Biological Classic Study Flashcards
What is the biological classic study?
Raine et al (1997)
What is the aim of this study?
- To look at direct measures of cortical and sub-cortical brain functioning by using PET scans in a group of murderers who had pleaded NGRI.
- To see if the expectation that murderers would show evidence of brain dysfunction in their prefrontal cortex as well as in other areas that have been linked to violent behaviour such as the limbic system were true.
Name the type of research method used.
Lab experiment: Matched pairs design
What was the sample?
-Control group: 41 people with a mean age of 37.1 years which wasn’t significantly different from the experimental group. They were thoroughly screened and showed no history of psychiatric illness. None of them had ever committed murder.
-Experimental group (murderers): Consisted of 41 people (39 men and 2 women) with a mean age of 34.4 years. All had been charge with murder or manslaughter and pleaded NGRI. 6 had schizophrenia 23 had head injuries or brain damage 3 had psychoactive substance abuse 2 had affective disorders 2 had epilepsy 3 had a history of learning disability 2 had paranoid personality disorder
What was controlled in this study?
-All offenders were in custody and were kept medication free for two weeks before the brain scan which was confirmed by urine tests after the PET scan.
Control group were also kept medication free.
-Tests were undertaken to make sure that being left handed or right handed had no effect on behaviour.
14 of the murderers were non white, but when compared to white murderers on the PET scan there were no significant differences between them.
what was the IV?
Murderer/Non murderer
what was the DV?
PET scans to measure brain activity in both groups.
Describe the procedure.
-Continuous performance task: Consisted of spotting targets on a screen and pressing a button to indicate the target has been recognised. This task was to engage the frontal lobes alongside the right temporal and parietal lobe.
Describe the procedure.
-Continuous performance task: Consisted of spotting targets on a screen and pressing a button to indicate the target has been recognised. This task was to engage the frontal lobes alongside the right temporal and parietal lobe.
- Researchers used individually moulded plastic to hold the p’s head in place so it wouldn’t move around and produce an unclear image.
- Their brains were scanned 10 times at 10mm intervals to pick up differences in glucose metabolism in both the cerebral cortex and the subcortical layers.
What were the results?
- PFC: Murderers had lower glucose metabolism than the control group, which can explain the impulsive behaviour and loss of control.
- Limbic system: Abnormal asymmetries of brain activity between the amygdala and the hippocampus in the murderers.
- Amygdala: Reduced left and greater right glucose metabolism in the murderers.
- Hippocampus: No significant differences in both groups.
What can be concluded?
- Deficits in the studied areas were linked with anti-social behaviour, violence and lapses in learning.
- The behaviours of the murderers cannot be concluded to a single brain mechanism that causes violence.
- The study only shows a correlation between brain abnormality and violent behaviour which means a cause and effect relationship cannot be established.
Objective
PET scans to show glucose metabolism for activity level.
Large sample
-Experimental group: 41 subjects which means any outliers could be identified.
Low generalisability
-Sample may not be representative towards all crime as all subjects were murderers and cannot explain why non violent crimes are committed.
Good reliability
-Standardised procedure: All subjects completed a CPT task for 32 minutes before undergoing PET scan.
