Genetic and neural explanations

• Genetic explanations propose that some people inherit a genetic predisposition to criminal behaviour.
• Lange (1930) investigated 13 identical and 17 non-identical twins where one of the twins in each pair had served time in prison.

  • He found that 77% of MZ twins (identical) and 12% of DZ twins (non-identical) both had criminal records, suggesting a genetic basis.
• Crowe (1972) 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 did not have a criminal record only had a 5% risk.
• Tihonen et al.. (2014) conducted a genetic analysis that revealed abnormalities on two genes that may be associated with violent crime - the MAOA gene and the CDH13.

  • Within the Finnish sample, individuals with this high-risk combination were 13 times more likely to have a history of violent behaviour.
• MAOA gene ("warrior gene") is a candidate gene of criminal behaviour.

  • Linked to aggression due to its role in regulating dopamine and serotonin.
• CDH13 gene is a candidate gene of criminal behaviour.

  • Associated with substance abuse and ADHD, which are risk factors for criminality.
• Brunner et al. (1993) investigated a Dutch family where many male members exhibited violent and impulsive behaviour (e.g., arson, attempted rape, and physical assault).

  • He found that Dutch males with a defective MAOA gene were linked to violent crime.
• Neural explanations suggest that criminals have differences in brain structure and neurotransmitter activity.

  • Much of the evidence in this area has investigated individuals diagnosed with antisocial personality disorder (APD).
• Antisocial personality disorder (APD) is formerly referred to as psychopathy. It is associated with reduced emotional responses, a lack of empathy for the feelings of others and is a condition which characterises many convicted criminals.
• Raine (1997) used brain scans to show that violent offenders had reduced activity in the prefrontal cortex, which is responsible for impulse control and decision-making.
• Raine et al.. (2000) found an 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to controls.
• Keysers (2011) found that criminals with antisocial personality disorder (APD) have a reduced mirror neuron response.

  • Implication: Unlike non-criminals, whose mirror neurons fire automatically when observing others in pain, APD individuals only showed activity in their mirror neuron system when explicitly asked to empathise.
  • Conclusion: This suggests that some offenders may have impaired neural processing of empathy, which could explain their lack of guilt or remorse.
• One strength of genetic explanations is that twin and adoption studies provide consistent evidence for a genetic influence on criminal behaviour. Mednick et al. (1984) found that adopted children with criminal biological parents were more likely to become offenders, even when raised in non-criminal environments. This suggests that genetic factors play a role in criminality, rather than just environmental influences. However, the concordance rates in twin studies are never 100%, meaning that genes cannot be the sole cause, and environmental factors must also contribute.
• A major limitation of genetic and neural explanations is that they do not establish causation. Just because offenders have brain abnormalities or genetic variations, it does not mean these factors cause criminal behaviour. Other factors, such as childhood neglect, trauma, or substance abuse, could lead to both brain dysfunction and criminality. For example, poor nutrition or head injuries could explain brain differences in offenders, rather than genetics alone. This means the approach may be too reductionist, as it ignores social and environmental influences.
• A limitation is that it raises ethical issues related to biological determinism. If criminal behaviour is genetically determined, it challenges the idea of free will and personal responsibility. This could lead to legal and moral dilemmas, such as whether people with a "criminal gene" should be held fully accountable for their actions. Additionally, if genetic screening for criminality were introduced, it could lead to discrimination and ethical concerns about labelling individuals as potential criminals from birth. Therefore, while genetic research is valuable, it must be used with caution.
• A limitation is that they ignore environmental factors. The diathesis-stress model suggests that criminality arises from a genetic predisposition (diathesis) combined with environmental triggers (stress). Someone may inherit a low-functioning MAOA gene, but they will only become criminal if exposed to stressors. Caspi et al. found that individuals with a defective MAOA gene were more likely to engage in antisocial behaviour, but only if they had experienced severe childhood abuse. This suggests that genes alone do not determine criminal behaviour, and environmental factors are crucial.