Classic Evidence: Raine, Buchsbaum & LaCasse (1997)
Methodology
Quasi Experiment - the researcher has not manipulated the IV directly & pps are not randomly allocated to each other
Matched Pairs Design - pairs of pps are matched in terms of key variable such as age and IQ. One member of each pair is allocated to one of the conditions under test and the second is allocated the other condition
IV - NGRI or not
DV - Brain Differences
Sample Size/pps: 41 murderers (39 men & 2 women) had an average age of 34.3 yrs
Mental Disorder & No. of pps:
Schizophrenia - 6
History of Head Injury/Organic Brain Damage - 23
History of Psychoactive Drug Abuse - 3
Affective Disorder - 2
Epilepsy - 2
History of Hyperactivity & Learning Disorder - 3
Personality Disorder - 2
Urine scan checked id pps were medication free 2 weeks prior to the brain scan
Control Group
Formed by matching each murderer with a normal individual of the same sex and age
The 6 schizophrenics were matched with 6 other schizophrenics from a mental hospital
None were tsking medication
Procedures
Sample was obtained using opportunity sampling
A PET Scan was used to study the active brain
All pps were given an injection of a tracer called Fluorodeoxyglucose (FDG) -> Tracer is taken up by the brain's active areas and therefore made it possible to compare the brains of NGRI & control group
All pps were asked to do a continuous performance task (CPT) -> task was aimed to activate the target areas of the brain so functions can be seen
1) pps were given a chance to practice the CPT before receiving the FDG injection
2) Thirty seconds before the FDG injection pps started the CPT so that the initial task would not be FDG labelled
3) 32 minutes after the FDG injection a PET Scan was done of each pps. 10 horizontal slices of their brain were recorded using:
- Cortical Peel Technique - lateral regions measured
- Box Techniques - medial & subcortical regions measured
Findings
NGRI:
Reduced Activity: Prefrontal Cortex, Parietal Lobe, Corpus Callosum, Amygdala (L), Hippocampus (L), Thalamus (L)
Increased Activity: Cerebellum, Occipital Lobe, Amygdala (R), Thalamus (R), Hippocampus (R)
No Difference: Caudate, Putamen, Globus Pallidus, Midbrain, Cingulate
Performance on CPT
No difference between murderers & controls in performance on CPT
Other Differences not Controlled For
Handedness - 6 murderers were left handed, little difference found between L&R handed people apart from Left handed showed high prefrontal activity & less abnormal amygdala amygdala asymmetry
Ethnicity - 14 murderers were non-white but no significant difference in brain activity was found
Head Injury - 23 murderers had a history of head injury but no difference was found compared to no history of head injury
Conclusions
- Past research has identified links between areas of the brain and aggression
- The findings provide preliminary evidence that murderers pleading NGRI have different brain function to normal individuals
- But neural processes underlying violence are complex and can't be reduced to a single brain mechanism
- Violent behaviour can best be explained by the disruption of a network of interacting brain mechanisms rather than any single structure
- A disruption would not cause violent behaviour but would predispose an individual to violent beahviour
Confounding Variable
- Study was designed involving a large sample and matched controls
- However, Raine et al acknowledged that head injury and IQ have not been ruled out as contributory factors
Warning
Results:
- Violent behaviour is determined by biology alone -> social, cultural, psychological & situational play a factor
- Do not show brain dysfunction causes violence
- Murderers pleading NGRI are not responsible for actions
Links between areas of the brain & aggression
Limbic System (Prefrontal Cortex, amygdala, hippocampus & Thalamus): Emotion - abnormal emotional response, Learning, Memory & Attention (abnormalities in functioning may results in reduced sensitivity to conditioning) - failure of violent offenders to learn from experience
Prefrontal Cortex: Deficit linked to impulsivity, loss of control, immaturity and inability to modify behaviour (associated with increased aggressive behaviour) - aggressive behaviour
Amygdala: aggressive behaviours in animals & humans. Destruction of amygdala in animals = lack of fear - fearlessness associated with violent activity
Hippocampus: modulates aggression in cats & with prefrontal cortex can inhibit aggressive behaviours - lack of inhibition of aggression
Angular Gyrus: damage to the left (deficits in verbal & arithmetic) - low verbal IQ, Poor school performance of violent offenders
Corpus Callosum: dysfunction related to a predisposition to violence & poor transfer of information between hemispheres - reduced processing of linguistic information
Right Hemisphere: dominance of right hemisphere (less regulation by left hemisphere) inability to process negative emotions & inappropriate emotional expression - lack of control over expressing violence
Evaluation: Methodology & Procedures
Quasi Experiment
Is an IV & DV
The IV was an existing condition of the individual not something manipulated by the experiments
Causal conclusions are not justified -> findings do not show that violent behaviour is determined by biology alone -> suggest psychological, cultural & situational factors play an important role in predisposition to violence
Readers may interpret findings and assume criminal behaviour is predetermined & inescapable
Research Techniques
Data was collected via PET Scans
Techniques have permitted researchers to study the brain in a way not possible until recently
In the past researchers relied on post-mortem examinations where brain physiology could not be linked to behaviour
PET Scans permit researchers to study detailed regions of the brain in action to be examined -> This meant Raine et al could see how the brains of different individuals differ in the way they process information
The Sample
The murderers were not typical of all violent people/individuals this is something Raine et al acknowledged
The finding do not show that all violent offenders have such brain dysfunction: the study can only draw conclusions about this kind of violent offenders -> an individual with some recognised form of mental impairment.
The crime is murder and many violent crimes do not involve murder
Conclusions are restricted to a very particular group of people
Evaluation: Alternative Evidence
Yany and Raine (2009) - meta-analysis of 43 imaging studies that considered both antisocial & violent behaviour -> Conclusion: There is significantly reduced prefrontal activity in antisocial and/or violent individuals
Further Supported by genetic studies that indicate a 'Criminal' gene -> MAOA causes abnormally high levels of dopamine
Tihonen et al (2015) analysed genes of 895 Finnish Prisoners & found an association between this gene & an increased likelihood of committing a violent crime
Genes are only a predisposing factor -> James Fallon analysed his own genes & found he had the genetic & brain characteristics of a violent criminal but he wasn't one -> Suggested it was because his positive experiences during childhood meant his criminal tendencies were not triggered
Ethical Issues & Social Implications
Valid Consent
May not have fully understood what they would be required to do
May have found performance task difficult which could have lowered their self esteem causing psychological harm
May have found PET Scan distressing if they did not realise that they would be involved in one
Murderers may not have been mentally competent enough to provide valid consent
May not have understood their right to withdraw because they felt like they didn’t have a choice
Socially Sensitive Research (SSR)
Any research that has consequences for the larger group of which the participants are apart of (SSR)
Our understanding of criminal behaviour is advanced by SSR
If indication is born rather than made it may have consequences that would be disadvantageous for people with similar brain abnormalities