Chimpanzees Help Each Other upon Request

Abstract

BackgroundThe 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.Methodology/Principal FindingsWe 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.Conclusions/SignificanceThese 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.

On the psychology of cooperation in humans and other primates: combining the natural history and experimental evidence of prosociality

“…Begging did not induce food donation in provisioning games among chimpanzees (Silk et al 2005;Jensen et al 2006), which may reflect low sensitivity to these signals if they are not made in immediate proximity. However, helping behaviour in response to explicit signals of need has been reported for chimpanzees (Warneken & Tomasello 2006;Warneken et al 2007;Yamamoto et al 2009) and capuchin monkeys (Barnes et al 2008) in targeted helping experiments (table 1). Crucially, signs of need such as struggling to solve a task (Yamamoto et al 2009) or reaching for an object without calling the subject's name (Warneken et al 2007) mostly did not induce helping in chimpanzees, unless they were well enculturated by humans (Warneken & Tomasello 2006).…”

Evolutionary foundations of human prosocial sentiments

“…Chimpanzees also provide tools that others need to complete food-related tasks (71). In this experiment, two chimpanzees were placed in adjacent enclosures, and each was presented with a food task that required a particular tool (stick or straw).…”

“…The experiment was designed to replicate the experiments in which a human experimenter reaches for an inaccessible object (70,71). Unlike the chimpanzees, the capuchins did not consistently distinguish between the test and control conditions (84).…”

Monkeys benefit from reciprocity without the cognitive burden

“…In the GAT, individuals have the choice between providing instrumental help to another or do nothing. In GAT's, chimpanzees reciprocally provide favors as long as the experimenter enforces a turn-taking structure (21)(22)(23). The chimpanzees do not spontaneously alternate doing favors, however (23).…”