How Should We Split It?

The split-it game

Story: One player gets to suggest a split. The other player can say yes or no. If they say no, both players get nothing.

Here’s a simple game with a twist.

I have HK$100. I get to propose how we split it. You can:

Let’s say I offer you HK$10 and keep HK$90 for myself.

If you accept: you get HK$10, I get HK$90.

If you reject: you get HK$0, I get HK$0.

This is why the game is interesting:

First 5 rounds you propose. Last 5 rounds they propose.

Your total 0

Round 1 /10

Other total 0

Rounds 1–5: You propose You split HK$100. The other player decides whether to accept.

Your offer to them HK$50 You keep: HK$50

A super-cold logic machine would accept any offer of HK$1 or more, because that is still better than zero.

But real humans usually do not think that way. Many people reject offers below about HK$30.

Why? Because the split feels unfair.

Big idea: people care about fairness, not only about getting the biggest number possible.

If you offer exactly HK$50:

That is the 50/50 split. It may not be the biggest possible grab, but it is the safe offer that almost everyone accepts.

Humans are not money calculators. We notice fairness. We remember fairness. We react to fairness.

That helps groups work well together, but it also means people sometimes turn down money just to say, “That deal was not fair.”

I have HK$100. I offer you HK$10. You accept. How much do you each get?

I have HK$100 and offer you HK$10. You REJECT. What happens?

Pure logic says: accept any offer ≥ HK$1, because HK$1 > HK$0. Why do real people reject offers of HK$10?

As a proposer, which offer gives you the best chance of being accepted AND keeping a good share?