Genetic explanation

• What is the genetic explanation for crime?

  • Suggests offenders inherit a gene or combination of genes that predispose them to commit crimes
• What twin studies illustrate the importance of genes in crime?

  • Lange (1930): investigated 13 identical (MZ) and 17 non-identical (DZ) twins where one of each pair had served prison time - 10 of the MZ twins and 2 of the DZ twins had a co-twin who had also been in prison
  • Christiansen (1977): Studied 3,500 pairs of twins, one of which was a know offender, found a concordance rate of 35% for MZ twins compared to 13% for DZ twins
• Which adoption study illustrates the importance of genes in crime?

  • Crowe (1930): adoptees whose biological mothers were criminals had a 50% risk of having a criminal record before 18 - as opposed to a control of adoptees whose risk was only 5%
  • Studies suggest that the more genetic material you share with an offender the more likely you are to be an offender yourself
• What is the role of candidate genes in the genetic explanation for crime?

  • Tiihonen et al (2014): genetic analysis of 900 Finnish offenders and found that the genes MAOA and CDH13 that are associated with violent crime
  • MAOA: regulates serotonin, linked to aggressive behaviour
  • CDH13: linked to substance abuse and ADHD
  • Individuals with this gene combination = 13x more likely to have a history of violent behaviour
  • Gene combination accounts for 5-10% of all violent crime in Finland
• What is a strength of the genetic explanation for crime?

  • Evidence to support from adoption studies: Mednick (1987) studied 14,000 adoptees - 15% of sons adopted by a criminal family went on to be criminals compared to 20% whose biological parents were criminals
  • Shows higher support for biological influences
• What is a limitation of the genetic explanation for crime?

  • Issues with twin evidence: Lange's judgement on zygocity was based off of appearance rather than DNA
  • Most twin study samples are small
  • Possibility of confounding variables like the shared environment twins are raised in
  • Shows issues with the validity of these studies in support for the genetic basis of crime