A prosocial character of head-gaze aversion in common marmosets

ABSTRACT Gaze aversion is a behavior adopted by several mammalian and non-mammalian species in response to eye contact and usually interpreted as reaction to perceived threat. Unlike many other primates, common marmosets ( Callithrix jacchus ) are thought to have high tolerance for direct gaze, barely exhibiting gaze avoidance towards conspecifics and humans. Here we show that this does not hold for marmosets interacting with a familiar experimenter who suddenly establishes eye contact in a playful interaction (“peek-a-boo”). In video footage synchronously recorded from the two agents, we found that our monkeys consistently alternated between eye contact and head-gaze aversion. The striking similarity with the gaze aversion’s dynamics exhibited by human infants interacting with their caregivers suggests a shared behavioral strategy to disengage temporarily from overwhelming social stimulation, in order to prepare for a new round of rewarding, affiliative face-to-face interaction. The potential of our finding for a marmoset model of autism is discussed.