Guinea baboons are strategic cooperators.

Humans are strategic cooperators; we make decisions on the basis of costs and benefits to maintain high levels of cooperation, and this is thought to have played a key role in human evolution. In comparison, monkeys and apes might lack the cognitive capacities necessary to develop flexible forms of cooperation. We show that Guinea baboons (Papio papio) can use direct reciprocity and partner choice to develop and maintain high levels of cooperation in a prosocial choice task. Our findings demonstrate that monkeys have the cognitive capacities to adjust their level of cooperation strategically using a combination of partner choice and partner control strategies. Such capacities were likely present in our common ancestor and would have provided the foundations for the evolution of typically human forms of cooperation.

Human and animal dominance hierarchies show a pyramidal structure guiding adult and infant social inferences.

This study investigates the structure of social hierarchies. We hypothesized that if social dominance relations serve to regulate conflicts over resources, then hierarchies should converge towards pyramidal shapes. Structural analyses and simulations confirmed this hypothesis, revealing a triadic-pyramidal motif across human and non-human hierarchies (114 species). Phylogenetic analyses showed that this pyramidal motif is widespread, with little influence of group size or phylogeny. Furthermore, nine experiments conducted in France found that human adults (N = 120) and infants (N = 120) draw inferences about dominance relations that are consistent with hierarchies' pyramidal motif. By contrast, human participants do not draw equivalent inferences based on a tree-shaped pattern with a similar complexity to pyramids. In short, social hierarchies exhibit a pyramidal motif across a wide range of species and environments. From infancy, humans exploit this regularity to draw systematic inferences about unobserved dominance relations, using processes akin to formal reasoning.

Bringing cumulative technological culture beyond copying versus reasoning.

The dominant view of cumulative technological culture suggests that high-fidelity transmission rests upon a high-fidelity copying ability, which allows individuals to reproduce the tool-use actions performed by others without needing to understand them (i.e., without causal reasoning). The opposition between copying versus reasoning is well accepted but with little supporting evidence. In this article, we investigate this distinction by examining the cognitive science literature on tool use. Evidence indicates that the ability to reproduce others' tool-use actions requires causal understanding, which questions the copying versus reasoning distinction and the cognitive reality of the so-called copying ability. We conclude that new insights might be gained by considering causal understanding as a key driver of cumulative technological culture.

Age effect in expert cognitive flexibility in Guinea baboons (Papio papio).

Cognitive flexibility in non-human primates is traditionally measured with the conceptual set shifting task (CSST). In our laboratory, Guinea baboons (N = 24) were continuously tested with a CSST task during approximately 10 years. Our task involved the presentation of three stimuli on a touch screen all made from 3 possible colours and 3 shapes. The subjects had to touch the stimulus containing the stimulus dimension (e.g., green) that was constantly rewarded until the stimulus dimension changed. Analysis of perseveration responses, scores and response times collected during the last two years of testing (approximately 1.6 million trials) indicate (1) that the baboons have developed an "expert" form of cognitive flexibility and (2) that their performance was age-dependent, it was at a developing stage in juveniles, optimal in adults, declining in middle-aged, and strongly impaired in the oldest age group. A direct comparison with the data collected by Bonté , Flemming & Fagot (2011) on some of the same baboons and same task as in the current study indicates that (3) the performance of all age groups has improved after 10 years of training, even for the now old individuals. All these data validate the use of non-human primates as models of human cognitive flexibility and suggest that cognitive flexibility in humans has a long evolutionary history.

Are monkeys sensitive to informativeness: An experimental study with baboons (Papio papio).

Informativeness (defined as reduction of uncertainty) is central in human communication. In the present study, we investigate baboons' sensitivity to informativeness by manipulating the informativity of a cue relative to a response display and by allowing participants to anticipate their answers or to wait for a revealed answer (with variable delays). Our hypotheses were that anticipations would increase with informativity, while response times to revealed trials would decrease with informativity. These predictions were verified in Experiment 1. In Experiments 2 and 3, we manipulated rewards (rewarding anticipation responses at 70% only) to see whether reward tracking alone could account for the results in Experiment 1. We observed that the link between anticipations and informativeness disappeared, but not the link between informativeness and decreased RTs for revealed trials. Additionally, in all three experiments, the number of correct answers in revealed trials with fast reaction times (< 250ms) increased with informativeness. We conclude that baboons are sensitive to informativeness as an ecologically sound means to tracking reward.

Probability matching is not the default decision making strategy in human and non-human primates.

Probability matching has long been taken as a prime example of irrational behaviour in human decision making; however, its nature and uniqueness in the animal world is still much debated. In this paper we report a set of four preregistered experiments testing adult humans and Guinea baboons on matched probability learning tasks, manipulating task complexity (binary or ternary prediction tasks) and reinforcement procedures (with and without corrective feedback). Our findings suggest that probability matching behaviour within primate species is restricted to humans and the simplest possible binary prediction tasks; utility-maximising is seen in more complex tasks for humans as pattern-search becomes more effortful, and we observe it across the board in baboons, altogether suggesting that it is a cognitively less demanding strategy. These results provide further evidence that neither human nor non-human primates default to probability matching; however, unlike other primates, adult humans probability match when the cost of pattern search is low.

Understanding Imitation in Papio papio: The Role of Experience and the Presence of a Conspecific Demonstrator.

What factors affect imitation performance? Varying theories of imitation stress the role of experience, but few studies have explicitly tested its role in imitative learning in non-human primates. We tested several predictions regarding the role of experience, conspecific presence, and action compatibility using a stimulus-response compatibility protocol. Nineteen baboons separated into two experimental groups learned to respond by targeting on a touch screen the same stimulus as their neighbor (compatible) or the opposite stimulus (incompatible). They first performed the task with a conspecific demonstrator (social phase) and then a computer demonstrator (ghost phase). After reaching a predetermined success threshold, they were then tested in an opposite compatibility condition (i.e., reversal learning conditions). Seven baboons performed at least two reversals during the social phase, and we found no significant difference between the compatible and incompatible conditions, although we noticed slightly faster response times (RTs) in the compatible condition that disappeared after the first reversal. During the ghost phase, monkeys showed difficulties in learning the incompatible condition, and the compatible condition RTs tended to be slower than during the social phase. Together, these results suggest that (a) there is no strong movement compatibility effect in our task and that (b) the presence of a demonstrator plays a role in eliciting correct responses but is not essential as has been previously shown in human studies.

Technical reasoning bolsters cumulative technological culture through convergent transformations.

Understanding the evolution of human technology is key to solving the mystery of our origins. Current theories propose that technology evolved through the accumulation of modifications that were mostly transmitted between individuals by blind copying and the selective retention of advantageous variations. An alternative account is that high-fidelity transmission in the context of cumulative technological culture is supported by technical reasoning, which is a reconstruction mechanism that allows individuals to converge to optimal solutions. We tested these two competing hypotheses with a microsociety experiment, in which participants had to optimize a physical system in partial- and degraded-information transmission conditions. Our results indicated an improvement of the system over generations, which was accompanied by an increased understanding of it. The solutions produced tended to progressively converge over generations. These findings show that technical reasoning can bolster high-fidelity transmission through convergent transformations, which highlights its role in the cultural evolution of technology.