INTRODUCTION For the sake of simplicity, let us consider a two-person situation. Imagine that I am interacting with another person and that the outcomes of our interaction depend upon what I do myself and what the other person does, that is, that we are interdependent. In the course of our interaction, we want to satisfy individual needs or interests. By doing so, each of us may affect the other's well-being in a positive (in no-conflict situations) or in a negative way. The latter varies from plain antagonistic situations (the more I get the more the other loses, i.e. constant sum games) to a wide range of mixedmotive situations in which there is only a partial, although sometimes very severe, conflict of interests. The best known example is the Prisoner's Dilemma Game.