Classic: Raine Flashcards
Aim
To investigate whether brain dysfunction predisposed people to violent behaviour.
Sample
41 murderers pleading not guilty by reason of insanity and 41 controls were used. The murderers were at an average age of 34.3 years of and were 39 men and two women. All had been referred to university of California Imaging Center to obtain evidence for their reason of insanity defence. The murderers consisted of 23 people with a history of brain damage, 6 schizophrenics, 3 with history of substance abuse, 2 with affective disorder, 2 with epilepsy, 2 with paranoid personality disorder and 3 with a learning disability. The control group were formed by matching each murderer with a non-murderer of same sex and age and similar in other ways e.g. schizophrenia.
Method
Each participant carried out a practice test, and then a FDG trace was injected. Ps. then carried out a continuous performance task and target recognition was recorded, After a 32 min period of FDG uptake, ps. were taken for a PET scan.
Results
No difference in performance between groups. In the cortical regions, murderers had lower metabolism in some of the prefrontal areas. In the parietal lobe, the murderers had lower glucose metabolism. In the temporal lobe, there was no significant difference. In the occipital lobe, the murderers had higher glucose metabolism. Sub cortical regions: in the corpus callosum the murderers had lower glucose metabolism, particularly those with a history of brain damage. The murderers had reduced activity in the left amygdala and greater activity in the right amygdala. Murderers had greater thalamic activity. Murderers had reduced left activity and increased right in medial temporal lobe.
There is no single mechanism in the brain that causes violent behaviour, but it is clear that murderers have different brain functioning to non-murderers.
+reliable
PET scanning is objective and results can be interpreted and replicated by more than one researcher – high reliability.
+generalisability
Large sample size so there are sufficient people from each group for conclusions to be firm – high generalisability to other murderers who plead not guilty by reason of insanity.
-generalisability
It can only be generalised to murderers who plead not guilty by reason of insanity as they were the specific group being studied, so the results cannot be applied to all violent offenders.
-EVs
Brain dysfunctions cannot be found in the study – the findings outline differences between murderers and non-murderers but cannot explain them. It could be that these differences were present at birth and are biologically given or could come from environmental influences, but this study cannot clarify which.
