Children, chimpanzees, and bonobos adjust the visibility of their actions for cooperators and competitors

Chimpanzees and bonobos are highly capable of tracking other's mental states. It has been proposed, however, that in contrast to humans, chimpanzees are only able to do this in competitive interactions but this has rarely been directly tested. Here, pairs of chimpanzees or bonobos (Study 1) and 4-year-old children (Study 2) were presented with two almost identical tasks differing only regarding the social context. In the cooperation condition, players' interests were matched: they had to make corresponding choices to be mutually rewarded. To facilitate coordination, subjects should thus make their actions visible to their partner whose view was partially occluded. In the competition condition, players' interests were directly opposed: the partner tried to match the subject's choice but subjects were only rewarded if they chose differently, so that they benefited from hiding their actions. The apes successfully adapted their decisions to the social context and their performance was markedly better in the cooperation condition. Children also distinguished between the two contexts, but somewhat surprisingly, performed better in the competitive condition. These findings demonstrate experimentally that chimpanzees and bonobos can take into account what others can see in cooperative interactions. Their social-cognitive skills are thus more flexible than previously assumed.Publisher PDFPeer reviewe

The strategies used by chimpanzees (Pan troglodytes) and children (Homo sapiens) to solve a simple coordination problem

The authors acknowledge support from the ESRC Network for Integrated Behavioural Science – ES/K002201/1.One of the challenges of collaboration is to coordinate decisions with others, and recent theories have proposed that humans, in particular, evolved skills to address this challenge. To test this hypothesis, we compared the coordination abilities of 4-year-old children and chimpanzees with a simple coordination problem. To retrieve a reward from a “puzzle box,” pairs of individuals were simply required to choose the same 1 of 4 options. If successful, they each received the same reward, so there were no conflicts of interest. Individuals were paired with multiple partners over time. Both species were able to coordinate, but there were marked differences in the way they did so. Children were able to coordinate quickly and flexibly, adjusting easily to new partners, suggesting an understanding of the coordination process. In contrast, chimpanzees took time to converge on a single solution with each new partner, with no gains across partners, suggesting that their coordination was based only on repeating successful past choices. Together, these results support the hypothesis that humans have evolved unique skills for coordinating decisions and actions with others in the pursuit of common interests.PostprintPeer reviewe

Cooperative problem solving in giant otters (Pteronura brasiliensis) and Asian small-clawed otters (Aonyx cinerea)

Open access funding provided by Max Planck Society.Cooperative problem solving has gained a lot of attention over the past two decades but the range of species studied is still small. This limits the possibility of understanding the evolution of the socio-cognitive underpinnings of cooperation. Lutrinae show significant variations in socio-ecology but their cognitive abilities are not well studied. In the first experimental study of otter social cognition, we presented two species - giant otters and Asian small-clawed otters - with a cooperative problem-solving task. The loose string task requires two individuals to simultaneously pull on either end of a rope in order to access food. This task has been used with a larger number of species (for the most part primates and birds) and thus allows for wider cross species comparison. We found no differences in performance between species. Both giant otters and Asian small-clawed otters were able to solve the task successfully when the coordination requirements were minimal. However, when the temporal coordination demands were increased, performance decreased either due to a lack of understanding of the role of a partner or due to difficulty inhibiting action. In conclusion, two species of otters show some ability to cooperate, quite similar to most other species presented with the same task. However, to draw further conclusions and more nuanced comparisons between the two otter species further studies with varied methodologies will be necessary.Publisher PDFPeer reviewe

How chimpanzees (Pan troglodytes) share the spoils with collaborators and bystanders

The study was funded by the Max Planck Society. S. Duguid wrote the manuscript supported by a grant awarded to A. P. Melis from the Templeton World Charity Foundation (TWCF0264).Chimpanzees hunt cooperatively in the wild, but the factors influencing food sharing after the hunt are not well understood. In an experimental study, groups of three captive chimpanzees obtained a monopolizable food resource, either via two individuals cooperating (with the third as bystander) or via one individual acting alone alongside two bystanders. The individual that obtained the resource first retained most of the food but the other two individuals attempted to obtain food from the "captor" by begging. We found the main predictor of the overall amount of food obtained by bystanders was proximity to the food at the moment it was obtained by the captor. Whether or not an individual had cooperated to obtain the food had no effect. Interestingly, however, cooperators begged more from captors than did bystanders, suggesting that they were more motivated or had a greater expectation to obtain food. These results suggest that while chimpanzee captors in cooperative hunting may not reward cooperative participation directly, cooperators may influence sharing behavior through increased begging.Publisher PDFPeer reviewe

Do 7-year-old children understand social leverage?

Individuals with an advantageous position during a negotiation possess leverage over their partners. Several studies with adults have investigated how leverage can influence the coordination strategies of individuals when conflicts of interest arise. In this study, we explored how pairs of 7-year-old children solved a coordination game (based on the Snowdrift scenario) when one child had leverage over the other child. We presented a social dilemma in the form of an unequal reward distribution on a rotating tray. The rotating tray could be accessed by both children. The child who waited longer to act received the best outcome, but if both children waited too long, they would lose the rewards. In addition, one child could forgo the access to the rotating tray for an alternative option—the leverage. Although children rarely used their leverage strategically, children with access to the alternative were less likely to play the social dilemma, especially when their leverage was larger. Furthermore, children waited longer to act as the leverage decreased. Finally, children almost never failed to coordinate. The results hint to a trade-off between maximizing benefits while maintaining long-term collaboration in complex scenarios where strategies such as turn taking are hard to implement.PostprintPeer reviewe

The ape lottery : chimpanzees fail to consider spatial information when drawing statistical inferences

Funding: this work was supported by a research grant of the German Science Foundation DFG (grant # RA 2155/3-1) to Hannes Rakoczy and Josep Call. We acknowledge additional support by the Leibniz Association through funding for the Leibniz ScienceCampus Primate Cognition.Humans and nonhuman great apes share a sense for intuitive statistics, making intuitive probability judgments based on proportional information. This ability is of tremendous importance, in particular for predicting the outcome of events using prior information and for inferring general regularities from limited numbers of observations. Already in infancy, humans functionally integrate intuitive statistics with other cognitive domains, rendering this type of reasoning a powerful tool to make rational decisions in a variety of contexts. Recent research suggests that chimpanzees are capable of one type of such cross-domain integration: The integration of statistical and social information. Here, we investigated whether apes can also integrate physical information into their statistical inferences. We tested 14 sanctuary-living chimpanzees in a new task setup consisting of two “gumball machine”-apparatuses that were filled with different combinations of preferred and non-preferred food items. In four test conditions, subjects decided which of two apparatuses they wanted to operate to receive a random sample, while we varied both the proportional composition of the food items as well as their spatial configuration above and below a barrier. To receive the more favorable sample, apes needed to integrate proportional and spatial information. Chimpanzees succeeded in conditions in which we provided them either with proportional information or spatial information, but they failed to correctly integrate both types of information when they were in conflict. Whether these limitations in chimpanzees' performance reflect true limits of cognitive competence or merely performance limitations due to accessory task demands is still an open question.Publisher PDFPeer reviewe

Chimpanzees and children avoid mutual defection in a social dilemma

A.S. was partially supported by a LaCaixa-DAAD grant (13/94418). J.C. was partially supported by an ERC-Synergy grant SOMICS grant 609819.Cooperation often comes with the temptation to defect and benefit at the cost of others. This tension between cooperation and defection is best captured in social dilemmas like the Prisoner's Dilemma. Adult humans have specific strategies to maintain cooperation during Prisoner's Dilemma interactions. Yet, little is known about the ontogenetic and phylogenetic origins of human decision-making strategies in conflict scenarios. To shed light on this question, we compared the strategies used by chimpanzees and 5-year old children to overcome a social dilemma. In our task, waiting for the partner to act first produced the best results for the subject. Alternatively, they could mutually cooperate and divide the rewards. Our findings indicate that the two species differed substantially in their strategies to solve the task. Chimpanzees became more strategic across the study period by waiting longer to act in the social dilemma. Children developed a more efficient strategy of taking turns to reciprocate their rewards. Moreover, children used specific types of communication to coordinate with their partners. These results suggest that while both species behaved strategically to overcome a conflict situation, only children engaged in active cooperation to solve a social dilemma.PostprintPeer reviewe

Chimpanzees’ understanding of social leverage

Social primates can influence others through the control of resources. For instance, dominant male chimpanzees might allow subordinates access to mate with females in exchange for social support. However, little is known about how chimpanzees strategically use a position of leverage to maximize their own benefits. We address this question by presenting dyads of captive chimpanzee (N = 6) with a task resulting in an unequal reward distribution. To gain the higher reward each individual should wait for their partner to act. In addition, one participant had leverage: access to an alternative secure reward. By varying the presence and value of the leverage we tested whether individuals used it strategically (e.g. by waiting longer for partners to act when they had leverage in the form of alternatives). Additionally, non-social controls served to show if chimpanzees understood the social dilemma. We measured the likelihood to choose the leverage and their latencies to act. The final decision made by the chimpanzees did not differ as a function of condition (test versus non-social control) or the value of the leverage, but they did wait longer to act when the leverage was smaller—particularly in test (versus non-social control) trials suggesting that they understood the conflict of interest involved. The chimpanzees thus recognized the existence of social leverage, but did not use it strategically to maximize their rewards.Publisher PDFPeer reviewe

The Evolution of Primate Short-Term Memory.

Short-term memory is implicated in a range of cognitive abilities and is critical for understanding primate cognitive evolution. To investigate the effects of phylogeny, ecology and sociality on short-term memory, we tested the largest and most diverse primate sample to date (421 non-human primates across 41 species) in an experimental delayed-response task. Our results confirm previous findings that longer delays decrease memory performance across species and taxa. Our analyses demonstrate a considerable contribution of phylogeny over ecological and social factors on the distribution of short-term memory performance in primates; closely related species had more similar short-term memory abilities. Overall, individuals in the branch of Hominoidea performed better compared to Cercopithecoidea, who in turn performed above Platyrrhini and Strepsirrhini. Interdependencies between phylogeny and socioecology of a given species presented an obstacle to disentangling the effects of each of these factors on the evolution of short-term memory capacity. However, this study offers an important step forward in understanding the interspecies and individual variation in short-term memory ability by providing the first phylogenetic reconstruction of this trait’s evolutionary history. The dataset constitutes a unique resource for studying the evolution of primate cognition and the role of short-term memory in other cognitive abilities.info:eu-repo/semantics/publishedVersio

Establishing an infrastructure for collaboration in primate cognition research

Inferring the evolutionary history of cognitive abilities requires large and diverse samples. However, such samples are often beyond the reach of individual researchers or institutions, and studies are often limited to small numbers of species. Consequently, methodological and site-specific-differences across studies can limit comparisons between species. Here we introduce the ManyPrimates project, which addresses these challenges by providing a large-scale collaborative framework for comparative studies in primate cognition. To demonstrate the viability of the project we conducted a case study of short-term memory. In this initial study, we were able to include 176 individuals from 12 primate species housed at 11 sites across Africa, Asia, North America and Europe. All subjects were tested in a delayed-response task using consistent methodology across sites. Individuals could access food rewards by remembering the position of the hidden reward after a 0, 15, or 30-second delay. Overall, individuals performed better with shorter delays, as predicted by previous studies. Phylogenetic analysis revealed a strong phylogenetic signal for short-term memory. Although, with only 12 species, the validity of this analysis is limited, our initial results demonstrate the feasibility of a large, collaborative open-science project. We present the ManyPrimates project as an exciting opportunity to address open questions in primate cognition and behaviour with large, diverse datasets