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* Correspondence should be addressed to Manuel Bohn (manyprimates@gmai l.com). 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. Publisher PDF

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In the eighteenth century, Daniel Bernoulli, Adam Smith and Jeremy Bentham proposed that economic choices rely on the computation and comparison of subjective values

Do macaques are able to take into account others' welfare during social decisions-making ? If so, what capacities allow them to apprehend it and which variables would influence their decisions in such social contexts ? From perception to the production of social behavior, a multitude of complex mental processes allow macaques to live in a dynamic society, structured and cohesive. Although the presence of pro-and antisocial behavior had already been described, their ultimate and proximate causes are not known. Does empathy, defined here as the ability to feel the emotions of others, could explain the expression of pro-social behavior? The answers to such questions might have important implications for science, but also in philosophy and ethics. The originality and relevance of our experimental approach lies in the objective measurement of social behavior using innovative devices and protocols developed and validated during this thesis. Indeed, we aimed to reproduce a social context in a controlled laboratory environment. Thus, by placing two animals face to face, we have developed a unique protocol for social decision allowing a macaque to delivered either an aversive stimulus (an air puff on the face), an appetitive stimulus (drop of fruit juice) to its partner, to an empty space or to itself. The choices are organized in pairs, the actor had to select either the prosocial option or antisocial option or, for non-social controls decision the rational or irrational option. Appropriate analyzes of eye tracking measures (level of mutual gaze and blink frequency) allowed us to establish relationships between emotional responses and pro (or anti) social trends. It revealed processes dependent on past experiences and relationships with the partner, thus homologous to those involved in human emotional empathy, Les macaques sont-ils capables de prendre en compte le préjudice porté à autrui occasionné par leurs actes ? Si oui, quelles facultés leur permettent de l'appréhender et quelles variables influenceraient leurs décisions dans de tels contextes sociaux ? De la perception à la production de comportements sociaux, une multitude de processus mentaux complexes permettent aux macaques de vivre au sein d'une société dynamique, structurée et cohésive. Bien que la présence de comportements pro et antisociaux y ait déjà été décrite, leurs causes ultimes et proximales ne sont pas évidentes. Est-ce que l'empathie, définie ici comme la capacité à ressentir les émotions d'autrui, pourrait expliquer l'expression de comportements prosociaux ? Les réponses à de telles questions peuvent avoir des répercussions importantes pour les sciences, mais aussi pour la philosophie et l'éthique. L'originalité et la pertinence de notre démarche expérimentale résident dans la mesure objective des comportements sociaux à l'aide de dispositifs et protocoles novateurs conçus et validés au cours de cette thèse. Nous avons en effet entrepris de reproduire un contexte social dans un environnement contrôlé de laboratoire. Ainsi, en plaçant deux animaux face à face, nous avons mis au point un protocole de décision sociale unique permettant à un macaque acteur de choisir de délivrer soit un stimulus aversif (un jet d'air comprimé sur le visage) soit un stimulus appétitif (une goutte de jus de fruit) à son partenaire, à un espace vide ou à lui-même. Les choix étant organisés en paires, l'acteur devait sélectionner soit l'option prosociale, soit l'option antisociale ou, pour des décisions contrôles non-sociales, soit l'option rationnelle, soit l'option irrationnelle. Des analyses appropriées des mesures oculométriques (niveau de regard mutuel et fréquence de clignement des yeux) nous ont permis d'établir des relations entre réponses émotionnelles et tendances pro- (ou anti-) social et de révéler des processus homologues à ceux impliqués dans l'empathie émotionnelle humaine, car dépendants des expériences passées et des relations entretenues avec le partenaire

Among animal societies, dominance is an important social factor that influences inter-individual relationships. However, assessing dominance hierarchy can be a time-consuming activity which is potentially impeded by environmental factors, difficulties in the recognition of animals, or disturbance of animals during data collection. Here we took advantage of novel devices, machines for automated learning and testing (MALT), designed primarily to study non-human primate cognition, to additionally measure the dominance hierarchy of a semi-free-ranging primate group. When working on a MALT, an animal can be replaced by another, which could reflect an asymmetric dominance relationship. To assess the reliability of our method, we analysed a sample of the automated conflicts with video scoring and found that 74% of these replacements included genuine forms of social displacements. In 10% of the cases, we did not identify social interactions and in the remaining 16% we observed affiliative contacts between the monkeys. We analysed months of daily use of MALT by up to 26 semi-free-ranging Tonkean macaques (Macaca tonkeana) and found that dominance relationships inferred from these interactions strongly correlated with the ones derived from observations of spontaneous agonistic interactions collected during the same time period. An optional filtering procedure designed to exclude chance-driven displacements or affiliative contacts suggests that the presence of 26% of these interactions in data sets did not impair the reliability of this new method. We demonstrate that this method can be used to assess the dynamics of both individual social status, and group-wide hierarchical stability longitudinally with minimal research labour. Further, it facilitates a continuous assessment of dominance hierarchies in captive groups, even during unpredictable environmental or challenging social events, which underlines the usefulness of this method for group management purposes. Altogether, this study supports the use of MALT as a reliable tool to automatically and dynamically assess dominance hierarchy within captive groups of non-human primates, including juveniles, under conditions in which such technology can be used.