Raine et al. (1997) Flashcards
What is the aim of Raine et al.’s study?
To find out if there is a difference in the structure of brain activity between people who have committed murder (NGRIs) and non-murderers.
What was the sample of the study?
41 offenders pleading NGRI to murder and 41 controls.
How many men and women were there?
39 males, 2 females.
What was the average age of the P’s?
34.3
How many P’s had brain damage or a mental disorder?
- 23 had brain damage.
- 3 had history of drug abuse.
- 6 had Sz
- 2 had epilepsy
- 7 had other emotional or learning disorders.
Who were the control group?
People of same age and sex with no history of crime or mental illness, excpet 6 controls who had sz.
What was the procedure?
- Injected with radioactive glucose tracer then performed the Continuous Performance Task (CPT) for 32 minutes.
- Then PET scan was carried out.
Where did the experiment take place?
University of California.
What other experimental controls did Raine use?
- P’s allowed to practice CPT 10 mins before glucose tracer was injected to make sure they were all equally familiar with it.
- Raine made sure no P’s were on medication (NGRIs had been kept medication free for 2 weeks before PET scan.
What does PET stand for?
Positron Emission Tomography
How much activity was in the frontal lobe?
NGRI’s showed less activity in the frontal lobe (especially in prefrontal cortex - associated with self-restraint).
How much activity was in the parietal lobe?
Less acitvity in the parietal lobe (associated with abstract thinking, e.g. morality).
How much activity was in the occipital lobe?
More activity in occipital lobe (associated with vision).
How much activity was in the corpus callosum?
Less activity (CC associated with long-term planning)
How much activity in the left and right hemisphere?
Imbalance of activity between the left and right hemispheres in the limbic system.
- Less in left side.
- More on right side in amygdala and MTL/hippocampus
- More activity on right side of thalamus.
- Areas of brain associated with aggression in animals.
- More activity on right side of thalamus.
What are some important results?
The mean relative glucose metabolism observed in…
- Corpus callosum: NGRIs = 0.56, Controls = 0.68.
- Amygdala (right hemi): 0.05 more in NGRIs than Controls.
- Thalamus (right hemi): 0.06 more in NGRIs than Controls.
What are the conclusions of Raine’s study?
- Prefrontal deficits might make someone more impulsive/emotional.
- Deficits in limbic system might make someone more agg.
- Deficits in corpus callosum make it ahrder for brain hemispheres to communicate, making it difficult to think through long term consequences and make decisions.
- Areas like partietal lobe, amygdala and hippo play a role in recognition; deficits here make it harder for someone to judge social situations, leading them to overreact.
Was Raine’s study generalisable?
Yes✅:
- Large sample (82). Anomalies, i.e. P’s who disrupted test by not focusing on CPT, shouldn’t skew data too much.
- Makes results representative of a wider population.
No❌:
- NGRIs are unusual offenders - murderers who don’t remember doing it or are too confused to stand trial.
- Not representative of “typical” murderers, still less of typical violent individuals: not all of NGRIs killed victims violently (as Raine pointed out).
Was Raine’s study valid?
Yes✅:
-
Construct validity: Bufkin & Luttrell (2005) carried out met-analysis of 17 studies that use brain imaging to study agg in humans.
- All study’s point to similar conclusions as Raine - adds construct validity to Raine’s study since it shows the results tie in with findings of other studies.
No❌:
- CPT was artificial and unconnected to violence and provocation. P’s were all doing unusual task and in unusual state of mind when PET test was carried out.
- Lowers ecological validity of study.
- Also, natural experiment which is correlational (cannot show cause-and-effect).
- e.g. NGRIs might have developed brain deficits after killing due to stress of event, arrest, imprisonment and upcoming trial.
Was Raine’s study reliable?
Yes✅:
- PET is reliable brain imaging technique that’s been used sicne 1970s. Produces objective and replicable results and can be tested and re-tested to check reliability.
No❌:
- Raine admits there were problems with reliability of PET scans in 1990.
- Unclear reuslts that had to be interpreted - introduces subjectivity from Raine making results less reliable.
