genetic and neural (biological explanations)

• supporting twin studies (GE)

  • Christiansen = studied over 3500 twin pairs in Denmark
  • found a concordance for offending behaviour of 35% for MZ males and 13% for DZ males (slightly lower rates for females)
  • supports a genetic component in offending
• supporting adoption studies (GE)

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

  • Tiihonen et al = a genetic analysis of ~800 offenders suggested 2 genes may be associated with violent crime
  • MAOA gene = regulates serotonin and linked to aggressive behaviour
  • CDH13 gene = linked to substance abuse and ADHD
  • this study found that 5-10% of all severe violent crime in Finland is attributable to the MOAO and CDH13 genotypes
• diathesis-stress model (GE)

  • if genes have an influence on offending, this influence is likely to be at least partly moderated by environmental factors
  • the diathesis-stress model suggests that a tendency to offending behaviour is due to a combination of:
  • genetic disposition (diathesis)
  • a biological or psychological stressor or 'trigger' (eg criminal role models or dysfunctional upbringing)
• genetic explanations (GE)

  • twin and adoption studies
  • candiate genes
  • diathesis-stress model
• limitation of twin studies = assume equal environments (GE)

  • often assumed that environmental factors are the same for MZ and DZ twins because they experience similar environments
  • BUT = because MZ twins look identical, people (especially parents) tend to treat them more similarly which, in turn, affects their behaviour
  • => higher concordance rates for MZs may be because they are treated more similarly than DZs, suggests conclusions lack validity
  • ALSO = MZ twins share 100% of genes, if genetics was only explanation, concordance should be 100% instead of 33%
  • => only partial/flawed explanation
• strength = support for the diathesis-stress model of offending (GE)

  • Mendick = studied 13000 danish adoptees having at least one court conviction
  • conviction rates 13.5% = biological or adoptive parents had no convictions
  • conviction rates 20% = one biological parent had convictions
  • conviction rates 24.5% = both adoptive and biological parents had convictions
  • data suggests that both genetic inheritance and environment influence criminality (supports model)
• adoption studies evaluation (nature vs nurture) (GE)

  • adoption studies separate nature and nurture (=> similarities due to biological parents can only be genetic)
  • BUT = many adoptions occur when children are older and many adoptees maintain contact with biological family (so still environmental influences)
  • => adoption studies can't fully separate nature and nurture
• antisocial personality disorder (APD) (NE)

  • there may be neural differences in the brains of offenders and non-offenders
  • APD is associated with a lack of empathy and reduced emotional responses
  • many convicted offenders have a diagnosis of APD
• less activity in prefrontal cortex (linked to APD) (NE)

  • Raine et al = found reduced activity and an 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to control
  • this is the part of the brain that regulates emotional behaviour, decision making, self-control
• mirror neurons (linked to APD) (NE)

  • Keysers = found that only when offenders were asked to empathise did they show an empathy reaction (controlled by mirror neurons in the brain)
  • suggests APD individuals do experience empathy, but may have a neural 'switch' that turns on and off - the role of mirror neurons is not automatic in offenders like it is with 'normal' people
  • in a normally-functioning brain the empathy switch is permanently turned on
• neural explanations (NE)

  • antisocial personality disorder (APD)
  • less activity in prefrontal cortex
  • mirror neurons
• strength = support for link between crime and frontal lobe (NE)

  • Kandel and Freed = researched people with frontal lobe damage (including the prefrontal cortex)
  • found evidence of impulsive behaviour, emotional instability and inability to learn from mistakes
  • supports the idea that structural abnormalities in the brain are a causal factor in offending behaviour
• limitation = link between neural differences and APD is complex (NE)

  • Farrington et al = studied adult males with high APD scores (they were raised by a convicted parent and were physically neglected)
  • these early experiences may have caused APD and associated neural differences (eg reduced activity in the frontal lobe due to trauma)
  • suggests the relationship between neural differences, APD and offending is complex and there may be intervening variables
• extra evaluation (biological determinism) (NE)

  • biological approach suggests offending behaviour is determined by factors which cannot be controlled, so no responsibility
  • BUT = justice system is based on individual responsibility - the identification of possible biological precursors to crime complicates this principle
  • it is ultimately not possible to 'excuse' some people because of biological justification as many could claim no responsibility