We know that we don't know: Children's understanding of common ignorance in a coordination game.

Common ground is the knowledge, beliefs, and suppositions shared between partners in an interaction. Previous research has focused extensively on what partners know they know together, that is, "common knowledge." However, another important aspect of common ground is what partners know they do not know together, that is, "common ignorance.

Young children use imitation communicatively.

There is growing evidence that children imitate not just to learn from others but also to affiliate socially with them. However, although imitation can convey a wealth of affiliative information to others, it is not yet known whether imitators intend for this to be the case. In particular, we do not know whether children imitate communicatively in some contexts, expending extra effort to make sure that the demonstrator sees their imitation.

Showing and giving: from incipient to conventional forms.

Understanding humans' motivation and capacity for social interaction requires understanding communicative gestures. Gestures are one of the earliest means that infants employ to communicate with others, and showing and giving are among the earliest-emerging gestures. However, there are limited data on the processes that lead up to the emergence of conventional showing and giving gestures.

When does it pay to follow the crowd? Children optimize imitation of causally irrelevant actions performed by a majority.

Cultural evolutionary theory posits that human cultural complexity rests on a set of adaptive learning biases that help to guide functionality and optimality in social learning, but this sits in contrast with the commonly held view that children are unselective "over-imitators." Here, we tested whether 4- and 6-year-old children use social learning biases flexibly to fine-tune their copying of irrelevant actions. Children watched a video of a majority demonstrating causally irrelevant actions and a minority demonstrating only causally relevant actions.

Young children share more under time pressure than after a delay.

Adults under time pressure share with others generously, but with more time they act more selfishly. In the current study, we investigated whether young children already operate in this same way, and, if so, whether this changes over the preschool and early school age years. We tested 144 children in three age groups (3-, 5-, and 7-year olds) in a one-shot dictator game: Children were given nine stickers and had the possibility to share stickers with another child who was absent.

Common knowledge that help is needed increases helping behavior in children.

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.

A new look at joint attention and common knowledge.

Everyone agrees that joint attention is a key feature of human social cognition. Yet, despite over 40 years of work and hundreds of publications on this topic, there is still surprisingly little agreement on what exactly joint attention is, and how the jointness in it is achieved. Part of the problem, we propose, is that joint attention is not a single process, but rather it includes a cluster of different cognitive skills and processes, and different researchers focus on different aspects of it.

Communicative eye contact signals a commitment to cooperate for young children.

Making commitments to cooperate facilitates cooperation. There is a long-standing theoretical debate about how promissory obligations come into existence, and whether linguistic acts (such as saying "I promise") are a necessary part of the process. To inform this debate we experimentally investigated whether even minimal, nonverbal behavior can be taken as a commitment to cooperate, as long as it is communicative.

The Whistleblower's Dilemma in Young Children: When Loyalty Trumps Other Moral Concerns.

When a group engages in immoral behavior, group members face the whistleblower's dilemma: the conflict between remaining loyal to the group and standing up for other moral concerns. This study examines the developmental origins of this dilemma by investigating 5-year-olds' whistleblowing on their in- vs. outgroup members' moral transgression.

Selective copying of the majority suggests children are broadly "optimal-" rather than "over-" imitators.

Human children, in contrast to other species, are frequently cast as prolific "over-imitators". However, previous studies of "over-imitation" have overlooked many important real-world social dynamics, and may thus provide an inaccurate account of this seemingly puzzling and potentially maladaptive phenomenon. Here we investigate this topic using a cultural evolutionary approach, focusing particularly on the key adaptive learning strategy of majority-biased copying.

Great apes distinguish true from false beliefs in an interactive helping task.

Understanding the behavior of others in a wide variety of circumstances requires an understanding of their psychological states. Humans' nearest primate relatives, the great apes, understand many psychological states of others, for example, perceptions, goals, and desires. However, so far there is little evidence that they possess the key marker of advanced human social cognition: an understanding of false beliefs.

The Early Emergence of Guilt-Motivated Prosocial Behavior.

Guilt serves vital prosocial functions: It motivates transgressors to make amends, thus restoring damaged relationships. Previous developmental research on guilt has not clearly distinguished it from sympathy for a victim or a tendency to repair damage in general. The authors tested 2- and 3-year-old children (N = 62 and 64, respectively) in a 2 × 2 design, varying whether or not a mishap caused harm to someone and whether children themselves caused that mishap.

What Is a Group? Young Children's Perceptions of Different Types of Groups and Group Entitativity.

To date, developmental research on groups has focused mainly on in-group biases and intergroup relations. However, little is known about children's general understanding of social groups and their perceptions of different forms of group. In this study, 5- to 6-year-old children were asked to evaluate prototypes of four key types of groups: an intimacy group (friends), a task group (people who are collaborating), a social category (people who look alike), and a loose association (people who coincidently meet at a tram stop).

I won't tell: Young children show loyalty to their group by keeping group secrets.

Group loyalty is highly valued. However, little is known about young children's loyal behavior. This study tested whether 4- and 5-year-olds (N=96) remain loyal to their group even when betraying it would be materially advantageous.

The effects of collaboration and minimal-group membership on children's prosocial behavior, liking, affiliation, and trust.

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.

Children draw more affiliative pictures following priming with third-party ostracism.

Humans have a strong need to belong. Thus, when signs of ostracism are detected, adults often feel motivated to affiliate with others in order to reestablish their social connections. This study investigated the importance of affiliation to young children following priming with ostracism.

Young children show the bystander effect in helping situations.

Much research in social psychology has shown that otherwise helpful people often fail to help when bystanders are present. Research in developmental psychology has shown that even very young children help and that the presence of others can actually increase helping in some cases. In the current study, in contrast, 5-year-old children helped an experimenter at very high levels when they were alone but helped significantly less often in the presence of bystanders who were potentially available to help.

Children infer affiliative and status relations from watching others imitate.

We investigated whether young children are able to infer affiliative relations and relative status from observing others' imitative interactions. Children watched videos showing one individual imitating another and were asked about the relationship between those individuals. Experiment 1 showed that 5-year-olds assume that individuals imitate people they like.

Young children create iconic gestures to inform others.

Much is known about young children's use of deictic gestures such as pointing. Much less is known about their use of other types of communicative gestures, especially iconic or symbolic gestures. In particular, it is unknown whether children can create iconic gestures on the spot to inform others.

Limitations to the cultural ratchet effect in young children.

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.

Stick with your group: young children's attitudes about group loyalty.

For adults, loyalty to the group is highly valued, yet little is known about how children evaluate loyalty. We investigated children's attitudes about loyalty in a third-party context. In the first experiment, 4- and 5-year-olds watched a video of two groups competing.

Eighteen-month-olds understand false beliefs in an unexpected-contents task.

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.

Three-year-olds' understanding of the consequences of joint commitments.

Here we investigate the extent of children's understanding of the joint commitments inherent in joint activities. Three-year-old children either made a joint commitment to assemble a puzzle with a puppet partner, or else the child and puppet each assembled their own puzzle. Afterwards, children who had made the joint commitment were more likely to stop and wait for their partner on their way to fetch something, more likely to spontaneously help their partner when needed, and more likely to take over their partner's role when necessary.

Young children help others to achieve their social goals.

From early in development, humans have strong prosocial tendencies. Much research has documented young children's propensity to help others achieve their unfulfilled goals toward physical objects. Yet many of our most common and important goals are social--directed toward other people.

Being mimicked increases prosocial behavior in 18-month-old infants.

Most previous research on imitation in infancy has focused on infants' learning of instrumental actions on objects. This study focused instead on the more social side of imitation, testing whether being mimicked increases prosocial behavior in infants, as it does in adults (van Baaren, Holland, Kawakami, & van Knippenberg, 2004). Eighteen-month-old infants (N = 48) were either mimicked or not by an experimenter; then either that experimenter or a different adult needed help.