Chimpanzees Help Each Other upon Request

• Published in: PloS one Vol. 4; no. 10; p. e7416
• Main Authors: Yamamoto, Shinya, Humle, Tatyana, Tanaka, Masayuki
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 14.10.2009; Public Library of Science (PLoS)
• Subjects: Altruism; Animal behavior; Animal Communication; Animals; Apprenticeship; Behavior, Animal; Chi-square test; Chimpanzees; Communication; Cooperation; Cooperative Behavior; Ecology/Behavioral Ecology; Evolutionary Biology/Animal Behavior; Evolutionary Biology/Human Evolution; Experiments; Female; Food; Interpersonal Relations; Male; Monkeys & apes; Pan troglodytes; Pan troglodytes - physiology; Pan troglodytes - psychology; Problem solving; Reciprocation; Social Behavior; Social Environment; Social Perception; Studies; Tool use; Tool Use Behavior; Trends
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0007416

The evolution of altruism has been explained mainly from ultimate perspectives. However, it remains to be investigated from a proximate point of view how and in which situations such social propensity is achieved. We investigated chimpanzees' targeted helping in a tool transfer paradigm, and discuss the similarities and differences in altruism between humans and chimpanzees. Previously it has been suggested that chimpanzees help human experimenters by retrieving an object which the experimenter is trying to reach. In the present study, we investigated the importance of communicative interactions between chimpanzees themselves and the influence of conspecific partner's request on chimpanzees' targeted helping. We presented two tool-use situations (a stick-use situation and a straw-use situation) in two adjacent booths, and supplied non-corresponding tools to paired chimpanzees in the two booths. For example, a chimpanzee in the stick-use situation was supplied with a straw, and the partner in the straw-use situation possessed a stick. Spontaneous tool transfer was observed between paired chimpanzees. The tool transfer events occurred predominantly following recipients' request. Even without any hope of reciprocation from the partner, the chimpanzees continued to help the partner as long as the partner required help. These results provide further evidence for altruistic helping in chimpanzees in the absence of direct personal gain or even immediate reciprocation. Our findings additionally highlight the importance of request as a proximate mechanism motivating prosocial behavior in chimpanzees whether between kin or non-kin individuals and the possible confounding effect of dominance on the symmetry of such interactions. Finally, in contrast to humans, our study suggests that chimpanzees rarely perform acts of voluntary altruism. Voluntary altruism in chimpanzees is not necessarily prompted by simple observation of another's struggle to attain a goal and therefore an accurate understanding of others' desires in the absence of communicative signals.