Outcome uncertainty diminishes third‐party intervention, while impact uncertainty yields divergent effects: Punishment wanes, help endures

Abstract Third‐party intervention (TPI), where unaffected observers invest their resources either to punish selfishness (third‐party punishment, TPP) or to help those treated unfairly (third‐party help, TPH), plays a crucial role in upholding social norms by actively restoring fairness. However, uncertainty pervades human social life, raising questions about people's willingness to intervene when the fairness of a situation or the impact of their intervention on others is unclear. Our research investigates how uncertainty, both in outcomes and impacts, influences TPI strategies, including TPP and TPH. We found that outcome uncertainty generally reduces willingness to engage in both TPP and TPH. In contrast, impact uncertainty has a nuanced effect across TPI strategies, diminishing the likelihood of TPP while retaining the inclination towards TPH. Our findings on the effects of uncertainty on TPH extend beyond existing research on uncertainty and prosocial behaviour. This research deepens our understanding of normative decision‐making and offers practical insights into managing social behaviours in real‐world contexts characterised by uncertainty.