Psychology UNIT TWO Aggression


Biological Explanation

Aggression: behaviour aimed at harming others

Hormones: chemicals released by our endocrine system that affect how our bodies function and how we behave. Males are more aggressive than females, so testosterone is thought to be a cause of aggression. Violent criminals have higher levels of testosterone than non-violent.

Chromosomes: the parts of each cell that carry the genetic information from our parents. There is a higher than normal proportion of men with an extra Y chromosome amongst violent offenders. Therefore, the XYY chromosome abnormality is a cause of aggression.

Limbic system: the part of the brain that causes aggressive behaviour

Prefrontal cortex: the very front of the brain, invovled in social and moral behaviour

Brain disease: damage to the brain caused by illness or trauma. Brain disease affecting either the limbic system or the prefrontal cortex may lead to abnormally high levels of aggression.

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Biological- Charles Whitman and Raine

Charles Whitman

In 1966, Charles Whitman climbed up the clock tower at the University of Texas and shot 12 people with a high-powered rifle. This was the last of a series of very aggressive acts he committed throughout his adult life. After he was killed by the Texas Rangers, a post mortem revealed he had a tumour pressing on the part of his brain that causes aggressive behaviour, the limbic system.


Aim: To investigate the brains of murderers

Method: Researchers gave 41 murderers in California a PET scan and compared them with a similar group of non-murderers

Results: There were some differences, for example activity in the prefrontal cortex of the murderers was lower than in non-murderers.

Conclusion: When the pre-frontal cortex (and other parts of the brain) is not working normally, it can lead to people commtting violent crimes.

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Biological- Young et al and Evaluation

Aim: To see what effect hormones have on aggressive behaviour.

Method: Young injected pregnant rhesus monkeys with testosterone and observed the levels of aggression in their offspring as they matured.

Results: The high levels of testosterone during pregnancy made the females grow up to behave like male monkeys- they engaged in rough and tumble play and challenged the males for dominance in their troop.

Conclusion: Testosterone does seem to play a vital part in aggressive behaviour.


  • studies used animals- could be unethical
  • population validity, all people in California
  • case study cannot be generalised
  • reductionist as it does not consider the environmental factors
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Psychodynamic Explanation

This was proposed by Freud. He suggested we have an unconcious drive that causes aggressive behaviour. Our aggressive behaviour is called by an internal force (instinct) called Thanatos. It is this that drives us towards self-destruction. All the time this instinct is building up inside us, it creates pressure, until sooner or later we cannot control it and it makes us do something aggressive.

Everyone has the instinct towards self-destruction and we protect ourselves using ego-defence mechanisms. These redirect our aggression outwardly, so rather than harming ourselves we will harm others or redirect our energy into something safe.

Displacement: being aggressive towards other people

Sublimation: channelling our aggression into other acceptable activites, eg boxing.

Dollard argued that Freud was wrong to suggest this aggressive instinct would suddenly spill over into aggressive behaviour for no reason. They said that we need something to trigger it off (loaded gun analogy). Dollard et al therefore proposed the frustration-aggression explanation, stating that as well as having an aggressive instinct we need something to frustrate us to release  our aggressive behaviour. 

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Psychodynamic- Barker and Megargee and Mendelsohn

Aim: to see the effect of frustration on aggressive behaviour

Method: Children were kept waiting a long time before being allowed to play in a room full of attractive toys. Their behaviour was then observed.

Results: The children were more aggressive and destructive than ther children who had not been frustrated by being kept waiting.

Conclusion: Being frustrated leads to an increase in aggression.

Aim: to see if there is a link between aggression and personality type.

Method: people who had committed brutally aggressive crimes were interviewed and given personality tests.

Results: these criminals seemed to have been 'over controlled' and repressed their anger until it built up to such an extent that it just exploded following something really trivial

Conclusion: If people don't let their aggressive instinct out in small amounts from time to time, the build up will be so great they won't be able to control it.

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Psychodynamic Evaluation

  • if all the participants of a study are violent offenders, it cannot be generalised to the rest of the population
  • people can lie in interviews and personality tests to give social desirable traits
  • it is difficult to standardise frustration, what is frustrating for one person may not be for the other
  • again is based on unconscious thoughts and feelings so is difficult to investigate
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Social Learning Theory

This theory suggests that aggressive behaviour is caused by people seeing how other people behave and copying it. As people encounter new situations, they look to other people for guidance as to how they should act- this happens mostly in children. This is known as 'imitation'.

The theory stresses the importance of vicarious learning- we can learn new ways to behave just by watching what other people are doing. This is most clearly demonstrated by young chukdren who swear, as they only do it because they have heard someone else do it. 

Children are more likely to imitate role models if they are similar (e.g the same age or sex), attractive, powerful or caring. It is most important that they see the model being reinforced for doing something, as if they see someone being reingorced for being aggressive, they expect to be reinforced for the same behaviour- like when they see a hero hitting a villain.

People monitor their own behaviour, as reinforcement can come from the inside in the form of pride or self satisfaction. If something feels good, it will strengthen the behaviour. 

Punishment can often mean that if a child is hit by their parent, they will then learn to hit others.

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Social Learning- Bandura and Liebert and Baron

Aim: to find out if 3-6 year old children would imiate the aggressive behaviour they see role models performing towards an inflatable bobo doll.

Method: 96 children were divided into four groups, three of which were shown something throwing, kicking and punching the bobo doll. Their behaviour was then observed.

Results: the children who watched teh videos showed more aggressive behaviour.

Conclusion: Children will copy how they see others behave.

Aim: to see if watching violent TV programmes affects aggressive behaviour in children

Method: one group of children was shown a violent TV progamme and the other was shown an equally exciting sporting event. The two groups were then observed.

Results: the group who had watched the violent programme were more aggressive.

Conclusion: watching violence on TV increases the level of aggression in children.

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Social Learning- Charlton and Evaluation

Aim: to see if the introduction of TV (and therefore aggressive role models) to a community would affect the aggressive behaviour of children.

Method: for two years after the island of St. Helena first received TV transmissions, the behaviour of the children was monitored.

Results: the children did not show an increase in aggressive behaviour after TV was introduced compared to before it was introduced

Conclusion: watching aggressive role models will not be sufficient to make children copy aggressive behaviour


  • lab based studies lack ecological validity and don't reflect real life
  • witnessing aggression may not have an effect if the child's parents are present to explain why such behaviour is wrong (parents are more influential)
  • contradictory evidence ^ that has high ecological validity as it was over a 2 year period and the children's behaviour was recorded in their natural surroundings
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Biological- Reducing Aggression

Drugs- the drug Ritalin, which stimulates activity in the brain, reduces the aggressive behaviour caused by ADHD. This is because it stimulates the prefrontal cortex, so it is able to control the aggressive instincts caused by the limbic system.

Psychosurgery- this involves removing or destroying the part of the brain that is not functioning properly. This may be done by inserting a probe to a very precise location and heating up the end to kill the nerves. It is usally part of the limbic system that is destroyed. This is used as a last resort because one brain tissue has been destroyed it will not grow back, so if a mistake is made the consequences are permanent. 

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Psychodynamic- Reducing Aggression

One method is to redirect our aggressive instncts into other safe activities using ego defence mechanisms scuh as displacement and sublimation.

The other is to release them through catharsis. Playwrights in ancient Greece filled their play with murders and violence because they believe that if people watched this on stage it would 'get it out of their system'. Freud would suggest it is a good thing to watch violence on television and in films because it is cathartic- it gest aggressive instincts out of your system.


  • the frustration-aggression theory suggests that the best way to reduce aggression is to avoid situations that cause frustration, and this can be very difficult
  • explanations often conflict
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Social Learning- Reducing Aggression Bandura

Aim: to see if observing a role model being punished would reduce the chance of aggression being copied

Method: children were shown an adult role model either being punished or reinforced for acting aggressively. 

Results: those who saw the model being punished were less aggressive than those who saw the model reinforced.

Conclusion: if children see that aggression brings a punishment, they will not copy it.


  • when children themselves receive reinforcement for being aggressive they all copied the aggression they had seen earlier
  • if children think there is no punishment for them they will still copy behaviour they know to be wrong
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Social Learning- Reducing Aggression Huesmann

Aim: to see if teaching children to think more carefully about what the see would reduce aggression.

Method: a group of children was taught to realise that what happens on TV is not real. The camera sometimes depicts things that do not happen, and people mostly use non-violent methods of resolving problems. The children's behaviour was then compared with that of another group of children who did not receive any training. 

Results: the children who received training showed less aggression than the other group

Conclusion: aggression will be reduced by making children think about how they behave so that role models on TV become less influential.


  • many parents would have difficult explaining such psychological ideas to their children
  • parents do not have the training to explain concepts in a way children can understand
  • parents are not always present when children are watching TV to be able to discuss the programme afterwards 
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there are a lot of errors that make some of it hard to understand other than that it helped with revision 

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