Is Tribalism a Natural Malfunction?

From an office at Carnegie Mellon, my colleague John Miller and I had evolved a computer program with a taste for genocide.

This was certainly not our intent. We were not scholars of race, or war. We were interested in the emergence of primitive cooperation. So we built machines that lived in an imaginary society, and made them play a game with each other—one known to engender complex social behavior just as surely as a mushy banana makes fruit flies.

The game is called Prisoner’s Dilemma. It takes many guises, but it is at heart a story about two individuals that can choose to cooperate or to cheat. If they both cheat, they both suffer. If they both cooperate, they both prosper. But if one tries to cooperate while the other cheats, the cheater prospers even more.

The game has a generality that appeals to a political philosopher, but a rigorous specificity that makes it possible to guide computer simulations. As a tool for the mathematical study of human behavior, it is the equivalent of Galileo’s inclined plane, or Gregor Mendel’s pea plants. Do you join the strike, or sneak across the picket line? Rein in production to keep prices