Infant macaque monkeys (Macaca mulatta) that receive more face-to-face interaction from their mothers become more sociable later in life, reports a paper published online this week in Nature Communications. This study suggests that, in non-human primates, experiences during infancy have a long lasting effect on social behaviours.

One of the mechanisms proposed to support early social development in humans is face-to-face interaction between caregivers and infants. Previous studies showed that, in rhesus macaques, mothers engage in face-to-face interactions with their infants.

Amanda Dettmer and colleagues showed that the benefits of this kind of mother-infant communication are long-lasting. They monitored natural variations in face-to-face interactions - measured in terms of mutual gaze and intermittent lip-smacking - in ten rhesus monkey mother-infant pairs living in a large, open air enclosure, and found that infant monkeys that received more face-to-face interaction from their mothers during the first month of life displayed increased social interactions - in terms of levels of social play, close proximity to other monkeys and grooming behaviour - at two and five months. In a separate experiment, the authors also examined groups of 48 monkeys that received nursery care from human caregivers. Monkeys randomly assigned to receive additional neonatal face-to-face interactions from human caregivers displayed increased social interest at two months, compared to monkeys who received only additional handling or no extra interactions.

This study of infant monkeys’ social development can aid understanding of human development because macaque monkeys and humans share similar child rearing behaviours and trajectories of social development.