03 October 2007

Understanding psychopaths

Researchers identified the part of the brain that processes the threat of punishment for flouting social rules, a finding that could help understanding psychopaths' behaviour.

Researchers have identified the part of the brain that processes the threat of punishment for flouting social rules, a finding that could have implications for understanding the behaviour of psychopaths, according to a study released on Wednesday.

In a series of experiments, investigators used brain scans to monitor the mental activity of volunteers as they thought about how to respond to a challenge involving a social norm - in this case the principle of fairness.

The challenge was configured two ways: one involving sanctions for behaviour that violated accepted standards of fairness, and one which didn't involve sanctions of any kind.

In the first scenario, the researchers instructed one person (person A) to decide how much money from a shared pot to give to a second person (person B).

Subjects’ morals tested
The recipient was later informed how much money the first person had withheld for themselves, and given the option of spending all or part of another pot of money which would reduce the first person's earnings.

In the second scenario, the second person was a passive recipient of the first person's largesse, without the power to reward or punish their actions.

Brain scans performed on the principal actors in the challenges, or person A, showed that areas of their prefrontal cortex lit up when they were making decisions they knew could bring punishment.

Those parts of the brain are known to be involved in control of decision-making related to issues of fairness and also evaluation of punishing stimuli.

Interestingly enough, when person B was taken out of the equation, and substituted by a computer, the threat of punishment produced much less intense activity in the minds of person A as shown by functional magnetic resonance imaging (fMRI).

The researchers also tested whether volunteers with Machiavellian personality traits - selfishness and opportunism - affected their responses on the tests.

They found that these individuals had the strongest response to the threat of sanctions, with a corresponding increase in brain activity, compared to the other people doing the challenges.

Understanding psychopathic behaviour
The findings could have implications for understanding psychopathic behaviour, since people with lesions in the prefrontal areas of the brain show an inability to behave in appropriate ways, even though they understand social norms.

Thus, a dysfunction in the areas involved "might also underlie certain psychopathological disorders characterised by excessively selfish tendencies and a failure to obey basic social norms," they wrote.

The authors suggested their findings also support the notion that the criminal justice system should hold juveniles, children and young adults to a different standard than adults, because the brain systems involved in processing what is socially acceptable are not fully mature yet in younger individuals.

The paper was written by researchers at the University of Ulm in Germany, and the University of Zurich in Switzerland and appears in the journal Neuron. – (Sapa/AFP)

Read more:
Few regrets when brain is damaged
Fairness switch in the brain




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