In the early 1950s, at Bell Telephone Laboratories in Murray Hill, New Jersey, engineer David Hagelbarger built a machine to play matching pennies against his colleagues. In the game, two players each secretly choose heads or tails; one wins if the choices match, the other if they differ. Against a truly unpredictable opponent, the game is a coin flip. Hagelbarger called his machine SEER, short for SEquence Extrapolating Robot.
SEER did not model its opponent deeply. It tracked three facts about the last two rounds: whether it had won or lost the play before last, whether it had played the same or differently, and whether it had won or lost the last play. These three yes-or-no facts produce eight situations, and for each one the machine kept a small reversible counter, stopping at plus and minus three, that recorded whether playing the same had been working. Hagelbarger described the stops as making the machine "forget ancient history."
Claude Shannon, who worked down the hall, built his own version. His memorandum of 18 March 1953 credited Hagelbarger plainly and contrasted the approach with game theory. Theory says to flip a mental coin and be genuinely random, so no opponent can beat you over time. Shannon's machine instead looked for patterns and assumed the player would repeat them. When no pattern had recurred at least twice, it moved at random, with randomness drawn from a commutator spinning about ten times a second and sampled at the moment the button was pressed.
Shannon also explained how to beat his machine. He estimated it could be beaten three times out of four on paper, though a person could not run the method in their head during play. That gap between what is possible in principle and what a person can do in the moment is the subject of the page, and Shannon named it in 1953.
Source: Hacker News · Summarized by HeadlinesBriefing