Models of how human morals develop are rooted in so-called ‘game theory’. They rely on the fact that two individuals will meet more than once — so, if somebody helped you the last time you met, you'll be more inclined to help him this time. But what if two individuals meet only once? It turns out that this situation could be very common, and a new study predicts that reputation is all important. By observing how an individual behaves in his interactions with others, you can predict how he's likely to behave if he comes into contact with you.
