Are mandatory oaths effective in groups?

Abstract Previous studies have shown that an oath can reduce lying in individual settings. Can it reduce lying in groups, a context where lying is more prevalent? Results from a lab experiment reveal that the impact depends on the incentive structures and procedures. A mandatory oath reduces lying when group members’ payoffs are independent, but only has a marginal effect when payoffs are dependent. Voluntary oath-taking enhances the effectiveness under both incentive structures by fostering intrinsic motivation to keep promises. The findings highlight the importance of peer effects and oath-taking procedures on the effectiveness of an oath in group settings.