You've got $10 to split with a friend. You propose the split — but if they say no, you both get nothing! What would you offer, and what would you accept?
🎮 Interactive Game Coming Soon!
We're building an interactive proposer-and-responder simulator. For now, explore the payoff matrix below to see how offers play out.
The Ultimatum Game has two roles: a Proposer and a Responder. The Proposer is given some money — let's say $10 — and must offer to split it with the Responder in any way they choose. The Responder then has a simple choice: accept the offer, in which case both players keep their share, or reject it, in which case both players get nothing at all.
If people were perfectly logical calculators, Responders would accept any offer above $0, because even $1 is better than nothing. But real people don't behave that way! When offers feel unfair — like a Proposer trying to keep $9 and only offer $1 — most Responders reject the deal, even though it costs them money, just to punish the unfair behavior. This shows that humans care deeply about fairness, not just about maximizing what they personally receive.
Smart Proposers learn to offer something closer to a fair split, like 50-50 or 60-40, because they know an unfair offer risks getting rejected and losing everything. This simple game reveals a lot about human psychology, negotiation, and why fairness matters even when logic says it shouldn't.
| Proposer's Offer | Responder Accepts ✅ | Responder Rejects ❌ |
|---|---|---|
| $5 / $5 (fair split) 🤝 | (5, 5) | (0, 0) |
| $8 / $2 (unfair) 😬 | (8, 2) | (0, 0) — likely! |
| $1 / $9 (very unfair) 😡 | (1, 9) | (0, 0) — very likely! |
Even though (8, 2) gives the Responder more than $0, real people often reject it out of a sense of fairness — sacrificing their own money to punish greed.
Use 10 coins or candies. One person proposes a split with a partner. If the partner accepts, both keep their share. If they reject, both give the coins back. Try several rounds with different splits and talk about which offers get rejected and why — notice how much fairness matters compared to pure logic.
What is the Ultimatum Game?
The Ultimatum Game involves two players splitting a sum of money. One player proposes a split, and the other can accept it (both get the split) or reject it (both get nothing).
Why don't people accept any offer, even a small one?
Pure logic says any amount is better than none, but real people often reject unfair offers because they value fairness and want to punish greedy behavior, even at a cost to themselves.
What counts as a fair offer in the Ultimatum Game?
Studies show most people offer close to a 50-50 split, and offers below about 20-30% of the total are frequently rejected by responders.
How is the Ultimatum Game different from the Dictator Game?
In the Dictator Game, one person simply decides the split with no power for the other person to reject it, which usually leads to less generous offers than the Ultimatum Game.