The linguist George Lakoff has written extensively about the metaphors that shape human languages. He points out that we often talk about abstract concepts and emotions using metaphors to physical objects. For example, we have a lot of language that treats the emotion anger as if it were heated fluid in a container. We might say, "John felt the pressure building up inside of him until he finally blew his top."
This metaphor for anger is an effective way of talking about anger. It also reflects a common belief about the way anger works.
There is a general assumption that anger and frustration build up inside of us and that they can come to be let out in an energetic fury. Based on this metaphor, people often believe that they can prevent themselves from blowing up by letting off a little steam (to use the metaphor some more...). For example, you might issue a primal scream or hit a punching bag to release some of your anger. People assume that this process, called catharsis, is an effective way of allowing your anger to bubble over to the surface.
Unfortunately, it doesn't work.
Brad Bushman, Roy Baumeister, and Angela Stack looked at this issue in a 1999 paper in the Journal of Personality and Social Psychology. They manipulated people's anger in a laboratory experiment. Participants wrote an essay on a sensitive topic and then told people that their essay would be evaluated by a peer. In actuality, the feedback they were given was assigned by the experimenter. In the high anger condition, people were told that their essay was poor and was "one of the worst they had ever read." This feedback is known to make people upset.
Soon afterward, some people were given the opportunity to punch a punching bag for two minutes. Others did nothing at all. Then, a short time later, everyone played a game against a (fictional) opponent. Over the course of the game, participants had a chance to punish their opponent with blasts of noise. The loudness of the noise and the length of the noise have been used as measures of aggression.
The belief in catharsis would predict that people would be less aggressive if they had a chance to punch a punching bag after getting angry than if they had to sit and do nothing after getting angry. Instead, the opposite result was obtained. The people who punched the punching bag were actually more aggressive than the people who did nothing.
What is going on here?
Punching a punching bag makes a connection for people between anger and aggression. That is, it reinforces the link between being angry and acting in an aggressive manner. These connections between emotional states and behavior are an important part of what determines the way we act.
So, these results suggest that it is better to take a few moments and do nothing when you are angry. Sitting quietly or meditating is a much more effective way of calming yourself down than attempting to let off steam through another aggressive act.