Brain scans by neuroscientists confirm that altruism carries its own rewards. A team including Dr. Jorge Moll of the National Institutes of Health found that when a research subject was encouraged to think of giving money to a charity, parts of the brain lit up that are normally associated with selfish pleasures like eating or sex.

The implication is that we are hard-wired to be altruistic. To put it another way, it’s difficult for humans to be truly selfless, for generosity feels so good.