Genetic and neural explanations

• Genetics – genes consist of DNA strands. DNA produces ‘instructions’ for general physical features of an organism (such as eye colour, height) and also specific physical features (such as neurotransmitter levels and size of brains structures). These may impact on psychological features (such as intelligence and mental disorder). Genes are transmitted from parents to offspring – inherited
• Genetic explanations for crime suggested that would-be offenders inherit a gene or combination of genes that predispose them to commit crime.
• Diathesis-stress model

  If genetics do have some influence of offending, it seems it is likely to be partly moderated by the effects of the environment
• Factors that may contribute to a tendency to criminal behaviour(Diathesis-stress model)


  • Genetic predisposition
  • Biological or psychological stressor or trigger (e.g. a criminal role model or dysfunctional upbringing)
• Diathesis-stress model - This demonstrates that both biology and environment play a role in criminal behaviour
• Diathesis-stress model: This is supported by Mendick et al 1984: when neither biological or adoptive parents had criminal convictions 13.5% of adoptees offended (quite hight). This rose to 20% if either the biological parents had convictions and 24.5% when both biological and adoptive parents had criminal convictions. Demonstrates that both  biology and environment play a role
• Twin studies suggest genes predispose offenders to crime.
• Lange (1930) studied 13 MZ twins and 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 2 of the DZ twins.
• Christiansen  1977 studied over 3500 twin pairs in Denmark and found concordance rates for offender behaviour of 35% for MZ twin males and 13% for DZ males (with slightly lower rates for females). This included all twins born between 1880 and 1910 in a region of Denmark. Offender behaviour was checked against Danish police records. This data indicates that it is not just the behaviour that might be inherited but the underlying predisposing traits.
• Crowe (1972) found that adopted children whose biological mother had a criminal record had a 50% risk of having a criminal record by 18 whereas adopted children whose biological mother didn’t have a criminal record only had a 5% risk – therefore criminality is attributable to genes
• Candidate genes: A genetic analysis of 800 Finnish offenders by Tiihonen et al 2015 suggested that 2 genes (MAOA and CDH13) gene has been associated with violent crime. Found 5-10% of all severe crime in Finland is attributed to these genes.

  The MAOA gene regulates serotonin in the brain. MAOA gene produces the enzyme that noradrenaline, dopamine & serotonin. A shortened version of MAOA produces lower levels of the enzyme that breaks down these neurotransmitters this has been linked to aggressive behaviour which is linked to violent crime.
• Candidate genes: CDH13 gene has been linked to substance abuse and attention deficit hyperactivity disorder.

  The analysis found that 5-10% of all severe violent crime in Finland is attributable to the MAOA and CDH13 genotypes
• Genetic explanation - Opposing Tiihonen et al study in 2015 is only 2-10% of all severe violent crime is attributable to these genes. This is a low percentage and there is a lot of violent crime. Therefore this suggests that the cause of crime may be to partly due to this but also from and interaction with the environment (diathesis-stress model). Also this study has not been replicated (scientific method). Also it did not have a control group so people who have not committed violent offences may also have these genes and it may just be a coincidence – lacks validity
• Genetic explanation - There is a lack of control of extraneous variables in adoption studies. They may still be in contact with biological parents. They may have experienced neglect but the parents may not be criminals (still a stressor). These may have impacted the findings – reducing validity
• One strength for a diathesis-stress model of crime.

  Mednick et al 1984 studied 13,000 Danish adoptees + criminality (operationalised as having at least one court conviction which was checked against police records). When neither biological nor adoptive parents had convictions, the percentage of adoptees that had a conviction = 13.5%. This rose to 20% when either of the biological parents did + 24.5% when both adoptive + biological parents did. This data suggests that both genetic inheritance + environment influence criminality – supporting the diathesis stress model of crime.
• One -ve with using twin studies is the assumption of equal environments - It is assumed by researchers studying twins that environmental factors are held constant because twins are bought up together + therefore experience similar environments. However, this ‘shared’ environment assumption may apply to more MZ twins than DZ twins because MZ twins look identical + people (especially parents) tend to treat them more similarly, which in turn affects their behaviour. Therefore higher concordance rates for MZs in twin studies may simply be because they are treated much more similarly than DZ twins.
• Also methodological issues with twin studies

  Lange’s research was poorly controlled. For instance judgements of whether twin pairs were MZ or DZ was based on appearance and not DNA testing. Methodological issues such as confounding variables mean twin studies of criminality may lack validity.
• A further 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 (nurture as well as nature
• Genetic + neural = One limitation is that these explanations are biologically reductionist

  Criminality is complex; explanations that reduce offending behaviour to a genetic or neural level ignore higher level explanations. Crime runs in families but so do poverty, deprivation and mental illness. This makes it difficult to disentangle the effects of genes and neural influences from other factors. This indicates that genetic and neural explanations in isolation are too simplistic.
• Genetic + neural Another limitation is that these explanations are also biologically determinist

  The notion of a ‘criminal gene’ presents a dilemma. The legal system is based on the premise that criminals have personal and moral responsibility for their crimes. Only in extreme cases (e.g. diagnosis of mental illness) can someone claim that they were not acting entirely of their own free will. This raises ethical questions about what society does with people who are suspected of carrying criminal genes and who therefore have a limited choice.
• Neural explanation – any explanation for behaviour (and its disorders) in terms of (dys)functions of the brain and nervous system. This includes the activity of brain structures such as the prefrontal cortex and neurotransmitters such as serotonin and dopamine.
• Neural explanations - Antisocial personality disorder

  Evidence suggests there may be neural differences in the brains of offenders and non-offenders. Much of the evidence in this area has involved people diagnosed with antisocial personality disorder (psychopathy).

  ADP is associated with reduced emotional responses, a lack of empathy for the feelings of others and is a condition that characterises many convicted offenders
• Prefrontal cortex

  Less activity in the prefrontal cortex = less emotional regulation

  Raine et al 2000, conducted many studies of the ADP brain, reporting that there are several dozen brain imaging studies  demonstrating that individuals with antisocial disorder have reduced activity in their prefrontal cortex.

  Raine et al 2000 found an 11% reduction in the volume of grey matter in the prefrontal cortex of people with ADP compared to controls.

  This is the part of the brain that regulates emotional behaviour.
• Mirror neurons

  Mirror neurons (empathy) may not always be turned on.

  Recent research suggests offenders with ADP can experience empathy but they do so more sporadically than the rest of us.

  Keysers 2011, found that only when criminals were asked to empathise (with a person depicted showing pain on film) did they show an empathy reaction (controlled by mirror neurons in the brain).

  This suggests that ADP individuals do experience empathy but they may have a neural ‘switch’ that can be turned on and off unlike the normal brain which has the empathy switch permanently on.
• one strength of the neural explanation is support for the link between crime and the frontal lobe.

  Kandel and Freed 1989 reviewed evidence of frontal lobe damage (including the prefrontal cortex) and antisocial behaviour. People with such damage tended to show impulsive behaviour, emotional instability and an inability to learn from their mistakes. The frontal lobe is associated with planning behaviour. This supports the idea that brain damage may be a causal factor in offending behaviour.
• Neural differences + APD

  Link may be complex
• Other factors may contribute to APD, and ultimately offending
• APD


  Antisocial Personality Disorder
• Farrington et al 2006 studied a group of men who scored high on APD
• Individuals with high APD


  • Experienced various risk factors during childhood e.g. raised by convicted parent, being physically neglected
• Early childhood experiences


  Caused APD and some of the neural differences associated with it e.g. reduced activity in the frontal lobe due to trauma (Rauch 2006)
• The relationship between neural differences, APD and offending is complex and there may be other intervening variables that impact
• Candidate genes MAOA and CDH13

  A genetic analysis of 900 offenders by Tihonen et al (2014) revealed 2 genes that may be associated with violent crime:

  • The MAOA gene controls serotonin and dopamine and is linked to aggressive behaviour
  • CDH13 is linked to substance abuse and ADHD

  This high-risk combination led to individuals being 13 times more likely to have a history of violent disorder