I teach undergraduate psychology courses at the University of Maryland, and my classes draw students with diverse interests. But every one of them perks up when I pose this question: Do you want two extra-credit points on your term paper, or six points?
I tell my students that the extra-credit offer is part of an exercise illustrating the interconnectedness of choices individuals make in communities. I explain that the exercise was inspired by an ecologist named Garrett Hardin and an address that he delivered 50 years ago this summer, describing what he called “the tragedy of the commons.” Hardin said that when many individuals act in their own self-interest without regard for society, the effects can be catastrophic. Hardin used the 19th-century convention of “the commons”—a cattle-grazing pasture that villagers shared—to warn against the overexploitation of communal resources.