Researchers found that one in four people carry a gene which appears to predispose them to parsimony

The gene - called COMT - comes in two variants, an 'A' version and a 'G' one. Volunteers for the study were asked to gamble on a computer game in which they could donate their winnings to poor children in Peru. They were then shown an image of a girl called Lina and a bracelet which she had made. The scientists found that the people with the G version gave away all their winnings while those with the A type - dubbed the "mean gene" - gave less than half.