Aggression in which harm is inflicted as a means to a desired end is called proactive aggression. Aggression aimed at harming someone for personal gain, attention, or even self-defense fits this definition. If the aggressor believes that there is an easier way to obtain the goal, aggression will not occur. Some researchers call this type of aggression instrumental aggression. Harm that is inflicted for its own sake, in contrast, is reactive aggression. Some researchers call this type of aggres- sion emotional aggression. Reactive aggression is often impulsive, carried out in the heat of the moment. The jealous lover strikes out in rage; fans of rival sports teams go at each other with fists and fury. Reactive aggression, however, can also be calm, cool, and calculating. Revenge, so the saying goes, is a dish best served cold.
Sometimes it is hard to distinguish between proactive and reactive aggression. Why does a frustrated fighter illegally head butt or bite the ear of his opponent— is it a deliberate, sneaky attempt to gain an advantage over a difficult opponent, or does it simply reflect someone losing control and lashing out unthinkingly in frustration? The line between the two types of aggression and motives can some- times be blurry.