Helping the ingroup versus harming the outgroup: Evidence from morality-based groups

The discrepancy between ingroup favoritism and outgroup hostility is well established in social psychology. Under which conditions does "ingroup love" turn into "outgroup hate"? Studies with natural groups suggest that when group membership is based on (dis)similarity of moral beliefs, people are willing to not only help the ingroup, but also harm the outgroup. The key limitation of these studies is that the use of natural groups confounds the effects of shared morality with the history of intergroup relations. We tested the effect of morality-based group membership on intergroup behavior using artificial groups that help disentangling these effects. We used the recently developed Intergroup Parochial and Universal Cooperation (IPUC) game which differentiates between behavioral options of weak parochialism (helping the ingroup), strong parochialism (harming the outgroup), universal cooperation (helping both groups), and egoism (profiting individually). In three preregistered experiments, we find that morality-based groups exhibit less egoism and more universal cooperation than non-morality-based groups. We also find some evidence of stronger ingroup favoritism in morality-based groups, but no evidence of stronger outgroup hostility. Stronger ingroup favoritism in morality-based groups is driven by expectations from the ingroup, but not the outgroup. These findings contradict earlier evidence from natural groups and suggest that (dis)similarity of moral beliefs is not sufficient to cross the boundary between "ingroup love" and "outgroup hate".