Abnormal social reward processing in autism as indexed by pupillary responses to happy faces
- Equal contributors
1 Department of Psychology, University of California, Los Angeles, CA, 90095, USA
2 Division of Humanities and Social Sciences, California Institute of Technology, Pasadena, CA, 91125, USA
3 Ahmanson-Lovelace Brain Mapping Center, Semel Institute for Neuroscience and Human Behavior, University of California Los Angeles, Los Angeles, CA, 90095, USA
4 Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, 90095, USA
5 Children’s National Medical Center, Washington, DC, 20010, USA
6 School of Psychology and Psychiatry, Monash University, Clayton Campus, Victoria , 3800, Australia
7 Japan Science and Technology Agency, Tokyo, Japan
8 Department of Neurology, Child and Adolescent Assessment Division, Sports Concussion Institute Health Services Research group, University of California Los Angeles, Los Angeles, CA, 90095, USA
Journal of Neurodevelopmental Disorders 2012, 4:17 doi:10.1186/1866-1955-4-17Published: 7 June 2012
Individuals with Autism Spectrum Disorders (ASD) typically show impaired eye contact during social interactions. From a young age, they look less at faces than typically developing (TD) children and tend to avoid direct gaze. However, the reason for this behavior remains controversial; ASD children might avoid eye contact because they perceive the eyes as aversive or because they do not find social engagement through mutual gaze rewarding.
We monitored pupillary diameter as a measure of autonomic response in children with ASD (n = 20, mean age = 12.4) and TD controls (n = 18, mean age = 13.7) while they looked at faces displaying different emotions. Each face displayed happy, fearful, angry or neutral emotions with the gaze either directed to or averted from the subjects.
Overall, children with ASD and TD controls showed similar pupillary responses; however, they differed significantly in their sensitivity to gaze direction for happy faces. Specifically, pupillary diameter increased among TD children when viewing happy faces with direct gaze as compared to those with averted gaze, whereas children with ASD did not show such sensitivity to gaze direction. We found no group differences in fixation that could explain the differential pupillary responses. There was no effect of gaze direction on pupil diameter for negative affect or neutral faces among either the TD or ASD group.
We interpret the increased pupillary diameter to happy faces with direct gaze in TD children to reflect the intrinsic reward value of a smiling face looking directly at an individual. The lack of this effect in children with ASD is consistent with the hypothesis that individuals with ASD may have reduced sensitivity to the reward value of social stimuli.