From birth, humans typically show a preference for social interaction, favoring the sound of a human voice over silence and the sound of their mother's voice to that of an unknown woman. By three months, infants develop a preference for looking more at a person's eyes than other parts of the face.
Diminished or unusual patterns of eye contact during social interactions are one of the hallmark symptoms of autism, which is part of a group of disorders called autism spectrum disorders (ASDs). ASDs range in severity, with autism being the most debilitating form while other disorders, such as Asperger syndrome, produce milder symptoms. Autism and other ASDs develop in early childhood and generally are diagnosed by age three.
In this study, Warren Jones, Katelin Carr, and Ami Klin, Ph.D., at Yale University assessed eye-tracking patterns in 2-year old children as they watched video clips showing actresses peering directly into the camera and trying to engage the children in interactions such as pat-a-cake. Among the 66 participants, 15 had autism, 36 were typically developing toddlers, and 15 had developmental delays but not autism.
Results of this study
Toddlers with autism preferred looking at the mouth during these video clips, while developmentally delayed and healthy toddlers looked more often at the eyes. Furthermore, for toddlers with autism, lower levels of fixation on the actresses' eyes in the videos were associated with greater social impairment in everyday life.
Altered patterns of eye contact may be a biomarker for autism as early as age two and possibly even earlier. Lack of eye contact in children with autism reflects an altered pattern of brain development, according to the researchers. Not showing the normal preference for eye fixation may also affect a child's social growth by lowering a child's ability to interpret and react to emotional cues communicated by the eyes. In addition, focusing on the mouth suggests that children with autism may follow an alternative path for learning language, possibly relying more on the association between the movement of the mouth and the sounds it makes, rather than learning speech as a social communication tool.
Further studies are needed to confirm these findings and to help researchers to determine which brain circuits and processes are linked with reduced eye contact. Learning more about these relationships can inform the development of treatments to reduce or possibly prevent the social, communicative and cognitive impairments associated with ASDs.