Angry co-rumination increases aggressive behavior.

Objective: Angry rumination is the prolonged thinking about provoking events and their causes and consequences.Angry rumination increases aggression.Although people often ruminate individually, they also do so with others, which is known as co-rumination.Co-rumination about anger-inducing situations and its potential influence on aggressive behavior have not been studied.Method: Two experiments tested the hypothesis that communally reliving a provoking incident with another person via discussion would increase aggression.Results: In Experiment 1, co-rumination produced higher levels of aggression relative to both individual rumination and distraction.Experiment 2 replicated the aggression-augmenting effect of co-rumination for both interpersonal and intergroup contexts.When the provocation was at the intergroup level, being in the intergroup context led to more ingroup affiliative tendencies and hostile feelings than when the provocation was interpersonal in nature.Ingroup fusion occurred among participants who were insulted at the intergroup level and subsequently co-ruminated.Conclusions: The findings suggest that using angry co-rumination to process anger-inducing situations may lead to increased aggression.Future research could examine the processes through which angry co-rumination increases aggression. Public Significance StatementPeople sometimes rehash times when they were angry, which is known as angry rumination.Sometimes, they do this with other people.Our experiments showed that people who ruminated with other people were more aggressive than people who ruminated by themselves.