The role of the human amygdala in real social interactions remains essentially unknown, although studies in nonhuman primates and studies using photographs and video in humans have shown it to be critical for emotional processing and suggest its importance for social cognition. We show here that complete amygdala lesions result in a severe reduction in direct eye contact during conversations with real people, together with an abnormal increase in gaze to the mouth. These novel findings from real social interactions are consistent with an hypothesized role for the amygdala in autism and the approach taken here opens up new directions for quantifying social behavior in humans.And a clip from their discussion:
It is intriguing ...to consider similarities between our findings and those in autism. People with autism do not fixate photographs and videos of faces normally, and are anecdotally reported to gaze at the mouth in social interactions. It has been suggested that the amygdala dysfunction is in part to blame for these abnormalities in autism, and recent findings using neuroimaging with photographs of faces support this hypothesis.