classic (Raine et al 1997)

Question 1

Aims

Answer 1

-to identify brain impairments in people charged with murder who pleaded not guilty by reason of insanity (NGRI).
-specifically that there would be dysfunctions in areas linked to violence in previous studies e.g., prefrontal cortex, amygdala and hippocampus.

Question 2

sample

Answer 2

• experimental group (39 men, 2 women) - people charged with murder or manslaughter, some assessed for defence of NGRI (free from all medication in the two weeks up to brain scans, urine tests)
• murdererd matched with controls on sex, age and ethnicity (no medication or history of psychiatric illness apart from six controls with schizophrenia, matched on this characteristic).

Question 3

Iv

Answer 3

merderer/ non-murderer

Question 4

dv

Answer 4

glucose metabolism (activity) in specific brain areas

Question 5

procedure

Answer 5

-difference experiment, not a true experiment, matched pairs, no random allocation.
-ppts did a continuous performance task (CPT, identifying targets on a screen for 32 minuets) and were injected with radioactive tracer during the task so that at the end, a PET scan could detect active areas of the brain.
-scan tool 10 images (‘slices’) through the brain at 10 mm intervals.

Question 6

findings

Answer 6

-in cortical regions, lower glucose metabolism )less activity) in murderers than controls in, for example, lateral/medial prefrontal areas.
-murderers: higher metabolism in occipital lobe (no prior link to violence).
-In subcortical regions, lower glucose metabolism in murderers than controls in, for example, left amygdala.
-Murderers had greater activity in right amygdala.

Question 7

conclusions

Answer 7

-therefore concluding the hypothesis was supported, murderers pleading NGRI had different brain activity from controls, with impaired functioning in brain areas earlier identified as involved with violent behaviour.
-Need caution in interpreting findings because there are other brain areas involved in violence that were not scanned.

Question 8

Generalisability

Answer 8

High- large sample of 82 which was the largest at the time for this sort of study. this means that anomalies, such as ppts with unusual brain structure or people who did not focus on the CPT, should not skew the data too much, making it representative of wider population.

Low- NGRIs are unusual offenders. They are not representative of typical murderers, and Raine points out, not all NGRIs killed their victims violently.

Question 9

reliability

Answer 9

high- PET is a reliable brain imaging technique that has been used with growing success. it produces objective and replicable results and it can be tested and re-tested to check its reliability.

low- however Raine admits that there were still problems with the reliability of PET scanning and the results were sometimes unclear and had to be interpreted, producing subjectivity and low reliability.

Question 10

validity

Answer 10

high- the cat used by Raine ensured that all ppts were concentrating on the same thing, ensuring they should all have similar types of brain activity which can be easily compared and accurately measured and compared, increasing internal validity of the findings.

low- the cat however could be criticised for being artificial and unconnected to violence. the ppts were all doing an unusual task and in an unusual state of mind when the PET scan was carried out. lowering ecological validity of the study.

low- as a natural experiment, this study cannot show cause-and-effect. for example, the NGRIs might have developed their brain deficits after the killing, because of the stress of the event, their arrest and imprisonment and their coming trial.