Biologocial Approach: Methodology
QUASI-EXPERIMENT with a MATCHED PAIRS DESIGN. IV=NGRI or not DV=Brain differences
Murderers: 41 murderers (39 men and 2 women) with a mean age of 34.3 years. Charged with murder or manslaughter and all pleaded NGRI. Schizophrenia-6 Head/brain damage-23 DRug abuse-3 Affective disorder-2 Epilepsy-2 Hyperactivity/learning disability-3 Personality disorder-2. Medication free 2 weeks before brain scanning.
Control group: Matched each murderer with a 'normal' individual of the same age and sex. The schizophrenics were also matched with schizophrenics. None of the other controls had any history of psychiatric illness or in any close relatives and no physical illness. None were taking medication.
Biological Approach: Procedures
Sample obtained used OPPORTUNITY SAMPLING. A PET Scan was used to study the brain. All participants were given a FDG tracer injection. It was taken up by active areas of the brain which is what made it possible to compare the brains of the NGRI and control groups.
The participants were asked to do a continuous performance task (CPT). This was done to activate target areas of the brain to show how different areas of the brain functioned.
1. Participats were able to practise the CPT before they were given the injection.
2. 30 seconds before the injection the participants started the CPT so that the initial task novelty wouldnt be labelled by FDG.
3. 32 minutes after the FDG injection a PET scan was done of each participant. 10 horizontal pictures (also called slices) of the brain were recorded using the cortical peel and box techniques. The article provides details of the scanning techniques so that the study could be replicated.
Biological Approach: Findings
Brain differences: Reduced activity in NGRI participants in the prefrontal cortext and corpus callosum. These areas are linked to violence. Increased activity in NGRI participants in the cerebellum and amygdala. These areas are not linked to violence. No difference between the groups in midbrain and putamen. Violence is not linked to these areas either.
Performance on CPT: Both groups performed similarly. This means that any brain differences were not related to the CPT.
Other differences not controlled for:
Handedness-6 of the muderers were left handed but had less amygdala asymmetry and higher medical prefrontal activity than right-handed murderers.
Ethnicity-14 of the murderers werent white but a compariosn between ethnicities showed no significant difference in brain activity.
Head injury-23 of the murderers had a history of head injury, no difference from murderers with no history of brain injury.
Biological Approach: Conclusions
This study supports previous findings that have shown links between areas of the brain and aggression. This provides evidence that murderers pleading NGRI have different brrain functioning to normal individuals.
Confounding variables: Large sample and matched controls. However, head injury and IQ have not been ruled out as contributory factors.
Warning: These results don't show that-
1. Violent behaviour is only determined by biology. Social, cultural etc factors have an impact
2. Murderers pleading NGRI are not responsible for their actions nor thst PET scans can diagnose violent individuals.
3. Violence can be explained by the results, the results only relate to criminal behaviour.
4. Brain dysfunction causes violence, may be an effect of violence
Findings DO suggest link between brain dysfunction and predisposition towards violence in this NGRI group.