What makes people recoil upon witnessing human tragedies, engage in costly helping behaviors, and violently protest against acts of injustice (Goodenough & Prehn, 2004; Zeki & Goodenough, 2004)? Strikingly, this inclination can go far beyond the interpersonal sphere, as humans often risk material resources, and even physical integrity, to uphold culturally shaped values in the form of societal causes, ideologies, or beliefs, for example. Moral and social values form the basis of personal and sociocultural identities, which is a core theme throughout this volume. It is thus not surprising that debates on the moral nature of humanity have occupied theologians, philosophers, and laymen for millennia. Here we will review how neuroscience is providing new insights on how the human brain enables complex moral cognition and behavior.

Defining morality is not a straightforward task, and any definition will suffer from shortcomings, especially when evaluated by scholars from different fields. The words “moral” (derived from the Latin moralis) and “ethical” (from the Greek êthikos) originally referred to the consensus of manners and customs (MacIntyre, 1985). This rather broad meaning of “moral,” however, does not address a central question for the cognitive neuroscience of morality: What distinguishes moral cognition from other forms of socially relevant abilities? Most instances of social behavior are morally relevant because they have effects on others and are thus liable to be evaluated as “right” or “wrong” depending on socioculturally shaped norms. Therefore, one may argue that on the outside, any kind of social behavior is also moral in nature and that the neural and cognitive mechanisms guiding moral and social behavior should therefore be identical.