Social dilemmas are situations in which individuals, groups or nations face a choice between their own short-term interests and the longer-term interests of all parties involved, including themselves. As a consequence, in the end they all regret the way they have acted. Examples of social dilemmas are easy to find: depletion of vital resources, arms races, over-production of hazardous substances and environmental pollutants, information hoarding, and the failure to provide and maintain public goods. Understanding the dynamics of social dilemmas constitutes a major challenge. One prominent...