People who are nicer have more active brains (specifically, larger posterior superior temporal sulci) than people who do not engage in altruistic helping behavior, according to a new study by Duke researchers.

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Altruism describes the tendency of people to act in ways that put the welfare of others ahead of their own. Why some people choose to act altruistically is unclear, says lead study investigator Dharol Tankersley, a graduate student in Huettel’s laboratory.

In the study, researchers scanned the brains of 45 people while they either played a computer game or watched the computer play the game on its own. In both cases, successful playing of the game earned money for a charity of the study participant’s choice.

The researchers scanned the participants’ brains using a technique called functional magnetic resonance imaging (fMRI), which uses harmless magnetic pulses to measure changes in oxygen levels that indicate nerve cell activity.

The scans revealed that a region of the brain called the posterior superior temporal sulcus was activated to a greater degree when people perceived an action — that is, when they watched the computer play the game — than when they acted themselves, Tankersley said. This region, which lies in the top and back portion of the brain, is generally activated when the mind is trying to figure out social relationships.

The researchers then characterized the participants as more or less altruistic, based on their responses to questions about how often they engaged in different helping behaviors, and compared the participants’ brain scans with their estimated level of altruistic behavior. The fMRI scans showed that increased activity in the posterior superior temporal sulcus strongly predicted a person’s likelihood for altruistic behavior.

According to the researchers, the results suggest that altruistic behavior may originate from how people view the world rather than how they act in it.

"We believe that the ability to perceive other people’s actions as meaningful is critical for altruism," Tankersley said.