Live interaction distinctively shapes social gaze dynamics in rhesus macaques

The dynamic interaction of gaze between individuals is a hallmark of social cognition. However, very few studies have examined social gaze dynamics after mutual eye contact during real-time interactions. We used a highly quantifiable paradigm to assess social gaze dynamics between pairs of monkeys and modeled these dynamics using an exponential decay function to investigate sustained attention after mutual eye contact. When monkeys were interacting with real partners compared with static images and movies of the same monkeys, we found a significant increase in the proportion of fixations to the eyes and a smaller dispersion of fixations around the eyes, indicating enhanced focal attention to the eye region. Notably, dominance and familiarity between the interacting pairs induced separable components of gaze dynamics that were unique to live interactions. Gaze dynamics of dominant monkeys after mutual eye contact were associated with a greater number of fixations to the eyes, whereas those of familiar pairs were associated with a faster rate of decrease in this eye-directed attention. Our findings endorse the notion that certain key aspects of social cognition are only captured during interactive social contexts and dependent on the elapsed time relative to socially meaningful events.