Context: Within the first week of life, typical human newborns give preferential attention to the eyes of others. Similar findings in other species suggest that attention to the eyes is a highly conserved phylogenetic mechanism of social development. For children with autism, however, diminished and aberrant eye contact is a lifelong hallmark of disability.
Objective: To quantify preferential attention to the eyes of others at what is presently the earliest point of diagnosis in autism.
Design: We presented the children with 10 videos. Each video showed an actress looking directly into the camera, playing the role of caregiver, and engaging the viewer (playing pat-a-cake, peek-a-boo, etc). Children's visual fixation patterns were measured by eye tracking.
Participants: Fifteen 2-year-old children with autism were compared with 36 typically developing children and with 15 developmentally delayed but nonautistic children.
Main outcome measure: Preferential attention was measured as percentage of visual fixation time to 4 regions of interest: eyes, mouth, body, and object. Level of social disability was assessed by the Autism Diagnostic Observation Schedule.
Results: Looking at the eyes of others was significantly decreased in 2-year-old children with autism (P < .001), while looking at mouths was increased (P < .01) in comparison with both control groups. The 2 control groups were not distinguishable on the basis of fixation patterns. In addition, fixation on eyes by the children with autism correlated with their level of social disability; less fixation on eyes predicted greater social disability (r = -0.669, P < .01).
Conclusions: Looking at the eyes of others is important in early social development and in social adaptation throughout one's life span. Our results indicate that in 2-year-old children with autism, this behavior is already derailed, suggesting critical consequences for development but also offering a potential biomarker for quantifying syndrome manifestation at this early age.