Genetic and neural

• Genetic explanations for crime suggest that would be offenders inherit a gene, or combination of genes that predisposes them to commit crime.
• Twin studies

  Christiansen studies over 3500 twin pairs in Denmark, and found concordance rates for offender behaviour of 35% of identical twin males and 13% of non-identical males.

  • Offender behaviour was checked against police records. This data indicates that it is not just the behaviour that might be inherited but the underlying predisposing traits.
• Adoption studies

  Crowe found that adopted children whose biological mothers had a criminal record has a 50% risk of having a criminal record by age 18, whereas adopted children whose biological mother didn't have a criminal record only had a 5% risk.
• Candidate genes

  = A genetic analysis of 800 Finish offenders by Tiihonen suggested that two genes may be associated with violent crime.

  • The MAOA gene regulates serotonin in the brain and has been linked to aggressive behaviour.
  • The CDH13 gene has been linked to substance abuse and attention deficit hyperactivity disorder.
  • Analysis found that 5-10% of all severe violent crimes in Finland is attributable to the MAOA and CDH13 gene.
• Diathesis-stress model

  = If genetics do have influence over offending, it is likely that this is partly moderated by the effects of the environment.

  • Diathesis-stress model applied to schizophrenia.
  • A tendancy towards offending behaviour may come about through the combination of genetic predisposition and biological or psychological trigger- eg: raised in a dysfunctional environment or having criminal role models.
• Genetic evaluation- issues with twin evidence

  Limitation= assumption of equal environments.

  • It's assumed by researchers studying twins that environmental factors are held constant because twins are brought up together and therefore must experience same environments.
  • However this shared environment assumption may apply much more to MZ twins than DZ twins because MZ twins look identical and people tend to treat them more similarly which affects their behaviour.
  • Therefore higher concordance rates for MZs in twin studies because they are treated more similarly than DZ twins.
• Genetic evaluation- support for diathesis-stress model

  A study of 13,000 Danish adoptees was conducted by Mednick. When neither the biological nor adoptive parents had convictions, the percentage of adoptees that did was 13.5%.

  • This figure rose to 20% when either of the biological parents had convictions and 24% when both adoptive and biological parents had convictions.
  • Shows that genetic inheritance plays an important role in offending but environmental influence is clearly also important, providing support for diathesis-stress model.
• Neural explanations

  Evidence suggests there may be neural differences in the brains of offenders and non-offenders.

  • Much evidence has involved individuals with antisocial personality disorder.
  • AP is associated with reduced emotional responses, a lack of empathy and is a condition that characterises many convicted offenders.
• Prefrontal cortex

  Raine has conducted many studies of the APD brain, reporting that there are several dozen brain-imaging studies demonstrating that individuals with antisocial personalities have reduced activity in the prefrontal cortex. (Which regulates emotional behaviour)

  • Found an 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to controls.
• Mirror neurones

  Research suggests offenders with APD can experience empathy but they do so more sporadically than the rest of us.

  • Keysers found that only when offenders were asked to empathise did their empathy reaction activate.
  • This suggests that APD individuals are not totally without empathy, but may have a neural 'switch' that can be turned on or off, unlike normal brain where empathy is always switched on.
• Neural evaluation- brain evidence

  Strength= support for the link between crime and frontal lobe.

  • Kandel and Freed reviewed evidence of frontal lobe damage and antisocial behaviour.
  • People with such damage tended to show impulsive behaviour, emotional instability and an inability to learn from their mistakes.
  • Frontal lobe is associated with planning behaviour.
  • This supports the idea that brain damage may be a causal factor in offending behaviour.
• Neural evaluation- intervening variables

  Other factors may contribute to APD, and ultimately crime.

  • Farrington studied a group of men who scored high on psychopathy. These individuals had experienced various risk factors during childhood, such as being raised by a convicted parent and being physically neglected.
  • It could be that these early childhood experiences caused APD and also some of the neural differences associated with it, such as reduced activity in the frontal lobe due to trauma.
  • There may be other intervening variables that have an impact.