Biological Psychology

Classic Study

Raine et al. (1997)

PET brain scans of murderers

Raine et al. (1997) PET Brain scans

Raine et al. (1997) PET Brain scans

Inject patient with fluourodeoxyglucose (FDG).

Shows metabolic rate in different brain areas.

Which brain areas were typically associated with aggression?

Which brain areas were typically associated with aggression?

Aim

See if violence & aggression is associated with brain dysfunction in:

• Prefrontal cortex
• Angular gyrus (part of parietal lobe)
• Amygdala
• Hippocampus (learning, emotion, memory)
• Thalamus (sensory perception & consciousness)
• Corpus callosum

Procedure

41 criminals

• Being tested for evidence of “not guilty by reasons of insanity” (NGRI)
• 39 males, 2 females
• Mix of different disorders: schizophrenia, brain injury, substance abuse etc
• Medication-free for 2 weeks before the experiment

41 control group

• Matched on age and gender
• 39 males, 2 females
• Screened for physical and mental health.

Procedure

• Continuous performance task (CPT) to complete
• Focus on blurred numbers
• Practiced for 10 minutes before injecting FDG
• 32 minutes on the CPT to complete the PET brain scan

Results

• Did the murderers have higher or lower activity in prefrontal cortex?

Results

Results

• Lower activity in prefrontal cortex and…
• Parietal areas
• Corpus Callosum
• Higher activity in
• Occipital lobe
• Right of thalamus
• Asymmetrical activity in
• Amygdala
• Temporal lobe and hippocampus

Conclusion

Brain differences are associated with violent behaviour.

Based on the function of these brain areas, why might they be linked to violence?

• Prefrontal cortex
• Hippocampus, amygdala & thalamus (all associated with learning from consequences)

Conclusion

Brain differences are associated with violent behaviour.

• Prefrontal cortex
• Linked to self control
• Loss of self control = aggression
• Hippocampus, amygdala & thalamus
• All associated with learning from consequences
• Cannot learn or change behaviour based on the consequence

Evaluation of Raine et al. 1997

Largest sample of violent offenders to be studied.

Control of confounding variables (no medication for 2 weeks, screened control participants).

Violent sample were severely violent (ie. killed people).

Sample had matched controls (normal people matched on age and gender).

PET scans are objective in measure brain activity.

All brains vary slightly in shape.

Does not consider environmental influences which may have increased violent behaviour or brain dysfunction.

Evaluation of Raine et al. 1997

Largest sample of violent offenders to be studied.

Control of confounding variables (no medication for 2 weeks, screened control participants).

Violent sample were severely violent (ie. killed people).

Sample had matched controls (normal people matched on age and gender).

PET scans are objective in measure brain activity.

All brains vary slightly in shape.

Does not consider environmental influences which may have increased violent behaviour or brain dysfunction.