Overview
The prisoner's dilemma is the most famous scenario in game theory. It shows how two individually rational choices can produce a collectively worse outcome.
How to solve The Prisoner's Dilemma
- Fix what the other prisoner does, then ask what's best for you.
- If they stay silent, betraying saves you a year; if they betray, betraying still saves you a year.
- So betraying is better no matter what — both betray and get 2 years each.
The key insight
Betraying is a dominant strategy: it beats staying silent in every case. Yet when both follow it they land at (2, 2), worse than the (1, 1) they'd get by cooperating — the tragedy at the heart of the dilemma.
Variations & echoes
- Repeated (iterated) play changes everything: strategies like tit-for-tat make cooperation pay.
- It models arms races, pricing wars, climate agreements, and public-goods problems.
Frequently asked questions
Isn't cooperating obviously better?
Jointly, yes — but neither can trust the other, and betraying is safer whatever the partner does. That's why the rational outcome is mutual betrayal.