According to studies by the Center on Philanthropy at Indiana University, People who make less than $50,000 donate more as a percentage of their income (an average of 4.2 percent in 2004) than do those making more than $100,000 (who contribute 2.2 percent). Exceptional donors also tend to be less materialistic. Paul K. Piff, a doctoral candidate in social psychology at the University of California at Berkeley, says people who have less are more likely to give and help others. In a series of experiments detailed in a recent article in the Journal of Personality and Social Psychology, Mr. Piff and his co-authors found that poor people were more likely to share money with others, or provide helpful information to a stranger, than wealthier people. But if wealthier people were primed to think about poverty by being exposed to a short video showing scenes of poor children, they exhibited greater generosity.