Atypical Updating of Face Representations with Experience in Children with Autism

Background:  Adaptive coding, or the calibration of perception through experience, is widely thought to enhance processing across sensory domains.  An elegant adaptation study conducted by Pellicano, Jeffery, Burr, & Rhodes (2007) revealed significantly reduced face identity aftereffects in children with autism relative to typical children.  The authors suggested that these reduced aftereffects might signal diminished perceptual updating of visual representations with experience in autism, which could contribute to observed face processing difficulties.  It remains an intruiguing, open question whether whether any diminished perceptual updating in autism is restricted to faces, or affects the perception of visual stimuli more broadly.  

Objectives:  This study investigated whether reduced perceptual updating in children with autism extends beyond faces, to non-face stimulus categories.  The selectivity of diminished aftereffects in autism may prove informative about the mechanisms driving reduced perceptual updating in autism, and the scope of its functional consequences.  Broadly diminished adaptation would arguably support a pervasive perceptual atypicality in autism.  In contrast, disproportionately reduced perceptual updating for face stimuli compared to non-face stimuli (relative to typical children) could signal that reduced adaptation is tied to social stimuli specifically, contributing to a face selective processing atypicality.

Methods:  A developmentally appropriate figural aftereffect task directly measured perceptual updating following exposure to figurally distorted (expanded/contracted) upright faces, inverted faces and cars, in typical children (n=29) and children with autism (n=29) of similar age and cognitive ability.  A size change between the study and test stimuli limited the likelihood that any processing atypicalities reflected group differences in adaptation to low-level features of the stimuli. 

Results:  Figural aftereffects for upright faces, but not inverted faces or cars, were significantly diminished in children with autism, relative to typical children.  Moreover, the group difference was amplified when we isolated the ‘face-selective’ component of the aftereffect, by partialling out the mid-level shape adaptation common to upright and inverted face stimuli.  Notably, aftereffects of typical children were disproportionately larger for upright faces than for inverted faces and cars, but the magnitude of aftereffects of children with autism was not similarly modulated by stimulus category. 

Conclusions:  This study provides an important step forward in our understanding of perceptual updating atypicalities in children with autism.  Consistent with a functional role for adaptation in face perception, our findings suggest that reduced perceptual updating in children with autism may constitute a high-level, and possibly face-selective, visual processing atypicality, relative to typical children.