All your life, you believe that it's better to give than to receive, so you share your resources to other people without expecting anything in return.

But what truly motivates these acts of kindness? What drives altruistic behavior, especially beyond the warm feelings we experience when we perform selfless acts?

A team of experts from the Netherlands who sought out to investigate these questions discovered that guilt — which is often accompanied by remorse — may have a hand in these acts of generosity.

Kindness Driven By Guilt

Neuroscientists from Radboud University tweaked a prominent psychological experiment as "trust game" and put their own spin to it. Participants are divided into pairs, in which one of them is given a certain amount of money, while the other receives a multiplication of that amount. They are both told how much each of them received.

Afterwards, the person who received more money should decide how much money they will give back to their partner. For example, if Anna received $10, the Beth would receive $40. The latter must decide how much from his $40 he would deduct, if any at all.

The researchers found that over the years, most people who received more money would give consistently about half of it to their partner, even though they are under no obligation to do that.

Neuroscientist Alan Sanfey, one of the authors of the study, said past studies have usually pointed to the "warm glow" as a reason why people share their resources. However, Sanfey noticed a different thing.

"I've found that people never look particularly happy when they're giving money back," he said.

This led Sanfey to consider whether there's a larger factor in the participants' decisions. It may be that the person would feel guilty if they choose not to give the other person a share of their money.

A Moral Dilemma

To test the theory, Sanfey and his colleagues actually lied to the participants about the amount they're given.

In the recent example, Anna received $10, and she and Beth are told the other received $40. In reality, Beth received six times Anna's money. Beth also knows she got six times more.

This puts Beth in a moral dilemma. Like others, she would tend to give Anna an equitable share of her earnings, but from Anna's perspective, that would only be $20. So should Beth give Anna the true equitable share or what Anna expects is equitable?

Sanfey argued that if fear of feeling guilty drives people to do acts of generosity, then simply meeting Beth's expectations would ease that. On the other hand, those who do acts of kindness to generate the warm, fuzzy feeling inside would tend to give half of their money away, regardless of what Beth expects.

Furthermore, the researchers ran this trust game while keeping a record of people's MRI scans. Data revealed that those who gave half of their money or the amount their partner expected they had displayed similar patterns in the region of the brain related with decision-making. These tendencies, which Sanfey dubbed as "moral phenotypes," predicts what kind of altruism people engage in when faced with a moral dilemma.

Researchers believe understanding all these brain patterns could explain why some people bristle at communism, while other people thrive under capitalism. Sanfey and his team are currently exploring how these patterns react to mockups of economic inequality.

The findings of the study were presented at the annual meeting of the American Association for the Advancement of Science.