Guess Who?

1 Overview

Guess Who? is a two-player deduction game published by Milton Bradley (now Hasbro) in 1979. Each player secretly selects a mystery character card. Players take turns asking yes-or-no questions about the opponent's character (does your person have red hair? glasses? a hat?) and flipping down characters that don't match. First player to correctly identify the opponent's mystery character wins.

It is one of the best-selling children's games ever made and remains an excellent introduction to logical deduction for ages 5 and up. Adults who play analytically quickly discover it has a surprisingly interesting strategy layer underneath the simple surface.

2 Components

• 2 game boards, each with 24 character faces in flip-down frames
• 48 character cards (24 per player) matching the faces on the boards
• 2 mystery character card holders

Classic characters include names like Bernard, Claire, Max, and Maria. Modern editions have updated the character roster to include more diversity.

3 Setup

1. Each player takes a game board with all 24 character faces standing upright.
2. Shuffle the character cards and each player draws one secretly -- this is your mystery character.
3. Place your mystery card in the card holder where only you can see it.
4. Decide who asks first.

4 Gameplay

Players alternate turns. On your turn:

1. Ask one yes-or-no question about your opponent's mystery character. Questions must be about visible physical features: hair color, eye color, facial hair, hat, glasses, etc. You cannot ask "Is your character a woman?" in all editions -- check your version's rules.
2. Your opponent answers "yes" or "no" honestly.
3. Flip down all characters on your board that do not match the answer.
4. Optionally, instead of asking a question, make a guess: "Is your character Bernard?" If correct, you win. If wrong, you lose immediately.

5 Winning

Win by correctly naming your opponent's mystery character. You can guess at any point on your turn instead of asking a question. If you guess wrong, you lose. Most players wait until only 1 or 2 characters remain before guessing to minimize risk.

6 Strategy Guide

Ask Binary-Split Questions

The optimal question eliminates exactly half the remaining characters. With 24 characters, your first question should ideally eliminate 12. Count the characters with a given trait before asking -- if 13 characters have brown hair and 11 do not, "Does your character have brown hair?" is close to optimal.

Know Your Character Distribution

In the classic game: 5 characters wear hats, 5 have glasses, 9 have brown hair, 14 are male (in the original). Knowing these numbers lets you plan your question sequence for maximum elimination power.

Don't Ask About Rare Features First

Asking "Does your character have a red hat?" when only 2 characters wear red hats gives you little information if the answer is "no" -- you only eliminate 2. Save rare-feature questions for when you're narrowing from 3 to 4 characters.

Sequence Your Questions

Plan 3 to 4 questions ahead. After asking about hair color, plan which feature question best halves the remaining set based on both possible answers. Good players mentally simulate the optimal question tree before the game begins.

7 The Math of Optimal Play

Guess Who? is an information theory problem. Each question provides at most 1 bit of information. With 24 characters, you need at least log2(24) = 4.58 questions to identify a character with perfect play -- meaning 5 questions minimum guaranteed.

In practice, perfect binary splitting is not always possible because character traits are not evenly distributed. An optimal player can typically identify the mystery character in 5 to 6 questions. Most casual players take 8 to 12.

The game has been studied as an example of the "20 Questions" optimal strategy problem. The key insight: always prefer questions that give the most information regardless of the answer (i.e., questions where yes and no both eliminate roughly equal numbers of characters).

8 FAQ