LIFE at the bottom is nasty, brutish and short. For this reason, heartless folk might assume that people in the lower social classes will be more self-interested and less inclined to consider the welfare of others than upper-class individuals, who can afford a certain noblesse oblige. A recent study, however, challenges this idea. Experiments by Paul Piff and his colleagues at the University of California, Berkeley, reported this week in the Journal of Personality and Social Psychology, suggest precisely the opposite. It is the poor, not the rich, who are inclined to charity.