Classroom · Game Theory
The prisoner's dilemma, played by your actual room.
Every pair chooses in silence: stay quiet or talk. The payoff matrix resolves on the projector, a boss on the outside changes the deal, and the same room plays the same round again — differently.
- In pairs
- About 30 min
- 2 acts
A practice run with fictional students. No real classroom or join code is created.
Try an answer on the phone. Lead the lesson from the screen.
On their phone
You are presenting
Setting up the room…
Lesson deck
Teach it as a ready-made lesson
Hook, how it works, the live game and takeaways. Edit anything.
Stay silent or talk?
A ready-to-teach lesson deck: a hook, how it works, the live game and takeaways for the debrief.
6 slides · 1 activity
What it teaches
Students meet a dominant strategy by holding one: whatever your partner does, talking pays you more — and when both of you follow that logic, you both land somewhere worse than silence would have put you. The second round re-prices the same choice, so the room feels how an equilibrium moves when the payoffs do, not just hears that it can.
- Dominant strategies
- Repeated games
Debrief, while the boards are still up
- 01
Why did talking feel safe even though silence paid the pair more?
- 02
What changed in round two, and who changed with it?
- 03
Where outside this room have you seen a game with this exact shape?
How it works
- 01
Add it to your library
Sign up free and pull the activity from Decka's built-in classroom catalog — one click copies it into your own library, ready to run from Decka or inside PowerPoint.
- 02
Students join by QR
Everyone scans from the projector and plays in their phone's browser. No app, no account, nothing to install.
- 03
You run the room
You move the activity phase by phase: collection closes, the boards resolve on the big screen, and the debrief happens while the results are still up.
What is the prisoner's dilemma game?
The prisoner's dilemma is the founding example of game theory: two people who would each be better off cooperating, and a payoff structure that punishes whichever of them tries it alone. Defecting is a dominant strategy — it beats cooperating no matter what the other person does — so two rational players end up at the one outcome both of them ranked below mutual silence. Explaining that sentence takes a diagram. Feeling it takes a partner.
That is what running it live changes. Each student chooses on their own phone without seeing their partner's screen, the room's choices land on the projector as a distribution rather than an anecdote, and the awkward minute where everyone finds out who talked is the lesson arriving. Then the deal changes — a boss starts dealing with whoever talks — and the same pairs play the same round under new payoffs, which is where dominant strategies stop being a definition and start being a thing the room watched move.
The preview above is the real thing: the same compiled activity, played with fictional classmates. You run the projector’s steps and play one student’s phone, so you make the choice yourself and watch the room’s choices land on the screen.
FAQ
Prisoner's dilemma questions, answered
Do students see what their partner chose?
Not while choosing. Each phone shows only its own choice until collection closes; then the pair's outcome lands on both phones and the room's distribution goes up on the projector. Private choice, public resolution — that ordering is the game.
Why two rounds?
The second round re-prices the same choice: between rounds a boss starts dealing with whoever talks, so the payoffs shift and the room gets to answer the question it just argued about — does the equilibrium move when the numbers do? Playing it twice is what turns the matrix from a picture into a variable.
How long does it take?
The default timing ships with the activity and is shown under the headline as "About N min". Every duration is a setting you control before you run it, so it fits a starter or the spine of a full lesson.
Do students need an app or an account?
No. Students scan a QR code from the projector (or open a link) and play in their phone's browser. Nothing to install and nothing to sign up for.
Does it work in PowerPoint or Google Slides?
In PowerPoint, yes: open the Decka add-in on a slide and choose the Classroom tile. Google Slides is not supported yet; there you present from Decka itself. Students play from their phones either way.
How many students can play at once?
Up to 50 participants per live activity on the free plan, 150 on Pro, and 300 on Badass.
More game theory games to run live
- Twenty coins, take it or leave it
- Chicken — four seconds on a single-track lane
- The stag hunt — one day, two ways to spend it
- Battle of the sexes — one evening, two plans
- Ten rounds in the pot
- Rock, paper, scissors — two rivals and a contract
- Matching pennies — the game where you want opposite things
- All game theory activities
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