When we feel ostracised, we're more likely to behave aggressively. Previous research suggests that vengeance on those who we think have wronged us can be driven by a sense of justice, and may activate neural reward centres. But being ostracised can also lead to generalised aggression, even lashing out at unrelated people, so there seems to be more going on. In new research in the Journal of Personality and Social Psychology, David Chester and C. Nathan DeWall tested the idea that social rejection, by making us feel wounded and unwanted, triggers a need to repair our mood by whatever means available, including through the satisfaction of causing harm to those who have made us suffer. They found that aggression can indeed be a viable method of mood repair....