Lesson 4: Genetic and Neural Explanations

Question 1

Genetic Explanations

Answer 1

Genetic explanations for crime suggest that would-be offenders inherit a gene, or combination of genes, that predisposes them to commit crime. Lange (1930) investigated 13 monozygotic (identical) twins and 17 dizygotic (non-identical) twins. At least one of the twins in each pair had served time in prison. 10 of the 13 pairs of monozygotic twins had both spent time in prison, whereas only 2 of the 17 pairs of dizygotic twins had both spent time in prison.

Question 2

Is criminal behaviour polygenic

Answer 2

Criminal behaviour could be polygenic; this means that no one single gene is responsible for offending. Instead, many genes might be responsible for causing criminal behaviour; and they are known as, candidate genes. Tilhonen et al. (2014) conducted a genetic analysis of over 900 Finnish offenders which revealed abnormalities on two genes that may be associated with violent crime. The first was the MAOA gene, which controls dopamine and serotonin in the brain and has been linked to aggressive behaviour. The second was the CDH13 gene, this gene has been linked to substance abuse and attention deficit disorder. Within the Finnish sample individuals with this high-risk combination of genes were 13 times more likely to have a history of violent behaviour compared to a control group.

Question 3

The diathesis-stress model

Answer 3

The diathesis-stress model holds that genetics influence criminal behaviour but this is at moderated by the effects of the environment. A tendency towards criminal behaviour may come through a combination of genetic predisposition and biological or psychological triggers, such as being raised in a dysfunctional environment

Question 4

Neural Explanations

Answer 4

Evidence suggests that there may be neural differences in the brains of criminals compared with non-criminals. Much of the evidence in this area has investigated individuals diagnosed with anti-social personality disorder (APD). APD is associated with reduced emotional responses and a lack of empathy, a condition that characterises many convicted criminals.

There are several dozen brain-imaging studies demonstrating that individuals with anti-social personalities have reduced activity in the pre-frontal cortex of the brain. This is the brain area that regulates emotional behaviour. Raine et al. (2000) found an 11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to a control group.

Recent research has suggested that criminals with APD can experience empathy but that they do so more sporadically than the rest of us. Keysers et al. (2011) found that only when criminals were asked to empathise (with a person on a film experiencing pain) did their empathy reaction (controlled by mirror neurons in the brain) activate. This suggests that APD individuals are not totally without empathy but may have a neural switch that needs to be turned on in order to experience it. In a normal brain the empathy switch is permanently switched on.

Question 5

Disadvantages of Genetic and Neural Explanations

Answer 5

• Concordance rates in MZ twins are not high and leave plenty of room for non-genetic environmental factors. Concordance rates may be due to shared learning experiences rather than genetics. Brain scanning studies (such as Raine et al., 2000) show pathology in brains of criminal psychopaths, but cannot conclude whether these abnormalities are genetic or signs of early abuse.
• The term ‘offending behaviour’ is too vague. Some specific forms of crime may be more biological than others e.g. physical aggression.
• The genetic and neural explanation of criminal behaiour is an example of biological reductionism. Criminality is complex and explanations that reduce offending behaviour to a gene or imbalanced neurotransmitter may be inappropriate and overly simplistic. Criminal behaviour does seem to run in families, but so does emotional instability, mental illness, social deprivation and poverty. Twin studies never show 100% concordance rates in monozygotic twins, so genetics cannot be the only explanation for criminal behaviour.
• The genetic and neural explanation of criminal behaviour is also an example of biological determinism. This presents us with a dilemma for our legal system. If someone has a criminal gene they cannot have personal and moral responsibility for their crime. If this is the case it would be unethical to punish someone who does not have free will.