Concepts · 3 min read
The Prisoner's Dilemma: Game Theory Basics With a Payoff Table
The payoff table (years in prison)
| Other stays silent | Other betrays | |
|---|---|---|
| You stay silent | 1, 1 | 3, 0 |
| You betray | 0, 3 | 2, 2 |
Lower is better. Each cell shows (your years, their years).
Best responses
If the other stays silent (C), your best reply is betray (0 year beats 1). If the other betrays (D), your best reply is betray (2 years beats 3). Betraying is best either way: a dominant strategy.
Nash equilibrium
When both players betray, neither can improve by changing alone. That stable outcome (2, 2) is the Nash equilibrium, even though (1, 1) would be better for both.
Why it matters
The same structure appears whenever individual incentives conflict with a shared benefit. Repeated games, reputation and enforcement can make cooperation rational. Compare with probability puzzles like Monty Hall.
Frequently asked questions
Is the dilemma realistic?
It is a simplified model. Real situations involve repetition, communication and enforcement that can change the outcome.
What is a dominant strategy?
One that is best for you no matter what the other player does.
Keep reading
The Monty Hall Problem Explained (Why Switching Wins 2/3)
The Monty Hall puzzle solved with a full enumeration table: why switching doors wins two times out of three and staying only one in three.
ConceptsStatistics vs Probability: What Is the Difference?
Probability predicts data from a known model; statistics infers the model from data. A coin-flip example computed both ways.
ConceptsThe Birthday Paradox: Why 23 People Is Enough
In a group of 23 people the chance two share a birthday is just over 50%. The full calculation and a table up to 70 people.
ConceptsStandard Deviation Explained With a Worked Example
What standard deviation measures, how to calculate it step by step, the sample vs population difference and the 68-95-99.7 rule.