Raine et al 1997

• Carried out by Adrian Raine on American prisoners charged its with murders but pleading not guilty by reason of insanity.
• Aim: 

  To find out if there is a difference in the structure of brain activity between murders and non murders, in particular looking at role of prefrontal cortex; corpus callosum, amygdala, medial temporal lobe, hippocampus and thalamus is predisposing people towards aggression.

  Also wanted to link animal brain structures to humans. 
• Independent variable:

  Whether participant is offender pleading not guilty by reason of insanity to murder, or a non murder in control group
• Dependent variable 

  Relative glucose levels in prefrontal cortex and other lobes in the brain
• Sample 

  • 41 offenders pleading NGRI to crime of murder and 41 controls
  • NGRIs 39 men, 2 women mean (age 34.3)
  • 23 had history of brain damage
  • 3 history with drug abuse
  • 6 suffered schizophrenia 
  • 2 epilepsy 
  • 7 with other emotional or learning disorders 
  • Controls were people of Sam age, sex with no history of crime mental illness except 6 controls with schizophrenia 
• Procedure 

  Tested at university of California each injected with glucose tracer and performed the continuous performance task for 32 minutes. Then PET was carried out
• Other experimental controls were

  • particepents were allowed to practice CPT ten mins before glucose tracer so that they were all equally familiar with it
  • Made sure non of the participants were on medication kept NGRIs medication free for 2 weeks before PET scan
• PET scan was broken down into digital slices enabling Rainer to measure relative amount of tracer present in brains 4 cortical regions 

  As expected NGRIs showed less activity in the frontal lobe especially prefrontal cortex associated with rational thinking, self restraint and memory
• Conclusions

  • brain abnormalities in NGRIs may translate to violence or antisocial behaviour 
  • Prefrontal deficits ( deficits are lack of activity) might make someone more impulsive and emotional 
  • Defects in limbic systems might make someone aggresssive
  • Deficits in corpus callosum make it harder for the brain’s hemisphere to communicate 
• Raine concludes that findings from animal studies into aggression can be generalised to humans and there is a link between brain structure and aggression.

  Raine is optimistic that these brain deficits can be prevented if they are identified early enough.
• • generalisability strength as the sample of both groups consisted of 39 men and 2 women. This gender split strength makes the sample representative of the target population meaning that the results on differences of brain functionality and activity between murders and non murders can be generalised to the wider population 
• • Strength in reliability as is it standardised due to each participants having the same amount of time between each task they also all performed the same CPT and had the same brain scan PET. This means that the study is easily repeated in the fixture to check for consistency 
• • Internal validity strength due to large sample size eliminating the risk of anomalies skewing the results of the study
• • sample was not ethnocentric due to the members all being Americans pleading NGRI therefore not generalisable to target population of typical murders
• • Frequent issues with reliability of pet scanning due to frequent difficulties interpreting scans differently leading to inconsistency and subjectivity within results
• • Reduced ecological validity as the CPT is not reflective of a real life situation and circumstance’s in which tension would arise such as an argument. The CPT is artificial and in a controlled environment which means that the brain activity is isolated to one single task. This limits affects of real life situations  
• The researchers are very moderate in claims for their findings – acknowledge the methodological limitations of their study, resist the temptation to attribute violent behaviour to biological factors alone. For example, it is not possible to establish the causes of the brain differences, and these could be due to environment effects.

  Even so, it is clear from the findings that brain dysfunctions play a potentially key role in violence (at least in specific groups). This means that the research has some potentially useful  practical applications, but they do raise very serious ethical concerns.