methodology and sample

• aim


  raine et al. (1997) wanted to investigate whether criminals who had committed murder and pleaded not guilty by reason of insanity (NGRI) had different brain structures from those who had not committed murder.
• what experiment

  quasi-experiment
• iv


  whether the participant is a murderer pleading NGRI, or a non-murderer in the control group
• dv


  brain differences as indicated by a Posistion emission tomography (PET) scan.
• experimental design


  matched pairs design
• in the experimental (NGRI) group there were 39 males and 2 females, with a mean age of 34.3 years
• the participants had a range of mental impairments and were referred to the University of California to obtain proof of their diminished capacity.

  • history of head injury - 23
  • schizophrenia - 6
  • others had a history of drug abuse, affective disorder, epilepsy, learning disability or personality disorder.
• participants were instructed to be medication free - checked with a urine sample two weeks before the PET scan
• control group was formed by matching each murderer with a "normal" person of the same age and sex.
• the 6 schizophrenics were matched with 6 schizophrenics from a mental hospital