Wiring the altruistic brain

Contrary to classical economic supposition (1), understanding people's preferences and decisions is not as simple as observing their actions. Indeed, there are many reasons for behaving altruistically, such as being moved by someone's suffering (empathy) or feeling obliged to return a favor (reciprocity) (2, 3). One of the major challenges for social psychologists and neuroscientists is to characterize the different motives underlying our interactions with other people. On page 1074 in this issue, Hein et al. (4) show that knowing how distinct areas in the human brain communicate with each other can tell us why someone behaves altruistically.