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 rgret the way they have acted. Examples of social dilemmas are easy to find: depletion of vital resources, arms races, overproduction 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 feature that dinstinguishes this book is the focus on computer simulations as a methodology for the exploration of the dynamic interplay of individual level processes and aggregate outcomes.