In economic situations a player often has preferences regarding not only his or her own outcome but also regarding what happens to fellow players, concerns that are entirely apart from any strategic considerations. While this can be modeled directly by simply writing down a player's final preferences, these are commonly unknown a priori. In many cases it is therefore both helpful and instructive to explicitly model these interactions. This paper, building on a model due to Bergstrom (1989, 1999), presents a simple structure in the context of game theory that incorporates the "synergies" between players. It is powerful enough to cover a wide range of such interactions and model many disparate experimental and empirical results, yet it is straightforward enough to be used in many applied situations where altruism, or a baser motive, is implied.
