Proactive prosociality in a cooperatively breeding corvid, the azure-winged magpie (Cyanopica cyana)

The proximate regulation of prosocial behaviour: towards a conceptual framework for comparative research

Humans and many other animal species act in ways that benefit others. Such prosocial behaviour has been studied extensively across a range of disciplines over the last decades, but findings to date have led to conflicting conclusions about prosociality across and even within species. Here, we present a conceptual framework to study the proximate regulation of prosocial behaviour in humans, non-human primates and potentially other animals. We build on psychological definitions of prosociality and spell out three key features that need to be in place for behaviour to count as prosocial: benefitting others, intentionality, and voluntariness. We then apply this framework to review observational and experimental studies on sharing behaviour and targeted helping in human children and non-human primates. We show that behaviours that are usually subsumed under the same terminology (e.g. helping) can differ substantially across and within species and that some of them do not fulfil our criteria for prosociality. Our framework allows for precise mapping of prosocial behaviours when retrospectively evaluating studies and offers guidelines for future comparative work.

Family first! Influence of parental investment in Guinea pigs (Cavia porcellus) prosocial choices

Literature often assumed that prosocial behaviours (behaviours that benefit others with or without a cost for the actor) would have evolved many species to improve the effectiveness of parental care (Decety and Cowell 2014). While this hypothesis is rarely questioned at a phylogenetic scale, it was never tested at an individual scale to the best of our knowledge. Therefore, we chose to study the impact of effective parental care on prosociality by comparing the prosocial tendencies of Guinea pigs before mating, during mating and after parturition. We conducted Prosocial Choice Tests on three groups of Guinea pigs (males, multiparous females, and nulliparous females). Subjects had to choose between three options: a prosocial option (subject and recipient being rewarded), a selfish option (only subject was rewarded), and a null option (no reward). Our results showed high prosociality towards their mating partner and their young both in male and in female subjects. Males became selfish towards other males after parturition. Among other interesting results, we found a direct reciprocity phenomenon. We also highlighted an ability in our subjects to consider both the identity and relationship shared with the recipient, such as tolerance (enhancing prosociality), dominance rank (being tested with a dominant recipient increasing selfish responses), and its behaviour (begging calls eliciting prosociality, while threatening ones decreasing it), to choose an option. These findings suggested that prosociality could be modulated by many factors and that the constraints and stakes induced by breeding would highly influence prosocial strategies.

Influence of age, breeding state and approach direction on sensitivity to human gaze: a field study on Azure-winged magpies

In predator-prey interactions, various factors affect the prey's perception of risk and decision to flee. Gaze sensitivity, the ability to react to the presence, direction, or movement of the head and eyes, has been reported in many birds. However, few studies have focussed on variation in sensitivity to human gaze in relation to other risks and potential breeding costs. Here, we studied the influence of human gaze on the escape behaviour of Azure-winged magpies (Cyanopica cyanus) and investigated the effects of breeding state (breeding season and nonbreeding season) and approach direction on gaze sensitivity. In Experiment 1, we tested whether magpies showed different sensitivities to human gaze according to age class and breeding state when approached directly. The results showed that the breeding state could affect the flight initiation distance (FID), with adults in the breeding season having a shorter FID compared to those in the nonbreeding season. Meanwhile, only adults were found to be averse to direct human gaze and juveniles showed no sensitivity. In Experiment 2, we conducted three different gaze treatments on adult magpies in the breeding season under three bypass distances (0 m, 2.5 m, 5 m). The results showed that approach direction had no effect on FID, while the sensitivity to human gaze differed under three bypass distances. Adults could clearly recognise human head and eye direction at a certain bypass distance (2.5 m). Our study reveals the cognitive ability of Azure-winged magpies to human head and eye direction and the effects of age, breeding state and approach direction, which may provide further insights into human-wildlife interactions, especially for birds in urban habitats.

Prosociality in a despotic society

Prosociality is the intent to improve others' well-being. Existing hypotheses postulate that enhanced social tolerance and inter-individual dependence may facilitate prosocial preferences, which may favor the evolution of altruism. While most studies are restricted to "tolerant" (cooperatively breeding and self-domesticated) species, despotic societies provide an alternative opportunity to investigate prosociality due to nepotism and ample inter-individual dependencies. Japanese macaques live in hierarchical matrilineal societies, with strong kin bonds. Besides, tolerance among non-kin may persist through reciprocity. Using a group service food-provision paradigm, we found prosocial preferences in a semi free-ranging group of Japanese macaques. The extent of provisioning was at levels comparable to tolerant species. Dyadic tolerance predicted the likelihood and magnitude of provisioning, while kinship predicted the magnitude. We emphasize the role of a complex socio-ecology fostering individual prosocial tendencies through kinship and tolerance. These findings necessitate a framework including different forms of interdependence beyond the generally tolerant species.

Prosociality and reciprocity according to parental status, communication, and personality in domestic canaries (Serinus canaria)

Prosociality (behaviours that benefit to a recipient without necessarily involving a cost to the actor) has recently been shown to exist in various taxa, including birds. Studies on prosociality in primates found that prosocial tendencies of the subject could be related to sex and parental care, communication from the recipient, cognitive abilities and personality. To investigate the existence of such associations on birds, we conducted a Prosocial Choice Task with domestic canaries (Serinus canaria). In our experiment, the subject could choose between three options: a prosocial, a selfish, and a null option (with no cost for the subject). We also conducted a food sharing experiment and measured several personality traits. Our results highlighted high levels of prosociality and a tendency to reciprocity among reproductive mates. We found a higher propensity to be prosocial in nulliparous individuals than in individuals that have previously been parents, but better sharing abilities in parents than in nulliparous individuals. When they were recipient, parents also used communication more efficiently than nulliparous subjects. Data suggest that parental expertise could enhance subjects' skills in eliciting prosociality. We also highlighted some interaction between prosociality, learning abilities, and some personality traits, proactive individuals being fast learners and more prosocial, while reactive individuals being slow learners and more reciprocal. Our results suggest that prosociality and reciprocity could be linked to personality and cognitive abilities, and that it might be interesting to consider them as parts of individual's cognitive style.

A comparative study of mirror self-recognition in three corvid species

Mirror self-recognition (MSR) assessed by the Mark Test has been the staple test for the study of animal self-awareness. When tested in this paradigm, corvid species return discrepant results, with only the Eurasian magpies and the Indian house crow successfully passing the test so far, whereas multiple other corvid species fail. The lack of replicability of these positive results and the large divergence in applied methodologies calls into question whether the observed differences are in fact phylogenetic or methodological, and, if so, which factors facilitate the expression of MSR in some corvids. In this study, we (1) present new results on the self-recognition abilities of common ravens, (2) replicate results of azure-winged magpies, and (3) compare the mirror responses and performances in the mark test of these two corvid species with a third corvid species: carrion crows, previously tested following the same experimental procedure. Our results show interspecies differences in the approach of and the response to the mirror during the mirror exposure phase of the experiment as well as in the subsequent mark test. However, the performances of these species in the Mark Test do not provide any evidence for their ability of self-recognition. Our results add to the ongoing discussion about the convergent evolution of MSR and we advocate for consistent methodologies and procedures in comparing this ability across species to advance this discussion.

Teamwork Makes the String Work: A Pilot Test of the Loose String Task with African Crested Porcupines (Hystrix cristata)

Comparative researchers have heavily focused their studies of social cognition on species that live in large social groups, while neglecting other potential predictors of social cognition. African crested porcupines (Hystrix cristata) are relatively rare among mammals in that they are cooperative breeders that pair for life. Little is known about their social cognition, but they are good candidates for exploring cooperative behavior due to the need to coordinate behavior to cooperatively raise young. Cooperation, as defined in this study, is the process by which two or more participants perform independent actions on an object to obtain a reward for all parties. Humans are thought to outperform all other species in the frequency and magnitude of cooperative behaviors. Yet, only by studying a variety of species can researchers fully understand the likely selection pressures for cooperation, such as cooperative breeding. Here, we pilot tested the feasibility of the popular loose-string task with a mated pair of African crested porcupines, a task that required the porcupines to cooperatively pull ropes to access an out of reach platform baited with food rewards. Other species presented with this task were able to work together to receive rewards but did not always demonstrate understanding of the role of their partner. The porcupines achieved success but did not appear to coordinate their actions or solicit behavior from their partner. Thus, similar to other species, they may achieve success in this task without taking their partner’s role into account. This study demonstrates that the loose string task can be used to assess cooperation in porcupines. However, further experiments are needed to assess the porcupine’s understanding of their partner’s role under this paradigm.

Azure-winged Magpies would rather avoid losses than strive for benefits based on reciprocal altruism

It is no doubt that the reciprocal altruism of humans is unparalleled in the animal world. However, how strong altruistic behavior in the non-human animal is still very controversial. Almost all previous researches allowed only one individual in the dyad for action or dyad to accomplish tasks and obtain rewards simultaneously. Here, we designed current study based on the prisoner's dilemma to investigate reciprocal altruism under interactions of Azure-winged Magpies (Cyanopica cyanus), which is direct reciprocity of allowing subjects obtain rewards, respectively. The results suggest that Azure-winged Magpies failed to show continuously altruistic behavior due to the empiricism that stemmed from interactions, that is, avoiding losses. Meanwhile, the resource exchange game paradigm, which is designed in our study, is worthwhile to study the evolution of cooperation in more species in the future.

Personality and social environment predict cognitive performance in common marmosets (Callithrix jacchus)

Consistent inter-individual variation in cognition has been increasingly explored in recent years in terms of its patterns, causes and consequences. One of its possible causes are consistent inter-individual differences in behaviour, also referred to as animal personalities, which are shaped by both the physical and the social environment. The latter is particularly relevant for group-living species like common marmosets (Callithrix jacchus), apt learners that display substantial variation in both their personality and cognitive performance, yet no study to date has interlinked these with marmosets' social environment. Here we investigated (i) consistency of learning speed, and (ii) whether the PCA-derived personality traits Exploration-Avoidance and Boldness-Shyness as well as the social environment (i.e., family group membership) are linked with marmosets' speed of learning. We tested 22 individuals in series of personality and learning-focused cognitive tests, including simple motor tasks and discrimination learning tasks. We found that these marmosets showed significant inter-individual consistency in learning across the different tasks, and that females learned faster than males. Further, bolder individuals, and particularly those belonging to certain family groups, learned faster. These findings indicate that both personality and social environment affect learning speed in marmosets and could be important factors driving individual variation in cognition.

Adult bonobos show no prosociality in both prosocial choice task and group service paradigm

Previous studies reported contrasting conclusions concerning bonobo prosociality, which are likely due to differences in the experimental design, the social dynamics among subjects and characteristics of the subjects themselves. Two hypotheses have been proposed to explain the occurrence of prosociality in animals: the cooperative breeding hypothesis and the self-domestication hypothesis. While the former predicts low levels of prosociality in bonobos because they are non-cooperative breeders, the latter predicts high levels of prosociality because self-domestication has been proposed to select for high levels of tolerance in this species. Here, we presented a group of thirteen bonobos with two platform food-provisioning tasks: the prosocial choice task (PCT) and the group service paradigm (GSP). The latter has so far never been applied to bonobos. To allow for free choice of participation and partner, we implemented both tasks in a group setting. Like in previous PCT studies, bonobos did not choose the prosocial option more often when a group member could benefit vs not benefit. In the GSP, where food provisioning is costly, only subadult bonobos showed a limited amount of food provisioning, which was much lower than what was previously reported for chimpanzees. In both experiments, adult subjects were highly motivated to obtain rewards for themselves, suggesting that bonobos behaved indifferently to the gains of group members. We suggest that previous positive food-provisioning prosociality results in bonobos are mainly driven by the behaviour of subadult subjects. The lack of prosociality in this study corresponds to the hypothesis that proactive food provisioning co-occurs with cooperative breeding and suggests that proactive prosociality might not be part of the self-domestication syndrome in bonobos.

On the use of evolutionary mismatch theories in debating human prosociality

According to some evolutionary theorists human prosocial dispositions emerged in a context of inter-group competition and violence that made our psychology parochially prosocial, ie. cooperative towards in-groups and competitive towards strangers. This evolutionary hypothesis is sometimes employed in bioethical debates to argue that human nature and contemporary environments, and especially large-scale societies, are mismatched. In this article we caution against the use of mismatch theories in moral philosophy in general and discuss empirical evidence that puts into question mismatch theories based on parochial prosociality. Evolutionary mismatch theories play at best a rhetorical role in these moral debates and may misrepresent the status of relevant evolutionary research. We finally recommend that moral philosophers interested in the evolutionary literature also engage with dispositions such as xenophilia and social tolerance to counterbalance the focus on psychological mismatches adopted so far.

Individual Goffin´s cockatoos (Cacatua goffiniana) show flexible targeted helping in a tool transfer task

Flexible targeted helping is considered an advanced form of prosocial behavior in hominoids, as it requires the actor to assess different situations that a conspecific may be in, and to subsequently flexibly satisfy different needs of that partner depending on the nature of those situations. So far, apart from humans such behaviour has only been experimentally shown in chimpanzees and in Eurasian jays. Recent studies highlight the prosocial tendencies of several bird species, yet flexible targeted helping remained untested, largely due to methodological issues as such tasks are generally designed around tool-use, and very few bird species are capable of tool-use. Here, we tested Goffin's cockatoos, which proved to be skilled tool innovators in captivity, in a tool transfer task in which an actor had access to four different objects/tools and a partner to one of two different apparatuses that each required one of these tools to retrieve a reward. As expected from this species, we recorded playful object transfers across all conditions. Yet, importantly and similar to apes, three out of eight birds transferred the correct tool more often in the test condition than in a condition that also featured an apparatus but no partner. Furthermore, one of these birds transferred that correct tool first more often before transferring any other object in the test condition than in the no-partner condition, while the other two cockatoos were marginally non-significantly more likely to do so. Additionally, there was no difference in the likelihood of the correct tool being transferred first for either of the two apparatuses, suggesting that these birds flexibly adjusted what to transfer based on their partner´s need. Future studies should focus on explanations for the intra-specific variation of this behaviour, and should test other parrots and other large-brained birds to see how this can be generalized across the class and to investigate the evolutionary history of this trait.

Carrion Crows and Azure-Winged Magpies Show No Prosocial Tendencies When Tested in a Token Transfer Paradigm

To study the evolution of humans' cooperative nature, researchers have recently sought comparisons with other species. Studies investigating corvids, for example, showed that carrion crows and azure-winged magpies delivered food to group members when tested in naturalistic or simple experimental paradigms. Here, we investigated whether we could replicate these positive findings when testing the same two species in a token transfer paradigm. After training the birds to exchange tokens with an experimenter for food rewards, we tested whether they would also transfer tokens to other birds, when they did not have the opportunity to exchange the tokens themselves. To control for the effects of motivation, and of social or stimulus enhancement, we tested each individual in three additional control conditions. We witnessed very few attempts and/or successful token transfers, and those few instances did not occur more frequently in the test condition than in the controls, which would suggest that the birds lack prosocial tendencies. Alternatively, we propose that this absence of prosociality may stem from the artificial nature and cognitive complexity of the token transfer task. Consequently, our findings highlight the strong impact of methodology on animals' capability to exhibit prosocial tendencies and stress the importance of comparing multiple experimental paradigms.

Prosocial and antisocial choices in a monogamous cichlid with biparental care

Human society is cooperative and characterized by spontaneous prosociality. Comparative studies on endotherm vertebrates suggest that social interdependence causes the evolution of proactive prosociality. To test the generality of this hypothesis, we modify a prosocial choice task for application to the convict cichlid, Amatitlania nigrofasciata, a monogamous fish with biparental care and a strong pair bond. We also affirm that male subjects learn to favor prosocial choices when their mates are the recipients in a neighboring tank. When the neighboring tank is empty, males choose randomly. Furthermore, in the absence of their mates, males behave prosocially toward a stranger female. However, if the mate of the subjects is also visible in the third tank, or if a male is a potential recipient, then subjects make antisocial choices. To conclude, fish may show both spontaneous prosocial and antisocial behaviors according to their social relationships with conspecifics and the overall social context.

Performance of Azure-winged magpies in Aesop's fable paradigm

In this study, the improved Aesop’s fable paradigm—a series of experiments originally used to test whether some animals understand the causality associated with water replacement—was used to explore the cognitive ability of Azure-winged magpies (Cyanopica cyanus). Experimental results on causal cue tasks showed that the Azure-winged magpies prefer water-filled tubes over sand-filled tubes, heavy objects over light objects, and solid objects over hollow objects. However, they failed to notice the diameter and water level of the tubes. They also failed to pass the counterintuitive U-shaped tube task in arbitrary cue tasks. Our results demonstrated that Azure-winged magpies have a certain cognitive ability but not an understanding of causality, a characteristic comparable to that of other corvids. Moreover, Azure-winged magpies exhibited the ability of training transfer and analogical problem solving from the perspective of cognitive psychology. We believe that object-bias has little effect on Azure-winged magpies in this study. We can conclude that the Azure-winged magpies partially completed the tasks by trial-and-error learning.

Sex-specific effects of cooperative breeding and colonial nesting on prosociality in corvids

The investigation of prosocial behavior is of particular interest from an evolutionary perspective. Comparisons of prosociality across non-human animal species have, however, so far largely focused on primates, and their interpretation is hampered by the diversity of paradigms and procedures used. Here, we present the first systematic comparison of prosocial behavior across multiple species in a taxonomic group outside the primate order, namely the bird family Corvidae. We measured prosociality in eight corvid species, which vary in the expression of cooperative breeding and colonial nesting. We show that cooperative breeding is positively associated with prosocial behavior across species. Also, colonial nesting is associated with a stronger propensity for prosocial behavior, but only in males. The combined results of our study strongly suggest that both cooperative breeding and colonial nesting, which may both rely on heightened social tolerance at the nest, are likely evolutionary pathways to prosocial behavior in corvids.

Azure-winged magpies' decisions to share food are contingent on the presence or absence of food for the recipient

Helping others is a key feature of human behavior. However, recent studies render this feature not uniquely human, and describe discoveries of prosocial behavior in non-human primates, other social mammals, and most recently in some bird species. Nevertheless, the cognitive underpinnings of this prosociality; i.e., whether animals take others’ need for help into account, often remain obscured. In this study, we take a first step in investigating prosociality in azure-winged magpies by presenting them with the opportunity to share highly desired food with their conspecifics i) in a situation in which these conspecifics had no such food, ii) in a situation in which they too had access to that highly desired food, and iii) in an open, base-line, situation where all had equal access to the same food and could move around freely. We find that azure-winged magpies regularly share high-value food items, preferably with, but not restricted to, members of the opposite sex. Most notably, we find that these birds, and specifically the females, seem to differentiate between whether others have food or do not have food, and subsequently cater to that lack. Begging calls by those without food seem to function as cues that elicit the food-sharing, but the response to that begging is condition-dependent. Moreover, analyses on a restricted dataset that excluded those events in which there was begging showed exactly the same patterns, raising the possibility that the azure-winged magpies might truly notice when others have access to fewer resources (even in the absence of vocal cues). This sharing behavior could indicate a high level of social awareness and prosociality that should be further investigated. Further studies are needed to establish the order of intentionality at play in this system, and whether azure-winged magpies might be able to attribute desire states to their conspecifics.

Investigation of cognitive mechanisms and strategy on solving multiple string-pulling problems in Azure-winged magpie (Cyanopica cyanus)

String-pulling tasks are a widely used paradigm in animal cognition research. The present study tested whether ten azure-winged magpies (Cyanopica cyanus) could solve a series of multiple-strings problems with the aim of systematically investigating which rules this species uses to solve different-patterned string tasks, i.e., tasks in which subjects have to choose between two strings only one of which is connected to bait. When the subjects faced the parallel strings task (T1), five birds (C3, C5, C8, C9, and C10) were able to solve the task and acted in a goal-directed manner. Three birds (C5, C8, and C9) successfully solved the oblique parallel strings task (T3). The azure-winged magpies exhibited proximity selection in the oblique parallel strings task (C1 and C4 in T2), and the task with one string folded at a right angle (C3, C6 and C8 in T5). Several subjects also performed simple strategies in other unresolved tasks, e.g., random selection, trial-and-error learning, and side bias strategies (i.e., a certain degree of "left-handed" tendency). These results demonstrated that the azure-winged magpie possesses the potential to solve simple multiple-string tasks, although when faced with more difficult problems they could not solve them.

Azure-winged magpies fail to understand the principle of mirror imaging

Mirror self-recognition (MSR) is considered a crucial step in the emergence of self-cognition. The MSR paradigm has become a standard method for evaluating self-cognition in several species. For example, Eurasian magpies and Indian house crows have passed the mark test for self-cognition, whereas efforts to find MSR in other corvid species have failed. However, no literature has conducted MSR tests on azure-winged magpies, a species of corvids. Therefore, the current research aimed to investigate the MSR behaviours of azure-winged magpies upon looking into a mirror for the first time. The study included four tests: (1) mirror preference and standardised mirror exploration, (2) single vertical mirror test, (3) mark test and (4) mirror-triggered search test. The azure-winged magpies displayed immense curiosity towards the mirror and their images in the mirror in Test 1&2. In the subsequent mark tests, they failed to recognise themselves in the mirror and regarded their images as conspecifics. Behaviour analysis showed no significant difference between marked and unmarked behaviours. Finally they seemed to infer the presence of bait from the image in the mirror, but were found to fail to understand that the location of the bait in the mirror was the same as that in the real world. For a better insight into the MSR behaviour of azure-winged magpies, research studies involving prolonged mirror exposure and training are recommended.

Parrots Voluntarily Help Each Other to Obtain Food Rewards

Helping others to obtain benefits, even at a cost to oneself, poses an evolutionary puzzle [1]. While kin selection explains such "selfless" acts among relatives, only reciprocity (paying back received favors) entails fitness benefits for unrelated individuals [2]. So far, experimental evidence for both prosocial helping (providing voluntary assistance for achieving an action-based goal) and reciprocity has been reported in a few mammals but no avian species [3]. In order to gain insights into the evolutionary origins of these behaviors, the capacity of non-mammalian species for prosociality and for reciprocity needs to be investigated. We tested two parrot species in an instrumental-helping paradigm involving "token transfer." Here, actors could provide tokens to their neighbor, who could exchange them with an experimenter for food. To verify whether the parrots understood the task's contingencies, we systematically varied the presence of a partner and the possibility for exchange. We found that African grey parrots voluntarily and spontaneously transferred tokens to conspecific partners, whereas significantly fewer transfers occurred in the control conditions. Transfers were affected by the strength of the dyads' affiliation and partially by the receivers' attention-getting behaviors. Furthermore, the birds reciprocated the help once the roles were reversed. Blue-headed macaws, in contrast, transferred hardly any tokens. Species differences in social tolerance might explain this discrepancy. These findings show that instrumental helping based on a prosocial attitude, accompanied but potentially not sustained by reciprocity, is present in parrots, suggesting that this capacity evolved convergently in this avian group and mammals.

Assessing African grey parrots' prosocial tendencies in a token choice paradigm

Prosociality is defined as a voluntary, typically low-cost behaviour that benefits another individual. Social tolerance has been proposed as a potential driver for its evolution, both on the proximate and on the ultimate level. Parrots are an interesting species to study such other-regarding behaviours, given that they are highly social and stand out in terms of relative brain size and cognitive capacity. We tested eight African grey parrots in a dyadic prosocial choice test. They faced a choice between two different tokens, a prosocial (actor and partner rewarded) and a selfish (only actor rewarded) one. We found that the birds did not behave prosocially when one subject remained in the actor role; however, when roles were alternated, the birds' prosocial choices increased. The birds also seemed to reciprocate their partner's choices, given that a contingency between choices was observed. If the food provisioned to the partner was of higher quality than that the actor obtained, actors increased their willingness to provide food to their partner. Nonetheless, the control conditions suggest that the parrots did not fully understand the task's contingencies. In sum, African grey parrots show the potential for prosociality and reciprocity; however, considering their lack of understanding of the contingencies of the particular tasks used in this study, the underlying motivation for the observed behaviour remains to be addressed by future studies, in order to elucidate the phylogenetic distribution of prosociality further.

Why intergroup variation matters for understanding behaviour

Intergroup variation (IGV) refers to variation between different groups of the same species. While its existence in the behavioural realm has been expected and evidenced, the potential effects of IGV are rarely considered in studies that aim to shed light on the evolutionary origins of human socio-cognition, especially in our closest living relatives—the great apes. Here, by taking chimpanzees as a point of reference, we argue that (i) IGV could plausibly explain inconsistent research findings across numerous topics of inquiry (experimental/behavioural studies on chimpanzees), (ii) understanding the evolutionary origins of behaviour requires an accurate assessment of species' modes of behaving across different socio-ecological contexts, which necessitates a reliable estimation of variation across intraspecific groups, and (iii) IGV in the behavioural realm is increasingly likely to be expected owing to the progressive identification of non-human animal cultures. With these points, and by extrapolating from chimpanzees to generic guidelines, we aim to encourage researchers to explicitly consider IGV as an explanatory variable in future studies attempting to understand the socio-cognitive and evolutionary determinants of behaviour in group-living animals.

Wolves, but not dogs, are prosocial in a touch screen task

Prosociality is important for initiating cooperation. Interestingly, while wolves rely heavily on cooperation, dogs’ do so substantially less thus leading to the prediction that wolves are more prosocial than dogs. However, domestication hypotheses suggest dogs have been selected for higher cooperation, leading to the opposing prediction- increased prosocial tendencies in dogs. To tease apart these hypotheses we adapted a paradigm previously used with pet dogs to directly compare dogs and wolves. In a prosocial choice task, wolves acted prosocially to in-group partners; providing significantly more food to a pack-member compared to a control where the partner had no access to the food. Dogs did not. Additionally, wolves did not show a prosocial response to non-pack members, in line with previous research that social relationships are important for prosociality. In sum, when kept in the same conditions, wolves are more prosocial than their domestic counterpart, further supporting suggestions that reliance on cooperation is a driving force for prosocial attitudes.

Mesotocin influences pinyon jay prosociality

Many species exhibit prosocial behaviour, in which one individual's actions benefit another individual, often without an immediate benefit to itself. The neuropeptide oxytocin is an important hormonal mechanism influencing prosociality in mammals, but it is unclear whether the avian homologue mesotocin plays a similar functional role in birds. Here, we experimentally tested prosociality in pinyon jays (Gymnorhinus cyanocephalus), a highly social corvid species that spontaneously shares food with others. First, we measured prosocial preferences in a prosocial choice task with two different pay-off distributions: Prosocial trials delivered food to both the subject and either an empty cage or a partner bird, whereas Altruism trials delivered food only to an empty cage or a partner bird (none to subject). In a second experiment, we examined whether administering mesotocin influenced prosocial preferences. Compared to choices in a control condition, we show that subjects voluntarily delivered food rewards to partners, but only when also receiving food for themselves (Prosocial trials), and administration of high levels of mesotocin increased these behaviours. Thus, in birds, mesotocin seems to play a similar functional role in facilitating prosocial behaviours as oxytocin does in mammals, suggesting an evolutionarily conserved hormonal mechanism for prosociality.

Piloting a new prosociality paradigm in dogs and wolves: The location choice task

The aim of this pilot study was to investigate whether or not dogs (Canis familiaris) and wolves (Canis lupus) show prosociality in a simple T-maze experiment based on a previous study by Hernandez-Lallement et al. (2015). Prosociality, i.e. "voluntary behaviour that benefits others", was initially thought to be uniquely human and, to trace its origin, has mainly been investigated in non-human primates. More recently however, some non-primate species showed considerable amounts of prosociality, suggesting convergent evolutionary paths. Here we tested if wolves and dogs are prosocial in a novel paradigm and, secondly, whether prosociality in dogs is a by-product of domestication or an ancestral trait shared with wolves. With the exception of one wolf, the current task did not reveal a prosocial response in either species, despite the same subjects showing prosocial tendencies in other tasks. Prosociality has been difficult to experimentally observe and it presents a methodological challenge. We are still at the beginning of this journey in Canids and this study adds another piece to the puzzle of how best to investigate this behaviour.

What constitutes "social complexity" and "social intelligence" in birds? Lessons from ravens

In the last decades, the assumption that complex social life is cognitively challenging, and thus can drive mental evolution, has received much support from empirical studies in nonhuman primates. While extending the scope to other mammals and birds, different views have been adopted on what constitutes social complexity and which specific cognitive skills are selected for. Notably, many avian species form "open" groups as non-breeders (i.e., seasonally and before sexual maturity) that have been largely ignored as potential sources of social complexity. Reviewing 30 years of research on ravens, we illustrate the socio-ecological conditions faced by these birds as non-breeders and discuss how these relate to their socio-cognitive skills. We argue that the non-breeding period is key to understand raven social life and, to a larger extent, avian social life in general. We furthermore emphasize how the combination of the large-scale perspective (defining social system components: e.g., social organization, mating system) and the individual-scale perspective on social systems allows to better capture the complete set of social challenges experienced by individuals throughout their life, ultimately resulting on a more comprehensive understanding of species' social complexity.

Bonobos voluntarily hand food to others but not toys or tools

A key feature of human prosociality is direct transfers, the most active form of sharing in which donors voluntarily hand over resources in their possession Direct transfers buffer hunter-gatherers against foraging shortfalls. The emergence and elaboration of this behaviour thus likely played a key role in human evolution by promoting cooperative interdependence and ensuring that humans' growing energetic needs (e.g. for increasing brain size) were more reliably met. According to the strong prosociality hypothesis, among great apes only humans exhibit sufficiently strong prosocial motivations to directly transfer food. The versatile prosociality hypothesis suggests instead that while other apes may make transfers in constrained settings, only humans share flexibly across food and non-food contexts. In controlled experiments, chimpanzees typically transfer objects but not food, supporting both hypotheses. In this paper, we show in two experiments that bonobos directly transfer food but not non-food items. These findings show that, in some contexts, bonobos exhibit a human-like motivation for direct food transfer. However, humans share across a far wider range of contexts, lending support to the versatile prosociality hypothesis. Our species' unusual prosocial flexibility is likely built on a prosocial foundation we share through common descent with the other apes.

Azure-winged magpies solve string-pulling tasks by partial understanding of the physical cognition

String-pulling is one of the most widely used paradigms in animal cognition research. We investigated how azure-winged magpies Cyanopica cyanus solve multiple-string problems that they have never encountered before. In Experiment 1, the strings were arranged in parallel, slanted, or crossed to investigate what rules azure-winged magpies use to solve multiple spatial relations of strings. Experiment 2 assessed whether the subjects understood the connection between the string and the bait while taking advantage of broken strings. In Experiment 3, the subjects were confronted with strings of different lengths attached to rewards in order to explore whether the string length, as a proxy for the pulling efficiency or reward distance, was crucial for the birds’ choice of which string to pull. Generally, the birds were successful in tasks where the reward was close to the correct string’s end, and they relied on a “proximity rule” in most cases. The results showed that azure-winged magpies had a partial understanding of the physical principles underlying the string-pulling but were stumped by complex spatial relations. They likely relied on simple strategies such as the proximity rule to solve the tasks. The effects of individual difference and experiential learning on string-pulling performance are also discussed.

Looking for unity in diversity: human cooperative childcare in comparative perspective

Humans engage in cooperative childcare, which includes some elements not found in other animals, such as the presence of post-reproductive helpers, extensive food sharing among adults and a pervasive sexual division of labour. In animals, cooperative offspring care has typically been studied in two different contexts. The first mainly involves helpers contributing care in cooperatively breeding family groups; the second context is allomaternal care in species usually not categorized as cooperative breeders (e.g. plural and communal breeders, often without male care). Comparative analyses suggest that cooperative breeding and allomaternal care in plural and communal breeders have distinct evolutionary origins, with humans fitting neither pathway entirely. Nevertheless, some critical proximate mechanisms of helping, including hormonal regulators, are likely to be shared across species. Other mechanisms may vary among species, such as social tolerance, proactive prosociality or conditional mother-infant bonding. These are presumably associated with specific details of the care system, such as whether all group members contribute, or whether mothers can potentially raise offspring alone. Thus, cooperative offspring care is seen in different contexts across animal lineages, but may nonetheless share several important psychological characteristics. We end by discussing how work on humans may play a unifying role in studying cooperative offspring care.

Social status and prenatal testosterone exposure assessed via second-to-fourth digit ratio affect 6-9-year-old children's prosocial choices

Prosocial behaviour (i.e., voluntary behaviour intended to benefit another) seems to be fully developed in children by the age of 6 years. However, questions about which factors modify prosocial behaviour at that age remain understudied. Here we used a resource allocation paradigm to test prosocial behaviour in 6-9-year-old school children. They could decide between a "selfish" (i.e., one sticker for themselves) and a "prosocial" option (i.e., one sticker for themselves and one for the receiver) and we tested whether friendship, social status and prenatal androgen exposure (approximated by the 2nd to 4th digit ratio; 2D:4D) influenced children's prosocial choices. We found that children behaved prosocially, and that their prosocial tendencies were negatively correlated with prenatal androgen exposure; i.e., children with high 2D:4D ratios (reflecting low prenatal androgen exposure) acted more prosocially than children with low 2D:4D ratios. Further, their social status in the classroom influenced their choices: children with fewer interaction partners chose the "prosocial" option more often than more 'popular' children. However, they did so irrespectively of whether they were paired with a recipient or not. Our results highlight the importance of considering social, as well as physiological factors when investigating prosocial behaviour in children.

Meerkats (Suricata suricatta) fail to prosocially donate food in an experimental set-up

Although humans are usually believed to be prosocial, the evolutionary origins of prosociality are largely debated. One hypothesis is that cooperative breeding has been one major precursor to the emergence of prosociality. In vertebrates, however, experimental evidence of prosociality has been mainly gathered in non-human primates. In this study, we tested the cooperative breeding hypothesis in cooperative breeding meerkats (Suricata suricatta). In particular, we tested whether meerkats take into account partners' benefits when distributing food rewards. Nine individuals were presented with two platforms baited with different food distributions (providing food to themselves, to a partner or both). In all conditions, the decision to operate the apparatus was based on the presence of food on the subject's side, and not on the possible benefits to partners. Despite being cooperative breeders, meerkats in this study failed to be prosocial, suggesting that prosociality in this species may be limited to specific contexts.