The Ash Twins Blog

Social norms often enjoin actions that impose small externalities on others. Before transmission of contagious diseases was understood, for example, public spitting was socially acceptable and quite common.  After physicians discovered saliva’s role in the spread of human diseases, however, a social norm against public spitting emerged and the practice was curtailed.  This norm served the public interest substantially, but it did not emerge organically from the members of the community working together.  Rather, as social scientist Jon Elster notes, the social norm against public spitting was founded in a legal norm: Governments passed no-spitting laws first, which then led to the social norm.  In cases like public spitting, moreover, the social norm often persists even after the legal norm withers away.  This dynamic of a social norm being established by an outside authority, argues Elster, is the common characteristic of those norms that serve the public interest: “Over and over again, we find that outside intervention is necessary to stop people from imposing these negative externalities on each other.”

Source:  Jon Elster, Explaining Social Behavior (2007)