Genetic Factors in Aggression

Genetic Factors in Aggression

1. Difficulties of determining the role of genetic factors

   • More than one gene usually contributes to a given behaviour
   • There are environmental influences on the manifestation of aggressive behaviour
   • Genetic factors may affect which environment factors have an influence and vice versa.

2. Problems of assessing aggression

   • Miles and Carey meta-analysis, mode of assessment was a significant moderator of aggressive behaviour
     • Genetic factors explained the variance in aggressive behaviour in studies which used self-report
       • However, those that used observational ratings showed less genetic contribution and greater influence of environmental factors. For example, Twin pairs were encouraged to act aggressively towards the doll by being exposed to adult models who acted aggressively towards it.
   • Researchers found no difference in correlations between monozygotic and dizygotic twins which suggest individual differences in aggression were a product of environment than genetics

3. The Inheritance of Criminal Violence

   • Methodological limitations
     • Fail to distinguish the difference between violent and non-violent crime. This makes it difficult to untangle the role of genetic factors in aggressive violence. They also fail to distinguish criminals who are habitually violent and those who are violent as a one off.
   • Inconclusive evidence
     • Meta-analysis study found a low to moderate correlation between heredity and crime, with better designed and recently published studies providing less support for gene-crime hypothesis than more poorly designed and earlier studies.