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Funding: The research of A.M.S. was supported by a ‘INQMINDS’ ERC Starting Grant no. (SEP-210159400). Attentional set shifting is a core ingredient of cognition, allowing for fast adaptation to changes in the environment. How this skill compares between humans and other primates is not well known. We examined performance of 3- to 5-year-old children and chimpanzees on a new attentional set shifting task. We presented participants with two shelves holding the same set of four boxes. To choose the correct box on each shelf, one has to switch attention depending on which shelf one is currently presented with. Experiment 1 (forty-six 3- to 5-year olds, predominantly European White) established content validity, showing that the majority of errors were specific switching mistakes indicating failure to shift attention. Experiment 2 (one hundred and seventy-eight 3- to 6-year olds, predominantly European White) showed that older children made fewer mistakes, but if mistakes were made, a larger proportion were switching mistakes rather than ‘random’ errors. Experiment 3 (52 chimpanzees) established suitability of the task for non-human great apes and showed that chimpanzees' performance was comparable to the performance of 3- and 4-year olds, but worse than 5-year olds. These results suggest that chimpanzees and young children share attentional set shifting capacities, but that there are unique changes in the human lineage from 5 years of age. Publisher PDF

Funding: This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement No. [639072]). We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), [funding reference number 2016-05552]. The use of abstract higher-level knowledge (also called overhypotheses) allows humans to learn quickly from sparse data and make predictions in new situations. Previous research has suggested that humans may be the only species capable of abstract knowledge formation, but this remains controversial. There is also mixed evidence for when this ability emerges over human development. Kemp et al. (2007) proposed a computational model of how overhypotheses could be learned from sparse examples. We provide the first direct test of this model: an ecologically valid paradigm for testing two species, capuchin monkeys (Sapajus spp.) and 4- to 5-year-old human children. We presented participants with sampled evidence from different containers which suggested that all containers held items of uniform type (type condition) or of uniform size (size condition). Subsequently, we presented two new test containers and an example item from each: a small, high-valued item and a large but low-valued item. Participants could then choose from which test container they would like to receive the next sample – the optimal choice was the container that yielded a large item in the size condition or a high-valued item in the type condition. We compared performance to a priori predictions made by models with and without the capacity to learn overhypotheses. Children's choices were consistent with the model predictions and thus suggest an ability for abstract knowledge formation in the preschool years, whereas monkeys performed at chance level. Publisher PDF

* 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

We are grateful to the Royal Zoological Society of Scotland (RZSS) and the University of St Andrews for core financial support to the RZSS Edinburgh Zoo’s Living Links Research Facility where this project was carried out. Humans’ flexible innovation relies on our capacity to accurately predict objects’ behaviour. These predictions may originate from a “physics-engine” in the brain which simulates our environment. To explore the evolutionary origins of intuitive physics, we investigate whether capuchin monkeys’ object exploration supports learning. Two capuchin groups experienced exploration sessions involving multiple copies of two objects, one object was easily opened (functional), the other was not (non-functional). We used two within-subject conditions (enrichment-then-test, and test-only) with two object sets per group. Monkeys then underwent individual test sessions where the objects contained rewards, and they choose one to attempt to open. The monkeys spontaneously explored, performing actions which yielded functional information. At test, both groups chose functional objects above chance. While high performance of the test-only group precluded us from establishing learning during exploration, this study reveals the promise of harnessing primates’ natural exploratory tendencies to understand how they see the world. Publisher PDF

This project has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (Grant Agreement 639072). Brandon Tinklenberg was supported by a grant from the Social Sciences and Humanities Research Council of Canada (SSHRC 435-2016-1051). Inhibition tasks usually require subjects to exert control to act correctly when a competing action plan is prepotent. In comparative psychology, one concern about the existing inhibition tasks is that the relative contribution of inhibitory control to performance (as compared to learning or object knowledge) is rarely explicitly investigated. We addressed this problem by presenting chimpanzees with a spatial foraging task in which they could acquire food more efficiently by learning which objects were baited. In Experiment 1, we examined how objects that elicited a prepotent approach response, transparent cups containing food, affected their learning rates. Although showing an initial bias to approach these sealed cups with visible food, the chimpanzees learned to avoid them more quickly across sessions compared to a color discrimination. They also learned a color discrimination more quickly if the incorrect cups were sealed such that a piece of food could never be hidden inside them. In Experiment 2, visible food of 2 different types was sealed in the upper part of the cups: 1 type signaled the presence of food reward hidden underneath; the cups with the other type were sealed. The chimpanzees learned more quickly in a congruent condition (the to-be-chosen food cue matched the reward) than in an incongruent condition (the to-be-avoided food cue matched the reward). Together, these findings highlight that performance in inhibition tasks is affected by several other cognitive abilities such as object knowledge, memory, and learning, which need to be quantified before meaningful comparisons can be drawn. Postprint

Funding: The research of A.M.S. was supported by an ‘INQMINDS’ ERC Starting Grant no. (SEP-210159400). Executive functions (EF) are a core aspect of cognition. Research with adult humans has produced evidence for unity and diversity in the structure of EF. Studies with preschoolers favour a 1-factor model, in which variation in EF tasks is best explained by a single underlying trait on which all EF tasks load. How EF are structured in nonhuman primates remains unknown. This study starts to fill this gap through a comparative, multi-trait multi-method test battery with preschoolers (N = 185) and chimpanzees (N = 55). The battery aimed at measuring working memory updating, inhibition, and attention shifting with three non-verbal tasks per function. For both species the correlations between tasks were low to moderate and not confined to tasks within the same putative function. Factor analyses produced some evidence for the unity of executive functions in both groups, in that our analyses revealed shared variance. However, we could not conclusively distinguish between 1-, 2- or 3-factor models. We discuss the implications of our findings with respect to the ecological validity of current psychometric research. Publisher PDF

The research of A.M.S. was supported by an “INQMINDS” European Research Council (ERC) Starting Grant (SEP-210159400). Attentional set shifting is a core part of cognition, allowing quick and flexible adaption to new demands. The study of its development during early childhood has been hampered by a shortage of measures not requiring language. This article argues for a revival of the Intradimensional/Extradimensional (ID/ED) shift task by presenting a new nonverbal version of the task (Shifting Tray task). Children (N = 95 3- to 5-year-olds; 49 girls; predominantly European White) were presented with pairs of trays, each filled with a substrate and an upside-down cup on top, and were asked to find stickers. In the pre-switch phase, children learned (through trial and error) which dimension (substrate or cup) was predictive of the rewards. In the post-switch phase, all stimuli were exchanged. For children in the intradimensional shift condition, the dimension predictive of the sticker was the same as the one predictive in the pre-switch phase. For children in the extradimensional shift condition, the previously irrelevant dimension was now relevant. Results showed that most 3-year-olds were able to switch, and older children did not outperform younger children. The easy and flexible nature of the task allows researchers to investigate the impact of labels and instructions and to use it in cross-cultural and comparative research. Publisher PDF

This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement no. 639072). Edinburgh Zoo's Living Links Research Facility is core supported by the Royal Zoological Society of Scotland (registered charity no.: SC004064) through funding generated by its visitors, members and supporters. The ability to infer unseen causes from evidence is argued to emerge early in development and to be uniquely human. We explored whether preschoolers and capuchin monkeys could locate a reward based on the physical traces left following a hidden event. Preschoolers and capuchin monkeys were presented with two cups covered with foil. Behind a barrier, an experimenter (E) punctured the foil coverings one at a time, revealing the cups with one cover broken after the first event and both covers broken after the second. One event involved hiding a reward, the other event was performed with a stick (order counterbalanced). Preschoolers and, with additional experience, monkeys could connect the traces to the objects used in the puncturing events to find the reward. Reversing the order of events perturbed the performance of 3-year olds and capuchins, while 4-year-old children performed above chance when the order of events was reversed from the first trial. Capuchins performed significantly better on the ripped foil task than they did on an arbitrary test in which the covers were not ripped but rather replaced with a differently patterned cover. We conclude that by 4 years of age children spontaneously reason backwards from evidence to deduce its cause. Publisher PDF

This paper is an output of the project ‘Rethinking Mind and Meaning: A case study from a co-disciplinary approach’ (Award Nr.: AH/ L015234/1), funded by the Arts and Humanities Research Council (AHRC), as part of the Science in Culture Theme (http://www.sciculture.ac.uk). A core component of any folk physical understanding of the world is object individuation - the cognitive ability to parse sensory input into discrete objects. Whereas younger human infants use spatio-temporal information to individuate objects, they do not use property and kind information until one year of age. Some researchers propose that object individuation based on property/kind information depends on language acquisition and sortal concepts. However, there is evidence that preverbal infants and nonhuman animals also use both types of information. The present study aimed to further explore the evolutionary origins of object individuation by testing a new-world monkey species, capuchin monkeys (Sapajus spp.), using both manual search (n = 29) and looking time (n = 23) measures. In Spatio-temporal trials, subjects saw one or two objects dropped into a box, but always found (or saw) only one. In Property/kind trials, subjects saw either object A or B being dropped into a box and then always found (or saw) object A. The capuchin monkeys looked longer and searched more on inconsistent trials – with outcome differing in quantity or in kind - which suggested that they had expectations based on both spatio-temporal and property-kind representations. Looking time and search measures gave convergent results at the group but not at the individual level. Our results add to the existing evidence contradicting the linguistic hypothesis of property/kind individuation. However, contrary to recent discussions, we argue that these and related results can be explained without appealing to the notion of sortal concepts or multiple representational systems, and suggest that a full picture of the ontogeny and phylogeny of object individuation requires further empirical and theoretical research. Publisher PDF

International audience; Allogrooming in primates serves not only a hygienic function, but also plays a crucial role in maintaining strong affiliative bonds between group members, which in turn, underpin the emergence of cooperative behavior. In contrast, although allopreening occurs in many avian species, we know little about its social functions. Our study addresses this issue by investigating allopreening in a broad comparative data set including six corvid and nine parrot species. We assessed whether rates of allopreening initiations, proportion of time spent allopreening, and the number of grooming partners in captive group-housed birds were comparable to patterns observed in captive chimpanzees and bonobos. While parrots and corvids were found to have similar rates of social grooming to bonobos and chimpanzees, Pan species dedicated significantly more time to social grooming. Animals in larger groups had more grooming partners, but when controlling for the number of potential partners, birds tended to have fewer grooming interaction partners than Pan species. We then investigated whether allopreening in parrots and corvids was predicted by behavioral markers of affiliative social bonds (close physical proximity, active feeding, and low levels of agonistic behavior). Results revealed that providing allopreening to a partner was significantly predicted by often being in close proximity, but not engagement in active feeding or agonistic behavior. We examined the region allopreened in a subset of species and found that preening a partner's head was predicted by both close physical proximity and active feeding, while body allopreening was only predicted by close physical proximity. Head preening may confer more hygienic benefits to recipients, and thus, may be more selectively provided to valued partners. Results support the hypothesis that allopreening in corvids and parrots helps maintain social bonds with an individual's most important social partners, showing some similarities to allogrooming in primates.

Highlights • We tested a new, non-verbal working memory task in children 3–7 years of age. • Updating and manipulation were measured within a single task, the Rotating Grid Task. • Updating trials were aided by visual tracking and were easier than manipulation trials. • Manipulation trials were difficult for children across the entire age range. • The study supports evidence that manipulation has a protracted development., We developed a non-verbal task assessing updating and manipulation of working memory contents. 80 3- to 7-year-olds (47 girls; predominantly European White) were tested with a 4 × 4 grid containing 8 boxes (in the 4 centre cells and 4 outer corners). A sticker was hidden and children searched for it after a delay phase. In the updating trials, the grid was rotated during delays, in the manipulation trials, the grid was both occluded and rotated. Rewards were hidden in either the inner or outer boxes (between-subjects design). Performance was affected by age, rotation degree and hiding condition. Performance was better in outer boxes trials, where visual tracking was easier. Occluded inner trials added a substantial cognitive load (which increased with degree of rotation), resulting in children performing at chance level, suggesting that manipulation involving mental rotation is a distinct skill from tracking invisible object displacement, with a more protracted development.

J.J.M.M. was funded by a Lise Meitner and a Stand Alone grant of the Austrian Science Fund (FWF, numbers M 1352 and P26806), and T.B. was funded by the DK Program Cognition and Communication (FWF no.: W 1234) and a START Grant (FWF no.: Y 366-B17). In recent years, there has been considerable research effort to determine whether other species exhibit prosocial motivations parallel to those of humans; however, these studies have focused primarily on primates, and with mixed results. We presented captive ravens with a modified prosocial choice task which aimed to address several criticisms of previous methods by including a stringent pretraining regime and a set-up that disentangles motivation to provision a conspecific from motivation to feed next to one. In this task six subjects received no rewards for themselves but could choose to deliver food rewards to either a conspecific or an empty, inaccessible compartment. Subjects did not demonstrate any prosocial tendencies (i.e. they did not preferentially choose to reward a conspecific over the empty compartment), and instead often ceased pulling on test trials when they received nothing for themselves (up to 70% of 80 trials with a partner present, up to 83% of 40 trials in a nonsocial control condition). The relationship between the subject and the partner had no influence on the subject's choices; however, subjects were more likely to pull immediately after performing socio-agonistic displays. Our results contribute to a growing body of evidence that despite their sophisticated social cognitive abilities and range of cooperative behaviours exhibited in the wild, unpaired (or unbonded) ravens do not seem to act to benefit conspecifics in the absence of immediate self-gain. Publisher PDF

This project has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant agreement No. 639072). Working memory (WM) is a core executive function that allows individuals to hold, process, and manipulate information. WM capacity has been repeatedly nominated as a key factor in human cognitive evolution; nevertheless, little is known about the WM abilities of our closest primate relatives. In this study, we examined signatures of WM ability in chimpanzees (Pan troglodytes). Standard WM tasks for humans (Homo sapiens) often require participants to continuously update their WM. In Experiment 1, we implemented this updating requirement in a foraging situation:zoo-housed chimpanzees (N=13) searched for food in an array of containers. To avoid redundant searches, they needed to continuously update which containers they had already visited (similar to WM paradigms for human children) with 15-sretention intervals in between each choice. We examined chimpanzees’ WM capacity and to what extent they used spatial cues and object features to memorize their previous choices. In Experiment 2, we investigated how susceptible their WM was to attentional interference, an important signature, setting WM in humans apart from long-term memory. We found large individual differences with some individuals remembering at least their last four choices. Chimpanzees used a combination of spatial cues and object features to remember which boxes they had chosen already. Moreover, their performance decreased specifically when competing memory information was introduced. Finally, we found that individual differences in task performance were highly reliable over time. Together, these findings show remarkable similarities between human and chimpanzee WM abilities despite evolutionary and life history differences. Postprint Postprint

Cooperation is central to what makes us human. It is so deeply entrenched in our nature that it can be seen at the heart of every culture, whether it takes the form of group hunting, shared child-rearing, or large-scale, multi-national institutions such as the UN. And yet in contrast to the constancy of other forms of cooperation in non-human animals, such as termite-mound building or honey bee dancing, the changing face of human cooperation makes it seem more fragile, and its mechanisms more elusive. As with other features of our behaviour, human cooperation is the product of both genetic and cultural evolution. Studying cooperation in children, in different cultural environments, and in contrast to other species, provides a valuable window into the ways in which these two forms of inheritance interact over development, and a chance to distil out its constitutive components. Postprint

Inferring the evolutionary history of cognitive abilities requires large and diverse samples. However, such samples are often beyond the reach of individual researchers or institutions, and studies are often limited to small numbers of species. Consequently, methodological and site-specific-differences across studies can limit comparisons between species. Here we introduce the ManyPrimates project, which addresses these challenges by providing a large-scale collaborative framework for comparative studies in primate cognition. To demonstrate the viability of the project we conducted a case study of short-term memory. In this initial study, we were able to include 176 individuals from 12 primate species housed at 11 sites across Africa, Asia, North America and Europe. All subjects were tested in a delayed-response task using consistent methodology across sites. Individuals could access food rewards by remembering the position of the hidden reward after a 0, 15, or 30-second delay. Overall, individuals performed better with shorter delays, as predicted by previous studies. Phylogenetic analysis revealed a strong phylogenetic signal for short-term memory. Although, with only 12 species, the validity of this analysis is limited, our initial results demonstrate the feasibility of a large, collaborative open-science project. We present the ManyPrimates project as an exciting opportunity to address open questions in primate cognition and behaviour with large, diverse datasets. Publisher PDF

Cognitive abilities cannot be measured directly. What we can measure is individual variation in task performance. In this paper, we first make the case for why we should be interested in mapping individual differences in task performance onto particular cognitive abilities: we suggest that it is crucial for examining the causes and consequences of variation both within and between species. As a case study, we examine whether multiple measures of inhibitory control for non-human animals do indeed produce correlated task performance; however, no clear pattern emerges that would support the notion of a common cognitive ability underpinning individual differences in performance. We advocate a psychometric approach involving a three-step programme to make theoretical and empirical progress: first, we need tasks that reveal signature limits in performance. Second, we need to assess the reliability of individual differences in task performance. Third, multi-trait multi-method test batteries will be instrumental in validating cognitive abilities. Together, these steps will help us to establish what varies between individuals that could impact their fitness and ultimately shape the course of the evolution of animal minds. Finally, we propose executive functions, including working memory, inhibitory control and attentional shifting, as a sensible starting point for this endeavour. This article is part of the theme issue ‘Causes and consequences of individual differences in cognitive abilities’.

The main aim of this paper is to highlight the need to address the conceptual problem of “implicit knowledge” or “implicit cognition” —a notion especially important in the study of the nonverbal minds of animals and infants. We review some uses of the term ‘implicit’ in psychology and allied disciplines,and conclude that conceptual clarification of this notion is not only lacking, but largely avoided and reduced to a methodological problem. We propose that this elusive notion is central in the study not only of animal and infant minds, but also the human adult mind. Some promising approaches in developmental and evolutionary psychology towards innovative conceptualisation of implicit knowledge remain conceptually underdeveloped and in need of reconsideration and re-elaboration. We conclude by suggesting that the challenge of implicit cognition and nonverbal minds will only be solved through a concerted interdisciplinary approach between psychology and other disciplines. Publisher PDF

This research was supported by The British Psychological Society Summer Bursary, awarded to Lauren Hogan. While social learning has been demonstrated in species across many taxa, the role it plays in everyday foraging decisions is not well understood. Investigating social learning during foraging could shed light on the emergence of cultural variation in different groups. We used an open diffusion experiment to examine the spread of a novel foraging technique in captive Amazon parrots. Three groups were tested using a two-action foraging box, including experimental groups exposed to demonstrators using different techniques and control birds. We also examined the influence of agonistic and pilfering behaviour on task acquisition. We found evidence of social learning: more experimental birds than control birds interacted with and opened the box. The birds were, however, no more likely to use the demonstrated technique than the non-demonstrated one, making local or stimulus enhancement the most likely mechanism. Exhibiting aggression was positively correlated with box opening, whilst receiving aggression did not reduce motivation to engage with the box, indicating that willingness to defend access to the box was important in task acquisition. Pilfering food and success in opening the box were also positively correlated; however, having food pilfered did not affect victims’ motivation to interact with the box. In a group context, pilfering may promote learning of new foraging opportunities. Although previous studies have demonstrated that psittacines are capable of imitation, in this naturalistic set-up there was no evidence that parrots copied the demonstrated opening technique. Foraging behaviour in wild populations of Amazons could therefore be facilitated by low-fidelity social learning mechanisms. Postprint

RLK was funded by a Royal Society Dorothy Hodgkin Fellowship; LMH by a BBSRC studentship (BBS/S/K/2004/11255 supervised by AW) and, at the time of writing, is funded by the Guthman Fund; WH by a BBSRC grant (BB/I007997/1); SFB by a NSF CAREER award (SES 0847351) and (SES 0729244). The chimpanzee colony is supported by NIH U42 (RR-15090). Evolutionary theory predicts that natural selection will fashion cognitive biases to guide when, and from whom, individuals acquire social information, but the precise nature of these biases, especially in ecologically valid group contexts, remains unknown. We exposed four captive groups of chimpanzees (Pan troglodytes) to a novel extractive foraging device and, by fitting statistical models, isolated four simultaneously operating transmission biases. These include biases to copy (i) higher-ranking and (ii) expert individuals, and to copy others when (iii) uncertain or (iv) of low rank. High-ranking individuals were relatively un-strategic in their use of acquired knowledge, which, combined with the bias for others to observe them, may explain reports that high innovation rates (in juveniles and subordinates) do not generate a correspondingly high frequency of traditions in chimpanzees. Given the typically low rank of immigrants in chimpanzees, a 'copying dominants' bias may contribute to the observed maintenance of distinct cultural repertoires in neighboring communities despite sharing similar ecology and knowledgeable migrants. Thus, a copying dominants strategy may, as often proposed for conformist transmission, and perhaps in concert with it, restrict the accumulation of traditions within chimpanzee communities whilst maintaining cultural diversity. Postprint

KLD was funded by a Bobby Jones scholarship and by the University of St Andrews. Imagining the future is a powerful tool for making plans and solving problems. It is thought to rely on the episodic system which also underpins remembering a specific past event [1, 2, 3]. However, the emergence of episodic future thinking over development and evolution is debated [4, 5, 6, 7, 8, 9]. One key source of positive evidence in pre-schoolers and animals is the “spoon test” or item choice test [4, 10], in which participants encounter a problem in one context and then a choice of items in another context, one of which is the solution to the problem. A majority of studies report that most children choose the right item by age 4 [10, 11, 12, 13, 14, 15, cf. 16]. Apes and corvids have also been shown to pass versions of the test [17, 18, 19]. However, it has been suggested that a simpler mechanism could be driving choice: the participant simply chooses the item that has been assigned salience or value, without necessarily imagining the future event [16, 20, 21, 22, 23]. We developed a new test in which two of the items offered to children were associated with positive outcomes, but only one was still useful. We found that older children (5-, 6-, and 7-year-olds) chose the correct item at above chance levels, but younger children (3- and 4-year-olds) did not. In further tests, 4-year-olds showed an intact memory for the encoding event. We conclude that positive association substantially impacts performance on item choice tests in 4-year-olds and that future planning may have a more protracted developmental trajectory than episodic memory. Postprint

This research was made possible through Wellcome Trust grants WT094440MA and WT098133A to A. Whiten. The study was begun while NC was supported by a Research Fellowship from the Fyssen Foundation and later by a John Templeton Foundation grant to AW. Wild and captive capuchin monkeys will anoint themselves with a range of strong smelling substances including millipedes, ants, limes and onions. Hypotheses for the function of the behaviour range from medicinal to social. However, capuchin monkeys may anoint in contact with other individuals, as well as individually. The function of social anointing has also been explained as either medicinal or to enhance social bonding. By manipulating the abundance of an anointing resource given to two groups of tufted capuchins, we tested predictions derived from the main hypotheses for the functions of anointing and in particular, social anointing. Monkeys engaged in individual and social anointing in similar proportions when resources were rare or common, and monkeys holding resources continued to join anointing groups, indicating that social anointing has functions beyond that of gaining access to resources. The distribution of individual and social anointing actions on the monkeys’ bodies supports a medicinal function for both individual and social anointing, that requires no additional social bonding hypotheses. Individual anointing targets hard-to-see body parts that are harder to groom, whilst social anointing targets hard-to-reach body parts. Social anointing in capuchins is a form of mutual medication that improves coverage of topically applied anti-parasite medicines. Publisher PDF

Research supported in part by an ERC Advanced Grant to K.N.L. (EVOCULTURE, ref: 232823) and grants to N.T.U. from the British Academy (Centenary Project ‘Lucy to Language: the Archaeology of the Social Brain’) and the Leverhulme Trust (ECF 0298). Hominin reliance on Oldowan stone tools—which appear from 2.5 mya and are believed to have been socially transmitted—has been hypothesized to have led to the evolution of teaching and language. Here we present an experiment investigating the efficacy of transmission of Oldowan tool-making skills along chains of adult human participants (N=184) using five different transmission mechanisms. Across six measures, transmission improves with teaching, and particularly with language, but not with imitation or emulation. Our results support the hypothesis that hominin reliance on stone tool-making generated selection for teaching and language, and imply that (i) low-fidelity social transmission, such as imitation/emulation, may have contributed to the ~700,000 year stasis of the Oldowan technocomplex, and (ii) teaching or proto-language may have been pre-requisites for the appearance of Acheulean technology. This work supports a gradual evolution of language, with simple symbolic communication preceding behavioural modernity by hundreds of thousands of years. Postprint

Tracing the evolution of human culture through time is arguably one of the most controversial and complex scholarly endeavors, and a broad evolutionary analysis of how symbolic, linguistic, and cultural capacities emerged and developed in our species is lacking. Here we present a model that, in broad terms, aims to explain the evolution and portray the expansion of human cultural capacities (the EECC model), that can be used as a point of departure for further multidisciplinary discussion and more detailed investigation. The EECC model is designed to be flexible, and can be refined to accommodate future archaeological, paleoanthropological, genetic or evolutionary psychology/behavioral analyses and discoveries. Our proposed concept of cultural behavior differentiates between empirically traceable behavioral performances and behavioral capacities that are theoretical constructs. Based largely on archaeological data (the ‘black box’ that most directly opens up hominin cultural evolution), and on the extension of observable problem-solution distances, we identify eight grades of cultural capacity. Each of these grades is considered within evolutionarybiological and historical-social trajectories. Importantly, the model does not imply an inevitable progression, but focuses on expansion of cultural capacities based on the integration of earlier achievements. We conclude that there is not a single cultural capacity or a single set of abilities that enabled human culture; rather, several grades of cultural capacity in animals and hominins expanded during our evolution to shape who we are today. Publisher PDF

Network optimality has been described in genes, proteins and human communicative networks. In the latter, optimality leads to the efficient transmission of information with a minimum number of connections. Whilst studies show that differences in centrality exist in animal networks with central individuals having higher fitness, network efficiency has never been studied in animal groups. Here we studied 78 groups of primates (24 species).We found that group size and neocortex ratio were correlated with network efficiency. Centralisation (whether several individuals are central in the group) and modularity (how a group is clustered) had opposing effects on network efficiency, showing that tolerant species have more efficient networks. Such network properties affecting individual fitness could be shaped by natural selection. Our results are in accordance with the social brain and cultural intelligence hypotheses, which suggest that the importance of network efficiency and information flow through social learning relates to cognitive abilities., SCOPUS: ar.j, info:eu-repo/semantics/published

Data collection with the New Caledonian crows was funded by an International Seedcorn Award from the University of York to M.L.L. This study was supported by a Rutherford Discovery Fellowship (A.H.T.). Our data are deposited at: http://dx.doi.org/10.5061/dryad.dq04j [48]. A range of non-human animals frequently manipulate and explore objects in their environment, which may enable them to learn about physical properties and potentially form more abstract concepts of properties such as weight and rigidity. Whether animals can apply the information learned during their exploration to solve novel problems, however, and whether they actually change their exploratory behavior to seek functional information about objects have not been fully explored. We allowed kea (Nestor notabilis) and New Caledonian crows (Corvus moneduloides) to explore sets of novel objects both before and after encountering a task in which some of the objects could function as tools. Following this, subjects were given test trials in which they could choose among the objects they had explored to solve a tool-use task. Several individuals from both species performed above chance on these test trials, and only did so after exploring the objects, compared with a control experiment with no prior exploration phase. These results suggest that selection of functional tools may be guided by information acquired during exploration. Neither kea nor crows changed the duration or quality of their exploration after learning that the objects had a functional relevance, suggesting that birds do not adjust their behavior to explicitly seek this information. Publisher PDF

A.R. was supported by ERC Advanced Grant 230604 SOMACCA to W. Tecumseh Fitch. SMP was supported by funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement n. [311870]. Cumulative tool-based culture underwrote our species' evolutionary success, and tool-based nut-cracking is one of the strongest candidates for cultural transmission in our closest relatives, chimpanzees. However the social learning processes that may explain both the similarities and differences between the species remain unclear. A previous study of nut-cracking by initially naive chimpanzees suggested that a learning chimpanzee holding no hammer nevertheless replicated hammering actions it witnessed. This observation has potentially important implications for the nature of the social learning processes and underlying motor coding involved. In the present study, model and observer actions were quantified frame-by-frame and analysed with stringent statistical methods, demonstrating synchrony between the observer's and model's movements, cross-correlation of these movements above chance level and a unidirectional transmission process from model to observer. These results provide the first quantitative evidence for motor mimicking underlain by motor coding in apes, with implications for mirror neuron function. Publisher PDF

Conformity is thought to be an important force in human evolution because it has the potential to stabilize cultural homogeneity within groups and cultural diversity between groups. However, the effects of such conformity on cultural and biological evolution will depend much on the particular way in which individuals are influenced by the frequency of alternative behavioral options they witness. In a previous study we found that in a natural situation people displayed a tendency to be 'linear-conformist'. When visitors to a Zoo exhibit were invited to write or draw answers to questions on cards to win a small prize and we manipulated the proportion of text versus drawings on display, we found a strong and significant effect of the proportion of text displayed on the proportion of text in the answers, a conformist effect that was largely linear with a small non-linear component. However, although this overall effect is important to understand cultural evolution, it might mask a greater diversity of behavioral responses shaped by variables such as age, sex, social environment and attention of the participants. Accordingly we performed a further study explicitly to analyze the effects of these variables, together with the quality of the information participants' responses made available to further visitors. Results again showed a largely linear conformity effect that varied little with the variables analyzed. Publisher PDF

Recent years have seen increasing encouragement by research institutions and funding bodies for scientists to actively engage with the public, who ultimately finance their work. Animal behaviour as a discipline possesses several features, including its inherent accessibility and appeal to the public, that may help it occupy a particularly successful niche within these developments. It has also established a repertoire of quantitative behavioural methodologies that can be used to document the public's responses to engagement initiatives. This kind of assessment is becoming increasingly important considering the enormous effort now being put into public engagement projects, whose effects are more often assumed than demonstrated. Here we report our first attempts to quantify relevant aspects of the behaviour of a sample of the hundreds of thousands of visitors who pass through the ‘Living Links to Human Evolution Research Centre’ in Edinburgh Zoo. This University research centre actively encourages the public to view ongoing primate research and associated science engagement activities. Focal follows of visitors and scan sampling showed substantial ‘dwell times’ in the Centre by common zoo standards and the addition of new engagement elements in a second year was accompanied by significantly increased overall dwell times, tripling for the most committed two thirds of visitors. Larger groups of visitors were found to spend more time in the Centre than smaller ones. Viewing live, active science was the most effective activity, shown to be enhanced by novel presentations of carefully constructed explanatory materials. The findings emphasise the importance and potential of zoos as public engagement centres for the biological sciences. Publisher PDF

International audience; Conformity is thought to be an important force in cultural evolution because it has the potential to stabilize cooperation in large groups, potentiate group selection and thus explain uniquely human behaviors. However, the effects of such conformity on cultural and biological evolution will depend much on the way individuals are influenced by the frequency of alternative behavioral options witnessed. Theoretical modeling has suggested that only what we refer to as 'hyper-conformity', an exaggerated tendency to perform the most frequent behavior witnessed in other individuals, is able to increase within-group homogeneity and between-group diversity, for instance. Empirically however, few experiments have addressed how the frequency of behavior witnessed affects behavior. Accordingly we performed an experiment to test for the presence of conformity in a natural situation with humans. Visitors to a Zoo exhibit were invited to write or draw answers to questions on A5 cards and potentially win a small prize. We manipulated the proportion of existing writings versus drawings visible to visitors and measured the proportion of written cards submitted. We found a strong and significant effect of the proportion of text displayed on the proportion of text in the answers, thus demonstrating social learning. We show that this effect is approximately linear, with potentially a small, weak-conformist component but no hyper-conformist one. The present experiment therefore provides evidence for linear conformity in humans in a very natural context. Citation: Claidière N, Bowler M, Whiten A (2012) Evidence for Weak or Linear Conformity but Not for Hyper-Conformity in an Everyday Social Learning Context. PLoS ONE 7(2): e30970.

Animal social learning has become a subject of broad interest, but demonstrations of bodily imitation in animals remain rare. Based on Voelkl and Huber's study of imitation by marmosets, we tested four groups of semi-captive vervet monkeys presented with food in modified film canisters (“aethipops’). One individual was trained to take the tops off canisters in each group and demonstrated five openings to them. In three groups these models used their mouth to remove the lid, but in one of the groups the model also spontaneously pulled ropes on a canister to open it. In the last group the model preferred to remove the lid with her hands. Following these spontaneous differentiations of foraging techniques in the models, we observed the techniques used by the other group members to open the canisters. We found that mouth opening was the most common technique overall, but the rope and hands methods were used significantly more in groups they were demonstrated in than in groups where they were not. Our results show bodily matching that is conventionally described as imitation. We discuss the relevance of these findings to discoveries about mirror neurons, and implications of the identity of the model for social transmission. Publisher PDF

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (Grant Agreement No. 639072). Human adults can infer unseen causes because they represent the events around them in terms of their underlying causal mechanisms. It has been argued that young preschoolers can also make causal inferences from an early age, but whether or not nonhuman apes can go beyond associative learning when exploiting causality is controversial. However, much of the developmental research to date has focused on fully-perceivable causal relations or highlighted the existence of a causal relationship verbally and these were found to scaffold young children’s abilities. We examined inferences about unseen causes in children and chimpanzees in the absence of linguistic cues. Children (N=129, aged 3-6 years) and zoo-living chimpanzees (N=11, aged 7-41 years) were presented with an event in which a reward was dropped through an opaque forked-tube into one of two cups. An auditory cue signaled which of the cups contained the reward. In the causal condition, the cue followed the dropping event, making it plausible that the sound was caused by the reward falling into the cup; and in the arbitrary condition, the cue preceded the dropping event, making the relation arbitrary. By 4-years of age, children performed better in the causal condition than the arbitrary one, suggesting that they engaged in reasoning. A follow-up experiment ruled out a simpler associative learning explanation. Chimpanzees and 3-year-olds performed at chance in both conditions. These groups’ performance did not improve in a simplified version of the task involving shaken boxes; however, the use of causal language helped 3-year-olds. The failure of chimpanzees could reflect limitations in reasoning about unseen causes or a more general difficulty with auditory discrimination learning. Publisher PDF

This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 639072). Children often learn from others’ demonstrations, but in the causal domain evidence acquired from observing others may be more ambiguous than evidence generated for oneself. Prior work involving tool-using tasks suggests that observational learning might not provide sufficient information about the causal relations involved, but it remains unclear whether these limitations can be mitigated by providing demonstrations using familiar manual actions rather than unfamiliar tools. We provided 2.5- to 3.5-year-old children (N = 67) with the opportunity to acquire experience with a causal trap task by hand or by tool actively or from observing others. Initially, children either generated their own experience or watched a yoked demonstration; all children then attempted the trap task with the tool. Children who generated their own experience outperformed those who watched the demonstration. Hand or tool use had no effect on performance with a tool. The implications of these findings for scaffolding self-guided learning and for demonstrations involving errors are discussed. Postprint