Reactive aggression has an underlying emotional component, with harm as its goal. Violence is an outcome of reactive aggression. An increase in both frequency and seriousness of acts of violence has been well documented.
Violence is most prevalent in team contact sports, such as ice hockey, football, and rugby.
Considerable research has been done on spectator violence. The evidence is inconclusive. Spectators do take cues from players, coaches, cheerleaders, and one another. Spectators often derive a sense of social identity and self-esteem from a team. Emulation of favorite players is an element of this identification.