Scrounging facilitates social learning in common marmosets <i>Callithrix jacchus</i>.

We investigated the effect of close social interaction on the ability to learn a new behaviour via observation. The task chosen involved sliding a small door horizontally to gain access to a food reward. We divided 59 common marmosets into five groups that received different pretest experience: observation of a trained demonstrator through wire mesh (O); joint interaction with a trained demonstrator allowing the possibility of scrounging (S); individual interaction with the apparatus (I); joint interaction with another naive individual (J); and no prior experience (control, C). Significantly more individuals from the scrounging group learned the new behaviour, compared with the group (0) that had purely observational experience. When animals from group O were later allowed to interact jointly with a trained demonstrator, the success rate of this group significantly increased. Social interaction with the demonstrator may have facilitated learning because it allowed subjects to understand the relation between the apparatus and the food or because social support facilitated interaction with the apparatus. However, results from the other conditions suggest that these factors alone do not account for the size of the effect. Thus, contrary to previous investigations of this phenomenon, scrounging facilitated social learning. This result probably depended on a complex interaction of a number of factors, including individual learning opportunities, social support and closer attention to the demonstrator. (C) 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.