Optimal guessing in Guess Who

Are you Richard? Are you Anne? We look at the strategic problem in the children s guessing game Guess Who, which is a form of zero-sum symmetric game with perfect information. We discuss some preliminary strategic insights and formally derive an optimal strategy and win-probabilities for the game. We discuss the first-mover advantage in the game and other strategic aspects coming out of the optimal strategy. While the paper is based on the popular children s game, our analysis generalises the actual game by allowing any initial game state with an arbitrarily large number of starting characters.