. Participants also completed the questionnaires of Baron-Cohen's Autism, Empathizing and Systemizing Quotients. As hypothesized, global distortions of perceived vertical were negatively correlated with systemizing, as well as the attention-to-detail subscale of the Autism Quotient. Surprisingly, systemizing was also found to be correlated with local contrast effects, but here the correlation was a positive one: higher levels of systemizing were associated with an increased susceptibility to the local contrast effects. These findings indicate that while autism is not simply associated with a decreased reliance on contextual cues, it is associated with a more complex shift from a general reliance on global contextual cues to an exaggerated reliance on local contextual cues.
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