Biological Classic Evidence Raine et al. WJEC AS/A2

Brain Abnormalities in murderers by PET

• Early theories about criminal behaviour suggested might be physical difference in criminal and non-criminal enable us to identify individuals before commiting a crime.
• Lombroso; physical features that criminals typically had narrow, sloping forehead, prominent eye ridges, large ears & protruding chin.
• Brain Scanning opened new way to research differences in criminals and non-criminals. Might be specific areas of brain are different in criminals, may predispose individuals to violent behaviour.
• Animal research and studies of people w/ brain damage have found this.
• Raine et al. focused on particular group criminals = Individuals committing a murder & entered plea of not guilty by reason of insanity (NGRI).
• Proposed on basis of previous research, that seriously violent individuals:
• Have brain dysfunction in prefrontal cortex, angular gyrus, amygdala, hippocampus, thalamus and corpus callosum.
• Not have brain dysfunction in areas of brain that have been implicated in mental illnesses, not previously related to violence; caudate,putamen, globus pallidus, midbrain, cerebellum.

Methodology

• Quasi-experiment with matched pairs design.
• IV: NGRI or not DV: Brain differences
• Participants;
• Murderers 41 (39 men, 2 women), mean age 34.3 yrs. All charged w/ murder or manslaughter & ALL pleaded not guilty by reasons for insanity NGRI or incompetent to stand trial.
• Referred to University California, examination obtain proof diminished capacity.
• Pp's instructed be medicated free, checked by urine scan, two weeks prior brain scanning.
• Control Group matching each murderer w/ normal individual of same sex & age.
• 6 Schizophrenic from mental hospital.
• Other controls NO history psychiatric illness, nor w/ close relatives & no significant physical illness. None taking medication.
• Schizophrenia 6
• History head injury or organic brain damage 23
• History psychoactive drug abuse 3
• Affective Disorder 2
• Epilepsy 2
• History hyperactivity & learning disability 3
• Personality disorder 2

Procedures

• Sample obtained using Opportunity Sampling.
• PET scan used to study active brain.
• ALL Pp's given injection of 'tracer' - FDG = Taken up by active areas of brain and possible compare brains of NGRI & Control Group.
• ALL Pp's asked to do continuous performance task - CPT = Aimed to activate target areas brain so could see different areas functioning.

Findings

• Brain Differences
• Found reduced activity in brain NGRI Pp's areas previously linked to violence; prefrontal cortex, left angular gyrus, corpus callosum, left hemisphere only reduced activity in amygdala, thalamus and hippocampus.
• Found increased activity in brain of NGRI Pp's areas NOT previously linked to violence; cerebellum, right hemisphere increased activity in amygdala, thalamus and hippocampus.
• Reduced Activity; some areas, notably areas previously linked to violence.
• Abnormal Asymmetries; reduced activity on left side brain, greater activity on right. Applied some areas identified in hypothesis linked to violence (amygdala, thalamus & hippocampus)
• No Differences; many brain structures, associated w/ mental illness but not violence.
• Performance on CPT = Both groups performed similarly, any observed brain differences not related to task performance.
• Other differences NOT controlled for;
• Handedness = 6 murderers left handed
• Ethnicity = 14 murderers Non-white, but showed no significant difference.
• Head Injury = 23 murderers history of head injury, didn't differ from murderers w/ no history of brain injury.

Conclusion

• Animal & human studies have identified links between areas of brain and aggression.
• However neural processes underlying violence are complex and can't be reduced to single brain mechanism.
• Vioent behaviour probably best explained by disruption of network interaction between the brain mechanisms rather than single structure.
• Such disruption NOT cause violent behaviour but would predispose an individual to violent behaviour
• Amygdala; Associated w/ aggressive behaviour in animals and humans. The destruction of the amygdala in animals results in lack of fear = (Might explain) Fearlessness associated w/ violent activity.
• Results NOT show violent behaviour is determined by biology alone; clearly social, psychological, cultural and situational factors play important roles in predisposition to violence.
• Results NOT show murderes pleading NGRI not responsible for actions, nor PET used as means of diagnosing violent individuals.
• NOT show brain dysfunction causes violence = even result brain dysfunction is an effect of violence.
• NOT show violence be explained results, results relate only to criminal behaviour.
• Findings DO suggest link between brain dysfunction and predisposition towards violence in specific group NGRI.