What is game theory?
Game theory is the mathematical study of strategic interaction: situations where two or more decision-makers each have to think about what the others will do. Mathematician John von Neumann and economist Oskar Morgenstern launched the field with Theory of Games and Economic Behavior (1944). A "game" here isn't just a pastime; it's any setting where outcomes depend on everyone's choices, from price wars and negotiations to elections and arms races.
The building blocks
- Players: the decision-makers (people, firms, countries)
- Strategies: the plans of action available to each player
- Payoffs: what each player gets from every combination of choices
- Information: what players know about each other's moves and payoffs
Games can be normal-form (simultaneous moves, shown as a payoff table) or extensive-form (sequential moves, drawn as a game tree), and cooperative (binding agreements are possible) or non-cooperative.
Nash equilibrium and classic games
John Nash (1950, 1951) defined an equilibrium as a situation where no player can do better by changing strategy alone while everyone else stays put. This is the Nash equilibrium.
- Prisoner's dilemma: each player's rational choice to defect leaves both worse off
- Chicken: whoever swerves first loses, but if neither does, both crash
- Coordination games: everyone wins by matching choices, like agreeing on a tech standard
- Ultimatum game: if the responder rejects the split, both get nothing
Where it's used
Game theory shows up in oligopoly pricing, auction design, labor negotiations, nuclear deterrence and evolutionary biology. How cooperation can emerge when a game is repeated is covered in The Evolution of Cooperation, and why shared resources get overused in the tragedy of the commons.
Limitations
Classical game theory assumes players are fully rational and good at calculating. In lab experiments, people often care about fairness or revenge and don't play the predicted strategy, which led to behavioral game theory. When a game has several equilibria, the theory alone can't always say which one will happen.
FAQ
- Is game theory only for economics majors?
- No. It's a standard tool in business strategy, political science, biology and computer science (AI and networks).
- Is a Nash equilibrium always the best outcome?
- No. In the prisoner's dilemma, the equilibrium is worse for everyone than mutual cooperation.
Sources reviewed: 2026-10-25
References
- von Neumann, J., & Morgenstern, O. (1944). Theory of Games and Economic Behavior. Princeton, NJ: Princeton University Press.
- Nash, J. F. (1950). Equilibrium points in n-person games. Proceedings of the National Academy of Sciences, 36(1), 48–49.
- Nash, J. (1951). Non-cooperative games. Annals of Mathematics, 54(2), 286–295.
- Osborne, M. J., & Rubinstein, A. (1994). A Course in Game Theory. Cambridge, MA: MIT Press.