5 - Genetic and Neural Explanations Flashcards
What is the theory of genetic explanations?
States that would-be offenders inherit a gene, or combination of genes, that predisposes them to commit crime.
What is the genetics explanation supported by?
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.
What does polygenic mean?
One single gene is not responsible for offending.
Instead, many genes might be responsible for causing criminal behaviour; and they are known as, candidate genes.
Where did the theory of genes causing crime come from?
Conducted a genetic analysis of over 900 offenders which revealed abnormalities on two genes that may be associated with violent crime.
What are the two genes that cause crime?
MAOA
CDH13
How does the MAOA and CDH13 gene cause crime?
MAOA - controls dopamine and serotonin in the brain and has been linked to aggressive behaviour
CDH13 - linked to substance abuse and attention deficit disorder
What is the evidence for the MAOA and CDH13 gene causing crime?
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.
How does the diathesis-stress model influence crime?
States 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.
Outline the neural explanation for crime. Who was this tested on?
Evidence suggests that there may be neural differences in the brains of criminals compared with non-criminals.
A lot of 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.
What are the neural differences between those diagnosed with APD and normal people?
Reduced activity in the pre-frontal cortex of the brain - area that regulates emotional behaviour.
11% reduction in the volume of grey matter in the prefrontal cortex of people with APD compared to a control group.
How do APD patients deal with empathy?
Criminals with APD can experience empathy but that they do so more sporadically than the rest of us.
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.
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.
Evaluate genetic and neural explanations
- Early twin studies: poorly controlled + judgments on whether a set of twins were monozygotic or dizygotic were based on appearance rather than DNA testing. Most sets of twins are raised in a very similar environment is a major confounding variable. Concordance rates may be due to shared learning experiences rather than genetics. As a result twin studies may lack validity.
- Twin studies typically have a very small sample, and twins are an unusual sample in themselves. This means they may not represent the target population.
- Criminal behaviour in adopted children compared to their biological and adopted parents. When neither the biological or adopted parents had a criminal record the chance that the adoptees had was 13.5%, this rose to 20% when one of the biological parents had a criminal record. However, the chance that an adoptee would have a criminal record was highest, 24.5%, when a biological AND an adopted parent has a criminal record.
- Presumed separation of genetic and environmental influences in adoption studies is complicated by the fact that many children are adopted late so have spent part of their infancy with their biological parents, also lots of adoptees maintain regular contact with their biological parents. Therefore, biological parents can still have had an environmental impact.
- 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.
- Biological determinism. 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.
