The Secret to Winning Rock-Paper-Scissors

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rock paper sciRemember how you used to resolve disagreements at the playground? For most kids, rock-paper-scissors was the tool of choice to decide everything from who got the last piece of pizza to who would have the first go at a new toy.

You might not have realized it back then, but the game of rock-paper-scissors is actually a centuries old Chinese invention that gained popularity in Europe in the 20th century. We all know how it works: two players choose one of the three hand gestures at random after chanting “Rock, paper, scissors, go!” Rock beats scissors, scissors beats paper and paper beats rock. It’s designed to produce a one-in-three opportunity for either winning, tying or losing. However, people do not really make plays at random. Like with almost every other choice in our lives, there are subconscious mental patterns at play.

So, while you’ve thought, all this time, that there is no way to win at rock-paper-scissors beyond sheer chance, it turns out that psychology and game theory can help you beat the odds and end up with all the pizza you want.

Chinese scientists working for Zhejiang University conducted a study involving 360 students who participated in what might have been the world’s biggest rock-paper-scissors tournament ever. Contestants were paid based on their number of wins – giving them an added incentive to perform well.

The research proved that when a player won a round, he or she was likely to repeat the winning hand, while losers usually changed their tactic. Therefore, the one-in-three probability was no longer rock solid. The chance that a player who lost when playing a “paper” hand would play a rock or scissors hand in the next round was greater than one-in-three.

Researchers at the the University of Tokyo came up with a robot that is unbeatable at rock-paper-scissors. The secret of its success is the slightly unfair, high-speed camera that recognizes a player’s movements and can determine, within milliseconds, the shape that an opponent’s hand is about to make and responds with a better hand.

Watch this video made by Numberphile.com and learn even more. You can also play against a digital opponent at the New York Times, but be warned, it learns your playing patterns and uses that information against you!

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