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By 4 or 5 years of age, children understand when their own past beliefs were incorrect, or when others' current beliefs are incorrect. In the current study, we asked whether young children understand when their own current belief might be incorrect. 3- and 5-year old children (N = 77) made a judgment and then experienced a puppet making a judgment about the same situation. Children of both ages rechecked their evidence more often when the puppet disagreed with them than when it agreed with them (and the nature of their rechecking was different in the two conditions as well). These results suggest that already by 3 years of age children understand that they might currently be wrong, and they know that rechecking the evidence can resolve their uncertainty., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Sometimes we have a personal preference but we agree with others to follow a different course of action. In this study, 3- and 5-year-old children (N = 160) expressed a preference for playing a game one way and were then confronted with peers who expressed a different preference. The experimenter then either got the participants to agree with the peers explicitly or just shrugged her shoulders and moved on. The children were then left alone to play the game unobserved. Only the older children stuck to their agreement to play the game as the peers wished. These results suggest that by 5 years of age children's sense of commitment to agreements is strong enough to override their personal preferences., (Copyright © 2023 Elsevier Inc. All rights reserved.)

We report two experiments on children's tendency to enhance their reputations through communicative acts. In the experiments, 4-year-olds (N = 120) had the opportunity to inform a social partner that they had helped him in his absence. In a first experiment, we pitted a prosocial act ("Let's help clean up for Doggie!") against an instrumental act ("Let's move these out of our way"). Children in the prosocial condition were quicker to inform their partner of the act and more likely to protest when another individual was given credit for it. In a second experiment, we replicated the prosocial condition but with a new manipulation: high-cost versus low-cost helping. We manipulated both the language surrounding cost (i.e., "This will be pretty tough to clean up" vs. "It will be really easy to clean this up") and how difficult the task itself was. As predicted, children in the high-cost condition were quicker to inform their partner of the act and more likely to take back credit for it. These results suggest that even 4-year-old children make active attempts to elicit positive reputational judgments for their prosocial acts, with cost as a moderating factor., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Young children share equally when they acquire resources through collaboration with a partner, yet it is unclear whether they do so because in such contexts resources are encountered as common and distributed in front of the recipient or because collaboration promotes a sense of work-based fairness. In the current studies, 5- and 8-year-old children from Germany (N = 193) acquired resources either by working individually alongside or by collaborating with a peer. After finding out that the partner's container was empty, they decided in private whether they wanted to donate some resources to the peer. When both partners had worked with equal efforts (Study 1), children shared more after collaboration than after individual work. When one partner had worked with much more effort than the other (Study 2), children shared more with a harder-working partner than with a less-working partner independently of whether they had collaborated or worked individually. Younger children were more generous than older children, in particular after collaboration. These findings support the view that collaboration promotes a genuine sense of fairness in young children, but they also indicate that merit-based notions of fairness in the context of work may develop independently of collaboration, at least by the beginning of middle childhood and in Western societies., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The cooperative eye hypothesis posits that human eye morphology evolved to facilitate cooperation. Although it is known that young children prefer stimuli with eyes that contain white sclera, it is unknown whether white sclera influences children's perception of a partner's cooperativeness specifically. In the current studies, we used an online methodology to present 5-year-old children with moving three-dimensional face models in which facial morphology was manipulated. Children found "alien" faces with human eyes more cooperative than faces with dark sclera (Study 2) but not faces with enlarged irises (Study 1). For more human-like faces (Study 3), children found human eyes more cooperative than either enlarged irises or dark sclera and found faces with enlarged irises cuter (but not more cooperative) than eyes with dark sclera. Together, these results provide strong support for the cooperative eye hypothesis., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Although theorists agree that social interactions play a major role in moral development, previous research has not experimentally assessed how specific features of social interactions affect children's moral judgments and reasoning. The current study assessed two features: disagreement and justification. In a brief training phase, children aged 4-5.5 years (N = 129) discussed simple moral scenarios about issues of fairness (how to allocate things between individuals) with a puppet who, in a between-participants factorial design, either agreed or disagreed with the children's ideas and either asked or did not ask the children to justify their ideas. Children then responded to another set of moral scenarios in a test phase that was the same for all children. Children in the "agree and do not justify" baseline condition showed an inflexible equality bias (preferring only equal allocations regardless of context), but children who had experiences of disagreement or experiences of being asked to justify themselves shifted toward making equitable decisions based on common ground norms and values. Furthermore, false belief competence was related to children's decisions and justifications. These findings support the classic Piagetian hypothesis that social interactions are a catalyst of cognitive disequilibrium and moral development., (Copyright © 2022 Elsevier Inc. All rights reserved.)

By around 3 years of age, collaboration induces in young children a normative sense of "we" that creates a sense of obligation (e.g., commitment, fairness) toward their collaborative partner. The current study investigated whether this normative sense of we could be induced purely verbally in 3- and 4-year-old children. Children joined a puppet at a table to draw. In one condition the puppet repeatedly framed things as "we" are going to sit at the table, "we" are going to draw, and so forth, whereas in the other condition the pronoun used was always "you." Dependent measures gauged children's commitment, resource distribution, and helping behavior toward their partner. Results showed that both 3- and 4-year-olds felt a greater sense of commitment to their partner after "we"-framing than after "you"-framing. The 4-year-olds evidenced this commitment by showing a greater reluctance to abandon their partner for a more fun game compared with the 3-year-olds. The 3-year-olds did not share this reluctance, but when they did abandon their partner they more often took leave following we-framing by "announcing" their leaving. There were no effects of we-framing on children's sharing with their partner or helping behavior. These results suggest that verbal we-framing, as compared with you-framing, is an effective means of inducing in children a sense of shared agency and commitment with a partner., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Although there is considerable evidence that at least some helping behavior is motivated by genuine concern for others' well-being, sometimes we also help solely out of a sense of obligation to the persons in need. Our sense of obligation to help may be particularly strong when there is common knowledge between the helper and the helpee that the helpee needs help. To test whether children's helping behavior is affected by having common knowledge with the recipient about the recipient's need, 6-year-olds faced a dilemma: They could either collect stickers or help an experimenter. Children were more likely to help when they and the experimenter had common knowledge about the experimenter's plight (because they heard it together) than when they each had private knowledge about it (because they heard it individually). These results suggest that already in young children common knowledge can heighten the sense of obligation to help others in need., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

To create social closeness, humans engage in a variety of social activities centered around shared experiences. Even simply watching the same video side by side creates social closeness in adults and children. However, perhaps surprisingly, a similar psychological mechanism was recently shown in great apes. Here we asked whether the process by which this social closeness is created is the same for children and great apes. Each participant entered a room to see an experimenter (E1) watching a video. In one condition, E1 looked to the participant at the start of the video to establish common ground that they were watching the video together. In another condition, E1 did not look to the participant in this way so that the participant knew they were watching the same video, but the participant did not know whether E1 was aware of this as well, so there was no common ground (E1 looked to the participant later in the procedure). Children, but not great apes, approached the experimenter faster after the common ground condition, suggesting that although both humans and great apes create social closeness by co-attending to something in close proximity, creating social closeness by sharing experiences in common ground may be a uniquely human social-cognitive process., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Individuals with an advantageous position during a negotiation possess leverage over their partners. Several studies with adults have investigated how leverage can influence the coordination strategies of individuals when conflicts of interest arise. In this study, we explored how pairs of 7-year-old children solved a coordination game (based on the Snowdrift scenario) when one child had leverage over the other child. We presented a social dilemma in the form of an unequal reward distribution on a rotating tray. The rotating tray could be accessed by both children. The child who waited longer to act received the best outcome, but if both children waited too long, they would lose the rewards. In addition, one child could forgo the access to the rotating tray for an alternative option-the leverage. Although children rarely used their leverage strategically, children with access to the alternative were less likely to play the social dilemma, especially when their leverage was larger. Furthermore, children waited longer to act as the leverage decreased. Finally, children almost never failed to coordinate. The results hint to a trade-off between maximizing benefits while maintaining long-term collaboration in complex scenarios where strategies such as turn taking are hard to implement., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Young children help and share with others, but little is known about the "how" and "who" of this early prosocial behavior. In the current study, we compared 2- and 3-year-old children's (N = 203; 101 girls) prosocial behavior of sharing and helping. We asked whether the process was different (a) if the social partner was an adult or a same-age peer and (b) if the child was actively interacting and engaged with the partner or not. The highest prosocial responses were found in bilateral joint tasks such as sharing the spoils after a collaborative effort and helping a partner finish a mutual activity. Prosocial responses were lower in unilateral autonomous tasks such as assisting another person in opening a locked box and distributing a windfall of resources. Children did not show an overall preference for helping or sharing with adults versus peers except that they were more likely to support a peer than an adult in an instrumental helping task. Together, these findings suggest that toddlers' early prosocial skills and motivations are more sensitive to how toddlers are engaged with a partner than to who that partner is, implying that children have a nondiscriminatory general inclination to benefit others, especially in bilateral interactive scenarios., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Collaborative reasoning requires partners to evaluate options and the evidence for or against each option. We investigated whether preschoolers can explain why one option is best (direct reasons) and why the other option is not (indirect reasons), looking at both problems that have a correct answer and those that require choosing the better option. In Study 1, both age groups produced direct reasons equally frequently in both problems. However, 5-year-olds produced indirect reasons more often than 3-year-olds, especially when there was a correct answer. In Study 2 with a nonverbal task with a correct answer, 3-year-olds produced indirect reasons more often than in Study 1, although 5-year-olds' indirect reasons were more efficiently stated. These results demonstrate that even 3-year-olds, and even nonverbally, can point out to a partner a fact that constitutes a reason for them to arrive at a correct joint decision., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Human social relationships are often formed through shared social activities in which individuals share mental states about external stimuli. Previous work on joint attention has shown that even minimal shared experiences such as watching something together facilitates social closeness between individuals. Here, we examined whether young children already connect with others through joint attention. In the current studies, children sat next to a novel adult who either watched a film with them or was not able to see the film and read a book instead. After the video, we measured children's willingness (i.e., latency) to approach the experimenter holding out a toy. In both studies, the 2.5-year-olds who watched the film together approached more quickly than the other children. These results show that both minimally interactive shared experiences and noninteractive shared experiences lead children to feel more comfortable with a novel adult. This suggests that joint attention interactions, and shared experiences in general, play an important role not only in children's cognitive development but also in their social development and the formation of their social relationships., (Copyright © 2019 Elsevier Inc. All rights reserved.)

A natural reaction to receiving help from someone is to help that person in return. In two studies, we investigated the developmental origins of children's motivation to return help. In Study 1, 18- and 24-month-old toddlers were either helped or not helped by an adult, and they could subsequently provide that adult with help or else observe another person providing help. We measured children's internal arousal, via changes in pupil dilation, both before and after help was provided. At both ages, children's internal arousal was higher when they could not help the adult who had previously helped them (and was lower when they could). On the other hand, if the adult needing help had not previously helped children, their internal arousal was equally low regardless of whether they or another person provided the help. Study 2 replicated this result and also found that if children had previously been helped but the person needing help was a different adult (not their benefactor), children's internal arousal was equally low regardless of whether they or another person provided the help. Together, these results suggest that young children are intrinsically motivated to return a received favor specifically to the previous benefactor, perhaps indicating a nascent sense of gratitude., (Copyright © 2019. Published by Elsevier Inc.)

This study investigated the influence of underlying intentions and outcomes of a partner's sharing behavior on young children's reciprocity. We provided 3- and 5-year-old children with the opportunity to share with a partner following different treatments of a partner's intention (to share or not to share) that led to different outcomes (children got or did not get stickers from their partner). For the 3-year-olds, we found that the outcome of the previous interaction influenced how much they shared, whereas the intention of their partner affected how readily they initiated sharing in response to social cues. For the 5-year-olds, we found that both outcome and intention affected how much they shared as well as how readily they initiated sharing. This suggests that already 3-year-olds are able to take into account outcome and intention information separately in reciprocal sharing. However, only 5-year-olds can combine both to flexibly maintain social interactions without running the risk of being exploited by others., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Children's moral behavior is guided, in part, by adults teaching children how to treat others. However, when circumstances change, such instructions may become either unhelpful or limiting. In the current study, 48 dyads of 5-year-olds played a collaborative game and either (a) received an instruction by an adult to share the spoils of the game equally, (b) did not receive any instruction (but still chose to share equally), or (c) agreed between themselves on a rule to share equally. Afterward, each child played with a new partner who was needier or worked harder in his or her collaboration and so plausibly deserved more than just half of the spoils. Results showed that children who were instructed by an adult shared less with their more deserving partner than children who did not receive any instruction. Thus, moral instruction by adults may, in some circumstances, make children more rigid in their moral decisions., (Copyright © 2019 Elsevier Inc. All rights reserved.)

When young children form a joint commitment with a partner, they understand that this agreement generates obligations. In this study, we investigated whether young children understand that joint commitments, and their associated obligations, may likewise be dissolved by agreement. The participants (3- and 5-year-olds; N = 144) formed a joint commitment with a puppet to play a collaborative game. In one condition, the puppet asked permission to break off and the children agreed; in a second condition, the puppet notified the children of his or her leaving; and in a third condition, the puppet just left abruptly. Children at both ages protested more and waited longer for the puppet's return (and said that the puppet deserved scolding and no prize at the end) when the puppet left abruptly than in the other two conditions (with "asking permission" leading to the least protest of all). Overall, 3-year-olds protested more, and waited longer for the partner's return, than 5-year-olds. Preschool children understand that the obligations of a joint commitment may be dissolved by agreement or, to a lesser degree, by notification., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Humans are frequently required to coordinate their actions in social dilemmas (e.g. when one of two drivers has to yield for the other at an intersection). This is commonly achieved by individuals following communally known rules that prescribe how people should behave. From relatively early in development, children swiftly pick up the rules of their culture and even start creating game rules among peers. Thus far, however, little is known about children's abilities create rules to regulate their own interactions in social dilemma situations in which individuals' interests are partially in conflict. Here, we repeatedly selected dyads of children (5- and 8-year-olds, N = 144) at random from a group and presented them with a chicken game - a social dilemma in which individuals have conflicting motives but coordination is required to avoid mutual failure. In game breaks, groups reconvened and had the opportunity to think of additional game rules. Eight- but not five-year-olds readily came up with and agreed upon impartial rules to guide their subsequent game behavior (but only after adult prompting). Moreover, when playing by the self-made rules, children achieved higher payoffs, had fewer conflicts, and coordinated with greater efficiency than when playing without a rule - which mimics the functional consequences of rules on a societal level. These findings suggest that by at least age 8, children are capable of using rules to independently self-regulate potential conflicts of interest with peers., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Humans cultivate their reputations as good cooperators, sometimes even competing with group mates, to appear most cooperative to individuals during the process of selecting partners. To investigate the ontogenetic origins of such "competitive altruism," we presented 5- and 8-year-old children with a dyadic sharing game in which both children simultaneously decided how many rewards to share with each other. The children were either observed by a third-person peer or not. In addition, the children either knew that one of them would be picked for a subsequent collaborative game or had no such knowledge. We found that by 8 years of age, children were more generous in the sharing game not only when their behavior was observed by a third party but also when it could affect their chances of being chosen for a subsequent game. This is the first demonstration of competitive altruism in young children, and as such it underscores the important role of partner choice (and individual awareness of the process) in encouraging human cooperation from an early age., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Prosocial and normative behavior emerges in early childhood, but substantial changes in prosocial behavior in middle childhood may be due to it becoming integrated with children's understanding of what is normative. Here we show that information about what is normative begins influencing children's costly sharing in middle childhood in a sample of 6- to 11-year-old German children. Information about what is normative was most influential when indicating what was "right" (i.e., "The right thing is to choose this"). It was less influential when indicating what was prescribed by a rule (i.e., "There is a rule that says to choose this") or when it indicated what the majority of people do (i.e., "Most people choose this"). These findings support the idea that middle childhood is when social norms begin to shape children's costly sharing and provide insight into the psychological foundations of the relationship between norms and prosocial behavior., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The current study investigated children's intention-based sociomoral judgments and distribution behavior from a third-party stance. An actor puppet showed either positive or negative intention toward a target puppet, which had previously performed a prosocial or antisocial action toward others (i.e., children witnessed various types of indirect reciprocity). Children (3- and 5-year-olds) were asked to make sociomoral judgments and to distribute resources to the actor puppet. Results showed that 5-year-olds were more likely than 3-year-olds to be influenced by intention when they made their judgment and distributed resources. The target's previous actions affected only 5-year-olds' intent-based social preference. These results suggest that children's judgments about intent-based indirect reciprocity develop from ages 3 to 5 years., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Young children engage in direct reciprocity, but the mechanisms underlying such reciprocity remain unclear. In particular, prior work leaves unclear whether children's reciprocity is simply a response to receiving benefits (regardless of whether the benefits were intended) or driven by a mechanism of rewarding or preferring all benefactors (regardless of whom they benefited). Alternatively, perhaps children engage in genuine reciprocity such that they are particularly prosocial toward benefactors who intentionally provided them with benefits. Our findings support this third, richer possibility; the 3-year-olds who received benefits through the good intentions of a benefactor were subsequently more generous toward the benefactor than children who either (a) received the same benefits from the benefactor unintentionally or (b) observed the benefactor bestow the same benefits on another individual. Thus, young children are especially motivated to benefit those who have demonstrated goodwill toward them, suggesting, as one possible mechanism, an early sense of gratitude., (Copyright © 2017 Elsevier Inc. All rights reserved.)

In collaborative decision making, children must evaluate the evidence behind their respective claims and the rationality of their respective proposals with their partners. In the main study, 5- and 7-year-old peer dyads (N = 196) were presented with a novel animal. In the key condition, children in a dyad individually received conflicting information about what the animal needs (e.g., rocks vs. sand for food) from sources that differ in reliability (with first-hand vs. indirect evidence). Dyads in both age groups were able to reliably settle on the option with the best supporting evidence. Moreover, in making their decision, children, especially 7-year-olds, engaged in various kinds of meta-talk about the evidence and its validity. In a modified version of the key condition in Study 2, 3- and 5-year-olds (N = 120) interacted with a puppet who tried to convince children to change their minds by producing meta-talk. When the puppet insisted and produced meta-talk, 5-year-olds, but not 3-year-olds, were more likely to change their minds if their information was unreliable. These results suggest that even preschoolers can engage in collaborative reasoning successfully, but the ability to reflect on the process by stepping back to jointly examine the evidence emerges only during the early school years., (Copyright © 2017 Elsevier Inc. All rights reserved.)

People accept an unequal distribution of resources if they judge that the decision-making process was fair. In this study, 3- and 5-year-old children played an allocation game with two puppets. The puppets decided against a fair distribution in all conditions, but they allowed children to have various degrees of participation in the decision-making process. Children of both ages protested less when they were first asked to agree with the puppets' decision compared with when there was no agreement. When ignored, the younger children protested less than the older children-perhaps because they did not expect to have a say in the process-whereas they protested more when they were given an opportunity to voice their opinion-perhaps because their stated opinion was ignored. These results suggest that during the preschool years, children begin to expect to be asked for their opinion in a decision, and they accept disadvantageous decisions if they feel that they have had a voice in the decision-making process., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Human adults incline toward moral objectivism but may approach things more relativistically if different cultures are involved. In this study, 4-, 6-, and 9-year-old children (N=136) witnessed two parties who disagreed about moral matters: a normative judge (e.g., judging that it is wrong to do X) and an antinormative judge (e.g., judging that it is okay to do X). We assessed children's metaethical judgment, that is, whether they judged that only one party (objectivism) or both parties (relativism) could be right. We found that 9-year-olds, but not younger children, were more likely to judge that both parties could be right when a normative ingroup judge disagreed with an antinormative extraterrestrial judge (with different preferences and background) than when the antinormative judge was another ingroup individual. This effect was not found in a comparison case where parties disagreed about the possibility of different physical laws. These findings suggest that although young children often exhibit moral objectivism, by early school age they begin to temper their objectivism with culturally relative metaethical judgments., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Promises are speech acts that create an obligation to do the promised action. In three studies, we investigated whether 3- and 5-year-olds (N=278) understand the normative implications of promising in prosocial interactions. In Study 1, children helped a partner who promised to share stickers. When the partner failed to uphold the promise, 3- and 5-year-olds protested and referred to promise norms. In Study 2, when children in this same age range were asked to promise to continue a cleaning task-and they agreed-they persisted longer on the task and mentioned their obligation more frequently than without such a promise. They also persisted longer after a promise than after a cleaning reminder (Study 3). In prosocial interactions, thus, young children feel a normative obligation to keep their promises and expect others to keep their promises as well., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The current study explored how freedom of choice affects preschoolers' prosocial motivation. Children (3- and 5-year-olds) participated in either a choice condition (where they could decide for themselves whether to help or not) or a no-choice condition (where they were instructed to help). Prosocial motivation was subsequently assessed by measuring the amount children helped an absent peer in the face of an attractive alternative game. The 5-year-olds provided with choice helped more than the children not provided with choice, and this effect was stronger for girls than for boys. There was no difference between conditions for the 3-year-olds. These results highlight the importance of choice in young children's prosocial development., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The age at which young children show an aversion to inequitable resource distributions, especially those favoring themselves, is unclear. It is also unclear whether great apes, as humans' nearest evolutionary relatives, have an aversion to inequitable resource distributions at all. Using a common methodology across species and child ages, the current two studies found that 3- and 4-year-old children (N=64) not only objected when they received less than a collaborative partner but also sacrificed to equalize when they received more. They did neither of these things in a nonsocial situation, demonstrating the fundamental role of social comparison. In contrast, chimpanzees (N=9) showed no aversion to inequitable distributions, only a concern for maximizing their own resources, with no differences between social and nonsocial conditions. These results underscore the unique importance for humans, even early in ontogeny, for treating others fairly, presumably as a way of becoming a cooperative member of one's cultural group., (Copyright © 2016 Elsevier Inc. All rights reserved.)

De Villiers (Lingua, 2007, Vol. 117, pp. 1858-1878) and others have claimed that children come to understand false belief as they acquire linguistic constructions for representing a proposition and the speaker's epistemic attitude toward that proposition. In the current study, English-speaking children of 3 and 4years of age (N=64) were asked to interpret propositional attitude constructions with a first- or third-person subject of the propositional attitude (e.g., "I think the sticker is in the red box" or "The cow thinks the sticker is in the red box", respectively). They were also assessed for an understanding of their own and others' false beliefs. We found that 4-year-olds showed a better understanding of both third-person propositional attitude constructions and false belief than their younger peers. No significant developmental differences were found for first-person propositional attitude constructions. The older children also showed a better understanding of their own false beliefs than of others' false beliefs. In addition, regression analyses suggest that the older children's comprehension of their own false beliefs was mainly related to their understanding of third-person propositional attitude constructions. These results indicate that we need to take a closer look at the propositional attitude constructions that are supposed to support children's false-belief reasoning. Children may come to understand their own and others' beliefs in different ways, and this may affect both their use and understanding of propositional attitude constructions and their performance in various types of false-belief tasks., (Copyright © 2016 Elsevier Inc. All rights reserved.)

From an early age, children can talk meaningfully about differences between moral and conventional norms. But does their understanding of these differences manifest itself in their actual behavioral and emotional reactions to norm violations? And do children discriminate between norm violations that affect either themselves or a third party? Two studies (N=224) were conducted in which children observed conventional game rule violations and moral transgressions that either disadvantaged themselves directly or disadvantaged an absent third party. Results revealed that 3- and 5-year-olds evaluated both conventional and moral transgressions as normative breaches and protested against them. However, 5-year-olds also clearly discriminated these types of transgressions along further dimensions in that (a) they tattled largely on the moral violation and less on the conventional violation and (b) they showed stronger emotional reactions to moral violations compared to conventional violations. The 3-year-olds' responses to moral and conventional transgressions, however, were less discriminatory, and these younger children responded rather similarly to both kinds of violations. Importantly, most children intervened both as victims of the transgression and as unaffected third parties alike, providing strong evidence for their agent-neutral understanding of social norms., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Young children can in principle make generic inferences (e.g., "doffels are magnetic") on the basis of their own individual experience. Recent evidence, however, shows that by 4 years of age children make strong generic inferences on the basis of a single pedagogical demonstration with an individual (e.g., an adult demonstrates for the child that a single "doffel" is magnetic). In the current experiments, we extended this to look at younger children, investigating how the mechanisms underlying this phenomenon are integrated with other aspects of inductive inference during early development. We found that both 2- and 3-year-olds used pedagogical cues to guide such generic inferences, but only so long as the "doffel" was linguistically labeled. In a follow-up study, 3-year-olds, but not 2-year-olds, continued to make this generic inference even if the word "doffel" was uttered incidentally and non-referentially in a context preceding the pedagogical demonstration, thereby simply marking the opportunity to learn about a culturally important category. By 3 years of age, then, young children show a remarkable ability to flexibly combine different sources of culturally relevant information (e.g., linguistic labeling, pedagogy) to make the kinds of generic inferences so central in human cultural learning., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Human institutional practices often involve competition within a cooperative structure of mutually accepted rules. In a competitive game, for instance, we not only expect adherence to the rules of the game but also expect an opponent who tries to win and, thus, follows a rational game-playing strategy. We had 3- and 5-year-olds (N=48) play for a prize against an opponent (a puppet) who played either rationally (trying to win) or irrationally (helping the children to win) while either following or breaking the rules of the game. Both age groups performed costly protest against an opponent who followed the rules but played irrationally by helping the children to win. When facing a rule-breaking opponent, 3-year-olds protested only the rule breaches of an irrational opponent but not irrational play. Five-year-olds also protested the rule breaches of a rational opponent, but in contrast to the 3-year-olds, they protested irrational behavior even in the context of rule breaches. Moreover, many children, in particular 3-year-olds, refrained from protesting. These findings suggest that 5-year-olds, but not 3-year-olds, fully understand the dual-level normative structure of cooperatively regulated competition., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Iconic gestures-communicative acts using hand or body movements that resemble their referent-figure prominently in theories of language evolution and development. This study contrasted the abilities of chimpanzees (N=11) and 4-year-old human children (N=24) to comprehend novel iconic gestures. Participants learned to retrieve rewards from apparatuses in two distinct locations, each requiring a different action. In the test, a human adult informed the participant where to go by miming the action needed to obtain the reward. Children used the iconic gestures (more than arbitrary gestures) to locate the reward, whereas chimpanzees did not. Some children also used arbitrary gestures in the same way, but only after they had previously shown comprehension for iconic gestures. Over time, chimpanzees learned to associate iconic gestures with the appropriate location faster than arbitrary gestures, suggesting at least some recognition of the iconicity involved. These results demonstrate the importance of iconicity in referential communication., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Young children are often considered "selfish" with resources because they are reluctant to give up things already in their possession (e.g., as in dictator games). In the current two studies, we presented pairs of 18- and 24-month-old toddlers with various situations involving resources that no one possessed ahead of time. We observed very few instances of individuals attempting to monopolize the resources; rather, the pair peaceably divided them such that each child got something. Equal divisions--even involving one child sacrificing his or her own resources to establish equality-were especially pronounced when children were acting together jointly even in the absence of active collaboration. Children's divisions were also influenced by cues to ownership such as a spatial pre-division of resources and resources marked by color (and originally spatially associated with one individual). These results suggest that young children are not selfish, but instead rather generous, with resources when they are dividing them among themselves., (Copyright © 2015 Elsevier Inc. All rights reserved.)

When it is not possible to distribute resources equitably to everyone, people look for an equitable or just procedure. In the current study, we investigated young children's sense of procedural justice. We tested 32 triads of 5-year-olds in a new resource allocation game. Triads were confronted with three unequal reward packages and then agreed on a procedure to allocate them among themselves. To allocate the rewards, they needed to use a "wheel of fortune." Half of the groups played with a fair wheel (where each child had an equal chance of obtaining each reward package), and the other half played with an unfair wheel. We analyzed children's interactions when using the wheel and conducted an interview with each child after the game was over. Children using the unfair wheel often decided to change the rules of the game, and they also rated it as an unfair procedure in the interview. In contrast, children who played with the fair wheel were mostly accepting of both the outcome and the procedure. Overall, we found that children as young as preschool age are already sensitive not only to distributive justice but to procedural justice as well., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Recent theoretical work has highlighted potential links between interpersonal collaboration and group membership in the evolution of human sociality. Here we compared the effects of collaboration and minimal-group membership on young children's prosocial behavior (i.e., helping and resource allocation), liking, affiliation, and trust. In a design that matched as closely as possible these two ways of connecting with others, we showed that 5-year-olds' behavior was affected similarly by collaboration and minimal-group membership; both increased children's preference for their partners on multiple dimensions and produced overall effects of a similar magnitude. In contrast, 3.5-year-olds did not have a strong preference for either collaborators or minimal in-group members. Thus, both collaboration and minimal-group membership are similarly effective in their influence on children's prosocial behavior and social preferences., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Children use normative language in two key contexts: when teaching others and when enforcing social norms. We presented pairs of 3- and 5-year-old peers (N=192) with a sorting game in two experimental conditions (in addition to a third baseline condition). In the teaching condition, one child was knowledgeable, whereas the other child was ignorant and so in need of instruction. In the enforcement condition, children learned conflicting rules so that each child was making mistakes from the other's point of view. When teaching rules to an ignorant partner, both age groups used generic normative language ("Bunnies go here"). When enforcing rules on a rule-breaking partner, 3-year-olds used normative utterances that were not generic and aimed at correcting individual behavior ("No, this goes there"), whereas 5-year-olds again used generic normative language, perhaps because they discerned that instruction was needed in this case as well. Young children normatively correct peers differently depending on their assessment of what their wayward partners need to bring them back into line., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Although many animal species show at least some evidence of cultural transmission, broadly defined, only humans show clear evidence of cumulative culture. In the current study, we investigated whether young children show the "ratchet effect," an important component of cumulative culture--the ability to accumulate efficient modifications across generations. We tested 16 diffusion chains--altogether consisting of 80 children--to see how they solved an instrumental task (i.e., carrying something from one location to another). We found that when the chain was seeded with an inefficient way of solving the task, 4-year-olds were able to innovate and transmit these innovations so as to reach a more efficient solution. However, when it started out with relatively efficient solutions already (i.e., the ones that children in a control condition discovered for themselves), there were no further techniques invented and/or transmitted beyond that. Thus, young children showed the ratchet effect to a limited extent, accumulating efficient modifications but not going beyond the inventive level of the individual., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Recent studies suggest that infants understand that others can have false beliefs. However, most of these studies have used looking time measures, and the few that have used behavioral measures are all based on the change-of-location paradigm, leading to claims that infants might use behavioral rules instead of mental state understanding to pass these tests. We investigated infants' false-belief reasoning using a different paradigm. In this unexpected-contents helping task, 18-month-olds were familiarized with boxes for blocks that contained blocks. When an experimenter subsequently reached for a box for blocks that now contained a spoon, infants based their choice of whether to give her a spoon or a block on her true or false belief about which object the block box contained. These results help to demonstrate the flexibility of infants' false-belief understanding., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Human social life is structured by social norms creating both obligations and entitlements. Recent research has found that young children enforce simple obligations against norm violators by protesting. It is not known, however, whether they understand entitlements in the sense that they will actively object to a second party attempting to interfere in something that a third party is entitled to do-what we call counter-protest. In two studies, we found that 3-year-old children understand when a person is entitled to do something, and so they actively defend this person's entitlement against unjustified interference from second parties. In some cases, they even enforce second-order entitlements, for example, in the case of ownership where an owner is entitled to entitle others to use the owner's property., (Copyright © 2013 Elsevier Inc. All rights reserved.)

In studies of children's resource distribution, it is almost always the case that "fair" means an equal amount for all. In the mini-ultimatum game, players are confronted with situations in which fair does not always mean equal, and so the recipient of an offer needs to take into account the alternatives the proposer had available to her or him. Because of its forced-choice design, the mini-ultimatum game measures sensitivity to unfair intentions in addition to unfair outcomes. In the current study, we gave a mini-ultimatum game to 5-year-old children, allowing us to determine the nature of fairness sensitivity at a period after false belief awareness is typically passed and before formal schooling begins. The only situation in which responders rejected offers was when the proposer could have made an equal offer. But unlike adults, they did not employ more sophisticated notions of fairness that take into account the choices facing the proposer. Proposers, in their turn, were also not adult-like in that they had a very poor understanding that responders would reject unequal offers when an equal one was available. Thus, preschool children seem to understand "fair=equal" in this task, but not much more, and they are not yet skillful at anticipating what others will find fair beyond 50/50 splits., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Contingent reciprocity is important in theories of the evolution of human cooperation, but it has been very little studied in ontogeny. We gave 2- and 3-year-old children the opportunity to either help or share with a partner after that partner either had or had not previously helped or shared with the children. Previous helping did not influence children's helping. In contrast, previous sharing by the partner led to greater sharing in 3-year-olds but not in 2-year-olds. These results do not support theories claiming either that reciprocity is fundamental to the origins of children's prosocial behavior or that it is irrelevant. Instead, they support an account in which children's prosocial behavior emerges spontaneously but is later mediated by reciprocity., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Recent studies have shown that in situations where resources have been acquired collaboratively, children at around 3 years of age share mostly equally. We investigated 3-year-olds' sharing behavior with a collaborating partner and a free-riding partner who explicitly expressed her preference not to collaborate. Children shared more equally with the collaborating partner than with the free rider. These results suggest that young children are sensitive to the contributions made by others to a collaborative effort (and possibly their reasons for not collaborating) and distribute resources accordingly., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The human capacity to synchronize body movements to an external acoustic beat enables uniquely human behaviors such as music making and dancing. By hypothesis, these first evolved in human cultures as fundamentally social activities. We therefore hypothesized that children would spontaneously synchronize their body movements to an external beat at earlier ages and with higher accuracy if the stimulus was presented in a social context. A total of 36 children in three age groups (2.5, 3.5, and 4.5 years) were invited to drum along with either a human partner, a drumming machine, or a drum sound coming from a speaker. When drumming with a social partner, children as young as 2.5 years adjusted their drumming tempo to a beat outside the range of their spontaneous motor tempo. Moreover, children of all ages synchronized their drumming with higher accuracy in the social condition. We argue that drumming together with a social partner creates a shared representation of the joint action task and/or elicits a specific human motivation to synchronize movements during joint rhythmic activity.

As compared with other primates, humans have especially visible eyes (e.g., white sclera). One hypothesis is that this feature of human eyes evolved to make it easier for conspecifics to follow an individual's gaze direction in close-range joint attentional and communicative interactions, which would seem to imply especially cooperative (mututalistic) conspecifics. In the current study, we tested one aspect of this cooperative eye hypothesis by comparing the gaze following behavior of great apes to that of human infants. A human experimenter "looked" to the ceiling either with his eyes only, head only (eyes closed), both head and eyes, or neither. Great apes followed gaze to the ceiling based mainly on the human's head direction (although eye direction played some role as well). In contrast, human infants relied almost exclusively on eye direction in these same situations. These results demonstrate that humans are especially reliant on eyes in gaze following situations, and thus, suggest that eyes evolved a new social function in human evolution, most likely to support cooperative (mututalistic) social interactions.

We conducted three experiments on social problem solving by chimpanzees, Pan troglodytes. In each experiment a subordinate and a dominant individual competed for food, which was placed in various ways on the subordinate's side of two opaque barriers. In some conditions dominants had not seen the food hidden, or food they had seen hidden was moved elsewhere when they were not watching (whereas in control conditions they saw the food being hidden or moved). At the same time, subordinates always saw the entire baiting procedure and could monitor the visual access of their dominant competitor as well. If subordinates were sensitive to what dominants did or did not see during baiting, they should have preferentially approached and retrieved the food that dominants had not seen hidden or moved. This is what they did in experiment 1 when dominants were either uninformed or misinformed about the food's location. In experiment 2 subordinates recognized, and adjusted their behaviour accordingly, when the dominant individual who witnessed the hiding was replaced with another dominant individual who had not witnessed it, thus demonstrating their ability to keep track of precisely who has witnessed what. In experiment 3 subordinates did not choose consistently between two pieces of hidden food, one of which dominants had seen hidden and one of which they had not seen hidden. However, their failure in this experiment was likely to be due to the changed nature of the competition under these circumstances and not to a failure of social-cognitive skills. These findings suggest that at least in some situations (i.e. competition with conspecifics) chimpanzees know what conspecifics have and have not seen (do and do not know), and that they use this information to devise effective social-cognitive strategies. Copyright 2001 The Association for the Study of Animal Behaviour.

We report a series of experiments on social problem solving in chimpanzees, Pan troglodytes. In each experiment a subordinate and a dominant individual were put into competition over two pieces of food. In all experiments dominants obtained virtually all of the foods to which they had good visual and physical access. However, subordinates were successful quite often in three situations in which they had better visual access to the food than the dominant, for example, when the food was positioned so that only the subordinate (and not the dominant) could see it. In some cases, the subordinate might have been monitoring the behaviour of the dominant directly and simply avoided the food that the dominant was moving towards (which just happened to be the one it could see). In other cases, however, we ruled out this possibility by giving subordinates a small headstart and forcing them to make their choice (to go to the food that both competitors could see, or the food that only they could see) before the dominant was released into the area. Together with other recent studies, the present investigation suggests that chimpanzees know what conspecifics can and cannot see, and, furthermore, that they use this knowledge to devise effective social-cognitive strategies in naturally occurring food competition situations. Copyright 2000 The Association for the Study of Animal Behaviour.

Two experiments on chimpanzee gaze following are reported. In the first, chimpanzee subjects watched as a human experimenter looked around various types of barriers. The subjects looked around each of the barriers more when the human had done so than in a control condition (in which the human looked in another direction). In the second experiment, chimpanzees watched as a human looked towards the back of their cage. As they turned to follow the human's gaze a distractor object was presented. The chimpanzees looked at the distractor while still following the human's gaze to the back of the cage. These two experiments effectively disconfirm the low-level model of chimpanzee gaze following in which it is claimed that upon seeing another animate being's gaze direction chimpanzees simply turn in that direction and look around for something interesting. Rather, they support the hypothesis that chimpanzees follow the gaze direction of other animate beings geometrically to specific locations, in much the same way as human infants. The degree to which chimpanzees have a mentalistic interpretation of the gaze and/or visual experience of others is still an open question. Copyright 1999 The Association for the Study of Animal Behaviour.

Individuals from five primate species were tested experimentally for their ability to follow the visual gaze of conspecifics to an outside object. Subjects were from captive social groups of chimpanzees, Pan troglodytes, sooty mangabeys, Cercocebus atys torquatus, rhesus macaques, Macaca mulatta, stumptail macaques, M. arctoides, and pigtail macaques, M. nemestrina. Experimental trials consisted of an experimenter inducing one individual to look at food being displayed, and then observing the reaction of another individual (the subject) that was looking at that individual (not the food). Control trials consisted of an experimenter displaying the food in an identical manner when the subject was alone. Individuals from all species reliably followed the gaze of conspecifics, looking to the food about 80% of the time in experimental trials, compared with about 20% of the time in control trials. Results are discussed in terms of both the proximate mechanisms that might be involved and the adaptive functions that might be served by gaze-following. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.