CAPTCHAs were inspired by the Turning Test, which has become a cultural point of reference and fascinated the public (outside the field of computer science) since the '80s and '90s.  In 1950, Alan Turing published his paper “Computing Machinery and Intelligence” that opened with the provocation “Can machines think?” To approach the question rather than simply it answer it Turing describes the Imitation Game. The Imitation Game has three participants: a man, a woman, and an interrogator of either sex. The interrogator must determine the sex of the two participants via a yes or no line of questioning. Both participants of both sexes will try to confuse the interrogator in an attempt to produce a misidentification. Adopted from that, the Turning Test for computers is in principle the same, except a machine replaces one of the contestants. The interrogator will attempt to determine which user is the computer, while both the human responder (through their intellect) and the computer (through programming) will employ various strategies to confuse the guesser. Turing conjectured “that in about fifty years’ time it will be possible, for programmed computers, with a storage capacity of about 109, to make them play the Imitation Game so well that an average interrogator will not have more than a 70 per cent chance of making the right identification after five minutes of questioning.” A CAPTCHA reverses the Turing Test and alters it slightly, demanding a user prove it is not a computer by solving a puzzle generated by the computer that the computer itself cannot solve.