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Game Theory — Strategy when others strategize too

A 13-slide tour of payoffs, equilibria, and the mathematics of mutual anticipation — from von Neumann's chessboard to the FCC spectrum auction.

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A 13-slide tour of payoffs, equilibria, and the mathematics of mutual anticipation — from von Neumann's chessboard to the FCC spectrum auction. Key sections include: Game Theory /; Strategy when others strategize too.; The Setup; Zero-Sum Games; Non-Zero-Sum Games; Prisoner's Dilemma; Nash Equilibrium; Repeated Games & Tit-for-Tat; The Stag Hunt; Mixed Strategies.

Key sections

  • 01Game Theory /
  • 02Strategy when others strategize too.
  • 03The Setup
  • 04Zero-Sum Games
  • 05Non-Zero-Sum Games
  • 06Prisoner's Dilemma
  • 07Nash Equilibrium
  • 08Repeated Games & Tit-for-Tat
  • 09The Stag Hunt
  • 10Mixed Strategies
  • 11Mechanism Design
  • 12Real Applications
  • 13Limits of Game Theory
  • 14Further Reading

Topics covered

Slide outline
  1. 01Game Theory /
  2. 02Strategy when others strategize too.
  3. 03The Setup
  4. 04Zero-Sum Games
  5. 05Non-Zero-Sum Games
  6. 06Prisoner's Dilemma
  7. 07Nash Equilibrium
  8. 08Repeated Games & Tit-for-Tat
  9. 09The Stag Hunt
  10. 10Mixed Strategies
  11. 11Mechanism Design
  12. 12Real Applications
  13. 13Limits of Game Theory
  14. 14Further Reading
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https://shipslides.com/d/catalog-math-game-theory
Category
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Updated
2026-05-17
LLM text
https://shipslides.com/d/catalog-math-game-theory/llms.txt

Presentation Transcript

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Slide 01

Game Theory /

  • Mathematics / Decision Sciences
  • Strategy when others strategize too.
  • A 13-slide tour of payoffs, equilibria, and the mathematics of mutual anticipation — from von Neumann's chessboard to the FCC spectrum auction.
  • Deck 01 — Game Theory in 13 moves
Slide 02

The Setup

  • Slide 02 — Foundations
  • Game theory is the study of strategic interaction: what should you do when the people you're playing against are doing the same calculation about you?
  • Three ingredients
  • Players — assumed rational, expected-utility maximizers.
  • Strategies — the menu of choices each player can make.
  • Payoffs — numerical reward for every combination of choices.
  • The hidden ingredient
  • Common knowledge. I know the rules. You know the rules. I know that you know. You know that I know that you know — recursively, all the way down.
  • Strip any layer of that mutual recursion and the predictions wobble.
Slide 03

Zero-Sum Games

  • Slide 03 — Pure Conflict
  • Every dollar I win is a dollar you lose. Chess, poker (heads-up), tennis. The total is fixed; we fight over slices.
  • Minimax theorem
  • von Neumann, 1928. In any finite two-player zero-sum game with mixed strategies, there is a value V such that:
  • Player 1 can guarantee at least V. Player 2 can prevent more than V. The pessimistic upper bound and pessimistic lower bound meet.
  • The first deep result of the field. Equilibrium exists, and it is computable.
  • Chess — finite, zero-sum, perfect information.
Slide 04

Non-Zero-Sum Games

  • Slide 04 — Beyond Pure Conflict
  • Most real life isn't a fight over a fixed pie. The pie can grow, shrink, or split unevenly. Both players might gain — or both might lose.
  • The pie can grow
  • Trade. Marriage. Joint ventures. The kingdom of cooperation.
  • The pie can shrink
  • Arms races. Price wars. Climate inaction. The kingdom of mutual harm.
  • The interesting question: when does a non-zero-sum game offer mutual gain — and what stops the players from grabbing it?
  • Cooperation is possible. It is not, however, always rational. That is the whole problem.
Slide 05

Prisoner's Dilemma

  • Slide 05 — The Canonical Trap
  • Two suspects, separately questioned. Stay silent (cooperate) or rat out the other (defect)?
  • B: Cooperate
  • B: Defect
  • A: Cooperate
  • −1−1
  • −100
  • A: Defect
  • 0−10
  • −5−5
  • Years in prison (negative). Shaded cell = Nash equilibrium.
  • Whatever the other does, defecting is better for me. So both defect — landing on (−5, −5), worse than the (−1, −1) we could have shared.
  • Individual rationality, collective tragedy. The single most-cited 2×2 in social science.
Slide 06

Nash Equilibrium

  • Slide 06 — The Big Idea
  • John Nash, 1950, 28-page Princeton thesis. The definition that earned a Nobel Prize:
  • A strategy profile is a Nash equilibrium if no player can improve their payoff by changing only their own strategy.
  • Everyone's choice is a best response to everyone else's choice. The fixed point of mutual anticipation.
  • What Nash proved
  • Every finite game has at least one equilibrium (in pure or mixed strategies).
  • Generalizes minimax beyond zero-sum.
  • Used Kakutani's fixed-point theorem — pure topology applied to choice.
  • What Nash didn't promise
  • Equilibria can be bad (see: Prisoner's Dilemma).
  • Multiple equilibria are common — which one are we in?
  • Players may not actually find them.
Slide 07

Repeated Games & Tit-for-Tat

  • Slide 07 — Repetition Changes Everything
  • If we play once, defection wins. If we play repeatedly, the future casts a shadow on the present — and cooperation becomes possible.
  • Axelrod's tournament (1980)
  • Robert Axelrod invited game theorists to submit programs to play repeated Prisoner's Dilemma. The shortest program won — twice.
  • TIT-FOR-TAT by Anatol Rapoport: cooperate first, then copy whatever the opponent did last move.
  • Why it wins
  • Nice — never defects first.
  • Retaliatory — punishes defection immediately.
  • Forgiving — returns to cooperation when opponent does.
  • Clear — opponent quickly learns the rule.
  • The folk theorem: with patient enough players, almost any reasonable outcome can be sustained as equilibrium in a repeated game.
Slide 08

The Stag Hunt

  • Slide 08 — Coordination
  • Rousseau's parable. Two hunters: cooperate to take down a stag (big payoff), or grab a hare alone (small but safe). The stag requires both — and faith in your partner.
  • B: Stag
  • B: Hare
  • A: Stag
  • A: Hare
  • Two equilibria: payoff-dominant (Stag, Stag) and risk-dominant (Hare, Hare).
  • Unlike the Prisoner's Dilemma, cooperation IS a Nash equilibrium here. The problem is trust: if you suspect your partner will hare, hare is safer for you too.
  • Models: building institutions, signing treaties, joining a startup, going to a party only if your friends do.
Slide 09

Mixed Strategies

  • Slide 09 — Randomization as Rationality
  • Some games have no equilibrium in pure strategies. The fix: randomize.
  • Matching pennies
  • I want our coins to match; you want them to differ. Any pure choice is exploitable. The unique equilibrium: each picks heads with probability 1/2.
  • Soccer penalty kicks
  • Empirically, professional kickers and goalkeepers randomize — and the observed frequencies match Nash predictions remarkably well (Chiappori, Levitt, Groseclose 2002).
  • Decision tree — matching pennies extensive form.
  • A mixed-strategy equilibrium is a probability distribution that makes the opponent indifferent. Indifference is the lock; randomness is the key.
Slide 10

Mechanism Design

  • Slide 10 — Reverse Game Theory
  • Standard game theory: given the rules, predict behavior. Mechanism design flips the question:
  • Given the behavior we want, design rules so that self-interested play produces it as the equilibrium.
  • Key principles
  • Incentive compatibility — telling the truth is in your interest.
  • Individual rationality — players prefer participating to leaving.
  • Revelation principle — anything achievable by any mechanism is achievable by a direct, truthful one.
  • Heroes of the field
  • Hurwicz, Maskin, Myerson — Nobel 2007.
  • Vickrey — second-price auctions, Nobel 1996.
  • Roth — kidney exchange & matching, Nobel 2012.
Slide 11

Real Applications

  • Slide 11 — Theory in the Wild
  • $Spectrum auctions
  • FCC, 1994 onward. Mechanism designers (Milgrom, Wilson) built simultaneous ascending auctions that have raised hundreds of billions while allocating spectrum efficiently.
  • +Kidney exchange
  • Alvin Roth's clearinghouse: incompatible donor-patient pairs are matched in chains and cycles. Thousands of transplants now happen that otherwise wouldn't.
  • @Search ad auctions
  • Google's AdWords / Generalized Second-Price auction. Every search query is a tiny auction. Game theory funds half the modern internet.
  • !Matching markets
  • Medical residents to hospitals (NRMP). Students to public schools. Deferred-acceptance algorithms produce stable, strategy-proof matches.
  • A coordination/matching graph — pairs find each other through a market.
Slide 12

Limits of Game Theory

  • Slide 12 — Where the Theory Strains
  • Bounded rationality
  • Real players don't compute Nash equilibria. They use heuristics, satisfice, get tired. Behavioral game theory (Camerer, Thaler) folds psychology back into the model.
  • Common knowledge is fragile
  • Most equilibrium concepts assume infinite recursion of beliefs. Drop one level and predictions diverge. Robert Aumann's "agreement theorem" looks beautiful but rarely holds in the wild.
  • Multiple equilibria
  • The theory often predicts several stable points. Which one we end up in depends on history, focal points (Schelling), or culture — variables outside the model.
  • Evolutionary games
  • Maynard Smith's reframing: strategies as genes, equilibria as evolutionarily stable states. No rationality required — selection does the optimizing. Used in biology, networks, cultural transmission.
  • The theory works best as a lens, less well as a crystal ball.
Slide 13

Further Reading

  • Slide 13 — End of the Match
  • Books
  • Theory of Games and Economic Behavior — von Neumann & Morgenstern (1944).
  • The Evolution of Cooperation — Robert Axelrod.
  • Thinking Strategically — Dixit & Nalebuff.
  • The Strategy of Conflict — Thomas Schelling.
  • Who Gets What — and Why — Alvin Roth.
  • Watch
  • YouTube: Prisoner's Dilemma — Game Theory
  • YouTube: Nash Equilibrium — Explained
  • People
  • von Neumann, Nash, Schelling, Aumann, Roth, Axelrod, Maynard Smith, Milgrom.
  • "In game theory, the assumption is that you know your opponent. In life, the discovery is that you barely know yourself."
  • — end of deck —
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