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What is the prisoner's dilemma?

MathematicsLesson on requestFree to read

Quick answer

The prisoner's dilemma is a classic game-theory puzzle showing why two people might not cooperate even when it's in their best interest. Each does better by betraying the other, so both betray and end up worse off than if they had trusted each other.

Key things to understand

  1. Two suspects are questioned separately and can stay silent or betray.
  2. Whatever the other does, betraying gives each a better individual result.
  3. So both betray — and get a worse outcome than mutual silence would.
  4. It shows how rational self-interest can lead to a bad shared result.
  5. Repeated versions reward cooperation, helping explain real-world trust.

People also ask

What is the point of the prisoner's dilemma?
It shows that two people acting in pure self-interest can end up worse off than if they had cooperated, even when cooperation was possible.
Why do both prisoners betray?
No matter what the other chooses, betraying yields a better personal outcome — so both reach for it and both lose out.
How does cooperation ever emerge?
When the game repeats, players can punish betrayal and reward trust over time, making cooperation the smarter long-term strategy.