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Chimpanzees collaborate with conspecifics in their daily life. However, the cognitive processes underlying partner recruitment aren’t fully understood. In the current study, chimpanzees needed to recruit a conspecific partner for either a cooperative or competitive experimental task. They spontaneously preferred to recruit cooperation partners who they have seen performing successfully before on a similar task, over partners who had failed. In contrast, the chimpanzees needed to experience the consequences of competing against co-action partners before settling on a preference for the unsuccessful partner. This divergent pattern may be due to increased cognitive demands of competitive compared to cooperative tasks. Despite the observed differences of social information use in our cooperative and competitive experimental tasks, the findings are exciting as they extend our knowledge of chimpanzee’s social evaluation abilities by showing that they can draw domain-specific inferences about conspecifics’ skills.

To cooperate effectively, both in small-scale interactions and large-scale collective-action problems, people frequently have to delay gratification (i.e., resist short-term temptations in favor of joint long-term goals). Although delay-ofgratification skills are commonly considered critical in children’s social-cognitive development, they have rarely been studied in the context of cooperative decision-making. In the current study, we therefore presented pairs of children (N = 207 individuals) with a modified version of the famous marshmallow test, in which children’s outcomes were interdependently linked such that the children were rewarded only if both members of the pair delayed gratification. Children from two highly diverse cultures (Germany and Kenya) performed substantially better than they did on a standard version of the test, suggesting that children are more willing to delay gratification for cooperative than for individual goals. The results indicate that from early in life, human children are psychologically equipped to respond to social interdependencies in ways that facilitate cooperative success.

Virtually all theories of the evolution of cooperation require that cooperators find ways to interact with one another selectively, to the exclusion of cheaters. This means that individuals must make reputational judgments about others as cooperators, based on either direct or indirect evidence. Humans, and possibly other species, add another component to the process: they know that they are being judged by others, and so they adjust their behavior in order to affect those judgments - so-called impression management. Here, we show for the first time that already preschool children engage in such behavior. In an experimental study, 5-year-old human children share more and steal less when they are being watched by a peer than when they are alone. In contrast, chimpanzees behave the same whether they are being watched by a groupmate or not. This species difference suggests that humans' concern for their own self-reputation, and their tendency to manage the impression they are making on others, may be unique to humans among primates.

The motivation to build and maintain a positive personal reputation promotes prosocial behavior. But individuals also identify with their groups, and so it is possible that the desire to maintain or enhance group reputation may have similar effects. Here, we show that 5-year-old children actively invest in the reputation of their group by acting more generously when their group’s reputation is at stake. Children shared significantly more resources with fictitious other children not only when their individual donations were public rather than private but also when their group’s donations (effacing individual donations) were public rather than private. These results provide the first experimental evidence that concern for group reputation can lead to higher levels of prosociality.

While bonobos and chimpanzees are both genetically and behaviorally very similar, they also differ in significant ways. Bonobos are more cautious and socially tolerant while chimpanzees are more dependent on extractive foraging, which requires tools. The similarities suggest the two species should be cognitively similar while the behavioral differences predict where the two species should differ cognitively. We compared both species on a wide range of cognitive problems testing their understanding of the physical and social world. Bonobos were more skilled at solving tasks related to theory of mind or an understanding of social causality, while chimpanzees were more skilled at tasks requiring the use of tools and an understanding of physical causality. These species differences support the role of ecological and socio-ecological pressures in shaping cognitive skills over relatively short periods of evolutionary time.

SignificanceHumans, as compared with other animals, create and follow conventional norms that determine how we greet each other, dress, or play certain games. Conventional norms are universal in all human societies, but it is an open question whether individuals in all societies also actively enforce conventional norms when others in their group break them. We show that 5- to 8-y-old children from eight highly diverse societies enforced conventional norms (i.e., game rules) when they observed a peer who apparently broke them. Magnitude and style of enforcement varied across societies. Third-party enforcement of conventional norms appears to be a human universal that is expressed in culturally variable ways. Individuals in all societies conform to their cultural group’s conventional norms, from how to dress on certain occasions to how to play certain games. It is an open question, however, whether individuals in all societies actively enforce the group’s conventional norms when others break them. We investigated third-party enforcement of conventional norms in 5- to 8-y-old children (n = 376) from eight diverse small-scale and large-scale societies. Children learned the rules for playing a new sorting game and then, observed a peer who was apparently breaking them. Across societies, observer children intervened frequently to correct their misguided peer (i.e., more frequently than when the peer was following the rules). However, both the magnitude and the style of interventions varied across societies. Detailed analyses of children’s interactions revealed societal differences in children’s verbal protest styles as well as in their use of actions, gestures, and nonverbal expressions to intervene. Observers’ interventions predicted whether their peer adopted the observer’s sorting rule. Enforcement of conventional norms appears to be an early emerging human universal that comes to be expressed in culturally variable ways.

Exploration is an important strategy for reducing the uncertainty that pervades daily life. Yet the evolutionary roots of adaptive exploration are poorly understood. We harness and adapt the human decisions-from-experience paradigm to investigate exploration under uncertainty in chimpanzees. In our study, chimpanzees ( N  = 15; eight females) are simultaneously confronted with an uncertain option (with outcome variance) and a safe option (without outcome variance) and tested in both stable and changing environments. Results reveal that, as in human exploration, how and how much chimpanzees explore depends on the environment. One key environmental property is change: Chimpanzees explore more across trials in changing than in stable conditions. Consistent with the assumption of classic economic models that variance indicates risk, chimpanzees also explore more when they experience variance in the options’ outcomes. Individual risk and uncertainty preferences did not have a statistically significant effect on exploratory efforts. These findings suggest that chimpanzees and humans share key similarities in the way they respond to risk and uncertainty. Exploration helps reduce uncertainty in daily life, but the evolutionary roots of adaptive exploration are unclear. Here, the authors show that chimpanzees, like humans, tailor their exploration depending on their environment.

Humans have many cognitive skills not possessed by their nearest primate relatives. The cultural intelligence hypothesis argues that this is mainly due to a species-specific set of social-cognitive skills, emerging early in ontogeny, for participating and exchanging knowledge in cultural groups. We tested this hypothesis by giving a comprehensive battery of cognitive tests to large numbers of two of humans' closest primate relatives, chimpanzees and orangutans, as well as to 2.5-year-old human children before literacy and schooling. Supporting the cultural intelligence hypothesis and contradicting the hypothesis that humans simply have more \"general intelligence,\" we found that the children and chimpanzees had very similar cognitive skills for dealing with the physical world but that the children had more sophisticated cognitive skills than either of the ape species for dealing with the social world.

Humans share the vast majority of their cognitive skills with other great apes. In addition, however, humans have also evolved a unique suite of cognitive skills and motivations—collectively referred to as shared intentionality—for living collaboratively, learning socially, and exchanging information in cultural groups.

Human children show unique cognitive skills for dealing with the social world but their cognitive performance is paralleled by great apes in many tasks dealing with the physical world. Recent studies suggested that members of a songbird family—corvids—also evolved complex cognitive skills but a detailed understanding of the full scope of their cognition was, until now, not existent. Furthermore, relatively little is known about their cognitive development. Here, we conducted the first systematic, quantitative large-scale assessment of physical and social cognitive performance of common ravens with a special focus on development. To do so, we fine-tuned one of the most comprehensive experimental test-batteries, the Primate Cognition Test Battery (PCTB), to raven features enabling also a direct, quantitative comparison with the cognitive performance of two great ape species. Full-blown cognitive skills were already present at the age of four months with subadult ravens’ cognitive performance appearing very similar to that of adult apes in tasks of physical (quantities, and causality) and social cognition (social learning, communication, and theory of mind). These unprecedented findings strengthen recent assessments of ravens’ general intelligence, and aid to the growing evidence that the lack of a specific cortical architecture does not hinder advanced cognitive skills. Difficulties in certain cognitive scales further emphasize the quest to develop comparative test batteries that tap into true species rather than human specific cognitive skills, and suggest that socialization of test individuals may play a crucial role. We conclude to pay more attention to the impact of personality on cognitive output, and a currently neglected topic in Animal Cognition—the linkage between ontogeny and cognitive performance.