"Economic models would suggest "only Bill Gates or Warren Buffett should be making
contributions, and everyone else should just free-ride," said one of the authors, economics professor William Harbaugh. "But that doesn't happen; there's high participation, where even low-income people are giving away a portion of their income."
In the study, female college students were given $100, then told either that a mandatory transfer would go from their account to a local food bank or that they could make a voluntary donation to the same charity. At the end of the study, the women were allowed to keep the remainder of the money.
Using MRI, the investigators found that both mandatory and voluntary transfers increased activity in brain areas called the nucleus accumbens and the caudate nucleus. These areas have previously been associated with the brain's response to rewarding stimuli, such as taking street drugs or viewing pictures of loved ones. The reward reaction was more intense with the voluntary giving.
In the Oregon study, not all brains showed an equal tendency toward generous behavior. Test subjects whose reward centers reacted more strongly to receiving money were less willing to make donations. "The brain is directly telling us, 'I like the food bank more than I like me,' or the other way around and can tell you who's going to give," said Colin Camerer, economics professor at the California Institute of Technology. "That's pretty cool."
Paul Zak of the Center for Neuroeconomics Studies at Claremont Graduate University, commented, "Economists have always been shocked [by unselfish altruism], and now we have a reason for it: It feels good to do this." But Zak wisely warned against drawing broad conclusions based upon this limited sample. "They picked female college students in Eugene, Ore., a very politically liberal place in which students have money, and are giving to a food bank -- who cannot like that? If I go to Tennessee and say the donation is going to an abortion clinic, it's a whole different ballgame."