Children's collaboration induces fairness rather than generosity.

Children across diverse societies reject resource allocations that place them at a disadvantage (disadvantageous inequity aversion; DI). In certain societies, older children also reject advantageous allocations (advantageous inequity aversion; AI). Other work demonstrates that after collaboration, children reduce inequity by sharing. However, it is unknown whether collaboration leads to greater sharing because it encourages prosociality (Generosity Hypothesis) or because collaboration elicits stronger equitable tendencies (Equity Hypothesis). Here we use measures of inequity aversion that can disambiguate between these hypotheses. We tested 7- to 13-year-old children from rural India, a population that has shown DI but not AI, and 4- to 10-year-old children from rural Canada, a population that shows both AI and DI. Pairs of children worked either collaboratively or in parallel obtaining candy that was then used in a test of DI and AI. Results showed that in both societies collaboration did not encourage children to accept DI offers, providing evidence against the Generosity Hypothesis. However, in both societies older children demonstrated AI after collaboration but not after parallel work. For children in India AI emerged in ages where it had not been previously observed and children in Canada showed AI during early middle childhood. This suggests that collaboration can induce a willingness to sacrifice an advantage to achieve equity, consistent with the Equity Hypothesis.