Matrilineal social rank is associated with patterns of attention to social scenes in male infant rhesus macaques

Visual attention to others in our immediate environments serves as an adaptive mechanism for early learning across primate species. This study leverages longitudinal eye-tracking data from male infant rhesus macaques collected at up to 14 timepoints from birth to six months to chart visual attention patterns to social videos of unknown conspecifics or mother-infant dyads in a group setting. The distribution of oculomotor movements that index the extent of infant attention to the video stimuli – fixations, saccades, and inattention, i.e., data lost to offscreen looks or movement – stayed constant during this developmental period. Attention to different body areas – mouth, head and body - showed subtle and progressive changes from birth to six months, except for attention to the eyes of conspecifics, which showed two distinct periods of significant increase. The matrilineal social rank of the infant was also investigated as a social factor related to patterns of attention. Rank was significantly associated with the percent of time infants spent making saccades, such that low-ranking infants spent more viewing time making saccades than their high-ranking peers. This association was established by five weeks of age. Collectively, these results provide insight into processes of social attention related to social status in rhesus macaques during infancy.