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Genetic Factors in Aggressive Behaviour Essay Plan
1. Describe twin studies- Coccaro- found that adult twin pairs had nearly 50% of the variance in
direct aggressive behaviour being down to genetic factors. Adoption studies- 14,000
adoptions in Denmark found that a significant number of adopted boys with criminal
convictions had biological parents (particularly fathers) with criminal convictions- Hutchings
2. Explain briefly a gene for aggression- MAOA- regulates the metabolism of serotonin in the
brain. Brunner- dutch family- found that many of its male members behaved in a particularly
violent and aggressive manner, and a large proportion had been involved in serious crimes of
violence including rape and arson. These men found to have abnormally low levels of MAOA
and a defect in this gene was later identified.
3. Caspi- 500 male children, discovered a variant of the gene associated with high levels of
MAOA and a variant associated with low levels. Those with low levels of MAOA were
significantly more likely to grow up to exhibit antisocial behaviour but only if they were
maltreated as children.
4. Describe genetics and violent crime- Brennan- series of adoption studies in which the criminal
history of an adopted male was compared with the criminal history of both his biological and
his adoptive fathers, found that genetic influences were significant in cases of property
crime, but not in cases of violent crime.
5. Critical Point 1: There is difficulty determining the role of genetic factors in aggression. This is
for a few reasons. Firstly, more than one gene contributes to a given behaviour that is, it can
be a combination of genes that make people aggressive. As a result of this, this explanation
is reductionist as it is not just genetic factors that influence aggressive behaviour it can be
environmental as well. Also it is an example of an oversimplification as it is saying that one
gene causes aggression when in reality it is several factors that can lead to aggressive
behaviour, both biological and environmental.
6. Critical Point 2: There is a second flaw to assuming that genetic factors are the underlying
cause of aggression. The way that the studies are examined is usually by either parental or
self-reports of aggressive behaviour this is biased as how participants feel about the subject
in question can depend on their mood. Plomin found no difference in correlations between
monozygotic and dizygotic twin pairs, implying that individual differences in aggression were
more a result of environmental influences, for instance family upbringing, than genetic
7. Critical Point 3: There are problems distinguishing between violent and non violent crime and
criminals who are habitually violent and those whom their violent crime is a one-off. Walters-
meta analysis- found only a low to moderate correlation between heredity and crime, with
better designed and more recently published studies giving less support for the gene crime
hypothesis. Consequently, this suggests that genetic factors do not play such a big role as it
was first thought.
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Critical Point 4: Also the studies that have found a strong correlation between aggressive
behaviour and genetic factors have been carried out on non human animals. As a result of
this, it is difficult to generalise the results for humans as human beings are a lot more
complex both in terms of their biological make up and our more advanced social skills.
Secondly, there are serious ethical issues concerned with this type of experimentation.…read more