CAPUCHIN MONKEYS, CEBUS-APELLA, FAIL TO UNDERSTAND A COOPERATIVE TASK

We investigated whether capuchin monkeys cooperate to solve a task and to what extent they take into account the behaviour of another indivi dual when cooperating. Two groups of capuchin monkeys (N=5 and 6) were tested in a task whose solution required simultaneous pulling of two handles which were too far from one another to be pulled by one monkey . Before carrying out the cooperation study, individual monkeys were t rained to pull one handle (training phase 1) and to pull two handles s imultaneously (training phase 2) for a food reward. Nine subjects were successful in training phase 1, and five in training phase 2. In the cooperation study seven subjects were successful, that is, pulled one handle while a companion pulled the other. Further analyses revealed t hat capuchins did not increase their pulling actions when a partner wa s close to or at the other handle, that is, when cooperation might occ ur. These data suggest that capuchin monkeys acted together at the tas k and got the reward without understanding the role of the partner and without taking its behaviour into consideration. Social tolerance, as well as their tendency to explore and their manual dexterity, were th e major factors accounting for the capuchins' success. (C) 1997 The As sociation for the Study of Animal Behaviour.