by Xiang Xiang Liew

Created on: April 15, 2008

Is violent behavior in humans caused by innate or environmental factors? The answer has important implications in the efforts to combat the rising levels of aggressive behavior in today's society. If violent behavior is innate, there may be little we can do to reduce aggression levels; on the other hand, if it is caused by external factors, then we might be able to reduce aggression by changing the environment.

It is a widespread assumption that biological factors are a major influence on violent behavior, specifically, that testosterone causes aggression. There have been many empirical studies supporting this theory. However, many of them are animal studies, so we need to be careful about generalizing the results to humans. Of course, there are also studies on testosterone involving humans. One example is a correlation involving American war veterans: the higher their testosterone levels, the more likely they were to have a violent history. However, since this was a correlation, we can't really establish a cause-and-effect relationship. There was also a correlational study which seemed to show that men in prison for aggressive crimes were more likely to have an extra Y chromosome. For a while this provided support for the opinion that we should identify potential criminals' based on their genes and put them under observation. Naturally, there was much debate around the matter until the study of a control group showed that non-aggressive males had the same ratio of XYY chromosomes as aggressive males. Thus, the theory that the extra Y chromosome increases violent behavior was disproved.

On the other hand, Freudian theory suggests that aggression is innate. Freud theorized that human behavior is largely driven by an unconscious psychological construct called the Id. The Id has an innate desire to be aggressive. Frued further theorized that we have a death instinct called Thanatos, which drives us to destroy others and ultimately ourselves. However, readers should bear in mind that this concept is not widely accepted by psychologists in general. It is also implied that violent behavior might result from ego defense mechanisms, such as displacement, where you displace your feelings of aggression onto a non-threatening target. Freud suggested catharsis as a way of safely getting rid of aggressive wishes. For example, by watching a violent program you indulge in your aggressive desires and therefore you don't feel the need to exhibit violent behavior yourself. However,

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