Reduced Functional Dissociation Between Action and Perception in Individuals with Autism

Perceptual changes are a widely acknowledged but poorly understood feature of autism. One hypothesis is that those changes are the result of reduced cortical specialization. Here, we sought to examine this hypothesis by exploiting the well-established functional dissociation between the ventral pathway that mediates vision-for-perception, and the dorsal pathway that mediates vision-for-action. We predicted that a reduced cortical specialization would lead to atypical intrusions of perceptual effects in action. To this end, we examined the effect of the Ponzo Illusion on perception and action in a group of typically developed adults and individuals with autism. Two objects that differ in their real size were placed on the illusory background such that there was a conflict between the real size and the perceived size of the objects. In each trial, participants made perceptual size discriminations and then grasped one of the objects based on its perceived size. Consistent with previous results, the maximum grip apertures (MGA) of the typically developed participants were scaled to the real size of the object, even in trials in which their overt perceptual decisions were deceived by the illusion. This, however, was not the case for individuals with autism. In particular, for this group, the MGA were not scaled to the real size of the objects when perceptual decisions were incorrect. These results provide novel evidence for a reduced functional dissociation between perception and action in individuals with autism.