http://www.nytimes.com/2005/02/17/business/17scene.html?oref=login ECONOMIC SCENE The Theory That Self-Interest Is the Sole Motivator Is Self-Fulfilling By ROBERT H. FRANK Published: February 17, 2005 ... (skipped beginning) [T]he economist's rational-actor model... assumes that people are selfish in the narrow sense... To be sure, self-interest is an important human motive, and the self-interest model has well-established explanatory power.... But some economists go so far as to say that self-interest explains virtually all behavior. As Gordon Tullock of the University of Arizona has written, for example, "the average human being is about 95 percent selfish in the narrow sense of the term." ... Does what we believe about human motivation matter? In an experimental study of private contributions to a common project, two sociologists from the University of Wisconsin, Gerald Marwell and Ruth Ames, found that first-year graduate students in economics contributed an average of less than half the amount contributed by students from other disciplines. Other studies have found that repeated exposure to the self-interest model makes selfish behavior more likely. In one experiment, for example, the cooperation rates of economics majors fell short of those of nonmajors, and the difference grew the longer the students had been in their respective majors. My point is not that my fellow economists are wrong to stress the importance of self-interest. But those who insist that it is the only important human motive are missing something important. Even more troubling, the narrow self-interest model, which encourages us to expect the worst in others, often brings out the worst in us as well.... Robert H. Frank is an economist at the Johnson School of Management at Cornell University and the author, most recently, of "What Price the Moral High Ground?"