DISCUSS GENETIC EXPLANATIONS TO AGRESSION (16)
Genetic explanations towards aggression suggest that aggressive acts are predetermined by
our genetic disposition- that our ability to act aggressive is determined completely by our
genes. A critical way to determine to what extent things are genetic is to look at twin studies,
comparing MZ twins, identical, who share 100% of the same genetic material to DZ twins,
who are non-identical and only share 50%. A study by Coccaro et al found that there was a
concordance rate of 50% for MZ twins and 19% for DZ, towards behaviour defined as direct
physical assault. Actions categorized within verbal aggression had a concordance rate of 28%
for MZs, and 7% for DZs. This suggests clearly that genetic disposition must have a critical
role in determining an element of aggressive behaviour, as DZ twins have a demonstrated
higher concordance rate than MZ. In comparison to twin studies, adoption studies can also
be used to attempt to consider the genetic factors within aggressive behaviour. It was found
in a meta-analysis by Rhee and Waldman that genetic influences accounted for 41% of the
variace in agression, within adoption studies focused on direct agression and antiosocial
behaviour. This demonstrates an element of consistency with the twin studes.
A limitation of the usage of twin studies is a lack of validity. It is assumed that DZ twins
share the same enviroment to the same extent that MZ twins do, as identical twins are often
raised in near-matching conditions- and this assumption reduces the the applicability of twin
studies- as it may be incorrect. DZ twins may be raised in completely different envrioments
and this variable not considered. Concordance rates are thus inflated and genetic influences
on aggressive behaviour may not be as great as they suggest. Therefore, the usage of twin
studies as supporting research towards genetic explanations of aggression is inherently
flawed, and cannot be used without considering environmental context.
When considering genetic influences towards aggression, a certain candidate gene has been
identified which may be linked towards stimulating aggressive acts. The MAOA gene codes
for the production of the enzyme monoamine oxidase, MAO-A, which is associated with
breaking down the neurotransmitter serotonin. The low activity variant of the MAOA gene,
MAO-L, results in low activity of the MAO-A enzyme, which in turn leads to lesser breaking-
down of serotonin in the synaptic cleft- leading to abnormally high levels being present,
which is associated with impulsive behaviour and aggression. The MAO-L gene is dubbed the
“warrior gene” as it was found in 56% of New Zealand Maori men.
Research support for the influence of the MAO-L gene causing aggression is prevalent within
Brunner et als research, where it was found that 28 men from a large Dutch family who were
repeatedly involved within aggressive violent criminal behaviours had abnormally low levels
of the MAO-A enzyme, alongside the MAOA-L gene variant. This demonstrates that the
concept of MAO-L increasing aggressive behaviours has been demonstrated in real life and is
not just theoretical- and thus provides supporting evidence towards the theory.
A limitation of considering the MAO-A gene to explain aggressive behaviour is that it could
be described as biologically reductionist. Not only is such a complicated behaviour like
aggression simplified to genetics only, which is a flawed argument in itself, but it is
simplified to one, singular gene. A multitude of genes could be involved within aggressive
behaviours and thus could be described as a polygenic behaviour. To simplify aggression to
one singular, specific gene without consideration of other genes, or other factors is therefore
flawed and reductionist. This is a weakness it reduces the overall explanatory power of the
explanation.
Genetic explanations towards aggression suggest that aggressive acts are predetermined by
our genetic disposition- that our ability to act aggressive is determined completely by our
genes. A critical way to determine to what extent things are genetic is to look at twin studies,
comparing MZ twins, identical, who share 100% of the same genetic material to DZ twins,
who are non-identical and only share 50%. A study by Coccaro et al found that there was a
concordance rate of 50% for MZ twins and 19% for DZ, towards behaviour defined as direct
physical assault. Actions categorized within verbal aggression had a concordance rate of 28%
for MZs, and 7% for DZs. This suggests clearly that genetic disposition must have a critical
role in determining an element of aggressive behaviour, as DZ twins have a demonstrated
higher concordance rate than MZ. In comparison to twin studies, adoption studies can also
be used to attempt to consider the genetic factors within aggressive behaviour. It was found
in a meta-analysis by Rhee and Waldman that genetic influences accounted for 41% of the
variace in agression, within adoption studies focused on direct agression and antiosocial
behaviour. This demonstrates an element of consistency with the twin studes.
A limitation of the usage of twin studies is a lack of validity. It is assumed that DZ twins
share the same enviroment to the same extent that MZ twins do, as identical twins are often
raised in near-matching conditions- and this assumption reduces the the applicability of twin
studies- as it may be incorrect. DZ twins may be raised in completely different envrioments
and this variable not considered. Concordance rates are thus inflated and genetic influences
on aggressive behaviour may not be as great as they suggest. Therefore, the usage of twin
studies as supporting research towards genetic explanations of aggression is inherently
flawed, and cannot be used without considering environmental context.
When considering genetic influences towards aggression, a certain candidate gene has been
identified which may be linked towards stimulating aggressive acts. The MAOA gene codes
for the production of the enzyme monoamine oxidase, MAO-A, which is associated with
breaking down the neurotransmitter serotonin. The low activity variant of the MAOA gene,
MAO-L, results in low activity of the MAO-A enzyme, which in turn leads to lesser breaking-
down of serotonin in the synaptic cleft- leading to abnormally high levels being present,
which is associated with impulsive behaviour and aggression. The MAO-L gene is dubbed the
“warrior gene” as it was found in 56% of New Zealand Maori men.
Research support for the influence of the MAO-L gene causing aggression is prevalent within
Brunner et als research, where it was found that 28 men from a large Dutch family who were
repeatedly involved within aggressive violent criminal behaviours had abnormally low levels
of the MAO-A enzyme, alongside the MAOA-L gene variant. This demonstrates that the
concept of MAO-L increasing aggressive behaviours has been demonstrated in real life and is
not just theoretical- and thus provides supporting evidence towards the theory.
A limitation of considering the MAO-A gene to explain aggressive behaviour is that it could
be described as biologically reductionist. Not only is such a complicated behaviour like
aggression simplified to genetics only, which is a flawed argument in itself, but it is
simplified to one, singular gene. A multitude of genes could be involved within aggressive
behaviours and thus could be described as a polygenic behaviour. To simplify aggression to
one singular, specific gene without consideration of other genes, or other factors is therefore
flawed and reductionist. This is a weakness it reduces the overall explanatory power of the
explanation.
