Gratitude promotes prosocial behavior even in uncertain situation.

Gratitude is pivotal in promoting and maintaining prosocial interactions in human society. However, it is unclear whether the prosocial function of gratitude can be observed even in situations of uncertainty about whether one can provide benefits to others. Here, we examined whether gratitude promotes prosocial behavior in uncertain situations. Participants (N = 60) were randomly assigned to either a gratitude or neutral group. Following the emotion-induced manipulation, we examined whether participants would choose a non-unique resource when selecting one of four resources (one unique and three non-unique) to leave the choice to the follower. This represented an uncertain situation in which choosing a non-unique resource does not necessarily mean the follower will choose the unique one. Results showed that participants in the gratitude group were more likely to choose non-unique resources than those in the neutral group, suggesting that gratitude promotes prosocial behavior even in uncertain situations. Our findings indicate that gratitude is widely prevalent as a lubricant for interpersonal and cooperative relationships in human society.