Classic Study: Raine et al

Aim

To investigate whether murderers pleading NGRI would show brain dysfunctions in areas of the brain linked with aggression

Who were the participants?

41 murderers pleading NGRI and 41 controls matched on sex, age, and if they had schizophrenia

Procedure

1. Participants were not allowed to take any drugs for 2 weeks before the experiment and this was confirmed by a urine test.

2. Each participant was injected with a radioactive tracer

3. The tracer will make areas of the brain undergoing metabolism “light up” on a computer scan

4. 32 minutes after the injection, participants took part in tasks such as identifying a target and hitting a button

5. These tasks were to increase activity/metabolism in areas of the brain that the researchers were interested in

6. Immediately after the tasks, a PET scan was taken of all the participants brains creating 10, 10mm images

Findings

The murderers had increased activity in the right amygdala, right thalamus and right temporal lobe when compared to the controls.

They also had less activity in the lateral and medial pre-frontal cortex, left amygdala and parietal cortex than the controls.

Conclusion

Murderers pleading NGRI did have different brain activity than the controls. Also no single area of the brain solely responsible for violent behaviour. Not all parts of the brain were scanned so it is not a holistic but it is a useful preliminary study.

Strength of Raine et al’s study

I: High internal validity

J: Participant variables were decreased by the use of a matched pair design matching participants on age sex and if they were schizophrenic. A standardised procedure was also used using the same dose of tracer on each participant and they all waited 32 minutes to complete tasks. Each participant also took a drug urine test to ensure they had no drugs in their system which could affect their brain activity.

E: Since all confounding variables that could’ve affected brain activity were controlled for a relationship between brain activity/structure and violence can be established

Weakness of Rain et al’s study

I: However, other key elements were not controlled for.

J: 23 murders had pre-existing head injuries which may have affected their brain activity rather than the current brain structure. Additionally, the upbringing of the participants may affected May have affected their brains.

E: therefore researchers cannot be absolutely certain that other factors other than brain structure did not lead to the murderers’s violent behaviour