Classic study: Raine et al. (1997)

Aim and sample

Aim: to compare brain functioning in murderers and controls, expecting differences in the prefrontal cortex and other areas linked to violence (including the amygdala, hippocampus, thalamus and corpus callosum).

Sample: 41 people (39 men, 2 women) charged with murder or manslaughter who pleaded not guilty by reason of insanity (NGRI), mean age 34.3. They had been medication-free for two weeks (checked by urine tests).

Controls: 41 participants of the same sex as the murderers and of similar age (mean 31.7), taking no medication and with no psychiatric history, except 6 with schizophrenia who were compared with the 6 murderers with schizophrenia.

Procedure

• Ten minutes before the injection, participants were given practice trials of a continuous performance task (CPT) (target recognition).
• They were injected with a glucose tracer and did the CPT for 32 minutes.
• A PET scan then showed which areas had used the most glucose (were most active).
• Activity was compared between hemispheres and groups using the 'cortical peel' and 'box' techniques.

Results

Raine et al. linked lower prefrontal activity to impulsivity and loss of self-control, lower parietal activity to learning and information-processing problems, the limbic imbalance to unusual emotional responses such as lack of fear, and lower corpus callosum activity to poor emotional expression and difficulty grasping long-term consequences.

Conclusions and evaluation

Conclusions: violence is linked to several brain areas, not one; the differences predispose people to violence alongside social, psychological and environmental factors. Differences were not explained by age, sex, schizophrenia, handedness, ethnicity or head injury.

Evaluation:

• Strengths: matched control group; PET is objective; standardised procedure (CPT) supports reliability; confounds such as medication were checked.
• Weaknesses: NGRI murderers are an unusual sample, so findings may not generalise to other violent people; only 2 women; correlational, so cause cannot be shown; the CPT is an artificial task.

Worked example

Explain why Raine et al. used a matched control group.

1. Without controls, we cannot know whether the murderers' brain activity is unusual.
2. Matching on sex and schizophrenia, with a similar mean age, means differences are less likely to be due to these variables.
3. This increases internal validity.

Answer: To compare with similar non-murderers so differences can be linked to murder rather than to sex, age or schizophrenia.

Check yourself

1. How many NGRI murderers were in Raine et al.'s sample?
   Show answer

   41 people. 41 murderers and 41 controls.

2. 2 of the 41 murderers were women. What percentage is that, to 1 decimal place?
   Show answer

   4.9 %. 2 / 41 x 100 = 4.9%.

3. What does NGRI stand for?
   • No genetic risk identified
   • Not guilty by reason of insanity
   • Neural glucose rate index
   • Non-guilty reported impulse
   Show answer

   Not guilty by reason of insanity. All murderers pleaded not guilty by reason of insanity.

4. What task did participants do before the PET scan?
   • A memory test of word lists
   • A hot sauce game
   • A continuous performance task
   • Watching a violent video
   Show answer

   A continuous performance task. The CPT is a target recognition task.

5. Which area showed MORE activity in the murderers?
   • Occipital areas
   • Prefrontal cortex
   • Corpus callosum
   • Parietal areas
   Show answer

   Occipital areas. Occipital activity was higher.

6. Why might Raine et al.'s findings not generalise to all violent people?
   • The sample included too many women
   • PET scans cannot show activity
   • The murderers had all pleaded NGRI, an unusual group
   • Controls were not matched
   Show answer

   The murderers had all pleaded NGRI, an unusual group. NGRI murderers may differ from other violent offenders.

7. State the conclusions of Raine et al. (1997).
   Show answer

   Murderers pleading NGRI showed abnormal activity in several brain areas, such as less prefrontal activity, so violence is linked to more than one region, and these differences predispose people to violence along with social and environmental factors rather than directly causing it.. Areas involved plus predisposition.

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Sources

• Pearson Edexcel International Advanced Subsidiary/Advanced Level in Psychology specification, Issue 5 (February 2021)
• Pearson IAL Psychology component guide: WPS02 (Issue 2, November 2024)
• Pearson IAL Psychology summary of studies: WPS02

Last updated 8 November 2026. Spotted a mistake? Tell us.