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Bat-Sheva Hadad; Atypical Basic Psychophysics in ASD. Journal of Vision 2014;14(10):675. doi: 10.1167/14.10.675.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual atypicalities are increasingly invoked as contributory causes of the fundamental characteristics of ASD. We tested typically developed (TD) individuals and those with an ASD, matched on age and IQ, on basic psychophysics involved in the perception of a single dimension of objects, as well as the processes mediating the integration of these elementary features in perceiving object's shape. The first study tested Weber's law, a psychophysical principle by which minimum detectable increment in stimulus magnitude (JNDs) increases proportionally with stimulus magnitude. Participants had to adjust the diameter of a disc varying in size to match the size of a real disc presented in front of them. Individuals with autism exhibited estimations that did not differ in accuracy from those of TD observers. However, while JNDs increased linearly with object size for TD observers, demonstrating the adherence of visual perception to Weber as early as 4 years of age, the results for individuals on the spectrum showed no such scaling of JNDs with object size. This sensitivity to the absolute metrics of visual information in ASD points to a qualitative difference in physics-perception relationship compared to TD individuals of comparable age and cognitive abilities. In a second study, participants were asked to make speeded classification judgments of the width of rectangular objects while ignoring height. In situations in which the elementary dimensions of an object's shape were perceived in an integral manner in TD, with judgment of one dimension substantially influenced by the other, the same dimensions were treated analytically in ASD. The results document differences in the way visual information is encoded by these two groups, even at a very basic level of processing. Preliminary results in other sensory domains suggest that a general mechanism rather than a visual one might underlie these perceptual alternations in ASD.
Meeting abstract presented at VSS 2014
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