Supplementary material from "The development of bribe-taking aversion in four societies"

Large scale cooperation between genetic strangers, albeit surprising, is viable thanks to social institutions that punish antisocial behavior and reward prosocial behavior. Nevertheless, an anti-egalitarian, self-serving aspect of human sociality—corruption—often threatens institutions’ integrity. While much is known about how prosocial reciprocity emerges in different settings, human preferences against corrupt reciprocity are poorly understood. Here we test how one of such preferences, aversion to taking bribes, develops in 3- to 11-year-old children (N = 697) from four societies that differ in their corruption and interdependence levels: Norway, Japan, USA, and Italy. To examine whether bribe rejection is grounded in basic egalitarian motives, we also test children’s inequity aversion. We find that inequity aversion is dissociated from bribe-taking aversion: Whereas humans’ rejection of unequal allocations emerges across settings by age 10 (and, in some settings and studies, as early as age 3), we find that bribe rejection is present during late childhood in some contexts only. We discuss these findings while considering questions about culture’s role in shaping preferences against human selfishness.