RAINE ET AL (1997) Flashcards
What was the aim of the study?
To find out whether there were brain differences between criminals + non-criminals.
What type of criminal did they focus on?
Those who had committed a murder but were pleading not guilty by reason of insanity (NGRI).
Where would criminals have dysfunction?
- Pre-frontal cortex
- Amygdala
- Angular gyrus
- Hippocampus
- Thalamus
- Corpus Callosum
PAAHTC - PAATCH
Where would criminals not have dysfunction?
- Caudate
- Globus pallidus
- Midbrain
- Cerebellum
CGMC
What was the research method used?
Quasi-experiment:
- matched pairs design, IV = NGRI, DV = brain difference.
- Quasi because IV was naturally occurring i.e. there was already a pre-existing group of people who had been found NGRI + another who had not committed any crime. Researcher was not in control of which P’s were exposed to the IV and which were not.
- Each NGRI P matched w/ non-criminal P, same sex + age, acted as their ‘control’ in the control condition.
- Their brains were compared to establish any differences.
What was the sample?
82 P’s in total.
- 41 NGRI
- 41 non-criminal
Obtained by opportunity sampling.
What were the experimental conidtions (NGRI)?
- 41 murderers (39 M + 2F)
- mean age 34.3
- all charged w/ murderer or manslaughter and pleaded NGRI or incompetence to stand trial
- P’s referred to University of Cali. for examination to obtain proof of their diminished capacity. Reason for referral = the murderers had some for of mental impairment.
What were the control group?
- 41 non-criminals
- 6 schizophrenics from a mental hospital, matched w/ 6 schizophrenic NGRI P’s.
- other controls = no history of psychiatric illness + no P’s were taking medication
What were the procedures?
All P’s were given a PET scan which studied their brain in action and used to compare the brains of the murderers w/ the control group:
1. CPT practice for 30s so any brain activity of getting used to a novel task would not show up on final scans.
- CPT aimed to target specific areas of the brain to see how different areas functioned in non-criminals + criminals.
2. All P’s were given an injection of radioactive ‘tracer’ FDG.
- active areas of the brain use more glucose + the radioactive FDG binds to this glucose.
The more active an area of the brain, the more glucose it uses + therefore the more FDG is drawn to that area. Different levels of activity show up as different colours on the scan.
- Most = Red
- Least = Blue
3. P’s were asked to complete the proper CPT so that the investigators could see how different areas functioned in the murderers compared to non.
4. 32mins after the FDG injection, PET scan was conducted.
- 10 horizontal slices of the brain were recorded
- Precise details of the scanning were published to allow for replication.
What were the findings?
Murderers showed…:
Reduced activity in areas previously linked to violence compared to the controls:
- Pre-frontal cortex
- Left angular gyrus
- Left hemisphere = amygdala, thalamus + hippocampus
Increased activity in areas not previously linked to violence:
- Cerebellum
- Right hemisphere = amygdala, thalamus + hippocampus
No significant differences between the groups in the caudate, putamen, globus pallidus + midbrain
Both groups preformed similarly on the CPT:
- 6 murderers were left handed, they has less amygdala asymmetry + higher prefrontal activity than right handed M’s.
- 14 M’s were non-white, no significant differences between them + white M’s.
- 23 M’s had a history of head injury, however they did not differ from the M’s who had no history of head injury other than the corpus callosum.
What was the conclusion?
This study supports past findings that there are links between areas of the brain + aggression.
- F’s provide preliminary evidence that M’s pleading NGRI have different brain functioning to normal individuals.
- However, neural processes underlying violence are complex + cannot be reduced to a single brain mechanism + violent behaviour is most likely explained by a network of interacting brain structures rather than a single area.
Raine et al thought it was important to point out that the results do not demonstrate:
- That brain dysfunction does not cause violence
- That violent behaviour is determined by biology alone
- That those pleading NGRI are not responsible for their actions.
Why is the research method Raine used problematic?
The IV, criminal status, was naturally occurring. It was not manipulated or controlled by the researcher.
- This lack of control is a problem because cause + effect conclusions drawn lack internal validity.
- They are unable to conclude w/ confidence that violent behaviour is caused by biology alone.
- P’s charged w/ murder also had social + cultural experiences which affected their later behaviour.
Why was the research technique an advantage?
Sophisticated technology was used.
- PET scans were used to examine the individuals’ brain + allows researchers to examine the brain ‘in action’ rather than a series of ‘still’ photographs.
This is a real advantage as it allowed Raine et al to investigate the difference in M’s + non-M’s in the way they process information.
Why did the findings lack population validity?
The M’s were not typical of all violent individuals.
- They all had some form of recognised mental impairment which is why they were able to plead NGRI. Therefore findings lack population validity, they do not show that all violent offenders have such brain dysfunctions + the conclusions are restricted to a certain type of individual.
Why is alternative evidence a strength?
Raine et al’s findings are supported by other research.
- E.g. 2009, Yang + Raine conducted a metanalysis of 43 imaging studies that looked at anti-social + violent behaviour.
- They concluded that there is significantly reduce prefrontal activity in antisocial +/or violent criminals.
Their findings are also supported by genetic studies that indicate a ‘criminal gene’.
This is a strength as it increases the internal validity of Raine’s findings.
