Levels of a brain chemical known as serotonin govern the way people react to unfair offers. Serotonin, which carries messages between neurons, is involved in emotional control, social behaviour and impulsivity. A recent study discovered that the expression of anger in women was affected by variations in a gene governing the receptors for serotonin in brain cells. To find out the mechanisms through which serotonin modulates self-control, British researchers had people play what is called the Ultimate Game, which is being used widely in psychological and neurological studies. The game has one player proposing a way to split a pot of money. If the other player accepts the offer, both get paid. If it is refused, neither gets a payment. The researchers had some players make deliberately unfair offers. It was found that the players who were given a chemical that lowered serotonin levels were more likely to reject an unfair offer but not fair offers, without showing changes in mood, fairness judgments, basic reward processing, or response inhibition. The findings suggest that lower serotonin levels meant a higher level of resentment, so that an offer that wasn't as good as it might be would be turned down. Conversely, higher serotonin levels would make it easier to live in an imperfect world i.e. people with higher serotonin levels may accept less than what they actually deserve. The results demonstrate the critical role of serotonin in regulating emotion during social decision-making.
Science
June 2008