Biological explanations: Genetic & neural explanations

• Genetic explanations:

  • Twin & adoption studies suggest genes predispose offenders to crime:

  Lange (1930) studied 13 MZ & 17 DZ twins where one of the twins in each pair spent time in prison. Ten of the MZ twins had a co-twin who was also in prison but this was only true for two of the DZ twins. Crowe (1972) found that adopted children who had a biological parent with a criminal record had a 50% greater risk of a criminal record by the age of 18. But adopted children whose mother didn’t have a criminal record only had a 5% risk. 
• Genetic explanations:

  • Candidate genes: MAOA & CDH13:

  A genetic analysis of 900 offenders by Tiihonen et al (2014) revealed two genes that may be associated with violent crime:

  ↳ The MAOA gene controls serotonin & dopamine & is linked to aggressive behaviour

  ↳ CDH13 is linked to substance abuse & ADHD

  The high-risk combination led to individuals being 13 times more likely to have a history of violent disorder
• Genetic explanations:

  • Diathesis-stress model: If genes have an influence on offending, this influence is likely to be at least partly moderated by environmental factors. A tendency to criminal behaviour may come about through a combination of:

  ↳ Genetic predisposition (diathesis)

  ↳ A biological or psychological stressor or ‘trigger’ (e.g. criminal role models or dysfunctional upbringing)
• Neural explanations:

  • Antisocial personality disorder (APD):

  There may be neural differences in the brains of criminals & non-criminals. For example, APD is associated with a lack of empathy & is suffered by many convicted criminals 

  • Less activity in prefrontal cortex = less emotional regulation

  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. This is the part of the brain that regulates emotional behaviour
• Neural explanations:

  • Mirror neurons (empathy) may not always be turned on:

  Keysers (2011) found that only when criminals were asked to empathise did they show an empathy reaction (controlled by mirror neurons in the brain). This suggests APD individuals do experience empathy, but may have a neural ‘switch’ that turns on & off. In a normally-functioning brain the empathy switch is permanently on.
• Limitation is the methodological problems with twin studies of criminality:

  Lange’s research was poorly controlled (whether twins were MZ or DZ was based on appearance not DNA testing). Also, most twins are reared in the same environment - so concordance rates may be due to shared learning experiences rather than genetics. Methodological issues such as confounding variables mean twin studies of criminality may lack validity
• Another limitation is methodological problems with adoption studies:

  Adoption studies are complicated by the fact that many children experience late adoption. So these children spent time with their biological parents before adoption. In addition, lots of adoptees maintain contact with their biological parents. Both of these points make it difficult to assess the environmental impact the biological parents might have had
• Limitation is that it is biologically determinist:

  The notion of a ‘criminal gene’ presents a dilemma. The legal system is based on the premise that criminals have personal & moral responsibility for their crimes. Only in extreme cases can someone say they were not acting entirely on their own free will. This raises ethical questions about what society does with people who are suspected of carrying criminal genes & who therefore have a limited choice