classic study: Raine et al. (1997)

Question 1

what was the aim of the study ?

Answer 1

they wanted to use brain scans to identify any brain impairments in murderers who had pleaded not guilty by insanity

Question 2

what was their hypothesis ?

Answer 2

that the brain scans would show dysfunctions in areas linked in previous research to violence

Question 3

what experimental design was used ?

Answer 3

matched pairs - 41 murderers and 41 non-murderers

Question 4

what is the independent variable

Answer 4

whether they are a murderer or not

Question 5

what is the dependent variable ?

Answer 5

the glucose metabolism (i.e activity) in specific brain areas

Question 6

where was this experiment done ?

Answer 6

california

Question 7

what were the murderers matched on ?

Answer 7

• age
• gender
• ethnicity

Question 8

what screening processes did the control group undergo ?

Answer 8

• they had a physical examination

- they had a psychiatric interview

Question 9

what are some other controls used on the control group ?

Answer 9

none were taking medication and none had a history of psychiatric illness - except the six who had schizophrenia which were matched on that characteristic

Question 10

what type of brain scan was used ?

Answer 10

PETscan - injected with radioactive tracer so that brain activity would ‘light up’

Question 11

explain the whole procedure ?

Answer 11

1) ppts injected with radioactive tracer
2) immediately after the injection the ppts did a continuous participation task (ppts had to identify targets on a screen) to increase uptake of radioactive tracer in areas of the brain that they wanted to investigate
3) they did the CPT for 32 minutes and then did the PETscan immediately after - the scan took 10 slices through the brain at 10mm intervals

Question 12

what were the findings in the cortical regions ?

Answer 12

• murderers had a significantly lower glucose metabolism than the controls in areas such as the prefrontal areas, left angular gyrus and the left and right parietal areas
• murderers showed higher metabolism than the controls in the occipital lobe, a brain area not previously linked to violence

Question 13

what the findings in the subcortical regions ?

Answer 13

• murderers had lower glucose metabolism than the controls in the corpus callosum, left amygdala and left medial temporal lobe (including hippocampus) (as supported in previous research)
• murderers had greater activity in the right amygdala, the right medial temporal lobe and the right thalamus (not previously implicated in violent behaviour)

Question 14

what are the conclusions of the study ?

Answer 14

• the hypothesis was supported
• findings showed that murderers pleading NGRI have different brain activity from people who are not violent offenders
• murderers had impaired functioning in areas of the brain previously linked to violent behaviour