Biological Explanations 2

Q: Neural Explanations of Criminal Behaviour

__Raine et al. (1997)__ conducted a study to examine the link between brain abnormalities and criminal behaviour. Their findings support the biological explanation of criminality.

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Genetic Explanations: Aggression and Y Chromosome Studies

There are three main pieces of evidence for the genetic explanation of criminality: adoption studies, genetic influences on aggression and extra Y chromosome studies.

Genetic influences on aggression

The second piece of evidence for the role of genetics in criminal behaviour would be levels of aggression.
Psychologists have stated that there is a link between aggression and criminal behaviour.
Higher levels of aggression could lead to criminal activity.

Christiansen (1977)

Studies have shown that there is a link between genetics and aggression.
Twin studies like Christiansen (1977) found that:
- Male identical twins had 35% concordance for criminality.
- Whereas male non-identical twins had only a 12% concordance rate.
- Females had a 21% concordance for identical.
- And 8% for non-identical.

Y chromosomes

The final piece of evidence for the role of genetics in criminal behaviour would be studies done on extra Y chromosomes.
Males are supposed to have an XY chromosome pattern.

Jacobs et al. (1965)

By examining a prison population, Jacobs et al. (1965) found that there was a higher percentage of prisoners with the atypical chromosome pattern (XYY) compared to non-prisoner population.
The study stated that the extra Y chromosome could be linked to increased testosterone production and increased violent behaviour.
These could lead to criminal behaviour.

Other studies

Other, later, studies found that the chromosomal pattern results in:
- Hyperactivity
- Increased impulsivity
- Lower IQ
These three factors could explain increased criminal behaviour.

Neural Explanations of Criminal Behaviour

Raine et al. (1997) conducted a study to examine the link between brain abnormalities and criminal behaviour. Their findings support the biological explanation of criminality.

Method:

PET scans create 3D images of processes that occur within the brain.
PET scans detect differences in glucose metabolism, an important process for neuron conduction.
Raine scanned 41 murderers and 41 control participants.
The murderers had plead not guilty by reason of insanity.

Results:

There were differences in glucose metabolism in three areas of the brain:
- Prefrontal cortex.
- Superior parietal gyrus.
- The corpus callosum.

Results cont.:

These three areas had reduced glucose metabolism in the murderers as compared to the controls.
There was also asymmetric activity in the two hemispheres in the murderers.
Overall, some brain processes were dysfunctional in the murderers.

Conclusions:

Raine et al. found evidence of neural differences in murderers compared to controls.
The evidence supports a link between brain dysfunction and violent criminal activity like murder.

Evaluation: Strengths

The researchers used a control group who were matched on age and sex, increasing the validity of the results.

Evaluation: Limitations

They found a correlation between brain dysfunction and violent behaviour, however, a causal relationship cannot necessarily be concluded.
The reason being that the researchers could not randomly assign the participants into the murderer group and the control group.
To study the causality of brain dysfunction on criminal behaviour, a longitudinal study would have to be done.