In The Field

FENS: seeing selfishness

Macchiavellians can be detected not only by their selfish and ingratiating behaviour, but also by their neurobiology, according to a new study presented today at the Federation of Neuroscience Societies in Vienna.


To separate the people who are generally fair from those who are more selfish, economics professor Ernst Fehr from the University of Zurich gave 100 ‘coins’ to 24 people who were told that they had to share their cash with an anonymous partner. In one experiment, the test subjects faced no punishment if they shared it unjustly. On average, they kept 90% of the money for themselves.

But in a second experiment they could be financially punished by partners who felt they had been treated unfairly. Faced with this prospect, the test subjects smartened up their act, giving nearly half of the money to their partners.

Some subjects started out much more firmly in the selfish camp, and responded more strongly to the threat of punishment than others. “These are what we call the ‘macchiavellian personalities’ – with a strong tendency towards both egoism and opportunism,” says Fehr, who reported the studies at the Federation of Neuroscience Societies in Vienna today. In the absence of threat of punishment, they got the best deal for themselves, and they also succeeded in avoiding economic punishment in the second experiment.

Contrary to popular belief, everyone responds to the threat of punishment to some degree, says Fehr. “Even psychopaths have a small response to the threat of punishment, though the individual differences are very big,” he says. (He didn’t, to his knowledge, have any psychopaths in this study, but adds that this fact falls out of previous research).

In order to identify the brain areas used in making these sharing decisions, Fehr and his colleague Manfred Spitzer from the University of Ulm scanned the brains of the test subjects using magnetic resonance tomography while they were deciding how to split their bounty.

The team found increased brain activity in two areas of the forebrain – the lateral orbital frontal cortex and the dorsal lateral prefrontal cortex – which are involved in processing punishing stimuli and in powerful impulses, such as the desire to take the last slice of cake without concern for others.

This brain activity was most pronounced in the Macchiavellian subjects.

“We speculate that these areas must also represent decisions related to ‘norm obedience’, because the greater the punishment threat, the greater the change in behaviour towards the ‘norm’ of sharing the pie equally.”

Fehr is now doing additional experiments to try to modify the behaviour of test subjects by using TMS to suppress firing in the two areas activated by the punishing stimuli. Theoretically, this should mean that selfish people would stay selfish, even under threat of punishment.

“This is going to be really thrilling,” he says. “We will see if we can actually change behaviour by suppressing the brain’s decision-making in this way.”

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