Eye tracking protocol.

Participants viewed calm, fearful, or happy faces (random order) for 3 seconds each while eye gaze behavior and pupil size was recorded using a Tobii 120 Hz eye tracker. Each face was preceded by its scrambled version, matched on luminance and color pattern (as a control for pupil light reflex) examining pupil change associated with the social content and sympathetic nervous system activation. The primary area of interest was the eye region (including eyebrows) for examination of proportion of looking time and number of visual fixations to that region. The individuals in this figure have given written informed consent to publish the image (https://macbrain.org/resources.htm).