Selflessness

Human beings routinely help others to achieve their goals, even when the helper receives no immediate benefit and the person helped is a stranger. Such altruistic behaviors (toward non-kin) are extremely rare evolutionarily, with some theorists even proposing that they are uniquely human. Here we show that human children as young as 18 months of age (prelinguistic or just-linguistic) quite readily help others to achieve their goals in a variety of different situations. This requires both an understanding of others' goals and an altruistic motivation to help. In addition, we demonstrate similar though less robust skills and motivations in three young chimpanzees.

Civil societies function because people pay taxes and make charitable contributions to provide public goods. One possible motive for charitable contributions, called "pure altruism," is satisfied by increases in the public good no matter the source or intent. Another possible motive, "warm glow," is only fulfilled by an individual's own voluntary donations. Consistent with pure altruism, we find that even mandatory, tax-like transfers to a charity elicit neural activity in areas linked to reward processing. Moreover, neural responses to the charity's financial gains predict voluntary giving. However, consistent with warm glow, neural activity further increases when people make transfers voluntarily. Both pure altruism and warm-glow motives appear to determine the hedonic consequences of financial transfers to the public good.

Humans often sacrifice material benefits to endorse or to oppose societal causes based on moral beliefs. Charitable donation behavior, which has been the target of recent experimental economics studies, is an outstanding contemporary manifestation of this ability. Yet the neural bases of this unique aspect of human altruism, which extends beyond interpersonal interactions, remain obscure. In this article, we use functional magnetic resonance imaging while participants anonymously donated to or opposed real charitable organizations related to major societal causes. We show that the mesolimbic reward system is engaged by donations in the same way as when monetary rewards are obtained. Furthermore, medial orbitofrontal-subgenual and lateral orbitofrontal areas, which also play key roles in more primitive mechanisms of social attachment and aversion, specifically mediate decisions to donate or to oppose societal causes. Remarkably, more anterior sectors of the prefrontal cortex are distinctively recruited when altruistic choices prevail over selfish material interests.