Social contagion of affiliation in female macaques

Social contagion of non-interactive behavior is widespread among animals including humans. It is thought to facilitate behavioral synchronization and consequently group cohesion, coordination, and opportunities for social learning. Contagion of interactive behavior - particularly affiliation - has received much less attention. Here, we investigated in female rhesus macaques (Macaca mulatta) the effect of observing group members groom on a subject’s subsequent grooming behavior and the potential modulation of contagion by relationship quality and social status. We recorded behavior after subjects witnessed a grooming event and compared it to behavior in a control condition with the same individuals in proximity but in the absence of a stimulus grooming event. Compared to the control condition, after observing others groom, females engaged in a grooming interaction sooner, and were more likely to be the initiator and to take on the active groomer role. Dominance rank of the focal individu...