Genetic explanation

• What is the genetic explanation for crime?


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

  • Christiansen (1977) studied over 3500 twin pairs in Denmark and found that concordance rates for offending behaviour was 35% for identical monozygotic twins and 13% for nonidentical dizygotic twins
  • Crowe (1930) found that adoptees whose biological mothers were criminals had a 50% risk of developing a criminal record themselves by the age of 18, whereas adoptees who's biological mothers were non-criminals had a risk of only 5%
  • Suggests the more genetical 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 (2015) conducted a genetic analysis of 800 Finnish offenders and found that the genes MAOA and CDH13 may be associated w/ violent crime
  • MAOA regulates serotonin and is linked to aggressive behaviour, CDH14 has been linked to substance abuse and ADHD
  • Genotypes account for 5-10% of all violent crime in Finland
• What is the diathesis-stress model in relation to offending behaviour?

  • The influence of genetics on offending behaviour is likely to be partly moderated by the effects of the environment
  • A tendency towards offending behaviour may come about through a combination of genetic predisposition and biological/psychological trigger like having criminal role models
• What is one strength of the genetic explanation for crime?

  • Research support for diathesis-stress model: Mednick et al. (1984) studied 13,000 Danish adoptees and found that 20% of adoptees who had a biological parent convicted of crime went on to be convicted themselves - this rose to 24.5% when both adoptive and biological parents had convictions
  • Shows genetic inheritance AND environmental influence play important roles in offending, supporting the model
• What is one limitation of the genetic explanation for crime?

  • Issues with twin evidence: researchers assume that environmental factors are held constant and similar because twins are raised together, yet this may apply more to identical twins than non-identical twins
  • Most twin study samples are small and confounding variables like shared environments cause a problem
  • Shows issues with the validity of twin studies in support for the genetic basis of crime
• What is another limitation of the genetic explanation for crime?

  • Nature and nurture: adoption studies like Mednick et al are a good way of separating the conflicting influences of nature and nurture, because if crime has a genetic component then adopted children should still experience the influence of their biological parents despite not living with them
  • BUT many adoptions happen when children are older so they still spend several years w/ biological parents and are also encouraged to keep in contact w/ them, so they can exert an environmental influence - raises the question of if researchers can ever truly separate the influences of nature and nurture, and if they do their research may have low external validity