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Click the buttons on screen to play each round and advance through the interactive. Works best on a desktop or laptop.

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Frequently Asked Questions about The Evolution of Trust

How do I play The Evolution of Trust?
Just click the on-screen buttons to make choices and press the arrows to advance. It is a guided interactive: you play short rounds of a trust game against different characters, then the story walks you through what the results mean. No keyboard needed.
Is The Evolution of Trust free to play online?
Yes! The Evolution of Trust on PlayBrain is completely free to play in your browser. No downloads, no sign-ups, and no ads blocking gameplay.
What is The Evolution of Trust about?
It is an interactive guide to the game theory of trust, based on the classic Prisoner's Dilemma. You learn why people cooperate or cheat, how repeated interactions change behavior, and what conditions help trust evolve in a society.
Is The Evolution of Trust educational?
Very. It is widely used in classrooms to teach game theory, the Prisoner's Dilemma, the tit-for-tat strategy, and the role of trust and miscommunication in cooperation. It turns abstract math into a hands-on experience.
Who made The Evolution of Trust?
It was created by Nicky Case, an independent developer known for playable explanations of complex ideas. The project is released into the public domain (CC0), which is what lets PlayBrain self-host the original open-source build.
Does it work on mobile?
It plays best on a desktop or laptop where there is room for the full interactive, but the controls are all click or tap based, so it can also work on a tablet or larger phone screen.

About The Evolution of Trust

The Evolution of Trust is a playable explanation of one of the most important ideas in social science: how cooperation can emerge between self-interested people. Built around the classic Prisoner's Dilemma, it lets you play short rounds against a cast of characters, each following a different strategy, from the always-cheating Cheater to the forgiving Tit-for-Tat. As you play, the interactive reveals why a single round rewards betrayal but repeated rounds reward trust, how a little miscommunication can poison cooperation, and what conditions let trust spread through a whole population. It has become a favorite teaching tool for game theory, economics, and psychology classes worldwide. The Evolution of Trust was created by Nicky Case and released into the public domain (CC0), which is what lets PlayBrain self-host the original open-source build for you to play here.

How to Play

  1. Click the start button to begin the guided experience.
  2. In each round, choose to cooperate or cheat against the character you are facing.
  3. See how your choices play out and what the payoff matrix rewards.
  4. Use the arrows to move forward and discover how trust evolves over many rounds.

Credits: The Evolution of Trust by Nicky Case, released into the public domain (CC0). Source: github.com/ncase/trust