"Our data show that the sense of gratification from acting generously comes from knowing that you only had to give up a little bit to help someone else a lot," Cendri Hutcherson says. (Credit: iStockphoto)

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What gives? Scientists try to predict generosity

Are human beings intrinsically selfish? Or are we only selfish when we take time to realize we can get away with it?

And what about willpower? How does it play a role in altruism—in other words, do we need to exercise self-control to be generous?

Scientists say the answers—and which brain mechanism are involved—aren’t clear.

However, new research based on brain scans suggests altruistic behavior could be explained and predicted by a simple computational model. A paper about the work appears in the journal Neuron.

“Generosity does not have to be a difficult decision,” says study lead Cendri Hutcherson, an assistant professor at the University of Toronto.

In fact, altruism becomes easier, the study found, when decision-makers consider how their actions will benefit the other person. The study also found that quick decisions led to more generous behavior— and less financial gain for the person making the choices.

Hutcherson conducted the work as a postdoctoral researcher in the laboratory of Antonio Rangel, a professor at the California Institute of Technology.

Keep or share the money?

Hutcherson, Rangel, and colleague Benjamin Bushong, a visiting professor at the Harvard Business School, used functional magnetic resonance imaging (fMRI) to examine the brain activity of 51 subjects as they decided to make either generous or selfish choices under a variety of conditions.

The decisions of the subjects resulted in either financial gain or loss for themselves or another person, who would remain anonymous to the subject. The amount of money in question ranged from $0 to $100.

The study falls within the scope of a discipline known as neuroeconomics, which seeks to characterize the computations made by the brain to make different classes of decisions as well as the neural circuits that implement those computations.

The researchers used an experimental paradigm from economics called the Dictator Game. They asked the subjects to choose between actions that either result in their own economic gain, in a financial reward for another person, or some combination of the two. For example, the subject might be asked to sacrifice $25 so that the other person might gain $100. If the proposal was rejected there was a default award of $50 for each. To keep the decision-making simple, subjects were given a four-second limit in which to make their choices.

Are humans selfish by nature?

The study was also able to determine under what circumstances generous choices occurred and whether they were made more rapidly than selfish ones or vice versa.

“One of the big debates has been about whether human beings are, by nature, selfish and require self-control or willpower in order to inhibit these selfish impulses,” Hutcherson says. “Some people have suggested that if a generous choice is faster, it is automatic, intuitive, and that you didn’t need self-control to do it.

“If, however, more time is required to make a generous choice, that would be evidence that we have to override our selfish tendencies to be generous—that it takes more mental ‘machinery.'”

“You can come up with counterexamples to either argument,” Hutcherson explains. “We have all had experiences where it felt hard to be nice to others, but we can also come up with examples where people have been extraordinarily altruistic.

“You hear about people who run into burning buildings to save complete strangers and said that they didn’t give it a second thought. The question of why people can make these choices without really thinking is a complex one.”

What the brain scans show

In the experiments, the researchers found that participants were willing to sacrifice money to help the other person an average of 21 percent of the time—even though the identity of recipient of the cash award was unknown to the test subject.

Recorded fMRI scans of the subjects’ brains, taken while they made their decisions, suggested that different brain areas represent one’s own and others’ interests. Self-oriented values correlated with activity in the ventral striatum, an area linked to basic reward processing.

Other-oriented values correlated with activation of the temporoparietal junction, which has been implicated in empathy. Hutcherson believes this is evidence that people are more likely to give away resources if they already have in mind how their donation will benefit someone else.

The study also indicates that self-control may be less of a factor in altruistic decision-making than previously thought. Rather, the more one considers the well-being of another, the easier it is to behave generously. Alternatively, the more one focuses on one’s own well-being, the more difficult altruistic choices become.


“Our data show that the sense of gratification from acting generously comes from knowing that you only had to give up a little bit to help someone else a lot,” Hutcherson says. “If we can highlight the utility of an action that is fairly trivial for ourselves—for example, the notion that for the price of a cup of coffee you can help a starving child—the model predicts that people will be more likely to behave generously.

“But if you have to give up a lot to give another person only a small benefit, that’s not so motivating. The satisfaction to the giver has to be worth the sacrifice.”

Hutcherson notes that such research may help to reveal how people can be encouraged to act more often in the interest of others and may have broader applications in many areas of human behavior, including charitable giving, military training, and criminal rehabilitation.

The National Science Foundation, the Gordon and Betty Moore Foundation, and the Lipper Foundation funded the study.

Source: Caltech

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