PSYA3 - Aggression - Biological Approach

Neural Mechanisms

The limbic system: responsible for instinctive behaviours such as eating, aggression and sexual activity. The hypothalamus and amygdala in the limbic system are said to be responsible for aggression.

Electrical stimulation, lesioning and brain imaging have shown that the hypothalamus and amygdala are responsible for acts of aggression.

Delgado et al (1954) stimulated the hypothalamus of monkeys using mild electric currents. They then attacked other moneys. Similar results have been found in cats. This supports the idea that the hypothalamus is responsible for aggressive behaviour.

• But, they only attacked if they were above other moneys in the hierarchy, if they were not superior they cowered in a corner as if threatened but not daring to attack - suggests SLT is the overriding factor.

Blair et al (2001) studied institutionalised psychopaths. He suggested they had damage to the amygdala. The amygdala is responsible for recognising emotion in others, so if it doesn't work it increases the chance of harming others without remorse since it leads to a lack of empathy.

Charles Whitman shot 12 people in 1966, a post-mortem revealed a tumour pressing on his limbic system.

The prefrontal cortex: controls inappropriate displays of aggression. It allows us to learn the rules of society regarding displays of aggression. Damage to the prefrontal cortex makes it difficult to control aggressive instincts.

Raine et al (1997) compared PET scans of the brains of 41 murderers with non-muderers. Murderers had a lower level of activity in the prefrontal cortex (so lacked control over inappropriate displays of aggression) and the amygdala (so didn't recognise emotion in others - lacked empathy).

• He used a good sample and controlled variables, however he did not control the levels of aggression in the murders.
• As the study took place after the murders, the results are only correlational.
• PET scans lack precision.

Phineas Gage became more aggressive after an explosion sent an iron bar through his left frontal lobe.

• The damage to his brain was extensive so it would be difficult to pin-point the responsible area.
• Have to rely on…