Capuchins observe but do not learn novel behaviours by imitation

Cammello, an adult male of capuchin, learns how to use a stick to push a peanut out of a tube. Brahms, an adult female, carefully watches him using the stick over and over again. Although there are plenty of sticks, Brahms occasionally prefers stealing Cammello’s peanut instead of using a stick herself. Why? Has not she learnt how to get the peanut? No, she has not. Indeed, capuchins do not learn by imitation.

Are capuchins able to learn by imitation? We know that they are very innovative and when presented with a problem they are likely to find a solution. They are also tolerant enough, so that approaching and observing novel activities performed by other group members is the norm. Despite this, when capuchins’ ability to learn novel behaviours by observation (for example, the use of a tool) from other group members was experimentally investigated, the results did not evidence an ability to learn by imitation these novel behaviours.

Figure. Tube task. Left, a monkey using a stick to get a peanut out of the tube is closely observed by a member of its group. Right, afterwards, the same individual fails to use the stick correctly despite having watched the skillful monkey solving this problem many times. The unsuccessful capuchin continued to contact the tube with the stick in the same manner as it did before observing the many solutions performed by the others (photos by E. Visalberghi).

We found that naïve individuals do not learn by watching a model repeatedly solving a task that involves the use of the tool. Rather, the main effect of the social input provided by models is to make the observer more interested in manipulating the tool: watching another monkey solving a problem brings the observer’s to develop an interest in the place and objects where the other worked or is working. Eventually, from this increased motivation and the repeated trial-and-error attempts the success may arise. This “socially-biased learning” is possible because capuchins are quite tolerant of one another (they accept other group members inspecting at a close range their activities), and they also are socially oriented (they are pretty interested in other individuals).

Interestingly, this occurs also when the skillful group members are not present and there is not ongoing behaviour to learn from. Therefore, the contribution of social context to learning a skill expands beyond the immediate presence of a model nearby. Thus, artefacts contribute to traditional technologies in non-humans.

Social learning and food choice: I learn with you, not from you

One capuchin is presented with two differently coloured foods: blue and yellow. He is trained to eat only the blue one while another monkey watches him. When the monkey is presented with the same two foods, does he make the same choice his companion did? No, he does not. He thinks for himself.

We investigated the effects of social influence on capuchins’ feeding behaviour. Overall, we found that the individual experience has a primary role on food acceptance and feeding behaviour: observing the others  eating motivates the observer to eat, but does not drive his/her food choices. Independently of social context, capuchins are equipped with the behavioral and physiological tools necessary to select energy-rich food and avoid deleterious ones indipendently from the social context. Nevertheless, other social influences are still at work. Social facilitation (i.e., repeating a familiar behaviour when other individuals perform it) and stimulus enhancement (i.e., the phenomenon according to which the observation of another individual acting on an object draws the observer’s attention to that object, thus evoking an independent response) increase the chances that a naïve individual would feed at the same time and place its group members do, with the result that his/her food choices would be similar to those of the others. In summary, the individual learning of food selection is socially biased: capuchins learn with others rather than from others.

The same thing happens for the response to novel foods. Capuchins are neofobic and the acceptance of a novel food is socially facilitated (i.e., it is easier for a capuchin to eat novel food if its group members are  eating it nearby). However, this does not necessary mean that capuchins learn whether to eat a food A or a food B from what other group members are eating. Nonetheless, social influences may speed the inclusion of novel foods into the individual's diet.

 I like to be imitated!

Two experimenters stay in front of a capuchin monkey, who chooses to stand closer to one of them. Who is the lucky one? The one who imitates him! Capuchins show affiliation toward humans who imitate them, a propensity that may be a prerequisite for altruistic behaviour.

During social interactions, humans often unconsciously and unintentionally imitate the other's behaviour of others. This effect gives strenght to the relashionship, bonding and empathy between interaction partners, and it is thought to be an evolutionary adaptation that facilitates group living and may be shared with other primate species. An experiment conducted in the Primate Center showed that capuchins look longer at human imitators over the non-imitators, they spend more time in proximity of imitators, and choose to interact more frequently with imitators in a token exchange task than to non imitators. In other words, capuchins prefer imitators than non imitators. These results demonstrate that imitation can promote affiliation in non human primates. Behavior matching that leads to prosocial behaviours toward the others may have been one of the mechanisms at the basis of the prosocial behavioural tendencies in capuchins and in other primates, including humans. 

Researchers involved

Elsa Addessi, Gloria Sabbatini and Elisabetta Visalberghi

Scientific publications

Capuchins and media