Children conform to the behavior of peers; other great apes stick with what they know.

All primates learn things from conspecifics socially, but it is not clear whether they conform to the behavior of these conspecifics--if conformity is defined as overriding individually acquired behavioral tendencies in order to copy peers' behavior. In the current study, chimpanzees, orangutans, and 2-year-old human children individually acquired a problem-solving strategy. They then watched several conspecific peers demonstrate an alternative strategy. The children switched to this new, socially demonstrated strategy in roughly half of all instances, whereas the other two great-ape species almost never adjusted their behavior to the majority's. In a follow-up study, children switched much more when the peer demonstrators were still present than when they were absent, which suggests that their conformity arose at least in part from social motivations. These results demonstrate an important difference between the social learning of humans and great apes, a difference that might help to account for differences in human and nonhuman cultures.

Majority-biased transmission in chimpanzees and human children, but not orangutans.

Cultural transmission is a key component of human evolution. Two of humans' closest living relatives, chimpanzees and orangutans, have also been argued to transmit behavioral traditions across generations culturally [1-3], but how much the process might resemble the human process is still in large part unknown. One key phenomenon of human cultural transmission is majority-biased transmission: the increased likelihood for learners to end up not with the most frequent behavior but rather with the behavior demonstrated by most individuals. Here we show that chimpanzees and human children as young as 2 years of age, but not orangutans, are more likely to copy an action performed by three individuals, once each, than an action performed by one individual three times. The tendency to acquire the behaviors of the majority has been posited as key to the transmission of relatively safe, reliable, and productive behavioral strategies [4-7] but has not previously been demonstrated in primates.

Children, but not chimpanzees, prefer to collaborate.

Human societies are built on collaborative activities. Already from early childhood, human children are skillful and proficient collaborators. They recognize when they need help in solving a problem and actively recruit collaborators [1, 2]. The societies of other primates are also to some degree cooperative. Chimpanzees, for example, engage in a variety of cooperative activities such as border patrols, group hunting, and intra- and intergroup coalitionary behavior [3-5]. Recent studies have shown that chimpanzees possess many of the cognitive prerequisites necessary for human-like collaboration. Chimpanzees have been shown to recognize when they need help in solving a problem and to actively recruit good over bad collaborators [6, 7]. However, cognitive abilities might not be all that differs between chimpanzees and humans when it comes to cooperation. Another factor might be the motivation to engage in a cooperative activity. Here, we hypothesized that a key difference between human and chimpanzee collaboration-and so potentially a key mechanism in the evolution of human cooperation-is a simple preference for collaborating (versus acting alone) to obtain food. Our results supported this hypothesis, finding that whereas children strongly prefer to work together with another to obtain food, chimpanzees show no such preference.