December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
Visual illusions modulate perception and action in autism spectrum disorder
Author Affiliations & Notes
  • Zoha Ahmad
    York University
  • Noam Karsh
    University of Haifa
  • Tzvi Ganel
    Ben-Gurion University of the Negev
  • Bat-Sheva Hadad
    University of Haifa
  • Erez Freud
    York University
  • Footnotes
    Acknowledgements  This research was funded by Natural Sciences and Engineering Research Council of Canada (NSERC) (EF) and by the Vision Science to Applications (VISTA) program funded by the Canada First Research Excellence Fund (CFREF, 2016–2023) (EF)
Journal of Vision December 2022, Vol.22, 3573. doi:
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      Zoha Ahmad, Noam Karsh, Tzvi Ganel, Bat-Sheva Hadad, Erez Freud; Visual illusions modulate perception and action in autism spectrum disorder. Journal of Vision 2022;22(14):3573.

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      © ARVO (1962-2015); The Authors (2016-present)

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Perceptual changes are a widely acknowledged but poorly understood feature of autism spectrum disorder (ASD). One hypothesis is that these changes are the result of reduced specialization of the different cortical systems. The goal of the current study is to examine this hypothesis in the context of the functional dissociation between perception and action. Past studies have demonstrated that unlike their robust effect on perception, visual illusions have little or no effect on grasping movements. Here, we examine whether this dissociation is observed in individuals with ASD using a version of the Ponzo illusion. We used two objects that differ in size (42 mm, 40 mm), and placed on an illusory background such that they were perceived as “close” or “far” from the observer. We examined the participants’ sensitivity to object size differences and their susceptibility to the illusion. Both groups were equally affected by the illusion in the manual estimation (perceptual) task, such that their estimations were larger for objects placed on the far surface. In contrast, in the grasping task, the two groups exhibited differential susceptibility to the illusion. Particularly, controls were not affected by the illusion, such that their maximum grip apertures (MGA) were scaled to the size of the object regardless of the illusory context. In contrast, the MGA of individuals with ASD were modulated by the illusion with larger apertures for objects placed on the “far” surface. Importantly, the observed susceptibility to the illusion could not be attributed to a deficit in motor control because sensitivity to size was similar for the two groups. Taken together, these results provide evidence for reduced functional dissociation between perception and action in ASD.


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