27th February 2012, 10:42am
Fear factor checks temptation to act selfishly
Cooperative behaviour Humans appear to have a primitive fear which reins in the temptation to gain selfish advantage over others, even when presented with strong incentives to do so, according to new brain scanning research.

The findings, published in the latest issue of the American Psychological Association's 'Journal of Neuroscience, Psychology, and Economics', show that the temptation to break pre-established norms triggers activity in an area of the brain called the amygdala, part of the primitive limbic system linked to basic emotions, especially fear.

The international research team, which included neuroscientists and philosophers from the universities of Lincoln, Milan and Exeter, used fMRI brain scanning to analyse how people respond to the opportunity to act selfishly in a 'Coordination Game', which theorists have proposed as a laboratory model of the evolution of cooperative behaviour in human societies.

Previous neuro-imaging studies which have examined selfish decision-making have used the classic 'Prisoner's Dilemma' game, a scenario central to early Game Theory. In the Prisoner's Dilemma, players are faced with the decision to cooperate or 'defect' with a second player on every round. However the authors of the current study reasoned that a more realistic scenario would be to embed such decisions within sequences of mutually rewarding cooperative interactions, as is the case in a coordination game.

Volunteers were grouped into pairs for the study with one player placed in the brain scanner whilst their fellow player sat in another room. Both players were presented with a simple decision press either a left or right response key over a series of rounds. If both players made the same choice, each would receive a prize of 50 pence. The volunteers could not communicate directly but were shown the other's response on a computer screen once they had made their own choice.

Most pairs quickly developed tactics to ensure they both pressed the same key. However, later in the game, the researchers introduced a 'special' round. On these rounds the player in the brain scanner was told they could receive a bigger reward of 2 if they pressed the opposite key to their teammate. If they did, the other player would win nothing.

The researchers found that tempted players only opted to take the extra payment on about 50 per cent of the 'special' rounds. The brain scan data also enabled the researchers to view which areas of the brain were activated as subjects weighed up whether or not to 'cheat' the other player.

Professor Timothy Hodgson, Professor of Cognitive Neuroscience in the School of Psychology at the University of Lincoln, said: "As well as expected activity in the brain's 'reward centres', a response was also seen in the amygdala, an area of the brain long associated with emotion responses, especially fear.

"Interestingly, the extent to which participant pairs had successfully cooperated prior to the first 'special' round made a difference to activity in the amygdala. Most of the activity was seen in players who had managed only two or three successful co-operations before the first temptation to defect.
"Rather than a fear of future retribution, the results may therefore reflect players' reluctance to endure the potential cost of breaking a hard won cooperative strategy."

The study was led by cognitive neuroscientist Timothy Hodgson, of the University of Lincoln, with colleagues Francesco Guala (University of Milan), Tim Miller and Ian Summers (both University of Exeter) and the research was funded by a project grant from the UK's Economic and Social Research Council.
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