Genetic AO3

• Christiansen - concordance rate between violent criminal twins

  55% monozygotic concordance rate

  22% dizygotic concordance rate

  shows that there is a genetic basis to violent behaviour
• Hutchings and Mednik

  adoption study. found that children who displayed aggression were also likely to have biological parents who displayed aggression. this suggests a genetic basis to aggression
• Brunner - case study on 5 dutch men

  dna analysis of a dutch family with excessive aggressive behaviour

  results showed that all 5 men had a mutation of the MAOA gene, causing less serotonin activity and therefore more aggressive behaviour
• Limitations of twin studies

  • assume that the impact of the environment is the same for monozygotic and dizygotic twins - that they are treated the same because they are identical twins
  • when in reality it could be completely different
• Limitations of adoption studies

  • children are usually placed with families similar to their biological families, meaning they have grown up in a similar environment to what they would be in if with their biological parents
  • this rather than genetics, may explain why they display similar behaviour to their biologial parents
  • this means that adoption studies lack validity
• the genetic explanation ignores gene environment interactions

  e.g - Caspi et al

  found that children with the short MAOA allele

  were more likely to become hyperaggressive as adults, but this effect depended on their environment as a child

  only those who were maltreated as a child became hyperaggressive