The Maintenance of Traditions in Marmosets: Individual Habit, Not Social Conformity? A Field Experiment

Abstract

BackgroundSocial conformity is a cornerstone of human culture because it accelerates and maintains the spread of behaviour within a group. Few empirical studies have investigated the role of social conformity in the maintenance of traditions despite an increasing body of literature on the formation of behavioural patterns in non-human animals. The current report presents a field experiment with free-ranging marmosets (Callithrix jacchus) which investigated whether social conformity is necessary for the maintenance of behavioural patterns within groups or whether individual effects such as habit formation would suffice.MethodsUsing a two-action apparatus, we established alternative behavioural patterns in six family groups composed of 36 individuals. These groups experienced only one technique during a training phase and were thereafter tested with two techniques available. The monkeys reliably maintained the trained method over a period of three weeks, despite discovering the alternative technique. Three additional groups were given the same number of sessions, but those 21 individuals could freely choose the method to obtain a reward. In these control groups, an overall bias towards one of the two methods was observed, but animals with a different preference did not adjust towards the group norm. Thirteen of the fifteen animals that discovered both techniques remained with the action with which they were initially successful, independent of the group preference and the type of action (Binomial test: exp. proportion: 0.5, p<0.01).ConclusionsThe results indicate that the maintenance of behavioural patterns within groups 1) could be explained by the first rewarded manipulation and subsequent habit formation and 2) do not require social conformity as a mechanism. After an initial spread of a behaviour throughout a group, this mechanism may lead to a superficial appearance of conformity without the involvement of such a socially and cognitively complex mechanism. This is the first time that such an experiment has been conducted with free-ranging primates.

Conformity without majority? The case for demarcating social from majority influences

“…A similar finding was reported by Whiten (1998): in this study, chimpanzees preferentially used their first-learned action pattern that had been demonstrated to them by one human experimenter, even after discovering that other sequences worked equally well (Whiten, 1998). These observations suggest that chimpanzees remain faithful to what they have learned first, or socially, and that these characteristics, not majority influences, can sufficiently account for the information diffusion and the reversion pattern that form the foundation of the conformity interpretation in primates (also see Hrubesch et al, 2009;Pesendorfer et al, 2009;van Leeuwen & Haun, 2013).…”

“…the reluctance to switch techniques once one technique has been proficiently mastered; Hrubesch, Preuschoft, & van Schaik, 2009;van Leeuwen, Cronin, Schütte, Call, & Haun, 2013;van Leeuwen & Haun, 2013;Pesendorfer et al, 2009). In that case, the reconvergence to the majority behaviour might not even be socially mediated (see van Leeuwen & Haun, 2013).…”

Selective attention to philopatric models causes directed social learning in wild vervet monkeys

“…Another important future direction would be to offer artificial fruits for an extended period of time and monitor similarities between members of the same group. The persistence of different opening methods in different groups would demonstrate the establishment of arbitrary traditions for which until now there has been no clear-cut evidence from the small number of field experiments (Thornton & Malapert 2008;Pesendorfer et al 2009). …”

Experimental field studies with non-human primates

“…Visual stimuli have been used to study economic decision-making [61], social learning [62], individual learning [63], cultural behaviour [64]; [65], or decision-making [66]. Predator presentations also have a long history in primate fieldwork [46], for instance to study anti-predator behaviour, mixed-species grouping or cognition [67], [68]*, [69], [70], [71], [51].…”