Social cognition and cooperation

Individual differences in sociocognitive traits in semi-free-ranging rhesus monkeys (Macaca mulatta)

Diaz, A.A., Hernández-Pacheco, R., & Rosati, A.G. (2025). Individual differences ­­in sociocognitive traits in semi-free-ranging rhesus monkeys (Macaca mulatta). American Journal of Primatology, 87: e23660. [PDF] [Supplementary] [Study Videos] [ Publisher’s version] Abstract

Characterizing individual differences in cognition is crucial for understanding the evolution of cognition as well as to test the biological consequences of different cognitive traits. Here, we harnessed the strengths of a uniquely large, naturally-living primate population at the Cayo Santiago Biological Field Station to characterized individual differences in rhesus monkey performance across two social cognitive tasks. A total of n = 204 semi-free-ranging adult rhesus monkeys participated in a data collection procedure, where we aimed to test individuals on both tasks at two time-points that were one year apart. In the socioemotional responses task, we assessed monkeys’ attention to conspecific photographs with neutral versus negative emotional expressions. We found that monkeys showed overall declines in interest in conspecific photographs with age, but relative increases in attention to threat stimuli specifically, and further that these responses exhibited long-term stability across repeated testing. In the gaze following task we assessed monkeys’ propensity to co-orient with an experimenter. Here, we found no evidence for age-related change in responses, and responses showed only limited repeatability over time. Finally, we found some evidence for common individual variation for performance across the tasks: monkeys that showed greater interest in conspecific photographs were more likely to follow a human’s gaze. These results show how studies of comparative cognitive development and aging can provide insights into the evolution of cognition, and identify core primate social cognitive traits that may be related across and within individuals.

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Insights from matched species comparisons for understanding cognition in the wild

De Petrillo, F., Bettle, R. & Rosati, A.G. (2022). Insights from matched species comparisons for understanding cognition in the wild. Current Opinion in Behavioral Sciences.

[PDF] [Publisher’s version] Abstract

Studies of cognition in the wild are crucial for understanding cognition in natural contexts, but studies of animal cognition in captive populations, living in conditions resembling those of their natural environment, complement this approach and provide new insights into the evolution of cognition. To show how these approaches can work in tandem, we use data from recent comparisons on cognition across different primate species in similar settings. We discuss how this work can disentangle stable species-specific differences in cognition from local environmental effects, distinguish specific cognitive mechanisms supporting behavior, and reveal hidden variables that shape cognition in captivity and the wild. Integration of research in both captive and wild settings will therefore provide a holistic understanding of the origins and function of different cognitive processes.

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Sensitivity to line-of-sight in tolerant versus despotic macaques (Macaca sylvanus and Macaca mulatta)

Bettle, R. & Rosati, A.G. (2022) Sensitivity to line-of-sight in tolerant versus despotic macaques (Macaca sylvanus and Macaca mulatta). Journal of Comparative Psychology, 136: 93–104.

[PDF] [Supplementary] [Study Video] [Publisher’s version] [Commentary] Abstract
Complex social life is considered important to the evolution of cognition in primates. One key aspect of primate social interactions concerns the degree of competition that individuals face in their social group. To examine how social tolerance versus competition shapes social cognition, we experimentally assessed capacities for flexible gaze-following in more tolerant Barbary macaques (Macaca sylvanus) and compared to previous data from despotic rhesus macaques (Macaca mulatta). Monkeys experienced one of two possible conditions. In the barrier condition, they observed an actor look upwards into an overheard barrier, so they could not directly see the target of the actor’s gaze without reorienting. In the no barrier condition, they observed an actor look upwards without a barrier blocking her line-of-sight, so they could observe the target of the actor’s gaze by also looking upwards. Both species (N = 58 Barbary macaques, 64 rhesus macaques) could flexibly modulate their gaze responses to account for the demonstrator’s line of sight, looking up more often when no barrier was present, and this flexible modulation declined with age in both species. However, neither species preferentially approached to look inside the barrier when their view of the target location was obscured, although rhesus macaques approached more overall. This pattern suggests that both tolerant and despotic macaques exhibit similar capacities to track other’s line of sight and do not preferentially reorient their bodies to observe what an actor looks at in this situation. This contrasts with other work indicating that competitive primates are especially adept at some aspects of theory of mind. Thus, it is important to understand both the similarities and differences in the social–cognitive abilities of primates with different social styles.

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Children show economic trust for both ingroup and outgroup partners

Grueneisen, S., Rosati, A.G., Warneken, F. (2021) Children show economic trust for both ingroup and outgroup partners. Cognitive Development, 59: 101077

[PDF] [Publisher’s version] Abstract
Trust is a critical aspect of human cooperation, allowing individuals to overcome the risks posed by such interactions because of others’ presumed cooperative inclinations. Adults sometimes mitigate these risks by preferentially trusting members of their own social group, yet it is currently unclear if the early emergence of children’s trust in others’ cooperative tendencies is affected by their intergroup psychology. Here we tested whether group membership impacts two key aspects of trust-based cooperation in young children – their trust in others’ willingness to reciprocate an investment (assessed using the Investment Game, Study 1), and their trust in others’ generosity (assessed using the Faith Game, Study 2). In both studies, children assigned to novel and otherwise arbitrary groups demonstrated general preferences for ingroup members on several measures. However, group membership did not influence their decisions about economic trust. In Study 1, 4- and 6-year-old children showed high levels of trust in both ingroup and outgroup members’ tendency to reciprocate an investment. In Study 2, 6- to 7-year-old children similarly showed high levels of trust in ingroup and outgroup members’ generosity, and they did so regardless of whether their group membership was a matter of common knowledge between themselves and the trustee. These findings show that young children’s preferences for ingroup members do not result in bias due to shared group membership when making economic trust decisions. Rather, children tend to exhibit trust in the cooperativeness of others regardless of group membership.

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The primate origins of human social cognition

Bettle, R. & Rosati, A.G. (2021). The primate origins of human social cognition. Language Learning and Development, 17: 96-127

[PDF] [Publisher’s version] Abstract
The ability to understand the mental states of other individuals is central to human social behavior, yet some theory of mind capacities are shared with other species. Comparisons of theory of mind skills across humans and other primates can provide a critical test of the cognitive prerequisites necessary for different theory of mind skills to emerge. A fundamental difference between humans and non-humans is language: while language may scaffold some developing theory of mind skills in humans, other species do not have similar capacities for or immersion in language. Comparative work can therefore provide a new line of evidence to test the role of language in the emergence of complex social cognition. Here we first provide an overview of the evidence for shared aspects of theory of mind in other primates, and then examine the evidence for apparently human-unique aspects of theory of mind that may be linked to language. We finally contrast different evolutionary processes, such as competition and cooperation, that may have been important for primate social cognition versus human-specific forms of theory of mind. We argue that this evolutionary perspective can help adjudicate between different proposals on the link between human-specific forms of social cognition and language.

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Variation in primate decision-making under uncertainty and the roots of human economic behaviour

De Petrillo, F. & Rosati, A.G. (2021). Variation in primate decision-making under uncertainty and the roots of human economic behaviour. Philosophical Transactions of the Royal Society B, 376: 20190671

[PDF] [Supplementary] [Publisher’s version] Abstract
Uncertainty is a ubiquitous component of human economic behaviour, yet people can vary in their preferences for risk across populations, individuals, and different points in time. As uncertainty also characterizes many aspects of animal decision-making, comparative research can help evaluate different potential mechanisms that generates this variation, including the role of biological differences or maturational change versus cultural learning, as well as identify human-unique components of economic decision-making. Here we examine decision-making under risk across primates, our closest relatives. We first review theoretical approaches and current methods for understanding decision-making in animals. We then assess current evidence for variation in animal preferences between species and populations; between individuals based on personality, sex, and age; and finally, between different contexts and individual states. We then use this primate data to evaluate the processes that can shape human decision-making strategies and identify the primate foundations of human economic behaviour.

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The evolutionary origins of natural pedagogy: Rhesus monkeys show sustained attention following nonsocial cues versus social communicative signals

Bettle, R. & Rosati, A.G. (2021). The evolutionary origins of natural pedagogy: Rhesus monkeys show sustained attention following nonsocial cues versus social communicative signals. Developmental Science, 24: e12987.

[PDF] [Supplementary] [Videos] [Publisher’s version] Abstract
The natural pedagogy hypothesis proposes that human infants preferentially attend to communicative signals from others, facilitating rapid cultural learning. In this view, sensitivity to such signals are a uniquely human adaptation and as such nonhuman animals should not produce or utilize these communicative signals. We test these evolutionary predictions by examining sensitivity to communicative cues in 206 rhesus monkeys (Macaca mulatta) using an expectancy looking time task modeled on prior work with infants. Monkeys observed a human actor who either made eye contact and vocalized to the monkey (social cue), or waved a fruit in front of her face and produced a tapping sound (nonsocial cue). The actor then either looked at an object (referential look) or looked towards empty space (look away). We found that, unlike human infants in analogous situations, rhesus monkeys looked longer at events following nonsocial cues, regardless of the demonstrator’s subsequent looking behavior. Moreover, younger and older monkeys showed similar patterns of responses across development. These results provide support for the natural pedagogy hypothesis, while also highlighting evolutionary changes in human sensitivity to communicative signals.

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Social selectivity in aging wild chimpanzees

Rosati, A.G., Hagberg, L., Enigk, D.K., Otali, E., Emery Thompson, M., Muller, M.N., Wrangham, R.W. & Machanda, Z.P. (2020), Social selectivity in aging wild chimpanzees. Science, 370: 473-476.

[PDF] [Supplementary] [Publisher’s Version] [Commentary] Abstract

Humans prioritize close, positive relationships during aging, and socioemotional selectivity theory proposes that this shift causally depends on capacities for thinking about personal future time horizons. To examine this theory, we tested for key elements of human social aging in longitudinal data on wild chimpanzees. Aging male chimpanzees have more mutual friendships characterized by high, equitable investment, whereas younger males have more one-sided relationships. Older males are more likely to be alone, but they also socialize more with important social partners. Further, males show a relative shift from more agonistic interactions to more positive, affiliative interactions over their life span. Our findings indicate that social selectivity can emerge in the absence of complex future-oriented cognition, and they provide an evolutionary context for patterns of social aging in humans.

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Shifting sociality during primate ageing

Machanda, Z.P. & Rosati, A.G. (2020). Shifting sociality during primate ageing. Philosophical Transactions of the Royal Society B, 375: 20190620.

[PDF] [Supplementary] [Publisher’s version] Abstract

Humans exhibit major age-related shifts in social relationships along with changes in social and emotional psychological processes that underpin these behavioral shifts. Does social aeging in nonhuman primates follow similar patterns, and if so, what are the ultimate evolutionary consequences of these social shifts? Here we synthesize empirical evidence for shifts in social behavior and underlying psychological processes across species. Focusing on three elements of social behavior and cognition that are important for humans—propensities to engage with others, the positive versus negative valence of these interactions, and capabilities to influence others, we find evidence for wide variation in the trajectories of these characteristics across primates. Based on this, we identify potential modulators of the primate social ageing process, including social organization, sex, and dominance status. Finally, we discuss how comparative research can contextualize human social ageing.

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Economic trust in young children

Rosati, A.G., Benjamin, N., Pieloch, K., Warneken, F. (2019). Economic trust in young children. Proceedings of the Royal Society B, 286: 20190822.

[PDF] [Supplementary] [Supplementary Scripts] [Publisher’s Version] Abstract
Mutually beneficial interactions often require trust that others will reciprocate. Such interpersonal trust is foundational to evolutionarily unique aspects of human social behaviour, such as economic exchange. In adults, interpersonal trust is often assessed using the ‘trust game’, in which a lender invests resources in a trustee who may or may not repay the loan. This game captures two crucial elements of economic exchange: the potential for greater mutual benefits by trusting in others, and the moral hazard that others may betray that trust. While adults across cultures can trust others, little is known about the developmental origins of this crucial cooperative ability. We developed the first version of the trust game for use with young children that addresses these two components of trust. Across three experiments, we demonstrate that 4- and 6-year-olds recognize opportunities to invest in others, sharing more when reciprocation is possible than in a context measuring pure generosity. Yet, children become better with age at investing in trustworthy over untrustworthy partners, indicating that this cooperative skill emerges later in ontogeny. Together, our results indicate that young children can engage in complex economic exchanges involving judgements about interpersonal trust and show increasing sensitivity to appropriate partners over development.

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Flexible gaze following in rhesus monkeys

Bettle, R. & Rosati, A.G. (2019). Flexible gaze following in rhesus monkeys. Animal Cognition, 22: 673-686.

[PDF] [Supplementary] [Videos] [Publisher’s Version] Abstract
Humans are characterized by complex social cognitive abilities that emerge early in development. Comparative studies of nonhuman primates can illuminate the evolutionary history of these social capacities. We examined the cognitive skills that rhesus monkeys (Macaca mulatta) use to follow gaze, a foundational skill in human social development. While rhesus monkeys can make inferences about others’ gaze when competing, it is unclear how they think about gaze information in other contexts. In Study 1, monkeys (n = 64) observed a demonstrator look upwards either in a barrier condition where a box was overhead so that monkeys could not see the target of her gaze, or a no barrier condition where nothing blocked her view. In Study 2, monkeys (n = 59) could approach to observe the target of the demonstrator’s gaze when the demonstrator looked behind a barrier on the ground or, in the no barrier condition, behind a window frame in the same location. Monkeys were more likely to directly look up in Study 1 if they could initially see the location where the demonstrator was looking, but they did not preferentially reorient their bodies to observe the out-of-view location when they could not see that location. In Study 2, monkeys did preferentially reorient, but at low rates. This indicates that rhesus monkeys can use social cognitive processes outside of competitive contexts to model what others can or cannot see, but may not be especially motivated to see what others look at in non-competitive contexts, as they reorient infrequently or in an inconsistent fashion. These similarities and differences between gaze-following in monkeys and children can help illuminate the evolution of human social cognition.

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Chimpanzee cooperation is fast and independent from self-control

Rosati, A.G., DiNicola, L.M., & Buckholtz, J.W. (2018). Chimpanzee cooperation is fast and independent from self-control. Psychological Science, 29: 1832-1845.

[PDF] [Supplementary] [Videos] [Publisher’s Version] Abstract
Large-scale cooperation is a hallmark of our species that appears unique amongst primates. Yet the evolutionary mechanisms that drove the emergence of human-like patterns of cooperation remain unclear. Studying the cognitive processes underlying cooperative behavior in apes, our closest living relatives, can help identify these mechanisms. Accordingly, we employed a novel test battery to assess the willingness of forty chimpanzees to donate resources, instrumentally help others, and punish a culpable thief. We found that chimpanzees were faster to make prosocial than selfish choices, and that more prosocial individuals made the fastest responses. Further, two measures of self-control did not predict variation in prosocial responding, and individual performance across cooperative tasks did not covary. These results show that chimpanzees and humans share key cognitive processes for cooperation, despite differences in the scope of their cooperative behaviors.

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Developmental shifts in social cognition: socioemotional biases across the lifespan in rhesus monkeys

Rosati, A.G., Arre, A.M., Platt, M.L., & Santos, L.R. (2018). Developmental shifts in social cognition: socioemotional biases across the lifespan in rhesus monkeys.Behavioral Ecology and Sociobiology, 72: 63.

[PDF] [Video] [Supplementary] [Publisher’s VersionAbstract
Humans exhibit a suite of developmental changes in social cognition across the lifespan. To what extent are these developmental patterns unique? We first review several social domains in which humans undergo critical ontogenetic changes in socio-cognitive processing, including social attention and theory of mind. We then examine whether one human developmental transition—a shift in socioemotional preferences—also occurs in nonhuman primates. Specifically, we experimentally measured socioemotional processing in a large population of rhesus macaques (Macaca mulatta) ranging from infancy to old age. We tested whether macaques, like humans, also exhibited developmental shifts from a negativity bias at younger ages, indicating preferential attention to negative socioemotional stimuli, to a positivity bias at older ages. We first assessed monkeys’ (n = 337) responses to negative socioemotional stimuli by comparing their duration of looking towards photos of negative conspecific signals (threat displays) versus matched neutral expressions. In contrast to the pattern observed in humans, we found that older monkeys were more attentive to negative emotional stimuli than were younger monkeys. In a second study, we used the same method to examine monkeys’ (n = 132) attention to positive (affiliative displays) versus matched neutral expressions. Monkeys did not exhibit an overall preference for positive stimuli, nor major age-related changes in their attention. These results indicate that while monkeys show robust ontogenetic shifts in social preferences, they differ from humans by exhibiting an increasing negativity bias with age. Studies of comparative cognitive development can therefore provide insight into the evolutionary origins of human socio-cognitive development.

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Chimpanzee cognition and the roots of the human mind

Rosati, A.G. (2017). Chimpanzee cognition and the roots of the human mind. In: Chimpanzees and Human Evolution (M. Muller, R. Wrangham & D. Pilbeam, eds.). Cambridge: The Belknap Press of Harvard University Press, pp. 703-745.

[PDF] Abstract
The origins of the human mind have been a puzzle ever since Darwin (1871, 1872). Despite striking continuities in the behavior of humans and nonhumans, our species also exhibits a suite of abilities that diverge from the rest of the animal kingdom: we create and utilize complex technology, pass cultural knowledge from generation to generation, and cooperate across numerous and diverse contexts. Why do humans exhibit these abilities, but other animals (mostly) do not? This is a fundamental question in biology, psychology, and philosophy. This puzzle involves two main parts. The first is concerned with identifying the psychological capacities that are unique to humans. This phylogenetic question can be addressed through careful comparisons of humans and other animals to pinpoint the cognitive traits that are likely derived in our species. The second is concerned with the function of these capacities, and the context in which they arose. This evolutionary question examines why, from an ultimate perspective, we evolved these specialized capacities in the first place. Solving these puzzles poses a special challenge because it is only possible to directly measure the cognition of living animals. The bodies of extinct species leave traces in the fossil record, and even some behavioral traits exhibit well-understood relationships with physical traits—such as relationships between dentition and dietary ecology, or mating system and sexual size dimorphism. These relationships provide important benchmarks when biologists infer the behavior of extinct species. Unfortunately, cognition does not fossilize, and neither do the brains that generate cognitive abilities. Even those features of neuroanatomy that do leave some trace in the fossil record—such as brain size or particular anatomical landmarks—are often related to the kinds of complex cognitive capacities potentially unique to humans in a coarse fashion. As such, identifying derived human cognitive traits requires reconstructing the mind of the last common ancestor of chimpanzees (Pan troglodytes), bonobos (Pan paniscus), and humans (Homo sapiens). This reconstruction then can be used to infer what cognitive characteristics have changed in the human lineage.

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Tolerant Barbary macaques maintain juvenile levels of social attention in old age, but despotic rhesus macaques do not

Rosati, A. G., & Santos, L. R. (2017). Tolerant Barbary macaques maintain juvenile levels of social attention in old age, but despotic rhesus macaques do not. Animal Behaviour, 130, 199-207.

[PDF]  [Supplementary]  [Publisher’s Version]  Abstract

Complex social life is thought to be a major driver of complex cognition in primates, but few studies have directly tested the relationship between a given primate species’ social system and their social cognitive skills. We experimentally compared lifespan patterns of a foundational social cognitive skill (following another’s gaze) in tolerant Barbary macaques, Macaca sylvanus, and despotic rhesus macaques, Macaca mulatta. Semi-free-ranging monkeys (N = 80 individuals from each species) followed gaze more in test trials where an actor looked up compared to control trials. However, species differed in ontogenetic trajectories: both exhibited high rates of gaze following as juveniles, but rhesus monkeys exhibited declines in social attention with age, whereas Barbary macaques did not. This pattern indicates that developmental patterns of social attention vary with social tolerance, and that diversity in social behaviour can lead to differences in social cognition across primates.

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