Winning at Rock-Paper-Scissors

Rock, Paper, Scissors is a simple game whose winner should be determined completely by luck. Yet here is a guide to winning at the game. (HT Andrew Sullivan.)

Against a rational player you should randomize and play Rock, Paper and Scissors each with 1/3 probability. If your opponent does this you can never come up with a strategy that will give you an advantage over him. But, as the guide says, “Humans, try as they might, are terrible at trying to be random, in fact often humans in trying to approximate randomness become quite predictable.” For example, according to the guide, an inexperienced player will never play the same thing three times in a row. Taking advantage of this, you can gain an edge over your opponent.

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  • Stuart Armstrong

    There was a computer program designed to play Rock, Paper, Scissors against humans, and after a short while, it would defeat nearly every human being.

    It would just look back into the players past performance, and find the longest sequences it could find that mimics the current sequence of play, and use that as a predictor. It was hideously good, implying that we humans are hideously predictable.

    (However, I don’t know if it was beatable by perfect play.)

  • http://www.blog.greenideas.com botogol

    In “You Only Live Twice” Bond plays RPS with Tiger Tanaka the head of the Japanese secret service. He contemplates trying to lose, but reflects that trying to lose is exactly as hard as trying to win (Aside: can you think of any other game where this is the case?), so in end determines that he will play randomly. Needless to say, it doesn’t occur to him that this is the optimum strategy.
    Needless to say, he wins.

  • Joseph

    Rock-paper-scissors is a microcosm for life.