Call playback artificially generates a temporary cultural style of high affiliation in marmosets

Cultural variation can be conceptualised in two main ways: as culture-specific qualitative differences in behavioural form, and also as quantitative variation in performance of constellations of universal behaviours (cultural style). Despite observation of both types in wild non-human primates, diffusion of qualitative culture has been scrutinised extensively experimentally whilst within-species transmission of cultural style has remained entirely unexplored. Here we investigated whether a cultural style of high affiliation could be artificially generated in a nonhuman primate (Callithrix jacchus), by daily playback of conspecific affiliative calls simulating nearby amicable individuals. We found that vocalisation playback influenced monkeys to spend more time in affiliative behaviours outwith playback hours, relative to silent playback. The effect was specific to affiliation, with no impact on other categories of affect. This change did not persist into the final phase of observation after all playbacks were complete. Findings are consistent with a temporary shift in cultural style effected through vocalisation playback, supporting existence of this conception of culture in wild primates and indicating auditory social contagion as a potential diffusion mechanism. The method presented here will allow researchers to test hypotheses concerning cultural transmission of cultural style, and the underlying processes, across a range of contexts and species