genetic and neural explanations

• genetic explanations - suggest that offenders inherit a gene or a combination of genes that predispose them to commit crimes
• twin studies

  • Lange investigated 13 MZ and 17 DZ twins where one twin in each pair had served time
  • found that 10 MZ but only 2 DZ had a co-twin who was also in prison
  • shows genetic factors must play part in offending behaviour
• adoption studies

  • Crowe found that adopted children who had bio parent with a criminal record had a 50% risk of having criminal records by age 18
  • adopted children whose bio parent didnt have a criminal record only had 5% risk
• candidate genes

  • Tihonen - genetic analysis of almost 900 offenders
  • revealed abnormalities on two genes that may be associated with violent crime
  • MAOA gene- controls dopamine and serotonin and has been linked to aggression
  • CDH13 - linked to substance abuse and ADHD
• diathesis- stress model

  • a tendency towards criminal behaviour may come about through the combination of genetic predisposition and a trigger
• neural explanations

  • neural differences in brains of criminals and non-criminals
  • much of the evidence come from people diagnosed with APD - associated with lack of empathy for feelings for others
• prefrontal cortex

  • brain-imaging studies demonstrate that those with APD have reduced activity in the pfc, the part of brain that regulates emotional behaviour
  • also an 11% reduction in volume of grey matter in the pfc
• mirror neurons

  • found that only when criminals were asked to empathise (with person on film experiencing pain)did their empathy reaction activate
  • suggests APD people arent totally without empathy, but may have neural switch that can be turned on or off
• W - problems with twin studies

  • early twin studies were poorly controlled - judgements related to whether twins were MZ to DZ were based on appearance rather than DNA testing - may lack validity
  • also the fact that most twins are raised in the same environment is a major confounding variable as concordance rates may be due to shared learning experiences rather than genetics
• W - problems with adoption studies

  • presumed separation of environment and genetic influences is complicated by fact that many children experience late adoption - mean that much of infancy and childhood may be spent with biological parents
  • this makes it difficult to asses whether criminal behaviour is actually a result of inherited genetics
• W - bio determinism

  • 'criminal gene' presents a dilemma
  • our legal system is based on premise that criminals have personal and moral responsibility for crimes
  • this raises ethical questions about what society does with those carrying this gene and what implications it has on sentencing - do we incarcerate those carrying the gene before they have committed a crime to prevent it? - prevent them from reproducing to stop gene being passed on?
• S - support for diathesis-stress model

  • 13,00 Danish adoptees
  • when neither bio or adopted parents had convictions - 13.5%
  • when a bio parent had convictions - 20%
  • when both adoptive and bio parents had convictions - 24.5%
  • suggests although genetic inheritance plays important role, environment cant be disregarded