Two travellers meet at a crossroads in the forest. Each carries something the other needs. They can trade fairly — or try to cheat. In the forest of choices, trust is the rarest bird of all.

The Prisoners' Dilemma

An interactive game about trust, betrayal, and the emergence of cooperation

The classic scenario: Two suspects are arrested and held in separate cells. Each can either stay silent (cooperate) with the other, or betray (defect) and testify against them.

If both stay silent, they each get a light sentence. If both betray, they each get a heavy sentence. But if one betrays while the other stays silent, the betrayer goes free and the silent one gets the harshest sentence of all.

The dilemma: betrayal is individually rational, but mutual cooperation makes everyone better off. In a one-shot game, rational players always defect. But when the game is repeated, something remarkable happens -- cooperation can emerge from pure self-interest.

You will play 10 rounds against AI opponents, each with a distinct strategy. Can you figure out who to trust?

Payoff Matrix
Opponent
CooperateDefect
You Cooperate
33
05
You Defect
50
11

Each cell shows: Your points · Their points

Your Opponents
Round 1 of 10
You:0
Opponent:0
Moves:
Switch Opponent
What will you do?
Show Payoff Matrix
Opponent
CooperateDefect
You Cooperate
33
05
You Defect
50
11

Running Score

You0
Opponent0

Round History

#YouOpponentYour PtsTheir Pts

No rounds played yet

Game Over

Here is how you fared against each opponent

What Did We Learn?

The Prisoners' Dilemma shows why cooperation is hard: defection is always individually tempting, yet mutual cooperation yields better outcomes for everyone.

In 1984, political scientist Robert Axelrod ran a famous computer tournament where strategies competed in a repeated Prisoners' Dilemma. The winner? Tit-for-Tat -- a simple strategy that cooperates first and then mirrors the opponent's last move. It succeeded because it is nice (never defects first), retaliatory (punishes defection immediately), forgiving (returns to cooperation), and clear (easy for opponents to understand).

The deeper lesson: in repeated interactions -- which is how most real-world relationships work -- "nice" strategies tend to win. Building a reputation for cooperation, while being willing to punish betrayal, creates the conditions for trust to emerge. This is why institutions, contracts, and social norms exist: they transform one-shot dilemmas into repeated games where cooperation becomes the rational choice.