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ABSTRACT Metacognition, or monitoring and controlling one's knowledge, is a key feature of human cognition. Accumulating evidence shows that foundational forms of metacognition are already present in young infants and then scaffold later‐emerging skills. Although many animals exhibit cognitive processes relevant to metacognition, it is unclear if other species share the developmental trajectories seen in humans. Here, we examine the emergence of metacognitive information‐seeking in rhesus monkeys (Macaca mulatta). We presented a large sample of semi‐free‐ranging monkeys, ranging from juvenility to adulthood, with a one‐shot task where they could seek information about a food reward by bending down to peer into a center vantage point in an array of tubes. In thehiddencondition, information‐seeking was necessary as no food was visible on the apparatus, whereas in thevisiblecontrol, condition information‐seeking was not necessary to detect the location of the reward. Monkeys sought information at the center vantage point more often when it was necessary than in the control condition, and younger monkeys already showed competency similar to adults. We also tracked additional monkeys who voluntarily chose not to approach to assess monkeys’ ability to actively infer opportunities for information‐seeking, and again found similar performance in juveniles and adults. Finally, we found that monkeys were overall slower to make metacognitive inferences than to approach known reward, and that younger monkeys were specifically slower to detect opportunities for information‐seeking compared to adults. These results indicate that many features of mature metacognition are already detectable in young monkeys, paralleling evidence for “core metacognition” in infant humans. 

The social intelligence hypothesis proposes that the demands of social life shape the evolution of cognition, but different aspects of social interactions may be relevant. To test how competitive versus cooperative interactions shape social cognition, we assessed multiple metrics of social cognition in Barbary macaques (Macaca sylvanus,n= 40) and rhesus macaques (Macaca mulatta,n= 60). These closely related species have similar social organization, but diverge in social styles: Barbary macaques are more tolerant, whereas rhesus macaques are more despotic. Monkeys completed a battery of experimental tasks measuringgaze-following(co-orienting with others),knowledge attribution(representing others’ underlying knowledge states),goal attribution(interpreting others’ actions in terms of underlying intentional goals) andtemperament(boldness in response to exploring novelty). While the rhesus macaques were more willing to approach a novel object than were Barbary macaques, both species showed similar success in each social task. However, individual Barbary macaques were more likely to show greater overall proficiency across all social measures combined than were individual rhesus monkeys. Overall, these results indicate that similar social cognitive capacities may evolve in distinct social contexts, and suggest socio-cognitive skills may be relevant for both competitive and cooperative interactions in primates. This article is part of the Theo Murphy meeting issue ‘Selection shapes diverse animal minds’. 

Cognitive control, or executive function, is a key feature of human cognition, allowing individuals to plan, acquire new information, or adopt new strategies when the circumstances change. Yet it is unclear which factors promote the evolution of more sophisticated executive-function abilities such as those possessed by humans. Examining cognitive control in nonhuman primates, our closest relatives, can help to identify these evolutionary processes. Here, we developed a novel battery to experimentally measure multiple aspects of cognitive control in primates: temporal discounting, motor inhibition, short-term memory, reversal learning, novelty responses, and persistence. We tested lemur species with targeted, independent variation in both ecological and social features (ruffed lemurs, Coquerel’s sifakas, ring-tailed lemurs, and mongoose lemurs; N = 39) and found that ecological rather than social characteristics best predicted patterns of cognitive control across these species. This highlights the importance of integrating cognitive data with species’ natural history to understand the origins of complex cognition. 

Cognitive flexibility is a core component of executive function, a suite of cognitive capacities that enables individuals to update their behavior in dynamic environments. Human executive functions are proposed to be enhanced compared to other species, but this inference is based primarily on neuroanatomical studies. To address this, we examined the nature and origins of cognitive flexibility in chimpanzees, our closest living relatives. Across three studies, we examined different components of cognitive flexibility using reversal learning tasks where individuals first learned one contingency and then had to shift responses when contingencies flipped. In Study 1, we tested n = 82 chimpanzees ranging from juvenility to adulthood on a spatial reversal task, to characterize the development of basic shifting skills. In Study 2, we tested how n = 24 chimpanzees use spatial versus arbitrary perceptual information to shift, a proposed difference between human and nonhuman cognition. In Study 3, we tested n = 40 chimpanzees on a probabilistic reversal task. We found an extended developmental trajectory for basic shifting and shifting in response to probabilistic feedback—chimpanzees did not reach mature performance until late in ontogeny. Additionally, females were faster to shift than males were. We also found that chimpanzees were much more successful when using spatial versus perceptual cues, and highly perseverative when faced with probabilistic versus consistent outcomes. These results identify both core features of chimpanzee cognitive flexibility that are shared with humans, as well as constraints on chimpanzee cognitive flexibility that may represent evolutionary changes in human cognitive development.