biostudies-literatureUnknown8(1)Ostner JSocial contagion of non-interactive behaviour is widespread among animals including humans. It is thought to facilitate behavioural synchronization and consequently group cohesion, coordination and opportunities for social learning. Contagion of interactive behaviour-particularly affiliation-has received much less attention. Here, we investigated in female rhesus macaques (<i>Macaca mulatta</i>) the effect of observing group members groom on a subject's subsequent grooming behaviour and the potential modulation of contagion by relationship quality and social status. We recorded behaviour after subjects witnessed a grooming event and compared it to behaviour in a control condition with the same individuals in proximity but in the absence of a stimulus grooming event. Compared to the controlRoyal Society open science201538https://www.ebi.ac.uk/biostudies/studies/S-EPMC7890474biostudies-literatureSocial contagion of affiliation in female macaques.PMC7890474Wilken JOstner JSchulke OfalseSocial contagion of affiliation in female macaques.Social contagion of non-interactive behaviour is widespread among animals including humans. It is thought to facilitate behavioural synchronization and consequently group cohesion, coordination and opportunities for social learning. Contagion of interactive behaviour-particularly affiliation-has received much less attention. Here, we investigated in female rhesus macaques (<i>Macaca mulatta</i>) the effect of observing group members groom on a subject's subsequent grooming behaviour and the potential modulation of contagion by relationship quality and social status. We recorded behaviour after subjects witnessed a grooming event and compared it to behaviour in a control condition with the same individuals in proximity but in the absence of a stimulus grooming event. Compared to the control2021-01-01T00:00:00Z2021 Jan2026-05-01T12:44:04.8Z2025-02-19T04:53:14.565ZS-EPMC78904743361408510.1098/rsos.201538