Give one child one piece of candy and another four. The child receiving less may immediately protest. But reverse the rewards, and the favored child may happily accept.
These reactions represent two forms of fairness. Disadvantageous inequity aversion means rejecting a deal because someone else receives more. Advantageous inequity aversion means sacrificing your own larger reward so the other person is treated equally.
A major experiment tested children aged four to fifteen in 866 pairs across Canada, India, Mexico, Peru, Senegal, Uganda and the United States. Children in every society eventually rejected allocations that left them worse off. But rejecting an unfair advantage emerged later and in only three societies—Canada, Uganda and the United States. Cross-cultural study
Well supported: children’s sense of fairness has multiple components. Resistance to receiving less develops widely across cultures, while willingness to surrender an advantage varies much more with age and society.
Plausible but debated: natural selection may have favored sensitivity to being shortchanged because individuals who tolerated exploitation lost resources and status. Fairness toward others may have developed later as humans became increasingly dependent on cooperation, reputation and trustworthy partners.
However, the evolutionary interpretation is not settled. Children learn from parents, peers, institutions and local sharing customs. Rejecting extra candy in an experiment may also reflect concern about rules or reputation—not an inherited desire for equality.
Human fairness may therefore begin with a self-protective cry—“Don’t give me less!” Culture then helps determine whether it grows into the more demanding principle: “Don’t give me more, either.”
