On some statistical and cerebral aspects of the limits of working memory capacity in anthropoid primates, with particular reference to Pan and Homo, and their significance for human evolution.

Some comparative ontogenetic data imply that effective working-memory capacity develops in ways that are independent of brain size in humans. These are interpreted better from neuroscientific considerations about the continuing development of neuronal architecture in adolescents and young adults, than from one about gross brain mass which already is reached in childhood. By contrast, working-memory capacity in Pan never develops beyond that of three- or four-year-old children. The phylogenetic divergence begs the question of whether it is any longer plausible to infer from the fossil record, that over the past two million years, an ostensibly gradual increase in endocranial volumes, assigned to the genus Homo, can be correlated in a scientifically-meaningful manner with the gradual evolution of our effective executive working memory. It is argued that whereas Pan's effective working-memory capacity is relatively similar to that of its storage working-memory, our working memory is relatively larger with deeper executive control.

Imitation fidelity increases with age in boys, but not in girls: An intriguing finding in a cohort of children aged 3 to 6 years.

Imitation that entails faithful reproduction of demonstrated behavior by reenacting a sequence of actions accurately is a fast and efficient way to acquire new skills as well as to conform to social norms. Previous studies reported that both culture and gender might impinge on young children's fidelity of imitation. We analyzed the imitative behavior of 87 children whose ages ranged from 3 to 6 years. An instrumental task was administered that offered partial (opaque apparatus) or total (transparent apparatus) information about causal connection between the demonstrated actions and their effect in achieving a desired reward. Imitative fidelity (imitating the actions that were demonstrated by an adult model yet were unnecessary for achieving the instrumental goal) increased as a function of age in boys, whereas no differences were found in girls. This lack of increase in girls can be ascribed to their displaying higher degrees of imitation fidelity at an earlier age.

Are there disciplinary boundaries in the comparative study of primate cognition?

A view continues to gain momentum that regards investigation of the cognition of great apes in captive settings as affording us a model for human cognitive evolution. Researchers from disciplines such as comparative psychology, anthropology, and even archaeology, seem eager to put their theories to the test by using great apes as their chosen experimental model. Questions addressed currently by comparative psychologists have long been the object of attention by neurophysiologists, psychobiologists and neuroscientists, who, however, often use rodents and monkeys as the species of choice. Whereas comparative psychology has been influenced greatly by ethology, much neuroscience has developed against a background of physiology and medicine. This separation of the intellectual contexts wherein they have arisen and flourished has impeded the development of fluid interaction between comparative psychologists and researchers in the other disciplines. We feel that it would be beneficial for comparative psychologists and neuroscientists to combine research endeavours far more often, in order to address common questions of interest related to cognition. We regard interdisciplinary cross-pollination to be particularly desirable, even if many comparative psychologists lack deep expertise about the workings of the brain, and even if many neuroscientists lack expert knowledge about the behaviour of different species. Furthermore, we believe that anthropology, archaeology, human evolutionary studies, and related disciplines, may well provide us with significant contextual knowledge about the physical and temporal background to the evolution in humans of specific cognitive skills. To that end, we urge researchers to dismantle methodological, conceptual and historical disciplinary boundaries, in order to strengthen cross-disciplinary cooperation in order to broaden and deepen our insights into the cognition of nonhuman and human primates.

To copy or not to copy? That is the question! From chimpanzees to the foundation of human technological culture.

A prerequisite for copying innovative behaviour faithfully is the capacity of observers' brains, regarded as 'hierarchically mechanistic minds', to overcome cognitive 'surprisal' (see 2.), by maximising the evidence for their internal models, through active inference. Unlike modern humans, chimpanzees and other great apes show considerable limitations in their ability, or 'Zone of Bounded Surprisal', to overcome cognitive surprisal induced by innovative or unorthodox behaviour that rarely, therefore, is copied precisely or accurately. Most can copy adequately what is within their phenotypically habitual behavioural repertoire, in which technology plays scant part. Widespread intra- and intergenerational social transmission of complex technological innovations is not a hall-mark of great-ape taxa. 3 Ma, precursors of the genus Homo made stone artefacts, and stone-flaking likely was habitual before 2 Ma. After that time, early Homo erectus has left traces of technological innovations, though faithful copying of these and their intra- and intergenerational social transmission were rare before 1 Ma. This likely owed to a cerebral infrastructure of interconnected neuronal systems more limited than ours. Brains were smaller in size than ours, and cerebral neuronal systems ceased to develop when early Homo erectus attained full adult maturity by the mid-teen years, whereas its development continues until our mid-twenties nowadays. Pleistocene Homo underwent remarkable evolutionary adaptation of neurobiological propensities, and cerebral aspects are discussed that, it is proposed here, plausibly, were fundamental for faithful copying, which underpinned social transmission of technologies, cumulative learning, and culture. Here, observers' responses to an innovation are more important for ensuring its transmission than is an innovator's production of it, because, by themselves, the minimal cognitive prerequisites that are needed for encoding and assimilating innovations are insufficient for practical outcomes to accumulate and spread intra- and intergenerationally.

Typological differences influence the bilingual advantage in metacognitive processing.

Previous studies showed a bilingual advantage in metacognitive processing (tracking one's own cognitive performance) in linguistic tasks. However, bilinguals do not constitute a homogeneous population, and it was unclear which aspects of bilingualism affect metacognition. In this project, we tested the hypothesis that simultaneous acquisition and use of typologically different languages leads to development of diverse processing strategies and enhances metacognition. The hypothesis was tested in the visual and auditory modalities in language and nonlanguage domains, in an artificial language learning task. In the auditory modality, the hypothesis was confirmed for linguistic stimuli, with no between-domain transfer of metacognitive abilities was observed at the individual level. In the visual modality, no differences in metacognitive efficiency were observed. Moreover, we found that bilingualism per se and the use of typologically different languages modulated separate metacognitive processes engaged in monitoring cognitive performance in statistical learning task. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Intermodality differences in statistical learning: phylogenetic and ontogenetic influences.

In Basque-Spanish bilinguals, statistical learning (SL) in the visual modality was more efficient on nonlinguistic than linguistic input; in the auditory modality, we found the reverse pattern of results. We hypothesize that SL was shaped for processing nonlinguistic environmental stimuli and only later, as the language faculty emerged, recycled for speech processing. This led to further adaptive changes in the neurocognitive mechanisms underlying speech processing, including SL. By contrast, as a recent cultural innovation, written language has not yet led to adaptations. The current study investigated whether such phylogenetic influences on SL can be modulated by ontogenetic influences on a shorter timescale, over the course of individual development. We explored how SL is modulated by the ambient linguistic environment. We found that SL in the auditory modality can be further modulated by exposure to a bilingual environment, in which speakers need to process a wider range of diverse speech cues. This effect was observed only on linguistic, not nonlinguistic, material. We conclude that ontogenetic factors modulate the efficiency of already existing SL ability, honing it for specific types of input, by providing new targets for selection via exposure to different cues in the sensory input.

On the working memory of humans and great apes: Strikingly similar or remarkably different?

In this article we review publications relevant to addressing widely reported claims in both the academic and popular press that chimpanzees working memory (WM) is comparable to, if not exceeding, that of humans. WM is a complex multidimensional construct with strong parallels in humans to prefrontal cortex and cognitive development. These parallels occur in chimpanzees, but to a lesser degree. We review empirical evidence and conclude that the size of WM in chimpanzees is 2 ± 1 versus Miller's famous 7 ± 2 in humans. Comparable differences occur in experiments on chimpanzees relating to strategic and attentional WM subsystems. Regardless of the domain, chimpanzee WM performance is comparable to that of humans around the age of 4 or 5. Next, we review evidence showing parallels among the evolution of WM capacity in hominins ancestral to Homo sapiens, the phylogenetic evolution of hominins leading to Homo sapiens, and evolution in the complexity of stone tool technology over this time period.

The benefits of being seen to help others: indirect reciprocity and reputation-based partner choice.

When one individual helps another, it benefits the recipient and may also gain a reputation for being cooperative. This may induce others to favour the helper in subsequent interactions, so investing in being seen to help others may be adaptive. The best-known mechanism for this is indirect reciprocity (IR), in which the profit comes from an observer who pays a cost to benefit the original helper. IR has attracted considerable theoretical and empirical interest, but it is not the only way in which cooperative reputations can bring benefits. Signalling theory proposes that paying a cost to benefit others is a strategic investment which benefits the signaller through changing receiver behaviour, in particular by being more likely to choose the signaller as a partner. This reputation-based partner choice can result in competitive helping whereby those who help are favoured as partners. These theories have been confused in the literature. We therefore set out the assumptions, the mechanisms and the predictions of each theory for how developing a cooperative reputation can be adaptive. The benefits of being seen to be cooperative may have been a major driver of sociality, especially in humans. This article is part of the theme issue 'The language of cooperation: reputation and honest signalling'.

The psychological foundations of reputation-based cooperation.

Humans care about having a positive reputation, which may prompt them to help in scenarios where the return benefits are not obvious. Various game-theoretical models support the hypothesis that concern for reputation may stabilize cooperation beyond kin, pairs or small groups. However, such models are not explicit about the underlying psychological mechanisms that support reputation-based cooperation. These models therefore cannot account for the apparent rarity of reputation-based cooperation in other species. Here, we identify the cognitive mechanisms that may support reputation-based cooperation in the absence of language. We argue that a large working memory enhances the ability to delay gratification, to understand others' mental states (which allows for perspective-taking and attribution of intentions) and to create and follow norms, which are key building blocks for increasingly complex reputation-based cooperation. We review the existing evidence for the appearance of these processes during human ontogeny as well as their presence in non-human apes and other vertebrates. Based on this review, we predict that most non-human species are cognitively constrained to show only simple forms of reputation-based cooperation. This article is part of the theme issue 'The language of cooperation: reputation and honest signalling'.

Behavioural mimicry as an indicator of affiliation.

Previous research has shown that behavioural mimicry fosters affiliation, and can be used to infer whether people belong to the same social unit. However, we still know very little about the generalizability of these findings and the individual factors involved. The present study intends to disentangle two important variables and assess their importance for affiliation: the matching in time of the behaviours versus their matching in form. In order to address this issue, we presented participants with short videos in which two actors displayed a set of small movements (e.g. crossing their legs, folding their arms, tapping their fingers) arranged to be either contingent in time or in form. A dark filter was used to eliminate ostensive group marks, such us phenotype or clothing. Participants attributed the highest degree of affiliation to the actors when their subsequent movements matched in form, but were delayed by 4-5 seconds, and the lowest degree when the timing of their movements matched, but they differed in form. To assess the generalizability of our findings, we took our study outside the usual Western context and tested a matching sample of participants from a traditional small-scale society in Kenya. In all, our results suggest that movements are used to judge the degree of affiliation between two individuals in both large- and small-scale societies. While moving in different ways at the same time seems to increase the perceived distance between two individuals, movements which match in form seem to invoke closeness.

Great apes (Pan troglodytes, Pan paniscus, Pongo abelii) exploit better the information of failure than capuchin monkeys (Sapajus spp.) when selecting tools to solve the same foraging problem.

In a previous study, chimpanzees, bonobos, orangutans, and capuchin monkeys faced a task that required the use of a rigid stick-like tool to displace an out-of-reach food reward, which was located outside the cage either hanging on a string (e.g., apes) or on a table (e.g., capuchins). Three unfamiliar stick-like tools were placed on a wooden platform for the subjects to choose. Testing consisted of two consecutive trials, each with the same set of tools. Previous to the test subjects learned about the rigidity of the tool either by handling the tools (manipulation), or by observing an experimenter bending and unbending them in sequence (observation); or did not receive any information since the three tools were presented lying on the platform (visual static). In the current study, we investigated whether failing to select the right type of tool in the first trial affected subjects' choices in the second trial. Results showed that when information about the tool rigidity was obtained before selection, great apes and capuchin monkeys changed options in their second choices. However, in the visual static condition, where no information about the rigidity of the tools had been provided before their selection, only great apes discarded wrong tool exemplars in their second trials benefitting from their own mistakes. In contrast, capuchin monkeys did not. We argue that lower attentional focus and lack of stimuli distinctiveness might account for capuchins monkeys' failure to benefit from their own experience. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Acute administration of 3-nitropropionic acid, a reactive oxygen species generator, boosts ethanol-induced locomotor stimulation. New support for the role of brain catalase in the behavioural effects of ethanol.

The antioxidant enzyme catalase by reacting with H(2)O(2), forms the compound known as compound I (catalase-H(2)O(2)). This compound is able to oxidise ethanol to acetaldehyde in the CNS. It has been demonstrated that 3-nitropropionic acid (3-NPA) induces the activity of the brain catalase-H(2)O(2) system. In this study, we tested the effect of 3-NPA on both the brain catalase-H(2)O(2) system and on the acute locomotor effect of ethanol. To find the optimal interval for the 3-NPA-ethanol interaction mice were treated with 3-NPA 0, 45, 90 and 135min before an ethanol injection (2.4mg/kg). In a second study, 3-NPA (0, 15, 30 or 45mg/kg) was administered SC to animals 90min before saline or several doses of ethanol (1.6 or 2.4g/kg), and the open-field behaviour was registered. The specificity of the effect of 3-NPA (45mg/kg) was evaluated on caffeine (10mg/kg IP) and cocaine (4mg/kg)-induced locomotion. The prevention of 3-NPA effects on both ethanol-induced locomotion and brain catalase activity by L-carnitine, a potent antioxidant, was also studied. Nitropropionic acid boosted ethanol-induced locomotion and brain catalase activity after 90min. The effect of 3-NPA was prevented by l-carnitine administration. These results indicate that 3-NPA enhanced ethanol-induced locomotion by increasing the activity of the brain catalase system.

Brain catalase mediates potentiation of social recognition memory produced by ethanol in mice.

The involvement of catalase in ethanol-induced locomotion has been clearly proven. However, studies addressing the role of this enzyme in the effects that ethanol exerts on memory are lacking. In the present study, the social recognition test (SRT) was used to evaluate ethanol effects on memory. In this test, the reduction in investigation time of a juvenile conspecific, when this social stimulus is presented for the second time, is considered a reliable index of memory. Exploration ratios (ER) were calculated to evaluate the recognition capacity of mice. Ethanol (0.0, 0.5, 1.0 or 1.5g/kg, i.p.) was administered immediately after the first juvenile presentation, and 2h later the juvenile was re-exposed to the adult. Additionally, adult mice received aminotriazole (AT) or sodium azide (two catalase inhibitors) 5h or 30 min before juvenile presentation, respectively. Ethanol (1.0 and 1.5g/kg) was able to reduce ER, indicating an improving effect on memory. This improvement was prevented by either AT or sodium azide pre-treatment. However, neither AT nor sodium azide attenuated the memory-enhancing capacity of NMDA or nicotine, suggesting a specific interaction between catalase inhibitors and ethanol in their effects on memory. The present results suggest that brain catalase activity could mediate the memory-enhancing capacity of ethanol and add further support to the idea that this enzyme mediates some of the psychopharmacological effects produced by ethanol.