How special is social looking in ASD: a review.

This review is primarily concerned with the view that individuals with autism spectrum disorder (ASD) look less at the eyes and more at the mouth compared to typically developing (TD) individuals. Such performance in ASD could reflect that the eyes are not meaningful or that they are perceived as threatening, two ideas that may seem intuitively appealing. However, our review shows that despite the fact that the excess mouth/diminished eye gaze hypothesis fits with clinical common sense and initial data from adults, it does not-as a generalization across ages and contexts-fit with the emerging pattern of eye-tracking data. In adolescents and adults, there is only partial support for the excess mouth/diminished eye gaze hypothesis, and regarding children, most studies do not support this hypothesis. In particular, independent studies have found longer looking durations on the mouth in TD children than in children with ASD, and no difference for the eye area. We describe recent evidence that mouth fixations are functional responses related to (early) stages of normative language development. We conclude that although individuals with ASD often give less preferential attention to social objects and events (faces, people, and social actions) than TD individuals, the excess mouth/diminished eye gaze hypothesis of ASD is not generally supported. Therefore, this hypothesis needs to be reevaluated, as do related theories of social perception in ASD.