AO1

• What was Karl Christensen's (1977) twin study?

  • Over 3500 pairs of twins in Denmark
  • Found concordance rates for offender behaviour of 35% for monozygotic twins
  • Around 13% for dizygotic twins in males (slightly lower in females)
  • This included all twins born between 1880 and 1910 in a region of Denmark
  • The behaviour was checked against Danish police records - the data revealed that it might not be just the behaviour that's inherited but also the predisposing traits
• What was Raymond Crowe's (1972) adoption study?

  • Crowe found that adopted children whose biological mother had a criminal record = 50% risk of having a criminal record by the time they are 18
  • Whereas, adopted children whose biological mother did not possess a record had a 5% risk
• Candidate Genes:

  • Tiihonen et al. (2015) - analysis of 800 Finnish offenders suggested that two genes - MAOA and CD13 may be associated with violent crime
  • The MAOA regulates and maintains serotonin and have been linked to aggressive behaviour
  • The CD13 gene has been linked to substance abuse and 'attention deficit hyperactivity disorder'.
  • The analysis concluded that about 5-10% of all severe violent crime in Finland is attributable to the MAOA and CD13 genes
• Diathesis Stress Model:

  • If genes had an effect on offending behavior it is likely to be influenced by the environment
  • A tendency towards offending behavior may come about through the combination of a genetic predisposition and a biological or psychological trigger e.g raised in a dysfunctional environment/ having criminal role models
• What is the Diathesis-Stress Model


  When a person is more vulnerable due to their predisposition - less stress is needed to 'fill the cup'