Genetic and neural

Genetic explanation

Any account that suggests that a physical or psychological behaviour is determined by genes.

Genes are the core elements of chromosomes.

Genes consist of DNA which produces chemical instructions for the physical (eye colour) and psychological (intelligence) features of an organism.

Transmitted from parents to offspring.

Neural explanation

Any account that suggests that a physical or psychological behaviour is determined by the nervous system.

Twin studies

Christiansen

Crowe

Studied over 3500 twin pairs in Denmark and found concordance rates for offender behaviour of 35% for MZ men and 13% for DZ men. Included all twins born between 1880 and 1910 in a region of Denmark.

Offender behaviour was checked using Danish police records. Indicates that it is not just the behaviour that might be inherited but also the underlying predisposing traits.

Found that adopted children whose biological mother had a criminal record had a 50% risk of having a criminal record by the age of 18 but adopted children whose biological mother didn’t have a criminal record had a 5% risk.

Candidate genes

Tiihonen

A genetic analysis of 800 Finnish offenders suggested that 2 genes may be associated with violent crime.

MAOA - Regulates serotonin in the brain. Linked to aggressive behaviour.

CDH13 - Linked to substance abuse and ADHD.

The analysis found that about 5-10% of all severe violent crime in Finland is attributable to the MAOA and CHD13 stereotypes

Diathesis-stress model

If genetics have an influence on offending, it seems likely that this is partly moderated by the effects of the environment.

A tendency towards offending behaviour may come about through the combination of genetic predisposition and biological or psychological stressor/stimulus e.g. being raised in a dysfunctional environment or having criminal role models.

Antisocial personality disorder

Associated with reduced emotional responses, a lack of empathy for the feelings of others and is a condition that characterises many convicted offenders.

Much evidence for neural differences in the brains of offenders and non-offenders has involved people diagnosed with APD.

Prefrontal cortex

Raine conducted many studies of the APD brain, reporting that there are a lot of brain-imaging studies demonstrating that individuals with antisocial personalities have reduced activity in the prefrontal cortex (regulates emotional behaviour)

Also found an 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to control.

Mirror neurons

Research suggests that offenders with APD can experience empathy but more sporadically than us.

Keysers found that only when offenders were asked to empathise did their empathy reaction (controlled by mirror neurons) activate.

Suggests that APD individuals are not totally without empathy but they may have a neutral switch that can be turned on and off unlike the neurotypical brain which has the empathy switch permanently on.

Genetic W Using twin studies as genetic evidence is the assumption of equal environments

Researchers studying twins assumed that environmental factors are held constant as twins are brought up together and must experience similar environments.

This ‘shared environment assumption’ may apply more to MZ twins than DZ twins as they look identical and people tend to treat them more similarly, so their environments are similar.

Higher concordance rates for MZs in twin studies may be because they are treated more similarly than DZ twins.

Genetic S Mednick

Support for the diathesis-stress model of offending

Studied over 14,000 Danish adoptees who had at least 1 court conviction.

When neither biological or adoptive parents had convictions the percentage of adoptees with convictions was 13.5%.

Rose to 20% when either of the biological or adoptive parents had convictions

24.5% when both adoptive and biological parents had convictions.

Shows that genetic inheritance plays an important role in offending but environmental influence is also important. Supports the diathesis-stress model of crime

Neural Kandell + Freed

Support for the link between crime and the frontal lobe

Reviewed evidence of frontal lobe damage and antisocial behaviour.

People with this damage showed impulsive behaviour, emotional instability and an inability to learn from their mistakes. The frontal lobe is associated with planning behaviour.

Supports the idea that brain damage may be a casual factor in offending behaviour.

Neural W Farrington

Link between neural differences and APD may be complex

Studied a group of men who scored high on APD. These people had experienced various risk factors in childhood like being raised by a convicted parent and being physically neglected.

It could be that these early childhood experiences caused APD and some of the neural differences associated with it like reduced activity in the frontal lobe due to trauma.

Suggests that the relationship between neural differences, APD and offending is complex and there may be other intervening variables that have an impact.