genetic and neural explanations

• genetic explanations

  genetic explanations for crime suggest that offenders inherit a gene or combination of genes that influence them to commit crime
• twin studies

  Johannes Lange investigated 13 identical (MZ) and 17 non-identical (DZ) twins where one twin in each pair had served time in prison. He found that 10 of the MZ twins but only 2 of the DZ twins had a co-twin who was also in prison. He concluded that genetic factors must play a part in offending behaviour
• adoption studies

  Crowe found that adopted children who had a biological parent with a criminal record had a 50% risk of having a criminal record by the age of 18, whereas adopted children whose mother didn't have a criminal record only had a 5% risk
• candidate genes

  a genetic analysis of almost 900 offenders revealed abnormalities on two genes that may be associated with violent crime.

  1. MAOA gene = which controls dopamine and serotonin in the brain has been linked to aggressive behaviour
  2. CDH13 = has been linked to substance abuse and attention deficit hyperactivity disorder

  in the finished sample, individuals with high risk combination were 13 times more likely to have a history of violent behaviour. however, the research has not been replicated
• diathesis-stress model

  if genetics have some influence in offending it seems likely to have effects of the environment too. a tendency towards criminal behaviour may come about through the combination of genetic predisposition and biological or physical trigger. e.g. being raised in a dysfunctional environment or having criminal role models
• neural explanations

  evidence suggests there may be neural differences in the brains of criminals and non-criminals. much of the evidence has investigated individuals with antisocial personality disorder. APD is associated with reduced emotional responses, a lack of empathy for the feelings of others and is a condition that characterises many convicted criminals
• prefrontal cortex

  Adrian Raine conducted many studies of APD brain, reporting that there are several brain-imaging studies demonstrating that individuals with APD have reduced activity in the prefrontal cortex, He also found 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to others
• mirror neurons

  Keysers found that only when criminals were asked to empathise did their empathy reaction (controlled by mirror neurons) activate. This suggests that APD individuals are not totally without empathy but may have a neural 'switch' that can be turned on and off
• A03 - problems with twin studies

  • early twin studies were poorly controlled and judgements based on whether twins were MZ or DZ were based on appearance rather than DNA testing
  • this there may lack validity
  • twin studies typically involve small sample sizes and twins are an unusual sample which may not represent the rest of the population
  • concordance rates may be due to shared learning experiences rather than genetics
• A03 - support for the diathesis-stress model

  • study of over 13,000 Danish adoptees where researchers defined criminal behaviour as being in possession of at least one court conviction
  • when neither the biological or adoptive parents had convictions the percentage of adoptees was 13.5%
  • the figure rose to 20% when either biological parents had conviction and 24.5% when both adoptive and biological parents did
  • data suggests that environment is also influenced as well as genetic
• A03 - problems with adoption studies

  • the separation of genetic and environmental influences is complicated by that many children experience late adoption, which means that much of their childhood may have been spent with their biological parents
  • lots of adoptees maintain regular contact with their biological parents following their adoption
  • Mendick's study only applied to petty offences such as burglary and not violent crime so does not apply to more serious forms