Individual Differences in Theory of Mind Predict Inequity Aversion in Children

Early in human development, children react negatively to receiving less than others, and only later do they show a similar aversion to receiving more. We tested whether theory of mind (ToM) can account for this developmental shift we see in middle childhood. We conducted a face-to-face fairness task that involved a ToM manipulation, measured individual differences in ToM, and collected parent-ratings of children's empathy, a construct related to ToM. We find that greater ToM capacities lead to more rejections of unequal offers, regardless of the direction of inequality, demonstrating that children with greater ToM are more likely to engage in costly compliance with fairness norms. Moreover, drawing attention to mental states sufficiently elicits aversion to advantageous inequity in younger children. These findings contribute to our growing understanding that people's concerns for fairness rely not just on their own thoughts and beliefs but on the thoughts, beliefs, and expectations of others.