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. Children and four puppets were allocated to novel groups. Two of these puppets (either in-group or out-group members) then told children a group secret and urged them not to disclose the secret. Another puppet (not assigned to either group) then bribed children with stickers to tell the secret. Across ages, children were significantly less likely to reveal the secret in the in-group condition than in the out-group condition. Thus, even young children are willing to pay a cost to be loyal to their group.

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. Two members of the losing group then spoke. The disloyal individual said she wanted to win and therefore would join the other group. The loyal individual said she also wanted to win but would stay with her group. Children were then asked five forced-choice questions about these two individuals' niceness, trustworthiness, morality, and deservingness of a reward. The 5-year-olds preferred the loyal person across all questions; results for the 4-year-olds were considerably weaker but in the same direction. The second experiment investigated the direction of the effect in 5-year-olds. In this experiment, children answered questions about either a loyal individual, a disloyal individual, or a neutral individual. Children rated both the loyal and neutral individuals more positively than the disloyal individual across a number of measures. Thus, whereas disloyal behavior is evaluated unfavorably by children, loyal behavior is the expected norm. These results suggest that, at least from 5 years of age, children understand that belonging to a group entails certain commitments. This marks an important step in their own ability to negotiate belonging and become trustworthy and reliable members of their social groups.

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. Children (n = 96) watched puppets representing their ingroup vs. outgroup members commit either a mild or a severe transgression. After the mild transgression, children tattled on both groups equally often. After the severe transgression, however, they were significantly less likely to blow the whistle on their ingroup than on the outgroup. These results suggest that children have a strong tendency to act on their moral concerns, but can adjust their behavior according to their group's need: When much is at stake for the ingroup (i.e., after a severe moral transgression), children's behavior is more likely to be guided by loyalty.

Human beings have remarkable skills of self-control, but the evolutionary origins of these skills are unknown. Here we compare children at 3 and 6 years of age with one of humans' two nearest relatives, chimpanzees, on a battery of reactivity and selfcontrol tasks. Three-year-old children and chimpanzees were very similar in their abilities to resist an impulse for immediate gratification, repeat a previously successful action, attend to a distracting noise, and quit in the face of repeated failure. Sixyear-old children were more skillful than either 3-year-olds or chimpanzees at controlling their impulses. These results suggest that humans' most fundamental skills of self-control -as part of the overall decision-making process -are a part of their general great ape heritage, and that their species-unique skills of self-control begin at around the age at which many children begin formal schooling. Research highlights• The first study to investigate the evolutionary bases, as well as the developmental changes, of humans' self-regulatory skills.• Broad comparison of children at 3 and 6 years of age with one of humans' two nearest relatives, chimpanzees, on a variety of reactivity and self-control tasks.• Six-year-old children showed better self-control than either 3-year-old children or chimpanzees.• The origins of human self-control lie within our general primate heritage, but uniquely human processes of self-control emerge roughly at school age.