Recalling experiences of scarcity reduces children's generosity relative to recalling abundance

Does a sense of having less or more than what one needs affect one's generosity? The question of how resource access influences prosocial behavior has received much attention in studies with adults but has produced conflicting findings. To better understand this relationship, we tested whether resource access affects generosity in the developing mind. In our preregistered investigation, we used a narrative recall method to explore how temporary, experimentally evoked states of resource abundance or scarcity affect children's sharing. In this study, 6- to 8-year-old American children (N = 148) recalled an experience of scarcity or abundance and then chose how many prizes to share with another child. We found that children in the scarce condition rated themselves as sadder, viewed their resource access as more limited, and shared fewer tokens than children in the abundant condition. Our results indicate that recalling past experiences of resource access creates distinct behavioral consequences for children and suggest that a sense of "having less" may encourage a strategy of resource conservation relative to a sense of "having more," even at a young age.

Children cooperate more with in-group members than with out-group members in an iterated face-to-face Prisoner's Dilemma Game

Adults are more likely to cooperate with in-group members than with out-group members in the context of social dilemmas, situations in which self-interest is in conflict with collective interest. This bias has the potential to profoundly shape human cooperation, and therefore it is important to understand when it emerges in development. Here we asked whether 6- to 9-year-old children (N = 146) preferentially cooperate with in-group members in the context of a well-studied social dilemma, the iterated Prisoner's Dilemma Game. We assigned children to minimal groups and paired them with unfamiliar same-age and same-gender peers. Consistent with our predictions, children were more likely to cooperate with in-group members than with out-group members in this minimal group context. This finding adds to the current literature on group bias in children's prosocial behavior by showing that it affects decision making in a context that calls on strategic cooperation. In addition, our analyses revealed an effect of gender, with girls more likely to cooperate than boys regardless of the group membership of their partner. Exploring this gender effect further, we found an interaction between gender and age across condition, with older girls showing less sensitivity to the group membership of their partner than younger girls and with older boys showing more sensitivity to the group membership of the partner than younger boys. Our findings suggest that risky cooperation in the face of social dilemmas is shaped by group bias during childhood, highlighting the potentially deeply rooted ties between cooperation and parochialism in humans.

How retributive motives shape the emergence of third-party punishment across intergroup contexts

This study examines how retributive motives-the desire to punish for the purpose of inflicting harm in the absence of future benefits-shape third-party punishment behavior across intergroup contexts. Six- to nine-year-olds (N = 151, Mage = 8.00, SDage = 1.15; 54% White, 18% mixed ethnicities, 17% Asian American; 46% female; from the USA) could punish ingroup, outgroup, or non-group transgressors by removing positive resources and allocating negative ones. Both punishments were described as retributive, yet allocating negative resources was perceived as more retributive than removing positive ones. We predicted that children would punish outgroups more so than ingroups and that this effect would be especially pronounced when punishment is perceived as particularly retributive. The results did not align with this prediction; instead, children similarly punished all agents.

The development and diversity of religious cognition and behavior: Protocol for Wave 1 data collection with children and parents by the Developing Belief Network

The Developing Belief Network is a consortium of researchers studying human development in diverse social-cultural settings, with a focus on the interplay between general cognitive development and culturally specific processes of socialization and cultural transmission in early and middle childhood. The current manuscript describes the study protocol for the network's first wave of data collection, which aims to explore the development and diversity of religious cognition and behavior. This work is guided by three key research questions: (1) How do children represent and reason about religious and supernatural agents? (2) How do children represent and reason about religion as an aspect of social identity? (3) How are religious and supernatural beliefs transmitted within and between generations? The protocol is designed to address these questions via a set of nine tasks for children between the ages of 4 and 10 years, a comprehensive survey completed by their parents/caregivers, and a task designed to elicit conversations between children and caregivers. This study is being conducted in 39 distinct cultural-religious groups (to date), spanning 17 countries and 13 languages. In this manuscript, we provide detailed descriptions of all elements of this study protocol, give a brief overview of the ways in which this protocol has been adapted for use in diverse religious communities, and present the final, English-language study materials for 6 of the 39 cultural-religious groups who are currently being recruited for this study: Protestant Americans, Catholic Americans, American members of the Church of Jesus Christ of Latter-day Saints, Jewish Americans, Muslim Americans, and religiously unaffiliated Americans.

Why imagining what could have happened matters for children's social cognition

Counterfactual thinking is a relatively late emerging ability in childhood with key implications for emerging social cognition and behavior.

Computational signatures of inequity aversion in children across seven societies

[Correction Notice: An Erratum for this article was reported online in Journal of Experimental Psychology: General on Aug 10 2023 (see record 2023-96713-001). In the original article, there were affiliation errors for the first and 14th authors. The affiliations for Dorsa Amir are Department of Psychology, University of California, Berkeley; and Department of Psychology, Boston College. The affiliation for Katherine McAuliffe is Department of Psychology, Boston College. All versions of this article have been corrected.] Inequity aversion is an important factor in fairness behavior. Previous work suggests that children show more cross-cultural variation in their willingness to reject allocations that would give them more rewards than their partner-advantageous inequity-as opposed to allocations that would give them less than their partner-disadvantageous inequity. However, as past work has relied solely on children's decisions to accept or reject these offers, the algorithms underlying this pattern of variation remain unclear. Here, we explore the computational signatures of inequity aversion by applying a computational model of decision-making to data from children (N = 807) who played the Inequity Game across seven societies. Specifically, we used drift-diffusion models to formally distinguish evaluative processing (i.e., the computation of the subjective value of accepting or rejecting inequity) from alternative factors such as decision speed and response strategies. Our results suggest that variation in the development of inequity aversion across societies is best accounted for by variation in the drift rate-the direction and strength of the evaluative preference. Our findings underscore the utility of looking beyond decision data to better understand behavioral diversity. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Having less means wanting more: Children hold an intuitive economic theory of diminishing marginal utility

Judgments surrounding resource acquisition and valuation are ubiquitous in daily life. How do humans decide what something is worth to themselves or someone else? One important cue to value is that of resource quantity. As described by economists, the principle of diminishing marginal utility (DMU) holds that as resource abundance increases, the value placed on each unit decreases; likewise, when resources become more scarce, the value placed on each unit rises. While prior research suggests that adults make judgments that align with this concept, it is unclear whether children do so. In Study 1 (n = 104), children (ages 5 through 8) were presented with scenarios involving losses or gains to others' resources and predicted the actions and emotions of the individuals involved. Participants made decisions that aligned with DMU, e.g., expecting individuals with fewer resources to expend more effort for an additional resource than individuals with greater resources. In Study 2 (n = 104), children incorporated information about preferences when inferring others' resource valuations, showing how quantity and preference are both included in children's inferences about others' utility. Our results indicate the early emergence of an intuitive economic theory that aligns with an important economic principle. Long before formal learning on this topic, children integrate quantity and preference information to sensibly predict others' resource valuations, with implications for economic decision-making, social preferences, and judgments of partner quality across the lifespan.

No strong evidence for universal gender differences in the development of cooperative behaviour across societies

Human cooperation varies both across and within societies, and developmental studies can inform our understanding of the sources of both kinds of variation. One key candidate for explaining within-society variation in cooperative behaviour is gender, but we know little about whether gender differences in cooperation take root early in ontogeny or emerge similarly across diverse societies. Here, we explore two existing cross-cultural datasets of 4- to 15-year-old children's preferences for equality in experimental tasks measuring prosociality (14 societies) and fairness (seven societies), and we look for evidence of (i) widespread gender differences in the development of cooperation, and (ii) substantial societal variation in gender differences. This cross-cultural approach is crucial for revealing universal human gender differences in the development of cooperation, and it helps answer recent calls for greater cultural diversity in the study of human development. We find that gender has little impact on the development of prosociality and fairness within these datasets, and we do not find much evidence for substantial societal variation in gender differences. We discuss the implications of these findings for our knowledge about the nature and origin of gender differences in cooperation, and for future research attempting to study human development using diverse cultural samples. This article is part of the theme issue 'Cooperation among women: evolutionary and cross-cultural perspectives'.

When not helping is nice: Children's changing evaluations of helping during COVID-19

A key aspect of children's moral and social understanding involves recognizing the value of helpful behaviors. COVID-19 has complicated this process; behaviors generally considered praiseworthy were considered problematic during the COVID-19 pandemic. The present study examined whether 6- to 12-year-olds (N = 228; residing in the United States) adapt their evaluations of helpful behavior in response to shifting norms. Specifically, we presented children with scenarios featuring helpful and unhelpful actions that involved physical interaction (e.g., hugging) or nonphysical interaction (e.g., recruiting a teacher); although all children were tested during the COVID-19 pandemic, stories portrayed individuals either before or during COVID-19. While children generally judged helpfulness positively and unhelpfulness negatively, children exhibited a selective shift in their judgments for COVID-19 scenarios: children considered helpfulness negatively and unhelpfulness positively if helping required physical interaction. These findings demonstrate that children flexibly tune their social evaluations of helping to align with evolving norms. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Children use common knowledge to solve coordination problems

Recent work suggests that common knowledge is an important cognitive mechanism for coordinating prosocial behavior, in part because it reduces uncertainty about others' cooperative behavior. However, it remains unclear whether children also rely on common knowledge to solve coordination problems. Here we examined whether 6- to 9-year-old children (N = 133) from the United States were more likely to attempt to coordinate when they had common knowledge about a joint payoff. Participants saw 3 vignettes that modeled the structure of a 2-player coordination problem and were provided with common knowledge, secondary knowledge, or private knowledge about the mutually beneficial, but risky, joint payoff. By 6 years of age, participants were more likely to attempt to coordinate when they had common knowledge than secondary knowledge, and secondary knowledge than private knowledge. Participants were also most likely to expect the other player to coordinate, and were most certain in their predictions, when there was common knowledge. Results indicate that, by middle childhood, children are able to solve coordination problems by relying on common knowledge, in part because it likely increases their certainty in others' cooperative behavior. Overall, findings suggest that common knowledge is an important cognitive mechanism for coordinating behavior and that it does so by reducing uncertainty about others' cooperative behavior. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The ontogeny of children's social emotions in response to (un)fairness

Humans have a deeply rooted sense of fairness, but its emotional foundation in early ontogeny remains poorly understood. Here, we asked if and when 4- to 10-year-old children show negative social emotions, such as shame or guilt, in response to advantageous unfairness expressed through a lowered body posture (measured using a Kinect depth sensor imaging camera). We found that older, but not younger children, showed more negative emotions, i.e. a reduced upper body posture, after unintentionally disadvantaging a peer on (4,1) trials than in response to fair (1,1) outcomes between themselves and others. Younger children, in contrast, expressed more negative emotions in response to the fair (1,1) split than in response to advantageous inequity. No systematic pattern of children's emotional responses was found in a non-social context, in which children divided resources between themselves and a non-social container. Supporting individual difference analyses showed that older children in the social context expressed negative emotions in response to advantageous inequity without directly acting on this negative emotional response by rejecting an advantageously unfair offer proposed by an experimenter at the end of the study. These findings shed new light on the emotional foundation of the human sense of fairness and suggest that children's negative emotional response to advantageous unfairness developmentally precedes their rejection of advantageously unfair resource distributions.

The ontogeny of children's social emotions in response to (un)fairness

Humans have a deeply rooted sense of fairness, but its emotional foundation in early ontogeny remains poorly understood. Here, we asked if and when 4- to 10-year-old children show negative social emotions, such as shame or guilt, in response to advantageous unfairness expressed through a lowered body posture (measured using a Kinect depth sensor imaging camera). We found that older, but not younger children, showed more negative emotions, i.e. a reduced upper body posture, after unintentionally disadvantaging a peer on (4,1) trials than in response to fair (1,1) outcomes between themselves and others. Younger children, in contrast, expressed more negative emotions in response to the fair (1,1) split than in response to advantageous inequity. No systematic pattern of children's emotional responses was found in a non-social context, in which children divided resources between themselves and a non-social container. Supporting individual difference analyses showed that older children in the social context expressed negative emotions in response to advantageous inequity without directly acting on this negative emotional response by rejecting an advantageously unfair offer proposed by an experimenter at the end of the study. These findings shed new light on the emotional foundation of the human sense of fairness and suggest that children's negative emotional response to advantageous unfairness developmentally precedes their rejection of advantageously unfair resource distributions.

Children strategically conceal selfishness

Can children exploit knowledge asymmetries to get away with selfishness? This question was addressed by testing 6- to 9-year-old children (N = 164; 81 girls) from the Northeastern United States in a modified Ultimatum Game. Children were assigned to the roles of proposers (who offered some proportion of an endowment) and responders (who could accept or reject offers). Both players in the Informed condition knew the endowment quantity in each trial. However, in the Uninformed condition, only proposers knew this information. In this condition, many proposers made "strategically selfish" offers that seemed fair based on the responders' incomplete knowledge but were actually highly selfish. These results indicate that even young children possess the ability to deceive others about their selfishness.

Trustworthiness is distinct from generosity in children

Interpersonal trust is a key component of cooperation, helping support the complex social networks found across societies. Trust typically involves two parties, one who trusts by taking on risk through investment in a second party, who can be trustworthy and produce mutual benefits. To date, the developmental literature has focused primarily on the trustor, meaning we know little about the ontogeny of trustworthiness. Whereas trusting can be motivated by self-interest, one-shot trustworthiness is more squarely situated in the prosocial domain, involving a direct tradeoff between self-interest and others' interests. However, this raises the question of whether trustworthiness is distinct from generosity. In this preregistered study, we examine the origins of trustworthiness using an intuitive version of the Trust Game, in which a first party invests resources in a second party who can split the gains. We recruited N = 118 5-to-8 year-old American children (Mage = 6.94, n = 59 girls, 57% White, 88% of parents with bachelor's degree or higher), split between the Trustworthiness condition, where another party's investment is instrumental for obtaining greater resources, and the Generosity condition, where the other party is a passive recipient. We found that children in the Trustworthiness condition shared significantly more resources than those in the Generosity condition. Further, children in the Trustworthiness condition predicted that the first party expected them to share a greater number of resources. Overall, these results demonstrate that trustworthiness is distinct from generosity in childhood and suggest that children spontaneously grasp and engage in a key aspect of cooperation. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

A comparative test of inequity aversion in domestic dogs (Canis familiaris) and dingoes (Canis dingo)

Despite much recent empirical work on inequity aversion in nonhuman species, many questions remain about its distribution across taxa and the factors that shape its evolution and expression. Past work suggests that domestic dogs (Canis familiaris) and wolves (Canis lupus) are averse to inequitable resource distributions in contexts that call upon some degree of training such as 'give paw' and 'buzzer press' tasks. However, it is unclear whether inequity aversion appears in other canid species and in other experimental contexts. Using a novel inequity aversion task that does not require specific training, this study helps address these gaps by investigating inequity aversion in domestic dogs and a closely related but non-domesticated canid, the dingo (Canis dingo). Subjects were presented with equal and unequal reward distributions and given the opportunity to approach or refuse to approach allocations. Measures of interest were (1) subjects' refusal to approach when getting no food; (2) approach latency; and (3) social referencing. None of these measures differed systematically across the inequity condition and control conditions in either dogs or dingoes. These findings add to the growing literature on inequity aversion in canids, providing data from a new species and a new experimental context. Additionally, they raise questions about the experimental features that must be in place for inequity aversion to appear in canids.

An earlier role for intent in children's partner choice versus punishment

Among the many factors that influence our moral judgments, two are especially important: whether the person caused a bad outcome and whether they intended for it to happen. Notably, the weight accorded to these factors in adulthood varies by the type of judgment being made. For punishment decisions, intentions and outcomes carry relatively equal weight; for partner choice decisions (i.e., deciding whether or not to interact with someone again), intentions are weighted much more heavily. These behavioral differences in punishment and partner choice judgments may also reflect more fundamental differences in the cognitive processes supporting these decisions. Exploring how punishment and partner choice emerge in development provides important and unique insight into these processes as they emerge and mature. Here, we explore the developmental emergence of punishment and partner choice decisions in 4- to 9-year-old children. Given the importance of intentions for partner choice decisions-from both theoretical and empirical perspectives-we targeted the sensitivity of these two responses to others' intentions as well as outcomes caused. Our punishment results replicate past work: Young children are more focused on outcomes caused and become increasingly sensitive to intentions with age. In contrast, partner choice judgments exhibit sensitivity to intentions at an earlier age than punishment judgments, manifesting as earlier partner choice in cases of attempted violations. These results reveal distinct developmental trajectories for punishment and partner choice judgments, with implications for our understanding of the processes underlying these two responses as well as the development of moral judgment more broadly. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Third-party punishment promotes fairness in children

Third-party punishment can promote fair behavior. However, the mechanisms by which this happens are unclear. Third-party punishment may increase fair behavior by providing direct feedback, helping shape the behavior of those punished, or through an influence on reputation, by encouraging the transgressor to behave appropriately before a third-party audience. Investigating whether and how third-party punishment leads to fairness in children during middle childhood-a key developmental period in the emergence of fairness-presents an ideal context in which to explore these 2 mechanisms. Six to nine-year-old children (N = 121) allocated resources between themselves and a partner in a forced-choice dictator game. In the Direct Feedback condition, a third party punished if the child chose the less fair option. In the Reputation condition, a third party merely observed the child. In the Baseline condition, no third party was present. We find that the Direct Feedback condition increased fairness relative to the other conditions, especially among younger children. These results highlight an important link between third-party punishment and fairness in children and, more broadly, help clarify the mechanisms through which third-party punishment can influence fair behavior and thereby human cooperation. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Children favor punishment over restoration

Why do people punish selfish behavior? Are they motivated to punish perpetrators of selfishness (retribution) or to compensate the victims of selfishness (restoration)? Developmental data can provide important insight into these questions by revealing whether punishment of selfishness is more retributive or restorative when it first emerges. Across two studies, we examined costly third-party intervention in 6- to 9-year-olds. In Study 1, children learned about a selfish actor who refused to share with a recipient. Children then chose to (1) punish the selfish actor by rejecting their payoff (retribution); (2) compensate the victim of selfishness by equalizing payoffs between the perpetrator and victim (restoration); or (3) do nothing. We found that children were more likely to punish than compensate in response to selfishness, suggesting that intervention in this context is more retributive than restorative. In Study 2, we tested third-party intervention in the face of generosity which, like selfishness, can lead to unequal outcomes. As in Study 1, children in this context could reject unequal payoffs, thereby depriving the recipient of the advantageous payoff but having no effect on the actor. Children could also use compensation in this context, equalizing the payoffs between actor and recipient. We found that children did not punish inequality that stemmed from generosity, suggesting that the retributive punishment in Study 1 was specifically targeting selfishness rather than inequality more generally. These results contribute to the debate on the function of third-party punishment in humans, suggesting that retributive motives toward selfish transgressors are privileged during ontogeny.

Children in the United States and Peru Pay to Correct Gender-Based Inequality

We explore the developmental origins of intervention against gender-based pay inequality in 4- to 9-year-old children in the United States (N = 123; Study 1) and Peru (N = 115; Study 2), two countries characterized by different norms surrounding gender pay equity. We presented children with scenarios that featured gender-based pay inequality, and they could intervene at a cost to redistribute the earnings. We examined whether children favor equality or show gender bias in intervention depending on the direction of gender pay inequality. Across both societies, both girls and boys intervened against gender inequality regardless of its direction, a tendency that grew stronger with age. These findings suggest that despite developing in societies with existing gender pay inequalities, children strongly privilege equality.

Children Show a Gender Gap in Negotiation

In the United States, there is an unfortunate yet pervasive gender gap in wages: Women tend to make less than men for doing the same work. One prominent account for why this wage gap exists is that women and men negotiate differently. However, we currently do not know whether differences in negotiation are a product of extensive experience or are deeply rooted in development. Here, we brought data from children to bear on this important question. We gave 240 children between the ages of 4 and 9 years old a chance to negotiate for a bonus with a female or a male evaluator. Boys asked for the same bonus from a male and a female evaluator. Older girls, in contrast, asked for a smaller bonus from a male than a female evaluator. Our findings suggest that a gender gap in negotiation emerges surprisingly early in development, highlighting childhood as a key period for interventions.

Does nonbinding commitment promote children's cooperation in a social dilemma?

Communication is a powerful tool for promoting cooperation in adults and is considered one of the most important solutions to social dilemmas. One feature that makes communication particularly useful in cooperative contexts is that it allows people to advertise their intentions to partners. Some work suggests that adults cooperate more after making nonbinding commitments to cooperate (i.e., commitments they do not need to uphold) than when they are not allowed to communicate their intentions to their partners. However, we know little about whether nonbinding commitments play a similar role in children. We addressed this gap by testing 6- to 9-year-old children in a simultaneous version of the iterated prisoner's dilemma game. In the communication condition, children could communicate their intended decision prior to their actual choice, whereas in the silent condition, they could not communicate. Overall, children in the communication condition were no more likely to cooperate than children in the silent condition. However, in the communication condition, but not in the silent condition, children's behavior was contingent on their previous decision; they were more likely to cooperate or defect when they had previously cooperated or defected, respectively. In addition, they rarely reversed their intended decisions in the game. Our findings suggest that, although nonbinding commitment does not promote children's cooperation in general, it may encourage children to stick to their chosen strategy, perhaps for the sake of appearing consistent. More broadly, these results contribute to our emerging understanding of the ways in which children solve social dilemmas.

Children avoid inefficient but fair partners in a cooperative game

Human adults use a range of social cues to obtain information about potential partners in cooperative contexts: we prefer partners who are competent, wealthy and generous, and those who abide by moral and social rules. One factor that carries particular weight is whether a prospective partner is fair. Here we ask whether children share this preference for fair partners and, if so, whether a prospective partner’s past fair behaviour influences children’s behaviour in a cooperative dilemma. Six- to nine-year-olds chose between partners who accepted or rejected resource allocations that were either strongly advantageously unequal, strongly disadvantageously unequal, or equal. They then played a one-shot Prisoner’s Dilemma Game with their chosen partner. Children overwhelmingly preferred to play with the partner who accepted rather than rejected allocations. Regardless of their partner choice decisions, children tended to defect in the Prisoner’s Dilemma Game, yet expected that their partners would be relatively more cooperative. Finally, children were more likely to cooperate with those they believed would cooperate. Together, these findings shed new light on the links between partner choice, fairness and cooperation in child development.

Ingroup bias does not influence inequity aversion in children

Ingroup favoritism influences third-party norm enforcement: Third-party punishers are more lenient when an ingroup member has been unfair. By contrast, in 2-party contexts, where punishers are the victims of unfairness, group bias effects are absent or inconsistent. Thus, group bias appears to be particularly influential when enforcing fairness among others, but less so when protecting oneself from unfairness. This would have implications for theories of how cooperation and intergroup cognition interact, but a more direct empirical test is lacking. To this end, developmental data are particularly useful as they can tell us whether and if so how group bias and fairness norm enforcement are related from their first emergence. Using a minimal groups manipulation, we induced ingroup bias in 6- to 9-year-olds and tested their willingness to reject disadvantageous (more for you) and advantageous (more for me) resource allocations when paired with in- and outgroup members. Group bias did not affect children's rejections of unfair allocations, although they reported that it was worse when an outgroup member had more. Our findings suggest that ingroup bias does not influence children's costly endorsement of equality, indicating that children perceive the equality norm to be indiscriminate and enforceable across group boundaries. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Costly fairness in children is influenced by who is watching

Advantageous inequity aversion emerges relatively late in child development, yet the mechanisms explaining its late emergence are poorly understood. Here, we ask whether children begin to reject advantageous inequity, a costly form of fairness, once reputational concerns are in place. Specifically, we examine the role of peer monitoring in promoting fair behavior. In Study 1 (N = 212 pairs; Ages 6 to 9), we test whether children are less likely to reject advantageous allocations depending on who is aware of their behavior. Results show that children are more likely to accept advantageous allocations when their peer partner is unaware of their advantage. In Study 2 (N = 134 pairs; Ages 8 and 9), we show that this effect is driven specifically by whether the affected peer partners can see the allocation and not by whether third-party peer observers witness the decision. Together, these results shed light on the factors influencing fairness development in childhood and, more specifically, suggest that advantageous inequity aversion is influenced by a desire to appear fair to those getting the short end of the stick. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Individual Differences in Theory of Mind Predict Inequity Aversion in Children

Early in human development, children react negatively to receiving less than others, and only later do they show a similar aversion to receiving more. We tested whether theory of mind (ToM) can account for this developmental shift we see in middle childhood. We conducted a face-to-face fairness task that involved a ToM manipulation, measured individual differences in ToM, and collected parent-ratings of children's empathy, a construct related to ToM. We find that greater ToM capacities lead to more rejections of unequal offers, regardless of the direction of inequality, demonstrating that children with greater ToM are more likely to engage in costly compliance with fairness norms. Moreover, drawing attention to mental states sufficiently elicits aversion to advantageous inequity in younger children. These findings contribute to our growing understanding that people's concerns for fairness rely not just on their own thoughts and beliefs but on the thoughts, beliefs, and expectations of others.

Do Dogs Prefer Helpers in an Infant-Based Social Evaluation Task?

Social evaluative abilities emerge in human infancy, highlighting their importance in shaping our species' early understanding of the social world. Remarkably, infants show social evaluation in relatively abstract contexts: for instance, preferring a wooden shape that helps another shape in a puppet show over a shape that hinders another character (Hamlin et al., 2007). Here we ask whether these abstract social evaluative abilities are shared with other species. Domestic dogs provide an ideal animal species in which to address this question because this species cooperates extensively with conspecifics and humans and may thus benefit from a more general ability to socially evaluate prospective partners. We tested dogs on a social evaluation puppet show task originally used with human infants. Subjects watched a helpful shape aid an agent in achieving its goal and a hinderer shape prevent an agent from achieving its goal. We examined (1) whether dogs showed a preference for the helpful or hinderer shape, (2) whether dogs exhibited longer exploration of the helpful or hinderer shape, and (3) whether dogs were more likely to engage with their handlers during the helper or hinderer events. In contrast to human infants, dogs showed no preference for either the helper or the hinderer, nor were they more likely to engage with their handlers during helper or hinderer events. Dogs did spend more time exploring the hindering shape, perhaps indicating that they were puzzled by the agent's unhelpful behavior. However, this preference was moderated by a preference for one of the two shapes, regardless of role. These findings suggest that, relative to infants, dogs show weak or absent social evaluative abilities when presented with abstract events and point to constraints on dogs' abilities to evaluate others' behavior.

When cooperation begets cooperation: the role of key individuals in galvanizing support

Life abounds with examples of conspecifics actively cooperating to a common end, despite conflicts of interest being expected concerning how much each individual should contribute. Mathematical models typically find that such conflict can be resolved by partial-response strategies, leading investors to contribute relatively equitably. Using a case study approach, we show that such model expectations can be contradicted in at least four disparate contexts: (i) bi-parental care; (ii) cooperative breeding; (iii) cooperative hunting; and (iv) human cooperation. We highlight that: (a) marked variation in contributions is commonplace; and (b) individuals can often respond positively rather than negatively to the contributions of others. Existing models have surprisingly limited power in explaining these phenomena. Here, we propose that, although among-individual variation in cooperative contributions will be influenced by differential costs and benefits, there is likely to be a strong genetic or epigenetic component. We then suggest that selection can maintain high investors (key individuals) when their contributions promote support by increasing the benefits and/or reducing the costs for others. Our intentions are to raise awareness in—and provide testable hypotheses of—two of the most poorly understood, yet integral, questions regarding cooperative ventures: why do individuals vary in their contributions and when does cooperation beget cooperation?

Exploring the Motivations for Punishment: Framing and Country-Level Effects

Identifying the motives underpinning punishment is crucial for understanding its evolved function. In principle, punishment of distributional inequality could be motivated by the desire to reciprocate losses ('revenge') or by the desire to reduce payoff asymmetries between the punisher and the target ('inequality aversion'). By separating these two possible motivations, recent work suggests that punishment is more likely to be motivated by disadvantageous inequality aversion than by a desire for revenge. Nevertheless, these findings have not consistently replicated across different studies. Here, we suggest that considering country of origin—previously overlooked as a possible source of variation in responses—is important for understanding when and why individuals punish one another. We conducted a two-player stealing game with punishment, using data from 2,400 subjects recruited from the USA and India. US-based subjects punished in response to losses and disadvantageous inequality, but seldom invested in antisocial punishment (defined here as punishment of non-stealing partners). India-based subjects, on the other hand, punished at higher levels than US-based subjects and, so long as they did not experience disadvantageous inequality, punished stealing and non-stealing partners indiscriminately. Nevertheless, as in the USA, when stealing resulted in disadvantageous inequality, India-based subjects punished stealing partners more than non-stealing partners. These results are consistent with the hypothesis that variation in punitive behavior varies across societies, and support the idea that punishment might sometimes function to improve relative status, rather than to enforce cooperation.

Fundamental problems with the cooperative breeding hypothesis. A reply to Burkart & van Schaik

The cooperative breeding hypothesis (CBH) states that cooperative breeding, a social system in which group members help to rear offspring that are not their own, has important socio‐cognitive consequences. Thornton & McAuliffe (2015; henceforth T&M) critiqued this idea on both conceptual and empirical grounds, arguing that there is no reason to predict that cooperative breeding should favour the evolution of enhanced social cognition or larger brains, nor any clear evidence that it does. In response to this critique, Burkart & van Schaik (2016 henceforth B&vS) attempt to clarify the causal logic of the CBH, revisit the data and raise the possibility that the hypothesis may only apply to primates. They concede that cooperative breeding is unlikely to generate selection pressures for enhanced socio‐cognitive abilities, but argue instead that the CBH operates purely through cooperative breeding reducing social or energetic constraints. Here, we argue that this revised hypothesis is also untenable because: (1) it cannot explain why resources so released would be allocated to cognitive traits per se rather than any other fitness‐related traits, (2) key assumptions are inconsistent with available evidence and (3) ambiguity regarding the predictions leaves it unclear what evidence would be required to falsify it. Ultimately, the absence of any compelling evidence that cooperative breeding is associated with elevated cognitive ability or large brains (indeed data suggest the opposite is true in non‐human primates) also casts doubt on the capacity of the CBH to explain variation in cognitive traits.

Group bias in cooperative norm enforcement

A hallmark of human social cognition is the tendency for both adults and children to favour members of their own groups. Critically, this in-group bias exerts a strong influence on cooperative decision-making: people (i) tend to share more with members of their in-group and (ii) differentially enforce fairness norms depending on the group membership of their interaction partners. But why do people show these group biases in cooperation? One possibility is that the enforcement of cooperative norm violations is an evolved mechanism supporting within-group cooperation (Norms-Focused Hypothesis). Alternatively, group bias in cooperation could be a by-product of more general affective preferences for in-group members (Mere Preferences Hypothesis). Here, we appraise evidence from studies of both adults and children with the goal of understanding whether one of these two accounts is better supported by existing data. While the pattern of evidence is complex, much of it is broadly consistent with the Mere Preferences Hypothesis and little is uniquely supportive of the Norms-Focused Hypothesis. We highlight possible reasons for this complexity and suggest ways that future work can continue to help us understand the important relationship between group bias and cooperation.

Children reject inequity out of spite

When confronted with inequality, human children and adults sacrifice personal gain to reduce the pay-offs of other individuals, exhibiting apparently spiteful motivations. By contrast, sacrifice of personal gain by non-human animals is often interpreted as frustration. Spite may thus be a uniquely human motivator. However, to date, no empirical study has demonstrated that psychological spite actually drives human behaviour, leaving the motivation for inequity aversion unclear. Here, we ask whether 4- to 9-year-old children and adults reject disadvantageous inequity (less for self, more for peer) out of spite or frustration. We show that children, but not adults, are more likely to reject disadvantageous allocations when doing so deprives their peer of a better reward (spite) than when their peer has already received the better reward (frustration). Spiteful motivations are thus present early in childhood and may be a species-specific component of humans' developing cooperative and competitive behaviour.

Dictator Game Giving: The Importance of Descriptive versus Injunctive Norms

Human behaviour is influenced by social norms but norms can entail two types of information. Descriptive norms refer to what others do in this context, while injunctive norms refer to what ought to be done to ensure social approval. In many real-world situations these norms are often presented concurrently meaning that their independent effects on behaviour are difficult to establish. Here we used an online Dictator Game to test how descriptive and injunctive norms would influence dictator donations when presented independently of one another. In addition, we varied the cost of complying with the norm: By stating that $0.20 or $0.50 cent donations from a $1 stake were normal or suggested, respectively. Specifying a higher target amount was associated with increased mean donation size. In contrast to previous studies, descriptive norms did not seem to influence giving behaviour in this context, whereas injunctive norms were associated with increased likelihood to give at least the target amount to the partner. This raises the question of whether injunctive norms might be more effective than descriptive norms at promoting prosocial behaviour in other settings.

Social influences on inequity aversion in children

Adults and children are willing to sacrifice personal gain to avoid both disadvantageous and advantageous inequity. These two forms of inequity aversion follow different developmental trajectories, with disadvantageous inequity aversion emerging around 4 years and advantageous inequity aversion emerging around 8 years. Although inequity aversion is assumed to be specific to situations where resources are distributed among individuals, the role of social context has not been tested in children. Here, we investigated the influence of two aspects of social context on inequity aversion in 4- to 9-year-old children: (1) the role of the experimenter distributing rewards and (2) the presence of a peer with whom rewards could be shared. Experiment 1 showed that children rejected inequity at the same rate, regardless of whether the experimenter had control over reward allocations. This indicates that children's decisions are based upon reward allocations between themselves and a peer and are not attempts to elicit more favorable distributions from the experimenter. Experiment 2 compared rejections of unequal reward allocations in children interacting with or without a peer partner. When faced with a disadvantageous distribution, children frequently rejected a smaller reward when a larger reward was visible, even if no partner would obtain the larger reward. This suggests that nonsocial factors partly explain disadvantageous inequity rejections. However, rejections of disadvantageous distributions were higher when the larger amount would go to a peer, indicating that social context enhances disadvantageous inequity aversion. By contrast, children rejected advantageous distributions almost exclusively in the social context. Therefore, advantageous inequity aversion appears to be genuinely social, highlighting its potential relevance for the development of fairness concerns. By comparing social and nonsocial factors, this study provides a detailed picture of the expression of inequity aversion in human ontogeny and raises questions about the function and evolution of inequity aversion in humans.

The origins of pedagogy: developmental and evolutionary perspectives

The question of whether and how information is actively transferred from knowledgeable to ignorant individuals has received much attention in psychology and evolutionary biology. Research in these fields has proceeded largely independently, with studies of nonhuman animals focusing on knowledgeable individuals and whether or not they meet a functional definition of teaching, while studies of children focus on the learner's assumptions and inferences. We argue that a comprehensive theory of teaching will benefit from integrating perspectives and empirical phenomena from evolutionary and developmental disciplines. In this review, we identify cases of seemingly purposeful information transfer (i.e. teaching) in human and nonhuman animals, discuss what is known about the cognitive processes that support teaching in different species, and highlight ways in which each discipline might be informed by extant theories and empirical tools from the other.