Psychology - The role of hormones and aggression


Male aggression and testosterone

In almost every culture males are far more aggressive than females. Could this be because they have more testosterone? Testosterone is a male sex hormone. Hormones are chemicals produced by the body that send messages to organs of the body via the bloodstream. 

Testosterone is secreted by the adrenal glands and testes and is needed to produce sperm, develop male reproductive organs and produce male features, such as facial hair and a deep voice. Women also have testosterone, but males produce up to 10mg of testosterone every day, which is ten times more than a woman. 

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Aggression in animals

Psychologists have researched the role of testosterone in aggression by studying animals. Injecting animals with testosterone or removing the testes leads to increased or decreased levels of aggression.

Castrating a male animal lowers its testosterone levels. This makes the animal less aggressive. But if the same animal is then injected with testosterone its aggression is restored to a level similar to that before the castration.

This is strong evidence that testosterone is responsible for aggression. But would we be able to say the same about humans? We would not be able to test this in a psychological study, as it is not ethical to deliberately increase testosterone in men to study aggression levels.

Instead, psychologists use animals, although they are naturally different from humans in many ways, both physically and behaviourally. Aggression in humans is less instinctive than in animals; humans consider the consequences of their actions and are more reasoned in their actions than animals.

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Aggression in humans

Psychologists can take blood from humans to see what level of testosterone they have and compare this to how aggressive they feel or act. Some correlation studies (studies that see if there is a link between two variables) have found a relationship between high testosterone levels and questionnaire results showing greater reported aggression. However, it is not certain whether testosterone causes increased aggression or aggression causes increased testosterone. 

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Evaluating the role of testosterone on aggression


  • In animals, there is a clear cause and effect relationship between testosterone and aggression.
  • Human studies show a relationship between aggression and testosterone in correlation studies. 


  • Not all humans with high testosterone levels are aggressive. Some have greater sporting ability or are driven in their careers. Testosterone creates a drive, but this need not be a violent one.
  • Correlation and animal studies have weaknesses. Animal studies may not apply to humans, and correlation studies just look for relationships and are not direct evidence.
  • If testosterone is the cause of aggressive behaviour, why are some woman more violent than men, and why aren't all men violent?
  • This explanation of aggression completely ignores the huge impact of upbringing and social circumstances on our behaviour. 
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Very informative cards which could easily be used by students who prefer visual learning styles.

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