Biological Explanations 2
Psychology: AQA A Level, topic 16.1.7
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.
Test yourself on Biological Explanations 2
Males are supposed to have an which kind of chromosome pattern?
Which of the following is NOT a characteristic caused by the atypical XYY chromosome pattern?
In which area of the brain did Raine et al. NOT find differences in glucose metabolism?