Perception of Motion Complexity is Deficient in Adults with Autism Spectrum Disorder

Preference for biological motion is characteristic of developing children but not for individuals with autism spectrum disorder (ASD). Work in biomechanics has shown that biological motion can be characterized by qualities of the movement variability (entropy). We hypothesize that a deficit in the perception of this variability may be characteristic of ASD, and the functional basis for non- discrimination of biological motion. Five adults without ASD (2 with) stood quietly on a force platform viewing an oscillating point -light, under two conditions. Point-light motion was driven by sinusoidal or chaotic rhythm. Measures of postural sway and gaze were collected during each condition. Sample entropy quantified the temporal structure of variability in each measure. Individuals with ASD exhibited significantly different gaze response to both stimulus conditions, compared to those without ASD. Although this finding is important, our primary hypothesis was that individuals without ASD would differentiate between the conditions whereas those with ASD would not; which is what we observed. Adults without ASD exhibited greater complexity of their gaze behavior towards the complex motion, whereas adults with ASD did not differ in their gaze patterns. This study provides preliminary evidence that the perception of the structure of movement variability differs for adults with ASD when compared with adults without ASD. This finding has potentially important implications relative to the lack of perception and motor response to biological motion reported for individuals with autism in prior research