biological explanations of aggression 25 marks essay

wrote this myself as part of mu revision for unit 3 exams jan 2010

proved to be very useful :)

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Outline and evaluate biological explanations of aggression
There are several biological explanations of aggression, all stemming from the assumption
that all that is psychological is first biological. Behaviour is influenced when biological body
structures (different areas of the brain) are stimulated, for example electrical stimulation of
the amygdala is thought to influence aggression. It is agreed that aggressive responses
originate from the limbic system of the brain, the part that's responsible for emotions and
selfidentity. This idea is supported by research from Raine et al, who used brain scans to
demonstrate that murderers were more likely to have abnormalities in their limbic system
than `normal' individuals. However this research can be criticised, as it doesn't consider the
fact that an abnormality may only create a predisposition to murder. Research has focused
on two areas of biology that are thought to influence aggressive behaviour: neural
mechanisms and hormonal mechanisms.
The effects of neural mechanisms originates from evidence that suggests that low levels of
a neurotransmitter called serotonin are linked to aggression. Feldman et al examined the
effects of serotonin on aggression in mice conducted research. He divided the mice into 3
groups: the first group were given an injection to increase serotonin, the second group were
given an injection to decrease serotonin whereas the third group were a control group. He
found an increase in aggressive behaviour in the first group, and a lowering of aggression in
the second group. However mice in the second group did show an increased attack
response. Feldman's research can be criticised as it is unethical because it tampered with
drugs that influence the behaviour of an animal, which could potentially cause physical harm
to the mice. The research can also be criticised as it assumes the findings can be applied to
humans: this is not the case. The methodology of this research can also be criticised as a
laboratory based experiment was used, which has low ecological validity. However this
method does employ a high level of control for the psychologist, so they could manipulate
any potential extraneous variables. Research into the effects of serotonin have also been
carried out using human studies, where it was also found that low serotonin levels correlate
with increased aggression. However this is only a correlational relationship, therefore cause
and effect cannot be established: did the low serotonin cause the aggression or did the
aggression cause the low serotonin? The levels of low serotonin were also associated with
aggression against oneself, for example suicide. Research has found that low levels of
serotonin are found in suicide victims, suggesting that suicide and violence result from the
same aggressive tendency.
Biological psychology assumes that behaviour is also thought to be influenced by the
different hormones in the body. Hormones are chemicals that control and regulate the
activity of certain cells and organs, and one of the key hormones identified as being related
to aggression is the androgen testosterone. Nelson found a positive correlation between
violence in prisoners and androgen levels. He used questionnaires, interviews, prisoner
records and a hormone analysis to assess the prisoners. Questionnaires and interviews have
several disadvantages because of demand characteristics, in particular social desirability.
The prisoners may have answered in a way to either support or deliberately alter the results
of the study, this not giving an accurate representation of their real views. However these
methods do produce both qualitative and quantitative data. But from this research it is
unclear whether androgens cause aggression or whether they just encourage social
dominance, competitiveness and impulsiveness because of the time that elapsed between the
aggressive/violent act and the hormone analysis. Another issue with this research is the fact
that not all aggressive acts are criminal, for example bullying. Also not all aggressive acts are
prosecuted or even reported, so these will not be included in the records that Nelson used.

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Harrison et al carried out further research into how hormonal mechanisms influence
aggression. They used a sample of 56 men aged 2050 years old and gave them all
injections of testosterone, which increased their aggressive behaviour whilst playing a
computer game. However this increase was not uniform across all individuals. This research
can be criticised because it ignores the influence of social factors, although it does account
for individual differences.…read more


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