Response to novel food and the role of social influences in common marmosets (Callithrix jacchus) and Goeldi's monkeys (Callimico goeldii)

Neophobia, defined as showing caution toward novel features of the environment, is widespread in birds and mammals; it can be affected by ecology, early experience, and social context. In this study, we aimed to (i) investigate the response to novel food in adult common marmosets and Goeldi's monkeys and GO assess the role of social influences. We used an experimental paradigm employed previously with capuchin monkeys and children, in which a subject (observer) was presented with a novel food under three conditions: (i) Presence: group members did not have food; (ii) Different color: group members received familiar food whose color differed from that of the observer's novel food; (iii) Same color: group members received familiar food of the same color as the observer's novel food. Although most common marmosets tasted and/or ate the novel food, none of the Goeldi's monkeys ate it and only two sampled it. Differences in home range size and early social experience might explain the divergent behavior of the two species. Observers of both species similarly attended to group members and their visual attention increased with the number of group members eating, especially when the observer's and group members' foods were perceptually similar. However, we observed social influences on explorative behavior in Goeldi's monkeys but not on explorative or eating behavior in common marmosets. This result might be explained by the different pattern of response to novel food observed in the two species. Moreover, social influences on Goeldi's monkeys' behavior were nonspecific, i.e. they were not based on an appreciation that the food is safe because eaten by group members.