What evidence links serotonin to impulsive aggression in humans?

Studies have found low levels of a serotonin breakdown product in the cerebrospinal fluid of impulsive violent offenders. Drugs that lower serotonin can increase aggressive responses in experiments.

How is testosterone thought to influence aggression?

Testosterone is an androgen made mainly in the testes, and higher levels are linked to dominance and aggression. Testosterone is thought to act on the amygdala, increasing reactivity to threat.

Evaluate the evidence that testosterone causes aggression.

Much of the evidence is correlational, and winning a competition can itself raise testosterone. Testosterone is only one factor, and its effect seems to depend on cortisol levels and social context.

CCEA A-Level Life and Health Sciences 0008

Experimental Techniques

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Human Body Systems

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Brain Science

The biology of aggression and methods of studying the brain

3 things to know
AS 4

Overview

The limbic system, serotonin, testosterone and the MAOA gene in aggression, the Brunner and Caspi studies, and invasive and non-invasive methods including lesions, deep brain stimulation, transcranial magnetic stimulation, fMRI, EEG and PET.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What role does the limbic system play in aggression?

Key term

What have animal studies shown about the limbic system and aggression?

Key term

Explain how low serotonin levels are thought to increase aggression.

Questions from this subtopic

Each one with the model answer underneath.

1
What role does the limbic system play in aggression?
Model answer
The amygdala detects threat and can trigger rapid, reactive aggression. The prefrontal cortex normally restrains the amygdala, so weak prefrontal control makes aggression more likely.
2
What have animal studies shown about the limbic system and aggression?
Model answer
Electrical stimulation of the amygdala or hypothalamus can trigger attack behaviour in animals. Lesions to the amygdala can make animals tamer and less aggressive.
3
Explain how low serotonin levels are thought to increase aggression.
Model answer
Serotonin normally dampens activity in brain areas that drive impulsive responses. Low serotonin weakens self-control, so a person reacts aggressively to provocation.
4
What evidence links serotonin to impulsive aggression in humans?
Model answer
Studies have found low levels of a serotonin breakdown product in the cerebrospinal fluid of impulsive violent offenders. Drugs that lower serotonin can increase aggressive responses in experiments.
5
How is testosterone thought to influence aggression?
Model answer
Testosterone is an androgen made mainly in the testes, and higher levels are linked to dominance and aggression. Testosterone is thought to act on the amygdala, increasing reactivity to threat.
6
Evaluate the evidence that testosterone causes aggression.
Model answer
Much of the evidence is correlational, and winning a competition can itself raise testosterone. Testosterone is only one factor, and its effect seems to depend on cortisol levels and social context.

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