Neural and hormonal mechanisms in aggression, including the roles of the limbic system, serotonin and testosterone. Genetic factors in aggression, including the MAOA gene.

What is the Basic Assumption of Neural and Hormonal Explanations of Aggression?

• Aggression is influenced by biological factors.
• Brain structures, neurotransmitters and hormones affect aggressive behaviour.

What is the Limbic System?

• A collection of brain structures involved in emotion and motivation.
• Important in processing emotional responses such as anger and fear.

What is the Role of the Amygdala in Aggression?

• The amygdala is part of the limbic system.
• It processes threats, fear and emotional responses.
• Abnormal amygdala activity may increase aggression.

How does an Overactive Amygdala Explain Aggression?

• An overactive amygdala may cause stronger emotional reactions.
• Individuals may respond aggressively to perceived threats.

What is Serotonin?

• A neurotransmitter involved in mood regulation and impulse control.
• Helps regulate emotional responses.

How does Serotonin Explain Aggression?

• Low serotonin levels may reduce control over aggressive impulses.
• This can increase impulsive and aggressive behaviour.

What happens when Serotonin Levels are Low?

• Reduced inhibition of aggressive responses.
• Poorer impulse control.
• Increased likelihood of aggression.

Mann et al. (1990) — Aim

• Investigate the relationship between serotonin levels and aggression.

Mann et al. (1990) — Procedure

• Reduced serotonin levels in participants.
• Measured changes in aggressive behaviour.

Mann et al. (1990) — Findings

• Participants showed increased aggression when serotonin levels were reduced.

Mann et al. (1990) — Conclusion

• Supports the idea that low serotonin levels are linked to aggression.

What is Testosterone?

• A male sex hormone (androgen).
• Associated with dominance and competitive behaviour.

How does Testosterone Explain Aggression?

• Higher testosterone levels may increase aggressive tendencies.
• Testosterone may influence dominance and threat responses.

Dabbs et al. — Aim

• Investigate the relationship between testosterone and aggression.

Dabbs et al. — Procedure

• Measured testosterone levels in male prisoners.
• Compared testosterone levels with criminal behaviour.

Dabbs et al. — Findings

• Prisoners convicted of violent crimes had higher testosterone levels.

Dabbs et al. — Conclusion

• Supports a link between testosterone and aggressive behaviour.

What is the Basic Assumption of Genetic Explanations of Aggression?

• Aggression may be influenced by inherited genetic factors.
• Certain genes may increase vulnerability to aggressive behaviour.

What is the MAOA Gene?

• A gene involved in producing the MAOA enzyme.
• Influences breakdown of neurotransmitters.

What Does the MAOA Enzyme Do?

• Breaks down neurotransmitters including serotonin, dopamine and noradrenaline.
• Helps regulate brain activity and behaviour.

What is a Low Activity MAOA Gene?

• A version of the MAOA gene producing less MAOA enzyme.
• Leads to slower breakdown of neurotransmitters.

How does the Low Activity MAOA Gene Explain Aggression?

• Less MAOA enzyme may affect neurotransmitter regulation.
• May increase impulsivity and aggressive behaviour.

Brunner et al. (1993) — Aim

• Investigate whether MAOA gene abnormalities are linked to aggression.

Brunner et al. (1993) — Procedure

• Studied a Dutch family with high levels of aggressive behaviour.
• Investigated their genetic differences.

Brunner et al. (1993) — Findings

• Many aggressive male family members had a mutation affecting the MAOA gene.

Brunner et al. (1993) — Conclusion

• Suggests aggression may have a genetic basis.
• Supports the role of MAOA in aggression.

Caspi et al. (2002) — Aim

• Investigate interaction between MAOA gene and environmental factors.

Caspi et al. (2002) — Findings

• People with low activity MAOA genes were more aggressive if they experienced childhood maltreatment.

Caspi et al. (2002) — Conclusion

• Aggression is influenced by both genes and environment.
• Supports an interactionist explanation.

Neural and Hormonal Explanation Evaluation — Research Support

• Mann et al. supports serotonin’s role.
• Dabbs supports testosterone’s role.
• Provides evidence for biological influences on aggression.

Neural and Hormonal Explanation Evaluation — Scientific Evidence

• Uses biological measures such as hormones and brain activity.
• Increases scientific credibility.

Neural and Hormonal Explanation Evaluation — Cause and Effect Problem

• It is unclear whether biological factors cause aggression.
• Aggressive behaviour may also influence biology.

Neural and Hormonal Explanation Evaluation — Reductionism

• Focuses mainly on biological explanations.
• May ignore social and environmental influences on aggression.

Genetic Explanation Evaluation — Research Support

• Brunner et al. found a link between MAOA mutation and aggression.
• Supports genetic influence.

Genetic Explanation Evaluation — Interactionist Support

• Caspi et al. showed genes interact with childhood experiences.
• Suggests aggression is not caused by genes alone.

Genetic Explanation Evaluation — Not Deterministic

• Having a low activity MAOA gene does not guarantee aggression.
• Environmental factors influence behaviour.

Overall Explanation of Aggression

• Aggression is likely caused by an interaction of biological and environmental factors.
• Genes, hormones, brain structures and experiences all contribute.