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Game Theory · 11 questions

Prisoner's Dilemma

One shot, many rounds, tit-for-tat, and the last move. A higher percent is more cooperative. The middle is where conditional cooperators live.

About this test

The prisoner's dilemma, named in the work of Merrill Flood, Melvin Dresher, and Albert Tucker, is a game in which each player does better by defecting no matter what the other does, and both do worse if both defect than if both cooperate. Robert Axelrod's tournaments found that tit-for-tat — start by cooperating, then copy the other player's last move — did strikingly well among repeated strategies. Anatol Rapoport submitted it. Reciprocal altruism (Trivers) and later evolutionary work (Nowak and others) ask when cooperation can survive temptation. These scenes are original. Payoffs are described in words so the dilemma stays visible. The percent is a cooperation lean, not a claim that cooperating is always rational.

Question 1 of 11

What this test asks
  1. You will never meet the other player, and nobody will hear what you did. If both of you cooperate, you both do fairly well. If you defect while they cooperate, you do better and they do badly. If both defect, you both do poorly. This is the only round.
  2. The same payoffs will repeat for many rounds. Both of you know that. Neither of you knows exactly when the last round is.
  3. They have cooperated every round so far. The payoffs have not changed. It is your move.
  4. After a long cooperative run, they defect once. It might be a test or a mistake. Your move.
  5. You answered their defection with one of your own. On the next round they cooperated again. What now?
  6. The organizer announces that the next round is the last. Both of you hear it. The history up to now is mutual cooperation.
  7. The temptation is now enormous. Defecting on a cooperator would help you much more than in the earlier rounds. They have been cooperating.
  8. The sucker's payoff is severe. If you cooperate and they defect, you lose something you cannot casually replace. They have been cooperating so far.
  9. They defected, and there is a real chance it was an accident — a mis-click, a misunderstood rule. You cannot ask them.
  10. Other people will hear exactly what you did, and you will play different partners later. This partner has been cooperating.
  11. They defected twice, then sent a clear offer to return to mutual cooperation and take the next loss if you need proof.