The reason why we help others at a cost to ourselves has long presented a puzzle for scientists. Why do some of us do it more than others? And are we doing it because we are truly moved by the suffering of others or simply because we feel we ought to return a favor or even get something in return? Looking at behavior alone, it can be hard to tell. Both empathy and the principle of reciprocity—giving to return a favor or expecting others to do so—are proposed explanations for altruism which have been impossible to separate until now.
Using functional magnetic resonance imaging (fMRI), which measures blood flow changes in the brain, a new study suggests that specific differences in connectivity between brain regions can predict whether someone is an empathy-driven altruist, a reciprocity-driven altruist—or just selfish.
In the experiment, 34 female participants were divided into two groups. Those in the “empathy” group witnessed an actor receive painful electric shocks—and received shocks themselves (so they knew it hurt). In the “reciprocity” group, participants were paired up with actors who kindly paid money so the participant received fewer shocks (although both groups received the same number of shocks overall).
