Genetic and neural explanations

Genetic Explanations

Genetic explanations for crime suggest that would-be offenders inherit a gene or combination of genes, that predispose them to commit crime.

The importance of genes is illustrated by twin studies. A twin study was conducted by Johannes Lange who investigated 13 identical twins (MZ) and 17 non-identical twins (DZ) where one of the twins in each pair had served time in prison. Lange found that 10 of the MZ twins had a co-twin who was also in prison whereas there was only 2 from the DZ twins. Lange concluded that genetic factors contribute to individuals to be predisposed to commit crime.

Karl Christiansen studied 87 MZ and 147 DZ twins and found a concordance of 33% for MZ's and 12% for DZ's which supports the view that offending may have a genetic component.

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Candidate genes: A genetic analysis of almost 900 offenders by Jari Tiihonen et al - found that abnormalities of two genes that may be associated with violent crimes. The MAOA gene which controls dopamine and serotonin the brain and has been linked to aggressive behaviour. CDH13 which has been linked to attention deficit disorder. Within the Finnish sample as part of their research - they found that individuals with this high risk combination of genes were 13 times more likely to have a history of violent behaviour. However, this research has not been replicated therefore having poor validity and representativness issues.

Diathesis-stress model: This model applies to schizophrenia however it shows how criminal behaviour may come about through the combination of genetic predisposition and biological or psychological trigger - for example, being raised in a dysfunational environment or having criminal role models. The diathesis-stress model says that both a vulnerability and stress-trigger are necessary in order to develop the condition but applying that to criminology this means that criminals who have a genetic vulnerability and has a stress-trigger such as dysfunational family can cause them to offend.

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Evidence suggests that there may be neural differences in the brains of criminals and non-criminals.

Much of the evidence is investigated on individuals diagnosed with antisocial personality disorder (psychopathy). APD is associated with reduced emotional responses, a lack of empathy for the feelings of others and is a condition that is featured in many convicted criminals

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Prefrontal cortex - Adrian Raine has studied on the APD brain and found that individuals who have antisocial personalities have reduced activity in the prefrontal cortex, this part of the brain regulates emotional behaviour. He also found that there is a 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to controls.

Mirror neurons - Chistian Keysers et al found that only when criminals were asked to empathise did their empathy reaction activate. Empathy is controlled by mirror neurons in the brain. APD individuals are not totally without empathy, but may have a neural 'switch' that can be turned on and off, unlike the 'normal' brain which has the empathy switch permanently on. Mirror neurons fire both in response to personal action and in response to action on the part of others. These neurons allow us to interpret intention and emotion in others and how we understand each other's intentions behind their behaviour and their emotions behind it.

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There is a problem with twin studies where the study was poorly controlled and judgements related to zygosity (whether twin pairs were MZ or DZ) were based on appearance rather than DNA testing. Therefore lacks validity.
Twin studies involved small sample sizes and twins are an unusual sample in themselves and may not represent the rest of the population.
Most twin studies were conducted in the same environment which is a major confounding variable as concordance rates may be due to shared learing experiences (environmental factors) rather than genetics. Therefore lacks internal validity.
The is support for the diathesis-stress model of crime where a big study was done on 13,000 Danish adoptees by Sarnoff Mednick et al. They found that when neither the biological nor adoptive parents has convictions, the percentage of of adoptees that did was 13.5%. This figure rose to 20% when either of the biological parents has convictions and 24.5% when both adoptive and biological parents had convictions. This suggests that genetic inheritance plays an important role in offending, environmental influence also has a influence on offending as well which supports the diathesis-stress model of crime.

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There is a problem with adoption studies because the seperation of genetic and environmental influences in adoption studies is complicated by the fact that many children experience late adoption, this means that much of their childhood may have been spent with their biological parents anyway. Also, many adoptees maintain regular contact with their biological parents following after their adoption. This makes it hard to understand the environmental impact the biological parents might have had on the adoptees.
In Mednick's study, - the figures quoted only applied to petty offences such as burglary and not violent crimes therefore their conclusions draws away from more serious forms of crime such as murder.
This approach to crime takes on a reductionst approach it breaks down the components into its constituent parts such as genes and neurons. This is said to be too simple because crime is a result of many factors. It fails to acknowledge the importance of criminals suffering from emotional instability, mental illness, social deprivation and poverty. This makes it difficult to disentangle the effects of genes and neural influences from other possible factors.

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