Competition is Crucial for Social Comparison Processes in Long-tailed Macaques

Humans modulate their self-evaluations and behaviour as a function of conspecific presence and performance. In this study, we tested for the presence of human-like social comparison effects in long-tailed macaques ( Macaca fascicularis). The monkeys' task was to extract food from an apparatus by pulling drawers within reach and we measured latency between drawer pulls. Subjects either worked on the task with a partner who could access the apparatus from an adjacent cage, worked in the absence of a conspecific but with food moving towards the partner's side or worked next to a partner who was denied apparatus access. We further manipulated partner performance and competitiveness of the set-up. We found no indication that long-tailed macaques compare their performance to the performance of conspecifics. They were not affected by the mere presence of the partner but they paid close attention to the partner's actions when they were consequential for food availability. If social comparison processes are present in long-tailed macaques, the present study suggests they may only manifest in situations involving direct competition and would thus be different from social comparisons in humans, which manifest also in the absence of direct competition, for example in evaluative contexts.