Discuss and evaluate biological explanations of aggression (24 marks)

Discuss biological explanations of aggression (8+16)

The biological theories of aggression start with the assumption that what causes the aggression is an internal factor. The theories believe that aggression has an organic cause and is innate, rather than being learnt. Neurotransmitters are chemicals that enable impulses within the brain to be transmitted from one area to another; serotonin and Dopamine are two of these neurotransmitters which have been linked with aggressive behaviour.

Serotonin is thought to reduce aggressiveness by inhibiting responses to the emotional stimuli. Low levels of serotonin have been linked with impulse behaviour such as aggression. Some drugs have been found to alter some serotonin levels, thus increasing the chance of aggressive behaviour.
Mann et al (1990) gave 35 participants dexfenfluramine which reduces serotonin levels, and then completed a questionnaire; Mann found an increase in aggression in males but not with females in aggression scores.

Similarly, it has been suggested there might be a link between dopamine and aggressive behaviour. Lavine (1997) stated that an increase in dopamine by the use of amphetamines has also been linked with aggressive behaviour. In addition, Buitelaar (2003) found that antipsychotics, which reduce cerebral dopamine levels, have been shown to reduce aggressive behaviour.

To evaluate, there is evidence to support the role of serotonin in aggression found by Scerbo and Raine (1993) in a meta-analysis of 29 studies. They examined neurotransmitter levels in antisocial children and adults. The studies consistently found lower levels of serotonin in those described as being aggressive- this was the case in all antisocial groups, but was particularly marked in those who had attempted suicide. This suggests that low levels of serotonin may lead to impulse behaviour, which in turn may lead to aggressive behaviour in various forms.
Raleigh et al (1991) adds further empirical support to the serotonin link when they found support for the importance of serotonin in aggressive behaviour in a study of vervet monkeys. It was found that individuals fed on experimental diets high in tryptophan exhibited decreased levels of aggression, and individuals fed on low tryptophan diets exhibited increased aggressive behaviour, suggesting that the difference in aggression could be attributed to serotonin links.
This is not to deny that such links exist, but rather that the complexity of human behaviour means that a biological explanation for aggression in humans is insufficient on its own to explain the many aspects of aggressive and violent behaviour; to say that all human aggression is due to one neurotransmitter is a reductionist approach because it ignores any social or cognitive factors that could contribute towards aggression.

Furthermore, Raleigh’s study is an anthromorphic study which lowers the finding’s external validity. Humans don’t share the same biological structure as animals so the vervet monkey findings can’t be generalised to humans because it can’t be assumed they behave in the same way.

Extra evidence for the serotonin explanation of aggression has come from the study…