Game theoryClassroom · multi-user
Keynesian Beauty Contest — Guess ⅔ of the Average
Everyone secretly picks a number 0–100; whoever lands closest to two-thirds of the class average wins. Watch guesses spiral toward zero.
You’ll learn: See why 'everyone is rational and knows everyone is rational' fails in practice, and how strategic reasoning deepens across rounds.
- Bounded rationality
- Iterated reasoning (level-k)
- Nash equilibrium
- Strategic expectations
Teacher guide
Students will learn to
- Experience how guessing the average depends on guessing what everyone else will guess.
- Connect the Nash equilibrium (everyone guesses 0) to what actually happens in a real room.
- See strategic learning: guesses fall round over round as players reason one step further.
Before the session — ask
- If everyone were perfectly rational, what number should they all pick — and why?
- Do you expect the class to actually land on that number in round one?
After the session — discuss
- How far was the first-round target from zero, and how did it move across rounds?
- Why don't real people jump straight to the equilibrium even when they can work it out?
- What does this say about assuming everyone is fully rational in markets?
Timing
- Briefing & the rules3–5 min
- Five guessing rounds6–10 min
- Debrief & discussion8–10 min
Run it with your class
Students join with a code or QR — no account needed. Teachers start a session from the dashboard.