Human infants can override possessive tendencies to share valued items with others.

Possessiveness toward objects and sharing are competing tendencies that influence dyadic and group interactions within the primate lineage. A distinctive form of sharing in adult Homo sapiens involves active giving of high-valued possessions to others, without an immediate reciprocal benefit. In two Experiments with 19-month-old human infants (N = 96), we found that despite measurable possessive behavior toward their own personal objects (favorite toy, bottle), infants spontaneously gave these items to a begging stranger. Moreover, human infants exhibited this behavior across different types of objects that are relevant to theory (personal objects, sweet food, and common objects)-showing flexible generalizability not evidenced in non-human primates. We combined these data with a previous dataset, yielding a large sample of infants (N = 192), and identified sociocultural factors that may calibrate young infants' sharing of objects with others. The current findings show a proclivity that is rare or absent in our closest living relatives-the capacity to override possessive behavior toward personally valued objects by sharing those same desired objects with others.

Altruistic food sharing behavior by human infants after a hunger manipulation.

Altruistic behavior entails giving valuable benefits to others while incurring a personal cost. A distinctively human form of altruistic behavior involves handing nutritious food to needy strangers, even when one desires the food. Engaging in altruistic food transfer, instead of keeping the food, is costly, because it reduces the caloric intake of the benefactor vis-à-vis the beneficiary. Human adults engage in this form of altruistic behavior during times of war and famine, when giving food to others threatens one's own survival. Our closest living primate relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), exhibit notable constraints on the proclivity to engage in such food transfer (particularly chimpanzees), although they share many social-cognitive commonalities with humans. Here we show that in a nonverbal test, 19-month-old human infants repeatedly and spontaneously transferred high-value, nutritious natural food to a stranger (Experiment 1) and more critically, did so after an experimental manipulation that imposed a feeding delay (Experiment 2), which increased their own motivation to eat the food. Social experience variables moderated the expression of this infant altruistic behavior, suggesting malleability.

Threats to social identity can trigger social deviance.

We hypothesized that threats to people's social (i.e., group) identity can trigger deviant attitudes and behaviors. A correlational study and five experiments showed that experiencing or recalling situations associated with the devaluation of a social identity caused participants to endorse or engage in deviant actions, including stealing, cheating, and lying. The effect was driven by the tendency to construe social identity threats not as isolated incidents but as symbolic of the continuing devaluation and disrespectful treatment of one's group. Supplementing sociological approaches to deviance and delinquency, the results suggest the relevance and utility of a social-psychological account.