Material Benefits Crowd Out Moralistic Punishment.

Across four experiments with U.S.-based online participants ( = 1,495 adults), I found that paying people to engage in moralistic punishment reduces their willingness to do so. In an economic game with real stakes, providing a monetary bonus for engaging in third-party punishment of unfair offers nearly cut participants' willingness to do so in half. In judgments of hypothetical transgressions, participants viewed punishers who accepted payment as having worse character and rated the punishers' punitive actions as less morally acceptable. Willingness to engage in punishment was restored if participants were offered large enough payments or were told that punishment accompanied by payment still signals moral virtue. Data were consistent with a signal-corruption mechanism whereby payment interferes with the prosocial signal that moralistic punishment provides about a punisher's motives. These findings have implications for the cultural evolution of punishment and suggest that understanding perpetrators' sociomoral incentives is essential to implementing conflict-reduction policies.