Toddlers' interventions toward fair and unfair individuals.

Cooperative societies rely on reward and punishment for norm enforcement. We examined the developmental origin of these interventions in the context of distributive fairness: past research has shown that infants expect resources to be distributed fairly, prefer to interact with fair distributors, and evaluate others based on their fair and unfair resource allocations. In order to determine whether infants would intervene in third-party resource distributions by use of reward and punishment we developed a novel task. Sixteen-month-old infants were taught that one side of a touch screen produces reward (vocal statements expressing praise; giving a cookie), whereas the other side produces punishment when touched (vocal statements expressing admonishment; taking away a cookie). After watching videos in which one actor distributed resources fairly and another actor distributed resources unfairly, participants' screen touches on the reward and punishment panels while the fair and unfair distributors appeared on screen were recorded. Infants touched the reward side significantly more than the punishment side when presented with the fair distributor but touched the screen sides equally when the unfair distributor was shown. Control experiments revealed no evidence of reward or punishment when infants saw food items they liked and disliked, or individuals uninvolved in the resource distribution events. These results provide the earliest evidence that infants are able to spontaneously intervene in socio-moral situations by rewarding positive actions.

Developmental Differences in Infants' Fairness Expectations From 6 to 15 Months of Age.

The present research investigated the developmental trajectory of infants' fairness expectations from 6 to 15 months of age (N = 150). Findings revealed a developmental transition in infants' fairness expectations between 6 and 12 months, as indicated by enhanced visual attention to unfair outcomes of resource distribution events (a 3:1 distribution) relative to fair outcomes (a 2:2 distribution). The onset of naturalistic sharing behavior predicted infants' fairness expectations at transitional ages. Beyond this period of developmental transition, the presence of siblings and infants' prompted giving behavior predicted individual differences in infants' fairness concerns. These results provide evidence for the role of experience in the acquisition of fairness expectations and reveal early individual differences in such expectations.

Nature and nurture in own-race face processing.

A standard visual preference task was used to examine 3-month-olds' looking times at own-race versus other-race faces as a function of environmental exposure to faces from the two categories. Participants were Caucasian infants living in a Caucasian environment, African infants living in an African environment, and African infants living in a predominantly Caucasian environment. The results indicate that preference for own-race faces is present as early as 3 months of age, but that this preference results from exposure to the prototypical facial environment.