On Quantifying Facial Expression-Related Atypicality of Children with Autism Spectrum Disorder

Children with Autism Spectrum Disorder (ASD) are known to have difficulty in producing and perceiving emotional facial expressions. Their expressions are often perceived as atypical by adult observers. This paper focuses on data driven ways to analyze and quantify atypicality in facial expressions of children with ASD. Our objective is to uncover those characteristics of facial gestures that induce the sense of perceived atypicality in observers. Using a carefully collected motion capture database, facial expressions of children with and without ASD are compared within six basic emotion categories employing methods from information theory, time-series modeling and statistical analysis. Our experiments show that children with ASD usually have less complex expression producing mechanisms; the differences in facial dynamics between children with and without ASD primarily come from the eye region. Our study also notes that children with ASD exhibit lower symmetry between left and right regions, and lower variation in motion intensity across facial regions.