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What is aggression?

Aggression has been defined as physical or verbal behavior intended to hurt someone.

What are some theories of aggression?

Instinct Theory

Instinct theory as put forth by Freud and Lorenz, posited that aggression was a natural adaptive human instinct. Evolutionary psychologists have noted that aggression was a strategy for gaining resources, eliminating rivals, and improving ones chances of genetic survival ((Buss and Shackleford, 1997)).

Neurological Basis


Arousal of the amygdala can cause increased aggression in humans. In a human experiment in which a woman's amygdala was electrically stimulated she threw a guitar at her psychologist in a fit of rage ((Moyer, 1976, 1983)).

Prefrontal Cortex

The prefrontal cortex acts as an inhibitory mechanism. It is responsible for constrained and appropriate behavior in social situations. It has been found that the prefrontal cortex in individuals with antisocial behavior is 15 percent smaller than those without, which may be responsible for their abnormally aggressive behavior.

Genetic Influence

Animals can be bred to be aggressive which shows that there may be some genetic component. It has also been found that a person's temperament usually endures throughout their life ((Larsen & Diener, 1986)).

Chemical Factors


Testosterone has been shown to be linked with aggressive behavior. After the age of 25, both testosterone levels and acts of violent crimes decrease greatly.


Alcohol has been shown to increase aggression especially when provoked. Alcohol disinhibits an individual. This can be compared to the long-term disinhibition that occurs in individuals with antisocial behavior due to an underdeveloped prefrontal cortex. Over half of all acts of rape occur while the aggressor is under the influence of alcohol.

What causes Aggression?






Reducing Aggression

Cathartic Model

It has been postulated that pent up emotions can fester inside of a person eventually leading the individual to burst out emotionally which can come at an inopportune time. Thus, encouraging individuals to release their emotions may seem beneficial. Quite the contrary has been found in relation to aggression. Aggression caused from sexual arousal tends to increase as sexual arousal increases. Viewing violent acts in person or on television also increases violent behavior ((Arms & others, 1979; Russell, 1983)). Nations that go to war also see an increase in homicides after the war is over ((Archer & Gartner, 1976)). Instead, it has been found that doing nothing at all can be more effective in reducing aggression than doing something in order to "blow off steam" ((Bushman, 2002)).

Social Learning

Encouraging positive acts as opposed to punishing negative acts can be seen as a more effective way to prevent aggression. Physical punishment of aggression can be seen as hypocritical because it is an aggressive act being used in order to prevent or deter an aggressive act. Ignoring aggressive behavior and rewarding nonaggressive behavior in children is more effective in decreasing aggressive acts than by just punishing aggressive acts alone ((Hamblin & others, 1969)).

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