Genetic and Neural explanations

• Candidate genes introduction

  Tiihonen et al conducted a genetic analysis of 900 Finnish offenders which revealed an abnormality on 2 genes that may be associated with violent behaviour.
• Candidate genes findings

  MAOA gene = controls dopamine and serotonin and is linked to aggressive behaviour. CDH13 = linked to substance abuse and ADD.
• Candidate genes conclusion

  According to this sample, individuals with this high risk combination are 13x more likely to have a history of violent behaviour. However, research is in early stages and has not been replicated.
• Diathesis-stress model

  tendency towards criminal behaviour is likely due to the combination of genetic predispositions and environmental triggers. Diathesis = genetic predispositions. Stress = environmental triggers.
• twin studies - Lange’s research

  looked at 13 MZ and 17 DZ twins where one twin in each pair had served time in prison. Over half of the twin pairs had a co-twin in prison. He concluded that genetic factors must play a dominant part in offending behaviour.
• twin studies - Christiansen’s research

  studied 87 MZ and 147 DZ pairs. He found a concordance of 33% for MZ’s and 12% for DZ’s. This supports the view that offending may have a genetic component.
• neural explanations

  there is evidence that suggests there may be neural differences in the brains of criminals and non-criminals. There is much research into those with APD. Those with APD have a lack of empathy and feeling for others. This is a condition which many criminals possess.
• pre-frontal cortex

  Raine conducted many studies of the brain of those with APD. Those with APD have reduced activity in the PFC. He found an 11% reduction in volume of grey matter in the PFC of people with APD compared to controls.
• mirror neurons introduction

  criminals with APD can experience empathy but they do so more sporadically than the rest of us.
• mirror neurons research

  Keysers et al found that criminals empathised with a sad film character only when they were asked to do so.
• mirror neurons conclusion

  This suggests that individuals with APD aren’t completely without empathy, but they may have a “neural switch” which can be turned on and off, unlike the normal brain, which has the switch permanently on.
• What is the negative (issues and debates)

  It is biologically reductionist. Reducing offending behaviour to a genetic or neural level may be inappropriate and overly simplistic.
• what is the negative of twin studies?

  Early twin studies of criminality were poorly controlled and judgements related to zygosity may lack validity, as they were based on appearance rather than DNA testing. Twin studies involve small sample, and twins are an unusual sample in themselves and are not representative of the rest of the population.