Raine et al (1997) Classic Study Flashcards
What did the aim investigate?
Differences in brain activity in NGRIs compared to a matched sample of non murderers using PET: specifically in prefrontal cortex, amygdala etc to see if brain disfunction predisposed people to violent behaviour
Number of participants?
41(39 males and 2 females) charged with murder who had pleaded ‘not guilty by reasons of insanity’ and a control group of 41
what were the control group matched on?
age and gender
What were the participants screened for?
general health
What were the participants told to do 2 weeks prior the experiment?
not take any medication
What did participants do before being injected with a radioactive glucose tracer?
they completed a 10 minute practice test
After being injected with the radioactive glucose tracer, participants completed a
continuous performance task for 32 minutes
Why did participants complete a 32 minute long continuous performance task?
Because it increases the activity in the frontal lobes of ‘normal participants’
What did the continuous performance task consist of?
A sequence of blurred numbers to focus on
A PET scan was performed immediately after the CPT which indicated
the level of activity in different areas of the brain
Murderers results for left medial prefrontal cortex
1.20
Murderers results for right medial prefrontal cortex
1.17
Non murderers results for left medial prefrontal cortex
1.25
Non murderers results for right medial prefrontal cortex
1.22
Murderers results for the left amygdala
0.94
Murderers results for the right amygdala
0.88
Non murderers results for the left amygdala
0.97
Non murderers results for the right amygdala
0.83
Murderers results for the right thalamus
1.15
Non murderers results for the right thalamus
1.09
Who had higher activity in the occiptial lobe?
Murderers
Conclusions?
Murderers have different brain functions to non murderers, the findings support that there are biological causes, prefrontal deficits cause implusivity and loss of self control
The hippocampus, amygdala and thalamus have all been related to
learning and it has been suggested that abnormal activity here could result in criminals being unable to modify their behaviour since they can’t learn from consequences
PET scanning was used and such scans can be interpreted objectively by more than one researcher meaning the results
tend to be reliable, as the same results can be found by different people , giving inter rater reliability
A large sample of 82 ppts which was the largest sample at the time using PET scans which means there were
sufficient people in each group for conclusions to be drawn and generalisation might have been possible to other murderers pleading not guilty by reason of insanity
The results of the study have application to real life as they are able to provide the possibility that there may be biological factors in the murderer’s behaviour, although
this cannot be shown by this research, it provides the basis for further research to investigate if it is the differences in brain function
Reliability is high as there were many controls like
> everyone did the 10min practice
the specific time gap of 32 mins between the injection and the PET
PET is objective
The researchers controlled potential factors that could have impacted the results since they
matched the groups and areas that were not matched were tested so comparisons could be drawn fairly giving internal validity
The findings describe the brain differences but do not explain them, it could be they were present from birth but it could be from the environment which
would suggest they are not caused biologically even if they are biological factors
The findings do not explain if the murderers are
responsible for their behaviour due to brain differences
Internal validity may be limited as the researchers commented on the fact that the PET scans were not clear which may have
affected their interpretation of images, meaning that mistakes could have been made due to subjectivity, meaning the results may not be accurate
The results can only be generalised to murderers pleading not guilty by reasons of insanity therefore the findings cannot be said to be true pf all violent behaviour as
they were not included in the sample, even though violence was being studied, making the sample not representative of the target population.
Generalisability is also limited as non violent criminals in the control group so
we cannot see if the same brain differences would be found in all criminals of different types
