Neural basis for egalitarian sharing in five-to six-year-old children

Preferring fair resource distribution reflects human cooperative nature, but its neural correlates in young children are not well known. We investigated the neural mechanism of egalitarian resource sharing in five-to six-year-old children to examine the possibility that early egalitarianism requires behavioral control to inhibit selfish impulses. In Study 1, children participated in a behavioral control task in which they either needed or did not need to inhibit their impulsive behavioral responses in order to quickly press a key. They subsequently allocated their resources to strangers by choosing a 2:2, 3:1, or 4:0 distribution. The activation of the dorsolateral prefrontal (dlpfc) regions was recorded by functional near-infrared spectroscopy measurements. We found that dlpfc regions were activated during cognitive tasks involving behavioral control and also during the equal, but not the more selfish, allocations. There was no difference among these allocations. The results did not show evidence of an ego depletion effect on children's sharing behavior, which predicts that children will share less after their behavioral control is taxed in a cognitive task (i.e., their self-control resource depleted). Study 2 showed no activation of the dlpfc regions during third-party equal allocations in which there was no conflict between fairness and self-interest in the distribution of resources. Overall, we showed that costly equal sharing in young children relates to the activation of dlpfc regions. These results suggest that costly equal allocation has a common neural basis with behavioral control in five-to six-year-old children, implying that early egalitarian sharing requires dealing with conflicts between maximizing self-interest and following moral norms.