Mark Buchanan in New Scientist:
Over the past decade, experiments devised by Ernst Fehr of the University of Zurich in Switzerland, among others, have shown that many people will cooperate with others even when it is absolutely clear they have nothing to gain. A capacity for true altruism seems to be a part of human nature. It is a heartening discovery, yet one that has also touched off a firestorm of debate.
The experiments at the centre of the controversy are as simple as they are illuminating. They ignore theory-based preconceptions about how individuals ought to behave and focus instead on finding out what they actually do when playing games in which there is real money at stake.
One of the most basic of these games is the “ultimatum game”.