The developmental roots of fairness: infants' reactions to equal and unequal distributions of resources.

The problem of how to distribute available resources among members of a group is a central aspect of social life. Adults react negatively to inequitable distributions and several studies have reported negative reactions to inequity also in non-human primates and dogs. We report two experiments on infants' reactions to equal and unequal distributions. In two experiments, infants' looking times and manual choices provide, for the first time, converging evidence suggesting that infants aged 12 to 18 months (mean age 16 months) attend to the outcomes of distributive actions to evaluate agents' actions and to reason about agents' dispositions. The results provide support for recent theoretical proposals on the developmental roots of social evaluation skills and a sense of fairness.