Biological explanations(neural and genetic)

• Genetic explanation for crime

  Offenders inherit a gene that predisposes them to commit crime
• Several studies have found a correlation between the low activity form of the MAOA gene and aggression
• Genes


  • Genetic explanation for crime suggests that offenders inherit a gene, and this gene predisposes them to commit crime
  • A genetic analysis of almost 900 offenders (2014) revealed abnormalities on two genes that may be associated with violent crime
• MAOA gene


  Contains dopamine and serotonin in the brain and has been linked to aggressive behaviour
• Low levels of serotonin have been associated with impulsive and aggressive behaviour
• CDH13


  Linked to attention deficit disorder
• Within the sample, people with these abnormalities were 13 times more likely to have a history of violent behaviour
• XYY 'supermale'


  Predisposed towards violent crime, above average height and below average intelligence
• It might be the latter characteristic (low intelligence) that accounts for their over representation in prison populations
• Genetic Transmission


  1. Concordance rates between identical or monozygotic (MZ) twin pairs and non-identical or dizygotic (DZ) twin pairs are compared

  2. If offending behaviour is genetic, we would expect a greater degree of similarity for that trait between MZ twins (who share 100% of their genes) than DZ twins (who only share 50% of their genes)
• Lange (1929) carried out the earliest twin study of criminality
• Concordance rates


  The percentage of twins who both display the same trait
• Lange (1929) twin study of criminality


  • Concordance rates of 77% for MZ twins and 12% for DZ twins
• High concordance rates for MZ twins suggest that criminality may be genetic
• High concordance rates for MZ twins support a biological explanation for criminality
• Similar shared environments for MZ twins could be a confounding variable in twin studies
• Neural correlates


  Measurements of the structure or function of the brain that occur in conjunction with an experience, in this case criminality
• Raine has conducted research using PET scanning and found abnormalities in some parts of the brain in violent criminals
• Most of the criminals in these studies have been diagnosed with

  • Antisocial Personality Disorder (APD)
• Individuals with Antisocial Personality Disorder

  • Have reduced activity in the prefrontal cortex of the brain, the part of the brain that regulates emotional behaviour
  • Find it difficult to control their impulses
  • Do not suffer from guilt or remorse
• Raine's study


  1. Studied 41 violent offenders

  2. Compared the activity in their prefrontal cortex to 41 non-criminals (including 6 schizophrenics)

  3. Used PET scans

  4. Violent offenders showed significantly less activity in prefrontal lobe than the other participants
• The prefrontal lobe develops relatively late, sometimes not fully developed until early 20s and later in males
• The prefrontal lobe not being fully developed


  May explain the peak in antisocial behaviour by male teenagers
• Biological reductionism


  Explanations that reduce offending behaviour to a genetic or neural level
• Criminality is complex, explanations that reduce offending behaviour to a genetic or neural level may be inappropriate and overly simplistic
• Crime does run in families, but so does mental illness and social deprivation
• This makes it near impossible to disentangle the effects of biology with the effects of the environment
• Biological determinism


  The notion of a criminal gene or a brain abnormality
• Our legal system is based on the premise that criminals have personal and moral responsibilities for their crimes, and only in extreme cases, such as a diagnosis of mental illness, can someone claim they were not acting under their own free will
• This raises ethical issues about what society does with people who are pre-determined to commit crime
• Biological explanations


  • They have supporting evidence gathered using scientific methods, such as PET scans and EEG's
  • This improves the internal validity for the research and increases reliability as studies can be repeated and checked for consistency
• Diathesis stress model


  Explains the interaction between nature (biology) and nurture (environment)
• Amygdala


  • Been identified as a structure with links to emotion regulation and aggression
  • Research suggests a correlation between poor emotion regulation and crime