Chimpanzee Autarky

Background: Economists believe that barter is the ultimate cause of social wealth—and even much of our human culture—yet little is known about the evolution and development of such behavior. It is useful to examine the circumstances under which other species will or will not barter to more fully understand the phenomenon. Chimpanzees (Pan troglodytes) are an interesting test case as they are an intelligent species, closely related to humans, and known to participate in reciprocal interactions and token economies with humans, yet they have not spontaneously developed costly barter. Methodology/Principle Findings: Although chimpanzees do engage in noncostly barter, in which otherwise value-less tokens are exchanged for food, this lack of risk is not typical of human barter. Thus, we systematically examined barter in chimpanzees to ascertain under what circumstances chimpanzees will engage in costly barter of commodities, that is, trading food items for other food items with a human experimenter. We found that chimpanzees do barter, relinquishing lower value items to obtain higher value items (and not the reverse). However, they do not trade in all beneficial situations, maintaining possession of less preferred items when the relative gains they stand to make are small. Conclusions/Significance: Two potential explanations for this puzzling behavior are that chimpanzees lack ownership norms, and thus have limited opportunity to benefit from the gains of trade, and that chimpanzees\u27 risk of defection is sufficiently high that large gains must be imminent to justify the risk. Understanding the conditions that support barter in chimpanzees may increase understanding of situations in which humans, too, do not maximize their gains

New Caledonian crows rapidly solve a collaborative problem without cooperative cognition

There is growing comparative evidence that the cognitive bases of cooperation are not unique to humans. However, the selective pressures that lead to the evolution of these mechanisms remain unclear. Here we show that while tool-making New Caledonian crows can produce collaborative behavior, they do not understand the causality of cooperation nor show sensitivity to inequity. Instead, the collaborative behavior produced appears to have been underpinned by the transfer of prior experience. These results suggest that a number of possible selective pressures, including tool manufacture and mobbing behaviours, have not led to the evolution of cooperative cognition in this species. They show that causal cognition can evolve in a domain specific manner-understanding the properties and flexible uses of physical tools does not necessarily enable animals to grasp that a conspecific can be used as a social tool

The spread of a novel behaviour in wild chimpanzees : new insights into the ape cultural mind

TP was funded by the Canadian Research Chair in Continental Ecosystem Ecology, and received computational support from the Theoretical Ecosystem Ecology group at UQAR. The research leading to these results has received funding from the People Programme (Marie Curie Actions) and from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013) REA grant agreement n°329197 awarded to TG, ERC grant agreement n° 283871 awarded to KZ. WH was funded by a BBSRC grant (BB/I007997/1).For years, the animal culture debate has been dominated by the puzzling absence of direct evidence for social transmission of behavioural innovations in the flagship species of animal culture, the common chimpanzee. Although social learning of novel behaviours has been documented in captivity, critics argue that these findings lack ecological validity and therefore may not be relevant for understanding the evolution of culture. For the wild, it is possible that group-specific behavioural differences emerge because group members respond individually to unspecified environmental differences, rather than learning from each other. In a recent paper, we used social network analyses in wild chimpanzees (Pan troglodytes schweinfurthii) to provide direct evidence for social transmission of a behavioural innovation, moss-sponging, to extract water from a tree hole. Here, we discuss the implications of our findings and how our new methodological approach could help future studies of social learning and culture in wild apes.Publisher PDFPeer reviewe

To Each According to His Need? Variability in the Responses to Inequity in Nonhuman Primates

While it is well established that humans respond to inequity, it remains unclear the extent to which this behavior occurs in our nonhuman primate relatives. By comparing a variety of species, spanning from New World and Old World monkeys to great apes, scientists can begin to answer questions about how the response to inequity evolved, what the function of this response is, and why and how different contexts shape it. In particular, research across nonhuman primate species suggests that the response is quite variable across species, contexts and individuals. In this paper, we aim to review these differences in an attempt to identify and better understand the patterns that emerge from the existing data with the goal of developing directions for future research. To begin, we address the importance of considering socio-ecological factors in nonhuman primates in order to better understand and predict expected patterns of cooperation and aversion to inequity in different species, following which we provide a detailed analysis of the patterns uncovered by these comparisons. Ultimately, we use this synthesis to propose new ideas for research to better understand this response and, hence, the evolution of our own responses to inequity

The influence of reward quality and quantity and spatial proximity on the responses to inequity and contrast in capuchin monkeys (Cebus [Sapajus] apella)

Recent evidence within the field of comparative psychology has demonstrated that small differences in procedure may lead to significant differences in outcome. Therefore, failing to fully explore the impact of different contexts on a behavior limits our ability to fully understand that behavior. A behavior that has exhibited substantial variation, both within and across studies, is animals’ responses to violations of their expectations, either when expectations were based on another’s outcome (inequity) or one’s previous outcome (contrast). We explored this further in capuchin monkeys, focusing on the following 2 factors that often vary in such tests but have not yet been rigorously explored: the relative values of the food rewards and the degree of separation of the subjects. Concerning the first, we examined responses to violation of expectations when the difference between what was expected (or what the partner got) and what was received differed in either quality or quantity. Concerning the second, we compared responses when the 2 individuals were separated by a clear partition (barrier condition) versus sharing the same enclosure without the partition (no-barrier condition). Our results suggest that responses to inequity are most likely to emerge when the food received is low-value food, regardless of the difference between the actual and the expected outcome. However, capuchins did not respond differently to different quantities of rewards, nor did the degree of separation between subjects significantly affect results. We consider the implications of this work for both studies of violation of expectation and other cognitive and behavioral tasks

Preference Transitivity and Symbolic Representation in Capuchin Monkeys (Cebus apella)

BACKGROUND: Can non-human animals comprehend and employ symbols? The most convincing empirical evidence comes from language-trained apes, but little is known about this ability in monkeys. Tokens can be regarded as symbols since they are inherently non-valuable objects that acquire an arbitrarily assigned value upon exchange with an experimenter. Recent evidence suggested that capuchin monkeys, which diverged from the human lineage 35 million years ago, can estimate, represent and combine token quantities. A fundamental and open question is whether monkeys can reason about symbols in ways similar to how they reason about real objects. METHODOLOGY/PRINCIPAL FINDINGS: Here we examined this broad question in the context of economic choice behavior. Specifically, we assessed whether, in a symbolic context, capuchins' preferences satisfy transitivity--a fundamental trait of rational decision-making. Given three options A, B and C, transitivity holds true if A > or = B, B > or = C and A > or = C (where > or = indicates preference). In this study, we trained monkeys to exchange three types of tokens for three different foods. We then compared choices monkeys made between different types of tokens with choices monkeys made between the foods. Qualitatively, capuchins' preferences revealed by the way of tokens were similar to those measured with the actual foods. In particular, when choosing between tokens, monkeys displayed strict economic preferences and their choices satisfied transitivity. Quantitatively, however, values measured by the way of tokens differed systematically from those measured with the actual foods. In particular, for any pair of foods, the relative value of the preferred food increased when monkeys chose between the corresponding tokens. CONCLUSIONS/SIGNIFICANCE: These results indicate that indeed capuchins are capable of treating tokens as symbols. However, as they do so, capuchins experience the cognitive burdens imposed by symbolic representation

Divergent personality structures of brown (Sapajus apella) and white-faced capuchins (Cebus capucinus)

One way to gain insights into personality evolution is by comparing the personality structures of related species. We compared the personality structure of 240 wild white-faced capuchin monkeys to the personality structure of 100 captive brown capuchin monkeys. An ancillary goal was to test the degree to which different personality questionnaires yielded similar personality dimensions. Both species were rated on a common set of 26 antonym pairs. The brown capuchin monkeys were also rated on the 54-item Hominoid Personality Questionnaire. Our cross-species comparisons revealed three personality dimensions---Assertiveness, Openness, and Neuroticism---shared by brown and white-faced capuchins, suggesting that these dimensions were present in the common ancestor of these species. Our comparison of the dimensions derived from the antonym pairs and the Hominoid Personality Questionnaire revealed that three common dimensions were identified by both questionnaires. In addition, the dimension Attentiveness was only identified using the Hominoid Personality Questionnaire. These results indicate that major features of capuchin personality are conserved and that the structure of some traits, such as those related to focus, persistence, and attention, diverged. Further work is needed to identify the evolutionary bases that led to the conservation of some dimensions but not others

Studying animal innovation at the individual level: a ratings-based assessment in capuchin monkeys (Sapajus [Cebus] sp.)

Large-scale studies of individual differences in animal innovation are rare firstly because discovery behaviour itself is often rare, and secondly because of logistical difficulties associated with obtaining observational data on a large number of innovative individuals across multiple groups and locations. Here we take a different approach, using observer ratings to study innovative behaviour in 127 brown capuchin monkeys (Sapajus [Cebus] sp.) from 15 social groups and 7 facilities. Capuchins were reliably rated by 1 to 7 raters (mean 3.2 ± 1.6 raters/monkey) on a 7-point Likert scale for levels of innovative behaviour, task motivation, sociality, and dominance. In a subsample, we demonstrate these ratings are valid: rated innovation predicted performance on a learning task, rated motivation predicted participation in the task, rated dominance predicted social rank based on win/loss aggressive outcomes, and rated sociality predicted the time that monkeys spent in close proximity to others. Across all 127 capuchins, individuals that were rated as being more innovated were significantly younger, more social, and more motivated to engage in tasks. Sociality, task motivation, and age all had independent effects on innovativeness, whereas sex, dominance and group size were non-significant. Our findings are consistent with long-term behavioural observations of innovation in wild white-faced capuchins. Observer ratings may therefore be a valid tool for studies of animal innovation, and our findings highlight in particular several possible scenarios through which innovative behaviour might be selected for among capuchins