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 (Macaca mulatta) 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 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 individual and more weakly also of the stimulus individuals affected the latency to the next grooming interaction of the focal subject. Latency to the next grooming interaction decreased with increasing rank of the subject potentially reflecting lower social constraints faced by high ranking individuals in this highly despotic species. Relationship quality between the subject and the stimulus individuals had no effect on latency to grooming. Collectively, our findings provide evidence for visual contagion of affiliation in rhesus macaques. Future studies should explore the systematic variation in contagion of interactive behaviour in relation to a gradient of social tolerance.

非互动行为的社会传染在包括人类在内的动物中普遍存在。人们认为，这有助于促进行为同步，从而促进群体凝聚力，协调性和社会学习机会。互动行为（尤其是从属关系）的蔓延受到的关注要少得多。在这里，我们调查了雌性恒河猴（猕猴）观察小组成员的修饰对对象随后的修饰行为以及因关系质量和社会地位而造成的潜在传染调节的影响。我们记录了受试者目睹修饰事件后的行为，并将其与对照组中有相同个体但没有刺激修饰事件的情况下的行为进行了比较。与对照条件相比，女性在观察其他人的修饰后，会更快地进行修饰互动，并且更有可能成为发起者并担当积极的修饰者角色。焦点个体的优势等级以及刺激个体的弱化等级影响了焦点受试者下一次梳理互动的潜伏时间。随下位修饰互动的潜伏时间随着对象等级的增加而降低，这可能反映出在这个高度专横的物种中高级人员所面临的社会限制较低。受试者与刺激个体之间的关系质量对梳理潜伏期没有影响。总的来说，我们的发现为恒河猴猕猴的视觉感染提供了证据。未来的研究应探索与社会容忍度梯度相关的互动行为传染的系统变化。