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Discuss neural and hormonal mechanisms in aggression. (8 marks + 16 marks)
Neural and hormonal mechanisms in aggression are a biological explanation which assumes
that aggression is located within the biological makeup of the individual rather than in the
environment around them.
Neural mechanisms concern neurotransmitters, which are chemicals that transmit
impulses from one area of the brain to another. Serotonin is a neurotransmitter. There have
been many studies into the effect of serotonin on aggression and these have involved a
variety of animals. Research in this area suggests that the serotonin influences aggressive
and violent behaviour. Davidson, Putnam and Larson (2000) suggested that serotonin may
provide an inhibitory function so that when comparing violent criminals to non-violent
ones, the levels of serotonin found in violent criminals were much lower. Research on mice
where the serotonin 1B receptor was not functioning found an increase in aggressive
behaviour, a point that was further supported by research involving Vervet monkeys.
Reducing the serotonin levels of the monkeys resulted in an increase in aggressive
behaviour, whereas increasing serotonin levels resulted in a decrease in aggressive
The problem with this research is clear; to what extent can we extrapolate from animals
such as monkeys to human behaviour? There is limited evidence to suggest that there are
some similarities, but it would be inane to assume that monkey brains and human brains
function in the exact same way. This then means that the results obtained cannot be fully
generalised to humans.
However, evidence from human studies supports those from animal studies. A
meta-analyses by Scerbo and Raine in 1993, examined neurotransmitter levels in antisocial
children and adults. These studies consistently found lower levels of serotonin in
individuals described as being aggressive. Indications of reduced levels of serotonin were
found in all antisocial groups, but were particularly marked in those individuals who had
attempted suicide. This suggests that serotonin depletion leads to impulsive behaviour,
which in turn may lead to aggressive behaviour in many forms.
This research has much strength such as the fact that it is a meta-analysis of many studies
involving both children and adults; male and female, and so it is a representative sample
which means is has high generalisability. Also, the studies within the analysis were
naturalistic observations and so they contain high ecological validity which therefore
means they have high mundane realism and population validity.
A slightly different neural aspect is hormonal mechanisms. It is often suggested that the
male sex hormone testosterone influences aggression. Evidence for this comes from a
number of sources. One study by Dabbs et al (1987) involved measuring salivary
testosterone in violent and non-violent criminals. They found that those with the highest
testosterone levels had a history of primarily violent crimes whereas those with the
lowest levels had committed only non-violent crimes. This study is supported by Lindman
at al. (1987) who found that young males who behaved aggressively when drunk had higher
testosterone levels than those who did not act aggressively.
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Research into testosterone has been criticised for only sampling men from prison which
means the results are biased as they cannot be generalised to the whole population and so
therefore the research lacks population validity. Also, perhaps the reason of their
aggressiveness is due to institutional factors such as the situation they are placed in
(prison) or interpersonal factors such as their own traits and social histories.…read more