Brain structure and aggression

The prefrontal cortex

The prefrontal cortex (PFC) is at the front of the frontal lobes. It is involved in planning, self-control and controlling impulses.

The explanation: if the PFC is damaged or less active, a person may be less able to stop impulsive, aggressive urges. Raine et al. (1997) linked lower prefrontal activity in murderers to impulsivity, loss of self-control and an inability to change behaviour.

The limbic system

The limbic system is a set of structures deep in the brain involved in emotion and memory, including the amygdala and the hippocampus, with the hypothalamus closely linked.

• The amygdala responds to threat and is involved in fear and anger. Unusual amygdala activity may mean someone reacts aggressively to threats, or lacks fear.
• The hippocampus is involved in memory, including memory of the consequences of actions.

Raine et al. (1997) found an imbalance between hemispheres in the amygdala and hippocampus of murderers: less activity on the left and more on the right.

Brain functioning: putting it together

Aggression may be more likely when the limbic system produces strong emotional reactions and the PFC is not active enough to control them. Raine et al. also found less activity in the corpus callosum, which links the two hemispheres.

Raine et al. concluded that violence cannot be put down to one brain region, and that brain differences predispose a person to violence rather than directly causing it; social, psychological and environmental factors also matter.

Evaluation

• Strength: brain scans such as PET give objective, scientific evidence of differences in brain activity.
• Strength: practical value, for example in understanding why some offenders struggle with self-control.
• Weakness: the evidence is correlational. Brain differences could result from experiences (such as abuse or head injury) rather than cause aggression.
• Weakness: samples such as Raine's murderers pleading not guilty by reason of insanity are unusual, so findings may not generalise to everyday aggression.
• Weakness: it is reductionist, ignoring learning, which is explained by social learning theory.

Worked example

A student says: 'Raine's study proves a damaged prefrontal cortex causes murder.' Explain why this is not correct.

1. Raine et al. compared brain activity in two groups; they did not manipulate the brain.
2. The data show a link (correlation), so other factors could be involved.
3. Raine et al. themselves said brain differences predispose people to violence alongside social and environmental factors.

Answer: The study shows an association and a predisposition, not cause and effect.

Check yourself

1. Which brain area is most linked to self-control and controlling impulses?
   • Occipital lobe
   • Cerebellum
   • Spinal cord
   • Prefrontal cortex
   Show answer

   Prefrontal cortex. The PFC is involved in planning and impulse control.

2. The amygdala is part of the
   • prefrontal cortex
   • limbic system
   • peripheral nervous system
   • corpus callosum
   Show answer

   limbic system. The amygdala is a limbic structure involved in fear and threat.

3. What did Raine et al. (1997) find in the prefrontal regions of murderers compared with controls?
   • More activity
   • No difference
   • Activity only on the right side
   • Less activity
   Show answer

   Less activity. NGRI murderers showed less prefrontal activity.

4. Raine et al. found an imbalance in the amygdala and hippocampus. Which describes it?
   • Less activity on the left and more on the right
   • More activity on the left and less on the right
   • Equal activity in each hemisphere
   • No activity at all
   Show answer

   Less activity on the left and more on the right. The left was lower and the right higher than in controls.

5. What did Raine et al. conclude about brain differences and violence?
   • They are the single cause of violence
   • They are found only in women
   • They predispose people to violence alongside social and environmental factors
   • They can be removed by surgery
   Show answer

   They predispose people to violence alongside social and environmental factors. Raine et al. concluded several areas are involved and the differences predispose rather than directly cause violence.

6. Explain one weakness of brain structure explanations of aggression.
   Show answer

   The evidence is correlational, so we cannot tell whether brain differences cause aggression or result from experiences such as head injury or abuse, and other factors such as learning may be involved.. Name the weakness and explain why it matters.

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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.