Game theory · Research Worlds
Cooperation can evolve without saints
If you will meet again, helping can win. You do not need kind souls — you need memory, repetition, and incentives.
Free · No account required · Runs in your browser
Watch the 90-second visual story ↗What will you explore?
Axelrod & Hamilton, 1981
If you will meet again, being fair can beat being selfish.
How does it work?
Watch a 90-second cinematic explanation, or explore a story that pauses so you can change its central mechanism. Inspect the source evidence, compare outcomes and resume the narration. This free Lesson Worlds adaptation needs no account or download; younger learners may want help from a parent or teacher.
Inside the cinematic story
Will we meet again?
A choice now can echo later.
The dilemma has a shape.
Illustrative payoff game: 3, 0, 5, 1
Memory enters the game.
A move now. A response next round.
Take control: Play eight rounds against tit-for-tat. Cooperate · Always defect · Defect once, then repair
Consequences accumulate.
Compare cumulative outcomes.
No universal winner.
Conditions matter: future, opponents, environment.
Change the sequence. See the echo.
The next meeting changes this one.
Discuss the evidence
Before starting, explain what you think this claim means: If you will meet again, being fair can beat being selfish. After exploring, choose one stage above and describe what its model helps you see. Separate what you observed in the adaptation from what the original researchers measured.
Read the original publication for its methods, evidence and limitations. Ask which part of the explanation the interactive model leaves out, and what additional evidence you would need to test the claim yourself.
An eight-round teaching game against tit-for-tat using 3/0/5/1 payoffs, not a replay of the tournaments or an evolutionary simulation. No strategy is universally best; outcomes depend on opponents, noise and future interaction.
Original research
Robert Axelrod & William D. Hamilton · Science 211, 1390–1396 (27 March 1981) · 1981
Educational adaptation by Lesson Worlds. Not affiliated with the authors, Science or AAAS. The original publication may have its own access terms.