Thus twenty skilful hypotheses will ascertain what two hundred thousand stupid ones might fail to do. He discussed the potential of twenty questions to single one subject out from among 2 20 and, pointing to skilful caution, said: In 1901 Charles Sanders Peirce discussed factors in the economy of research that govern the selection of a hypothesis for trial: (1) cheapness, (2) intrinsic value (instinctive naturalness and reasoned likelihood), and (3) relation (caution, breadth, and incomplexity) to other projects (other hypotheses and inquiries). The process is analogous to a binary search algorithm in computer science or successive-approximation ADC in analog-to-digital signal conversion. Accordingly, the most effective strategy for twenty questions is to ask questions that will split the field of remaining possibilities roughly in half each time. Mathematically, if each question is structured to eliminate half the objects, 20 questions allow the questioner to distinguish between 2 20 = 1 048 576 objects. The game is often used as an example when teaching people about information theory. The game suggests that the information (as measured by Shannon's entropy statistic) required to identify an arbitrary object is at most 20 bits. The abstract mathematical version of the game where some answers may be wrong is sometimes called Ulam's game or the Rényi–Ulam game. A version of twenty questions called yes and no is played as a parlour game by characters in Charles Dickens' A Christmas Carol.Ĭomputers, scientific method and situation puzzles In Hungary a similar game is named after Simon bar Kokhba.

Other versions specify that the item to be guessed should be in a given category, such as actions, occupations, famous people, etc. Another variant is 'person, place, or thing'. These categories can produce odd technicalities, such as a wooden table being classified as a vegetable (since wood comes from trees), or a belt being both animal (if leather) or vegetable (if cloth), and mineral (if it has a metal or plastic buckle). In this version, the answerer tells the questioners at the start of the game whether the subject belongs to the animal, vegetable or mineral kingdom. This is taken from the Linnaean taxonomy of the natural world. For example, a question such as 'Does it involve technology for communications, entertainment or work?' can allow the questioner to cover a broad range of areas using a single question that can be answered with a simple 'yes' or 'no', significantly narrowing down the possibilities.Ī variant is called 'animal, vegetable, or mineral'. If 20 questions are asked without a correct guess, then the answerer has stumped the questioners and gets to be the answerer for another round.Ĭareful selection of questions can greatly improve the odds of the questioner winning the game. If a questioner guesses the correct answer, they win and become the answerer for the next round. Sample questions could be: ' Is it bigger than a breadbox?', 'Is it alive?', and finally 'Is it this pen?' Lying is not allowed.

In variants of the game, answers such as 'maybe' are allowed.

They take turns asking a question which the answerer must answer with 'yes' or 'no'. In the traditional game, the 'answerer' chooses something that the other players, the 'questioners', must guess. It escalated in popularity during the late 1940s, when it became the format for a successful weekly radio quiz program.

It originated in the United States and was played widely in the 19th century. Twenty questions is a spoken parlor game, which encourages deductive reasoning and creativity. For the computer-human game show, see 20Q (game show).

20q gameshow