There is evidence that brain damage leads to a change in behaviour for example, from law-abiding to a criminal. Thus it can explain criminality in that damage sustained by certain areas of the brain e.g. pre-frontal cortex, can affect the impulsiveness and fearlessness etc of an individual, driving them to crime.
- Main study - Raine:
- Looked at patterns of brain activity in murderers compared to non-murderers using PET scans.
- 41 p's charged with murder, pleaded NGRI but convicted, 39 M 2 F. Control group matched for age and sex. 6 p's had schizo - controls also matched.
- P's injected with a glucose tracer following a practice task, they then did a continous performance task. PET scans were taken immediately after 10 horizontal images and 10 mm intervals. Scans used to indicate brain activity in different areas.
- Findings: Sig. differences in activity levels between murderers and control. Reduced activity on left side of brain and in pre-frontal cortex + corpus callosum (implicated w/ aggression). Reduced activation in hippocampus, thalamus and amygdala.
The areas with abnormal activity are associated with lack of fear, low self-control, increased aggression and impulsiveness. All linked with committing acts of extreme violence.
Genes and Serotonin
Christiansen looked at over 3000 twin pairs in Denmark and found a 52% concordance rate for criminality in monozygotic twins compared to 22% concordance rate for dizygotic twins - thus suggesting there is a strong genetic component to criminality.
Main study - Brunner:
- Brunner et al aimed to explain the behaviours of males in a Dutch family, who were affected by a syndrome of borderline mental retardation and abnormal violent behaviour. This included arson, attempted **** and exhibitionism.
- 5 affected males were studied with urine samples collected and analysed over 24 hours.
- Analysis showed a disturbed monoamine metabolism associated with a deficit of MAOA enzyme. A point mutation was identified on the x chromosome of the gene responsible for MAOA production.
- As less MAOA was being produced, this meant less serotonin was being broken down.
Conclusion: MAOA is involved in serotonin metabolism. Impaired seratonin metabolism is likely to be responsible for mental retardation and linked to aggressive behaviour and failure to control aggression.
Evolutionary psychologists will explain criminality through adaptiveness and reproductive success. In the past, males exhibited risk taking behaviour in order to hunt and provide food, as well as for mating purposes. They also have higher levels of testosterone - this risk taking behaviour ensures that males survive and their genes are passed on.
- Main Study - Raine :
- A multi-factorial approach to understanding anti-social behaviour - a meta-analysis where he reviewed and summarised findings from a selection of articles on neurology, neurobiology etc.
- Raine found that:
- Low resting heart rate was the most common factor in anti-social children.
- Males have a lower resting heart rate than females.
- Low heart rate is inherited.
- Males seek to raise their low heart rate by engaging in risky behaviour. - In some cases this can be crime.
- There is a relationship between heart rate and psycho-social risk factors.
Thus intervention schemes can be useful in reversing the biological deficit and preventing those at risk (biological disposition) from turning to crime.