Why do we give to others?

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Why are we altruistic? Guilt may play a role

BOSTON—Why do we share our resources with people even though we’re unlikely to see any direct benefit? Research into altruistic behavior has centered largely on the warm, fuzzy feelings we get when we give selflessly. But according to new findings reported here today at the annual meeting of AAAS, which publishes Science, some people’s altruism might be motivated by a very different emotion: guilt.

The results come from a tweak to a well-known psychological experiment called the trust game. In it, participants are paired with a partner. One is given a sum of money and the other receives some multiplication of that. (Both know how much the other got.) Then, the latter person must choose how much money they want to give back to their partner, if any. For instance, if Peter receives $10, then Paul will receive, say, $40 and decide how much of that sum to give back to Peter.

Over the years, researchers have learned that most people who receive the multiplied amount consistently give about half of it back to their partner, despite being under no obligation to do so.

“The usual explanation has been that people do this for the so-called ‘warm glow,’” said Alan Sanfey, a neuroscientist at the Donders Center for Cognitive Neuroimaging at Radboud University in Nijmegen, the Netherlands. “But I’ve found that people never look particularly happy when they’re giving money back.”

That led him to wonder whether a bigger factor in their decisions might be that people expect they would feel guilty if they didn’t give their partner an equal share. “And as an Irish Catholic, I feel very well qualified to study guilt,” Sanfey said.

To test this, he and researchers tweaked the trust game so that Peter is told Paul will get four times the amount he is given, when unbeknownst to his partner, Paul actually receives six times the amount. (Peter gets $10 and thinks Paul will get $40, but Paul really gets $60.) Paul also knows he got more than his partner thinks he did.

That puts Paul in a moral quandary. Like others who have played the trust game, he tends to want to give Peter an equitable share of the winnings, but from Peter’s perspective that would only be $20. So should he give back a truly equitable share, or just what Peter expects is a fair share? If fear of feeling guilty motivates people to act altruistically, Sanfey reasoned, then simply meeting Peter’s expectations would assuage that, whereas those who are in it for the warm fuzzy feelings would tend to give half away regardless of Peter’s beliefs.

Sanfey and colleagues ran this experiment with a few dozen university students with various multiplications of money. They found that some people were inveterately equitable, always giving half the actual winnings. Others always gave only what their partners would expect to be half. Then there was a group Sanfey called “moral opportunists” whose behavior shifted toward keeping a larger share as the winnings went up.

Running the game while recording people’s brain activity with a functional MRI machine revealed that people who made similar giving choices (either to give half or what they had, or half of what their partner thought they had) showed similar brain patterns in the medial prefrontal cortex, a region associated with decision-making. Sanfey calls these tendencies “moral phenotypes,” categories that predict exactly what flavor of altruism people engage in when faced with complex moral scenarios.

Understanding these patterns in individuals and groups could shed light on why, for example, some people bristle at communism and thrive under capitalism and vice versa. His lab is currently exploring how these moral phenotypes react to experimental mockups of economic inequality.

The work is thought provoking, says Warren Page, a professor emeritus of mathematics at the City University of New York in New York City, who attended the session. But he would like Sanfey to explore in future studies how a different motivation, loss aversion, also plays into these findings. “The pain of losing money is greater than the satisfaction we get from gaining money,” he said. With larger sums of money, the expected pain of giving so much away might deter even the most altruistic, he added.

Check out our full coverage of AAAS 2017.