Young children endorse fairness, but often don't practice what they preach

This phenomenon has rarely been explored in the context of a single study. Using a novel approach, the researchers presented clear evidence of this discrepancy and go on to examine possible explanations for its diminution with age. In one part of the study, three-to-eight-year-old children readily stated that they themselves should share equally, asserted that others should as well, and predicted that others had shared equally with them. Nevertheless, children failed to engage in equal sharing until ages seven to eight.

In another part of the study, seven-to-eight-year-olds correctly predicted that they would share equally, and three-to-six-year-olds correctly predicted that they would favor themselves, ruling out a failure-of-willpower explanation for younger children's behavior. Similarly, a test of inhibitory control failed to explain the shift with age toward adherence to the endorsed norm. The data suggest that, although three-year-olds know the norm of equal sharing, the weight that children attach to this norm increases with age when sharing involves a cost to the self.