genetic explanation

twin studies - twin studies have shown that heritability accounts for 50% of variance in aggressive behaviour

caccaro et al studied MZ and DZ male twins. Because MZ share 100% of their DNA we would expect to find a higher CR. both MZ and DZ share the same environment but differ on genetic similarity. the CR for physical aggression was 50% in MZ twins and 19% in DZ twins. the difference supports the role genes play in aggressive behaviour

adoption studies - similarities in the adopted child and biological parent suggest genetic influences. similarities between the child and adoptive parents suggest environmental influences.

rhee and waldman carried out a meta analysis of adoption studies looking at anti social and aggressive behaviour. they found that genetics accounted for 41% of the variance which is in line with the twin studies

MAOA - monoamine oxidase A - enzyme that breaks down neurotransmitters such as serotonin. one variant is MAOA - L and is associated with various forms of aggression

Brunner et al studied 28 male members of a large Dutch family repeatedly involved in violent criminal behaviour. these men had low levels of MAOA and the low activity variant of the gene.

Stuart et al studied 97 men from a treatment programme for domestic abusers. men with low activity of MAOA gene were the most violent perpetrators of IPV - greatest physical and psychological aggression and worst injuries

P - a strength of the genetic explanation is that there is research evidence supporting it

E - mice were genetically modified to have the low levels of MAOA and were found to be more aggressive

E - further studies by Godar showed that MAOA knockout mice had high serotonin levels and were hyperaggressive. furthermore when serotonin was blocked with fluoxetine, the mice reverted back to being non aggressive

L - this supports the genetic explanation, specifically the role of MAOA

P - a criticism of the genetic explanation is that genes are not fully responsible for aggression as it does not act in isolation

E - 1/3 of men carry the warrior gene yet the vast majority dont act aggressively. this suggests that another factor, such as environment, must play a role in aggression too

E - Frazzetti found a positive correlation between aggression and low activity of the MAOA gene, as expected but this was only in the case of those who has experienced significant trauma. those who did not experience trauma did not show the same high levels of aggression, despite possessing the gene variant

L - this suggests that the genetic explanation is not sufficient to explain aggression and is reductionist. the diathesis stress model would be more appropriate as it takes on an interactionist approach.

P - a limitation of the genetic explanation is that it exaggerates the role of nature in the nature vs nurture debate'

E - the genetic explanation suggests that aggression is inherited and occurs as a result of your genetic makeup

E - However, Caspi et al found that other factors such as childhood trauma play a role too. therefore, the diathesis stress model is a more approppriate explanation as it takes on a more interactionist approach

L - therefore, the genetic explanation is undermined because it oversimplifies aggression and is an insuffiecent explanation