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.