Outline and Evaluate Genetic Factors in Aggression

The biological approach to aggression includes the belief that genetic factors play a role in aggressive behaviour and lies within an individual’s genetic make-up. There is supporting evidence of a genetic component of aggression. Psychologists have looked at twin studies to try and find evidence for a genetic basis o compare the degree of similarity of aggression between sets of monozygotic (MZ) twins and dizygotic (DZ) twins. In general it was found that aggressive behaviour is more highly correlated in MZ twins than DZ twins. For example, Gottesman found a concordance rate of 87% for aggressive behaviour for MZ twin pairs, compared with 72% for DZ twin pairs. However, solely relying on evidence from twin studies can be problematic as it is hard to disentangle nature and nurture. It has been suggested that MZ twins are treated more alike and share more similar environments than DZ twins due to them acting more like 'one' person rather than two separate people. This may affect how alike they are and how likely they both are to express aggression.
However, there are gender differences involved in twin studies. Button et al studies 258 twin pairs and found that both aggressive and non-aggressive antisocial behaviour are subjected to significant gender differences. The heritability of aggressive antisocial behaviour was significantly higher in girls than boys, suggesting a stronger genetic effect on aggression in females than in males.
Adoption studies can help to disentangle the relative contributions of the environment and genetics. If researchers find a greater similarity in levels of aggression between adopted children and biological parents than between their adoptive parents, it suggests genetics are an important influence. The Danish study by Mednick reviewed over 14000 adoptions in Denmark and found a significant positive correlation between the number of criminal convictions for criminal violence among biological parents and their adopted songs, thus