Strategy game / cooperation

The Prisoner's Dilemma

Choose before you see the payoffs. Then play again when memory, retaliation, forgiveness and mistakes become possible.

Choice 1 of 13

The sealed choice

Choose before seeing the matrix

You and another player make one move without communicating. Their answer is already sealed. You will see both choices together.

The structure revealed

One move was individually safer

Why the dilemma? Defect gives you more points whether the other player cooperates or defects. Yet if both follow that incentive, each gets 1 instead of the 3 each would receive through mutual cooperation.

Each cell gives your points first, then the other player's points.
Your move	They cooperate	They defect
You cooperate	3 / 3Jointly strong	0 / 5Your move is exploited
You defect	5 / 0You take the advantage	1 / 1Both protect, both lose ground

Your repeated-play record

Cooperation

Mutual cooperationjointly strong rounds

One-sided advantagetimes you defected against cooperation

After their defection

What changed with the strategy?

The conceptual hinge

Repetition changes the game around the matrix

The one-round incentive to defect does not disappear. What changes is that today's move can affect tomorrow's response. Reciprocity may support cooperation; unforgiving retaliation may lock in mutual defection; forgiveness may repair a mistake but can be exploited.

Inspect every move and payoff

Stage	Your move	Their intention	Delivered move	Points

Script-free explainer

The complete dilemma in plain language

Defection pays more for you against either single move: 5 rather than 3 against cooperation, and 1 rather than 0 against defection. But mutual cooperation gives both players 3, while mutual defection gives both only 1.

Mutual cooperation: 3 / 3. Both restrain the immediate advantage, so both receive a strong outcome.
You cooperate; they defect: 0 / 5. Your cooperation is exploited: you receive nothing and the other player takes the largest payoff.
You defect; they cooperate: 5 / 0. You take the largest immediate payoff while the other player's cooperation is exploited.
Mutual defection: 1 / 1. Both protect against exploitation, but both finish below the mutual-cooperation payoff.

Three repeated strategies

The Open Hand: Cooperates every round, even after defection. A cooperative environment creates a tempting opportunity to take more, but unconditional cooperation cannot answer exploitation.
The Mirror: Cooperates first, then repeats your previous delivered move. Repetition makes reciprocity possible: a move can change not only this payoff but the response available next round.
The Repairer: Reciprocates, but cooperates after mutual defection to reopen the relationship. A forgiving move can halt retaliation after a mistake, though it also creates another opportunity to exploit cooperation.

Take it further

Where does cooperation come from?

Each prisoner can shorten their own sentence by betraying the other. If both betray, both suffer. Rational self-protection manufactures a worse world.

Individual incentive

In the one-shot matrix, defection pays more whatever the other player does.

Joint outcome

Mutual cooperation is better for both than mutual defection, even though it is not individually dominant.

Repeated relationship

Memory makes conditional cooperation, retaliation, reputation and repair possible.