Context/background
Damage to the pre-frontal cortex results in impulsivity, immaturity, altered emotions, loss of self control and more general aggression
The amygdala controls neurones in the medial temporal lobe and processes emotions
Ngri = not guilty by reason of insanity
PET scans = to see if there are brain abnormalities in murderers who plead NGRI and to see if significant differences could be found between patterns of glucose metabolism in brains of individuals and murderers. This may show that the murderers pleading NGRI may be more prone to violence naturally
Aim
To study brain activity in non murderers and murderers using PET scans to see if there are any differences in the areas associated with violence
Pet scan = positron emission tomigrahy, a brain scanning technique where a participant is injected with a radioactive tracer used in brain respiration
The molecules of the tracer travel through the bloodstream and break down is detected by the scanner, which indicates levels of brain activity
Method
Sample
Murderers = 39 M and 2 F, on average 34 years, each pleaded NGRI but had been convicted
Control group = matched p's, 6 were schizophrenic
No one took drugs 2 weeks before the study
P's were scanned before in a continuous performance task (cpt) to increase brain activity
30 seconds before being injected, they began CPT, so that the novelty of starting the task wouldn't show up as an 'event' on the scan
The CPT was 32 minutes long, then 10 "slices" of the brain were taken (images of the brain) at 10 mm intervals
Cortical peel technique = used for lateral brain areas (sides/surfaces)
Box technique = used for medial area (inside)
Results
All the tests were 2-tailed
Means and standard deviations for calculated for the 2 IV levels
Murderers showed less brain activity in lateral, medial and prefrontal cortex, they also had abnormal asymmetric activation in their limbic systems and lower activity in their hippocampus and thalamus
Conclusion
Areas that had abnormal activity were associated with aggressive behaviour, lack of fear, impulse control and expression of emotions
These all lead to extreme violence, so the brain activity could be 1 factor of criminal behaviour
Evaluation
Brain scanning is valid and reliable
Precision of location of the scans in p's are hard to maintain, so lower internal reliability
The sample is generalisable
Because the p's were prisoners, it's hard to know how much informed consent they wanted to give and how much they felt they had to give
Biological strategy for preventing criminal behaviour
Lewinson found that 450 facial reconstruction operation patients in a prison who's behaviour was observed after both in prison and prison release over the next 10 years increased in cooperation with authority and increased participation in prison activities
They also experienced higher self esteem and it gave them a "new start"