Aggression: Neural and Hormonal Mechanisms in Aggression

Question 1

Name two Neurotransmitters which are associated with increased levels of aggression

Answer 1

> Serotonin

> Dopamine

Question 2

Describe Serotonin and Aggression

Answer 2

Serotonin is thought to reduce aggression by inhibiting responses to emotional stimlu tht would otherwise lead to an aggressive response. Low levels of serotonin in the brain have been linked to increased aggression.

Question 3

What study supported the link between serotonin and increased aggression?

Answer 3

Mann et al.

Question 4

What did Mann et al. find

Answer 4

Mann et al gave 35 healthy subjects dexflenfluaramine, which is known to deplete serotonin. Using a questionnaire to assess hostility and aggression levels, they found that dexflenfluarmine teatement in males (not in females) was associated with an increase in aggression.

Question 5

Describe Dopamine and Aggression

Answer 5

Although the link between dopamine between high levels of dopamine and aggressive behaviour is not as established as with serotonin, there is some evidence to suggest that such a link exists.

Question 6

Which study supports the link between dopamine and aggression?

Answer 6

Lavine

Question 7

What did Lavine find

Answer 7

Increases in dopamine activity via the use of amphetamines have also been associated with increases in aggressive beahviour.

Question 8

What did did research using antipsychotics find?

Answer 8

Antipsychotics, which reduce dopamine activity in the brain, have been shown to reduce aggressive behaviour in violent delinquents.

Question 9

Name two Hormones which are associated with increased levels of aggression

Answer 9

> Testosterone

> Cortisol

Question 10

Describe Testosterone

Answer 10

Testosterone is the male sex hormone, which is thought to influence aggression from young adulthood onwards due to its action on brain areas involved in controlling aggression.

Question 11

Which study supports the association between testosterone and aggression?

Answer 11

Dabbs et al.

Question 12

What did Dabbs find

Answer 12

Dabbs measured salivary testosterone in violent and non-violent criminals. Those with the highest testosterone had a history of primarily violent crimes, whereas those with the lowest levels had committed only non-violent crimes. This shows that testosterone is linked to increased aggression.

Question 13

Describe Cortisol

Answer 13

Cortisol appears to have a mediating effect on other aggression-related hormones such as testosterone , possibly anxiety and the likelihood of social withdrawal.

Question 14

Which study demonstrates the effect of cortisol on levels of aggression?

Answer 14

Virkunnen

Question 15

What did Virkunnen find

Answer 15

High levels of cortisol inhibit testosterone levels and so inhibit aggression. Virkunnen found that low levels of cortisol in habitual violent offenders. This suggests that although relatively high testosterone is the primary biochemical influence on aggression, low cortisol also plays an important role by increasing the likelihood of aggressive behaviour.

Question 16

Name evidence which supports the link between Serotonin and increased aggression

Answer 16

Evidence for the role of serotonin comes from the use of drugs that raise levels of serotonin in the brain, such as antidepressants. In clinical studies, antidepressant drugs which elevate serotonin levels (e.g. SSRIs) also tend to reduce irritability and impulsive aggression. This suggests that increased serotonin levels do lead to reduced aggression. However, this relationship may not be causal.

Question 17

Name evidence which supports the link between Dopamine and increased aggression

Answer 17

Evidence for the causal role of dopamine in aggression is inconclusive. A study by Couppis and Kennedy, which involved mice, found that dopamine may be a consequence of aggressive behaviour rather than a cause. They suggest that people may seek out aggressive encounters because dopamine is released as a positive reinforcer whenever they engage in aggressive behaviour.

Question 18

Name evidence which supports the link between Testosterone and increased aggression

Answer 18

Mazur suggest that we should distinguish aggression from dominance. Aggression refers to the intent to inflict injury, while dominance is the desire to achieve or maintain status over another. Aggression may be just one form of dominant behaviour. The influence of testosterone on dominance is likely to be expressed in more varied and subtle ways. According to this view, much of the research into aggression was actually measuring dominance, making this research invalid.

Question 19

Name evidence which supports the link between Cortisol and increased aggression

Answer 19

The moderating effect of cortisol on aggressive behaviour is supported by McBurnett et al. who performed a four-year study of boys with behavioural problem. The boys with consistently low cortisol levels began antisocial acts at a younger age and exhibited three times the number of aggressive symptoms than boys with higher or fluctuating cortisol levels. This demonstrates that cortisol levels are strongly and inversely related to aggression.

Question 20

AID: Reductionism

Answer 20

A criticism of these links between neurotransmitters, hormones and aggression is that they can be described as reductionist. The complexity of human behaviour means that biological explanations are insufficient on their own to explain the many different aspects of human aggression. For example, research by Bandura et al. found that social learning can be a powerful influence on the aggressive behaviour of children.

Question 21

AID: Real World Application

Answer 21

Research has shown that simple exposure to certain stimuli can increase testosterone levels and thus aggression. Klinesmith et al. found that when participants assembled a gun, their testosterone levels increased and they became more aggressive towards other participants. This has an important real-world implication, as some countries’ governments (e.g. that of the USA) are debating whether gun ownership increases or decreases violence. This study would suggest that more guns would lead to more violent behaviour.