That good feeling you get by writing a check to your favorite charity could be your brain patting itself on the back.
According to the journal Science, a team of economists and psychologists at the University of Oregon have found that donating money to charity activates regions of the brain associated with pleasure.
The study represents a major advance in the young field of neuroeconomics, a collaboration between economists and psychologists to determine how the brain directs the way people handle money.
Economic models would suggest "only Bill Gates or Warren Buffett should be making contributions, and everyone else should just free-ride," "But that doesn't happen; there's high participation, where even low-income people are giving away a portion of their income."
Giving to others produces a "warm glow," said one of the authors, economics professor William T. Harbaugh. "People feel good knowing that they're a charitable giver."
Brain-imaging technologies such as functional magnetic resonance imaging, or MRI, which uses magnetic waves to monitor acute changes in brain activity, may allow economists to uncover answers about human behavior and motivation that were previously hidden.
"As an economist, I was fascinated that one can actually look inside a person's brain and see them make economic decisions," said Harbaugh. "Once I heard it was possible there was no way I could stop myself" from doing this research.
In the study, female college students were given $100, then told either that a mandatory transfer of money 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, which the authors argue supports the notion of a "warm glow" phenomenon.
"It's mysterious that human beings among all mammals are so hyper-social that our brains are wired to help other people, even strangers. There's very little evidence that other animals have that capacity," said Paul Zak, director of the Center for Neuroeconomics Studies at Claremont Graduate University. "Economists have always been shocked (by unselfish altruism), and now we have a reason for it: It feels good to do this."
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, professor economics at the California Institute of Technology. "That's pretty cool."
"Part of the growing interest in neuroeconomics is in trying to predict people's choices from neural signals directly," he said. "Sometimes it's better to ask the brain, not ask the person, as it may be useful for predicting behaviors people will subconsciously exaggerate. Direct bio measurements are like a lie detector to tell you what will really happen."
The authors argue their study supports the idea of "pure altruism" that people take action even if the behavior is not explicitly in their own interest.
"Evolutionary brain pleasure areas respond not only to what's good for you but to what's good for other people," said Ulrich Mayr, another study author.