How To Win At Rock-Paper-Scissors With Science

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Can’t agree on who should get that last slice of pie? ”Rock, Paper, Scissors!”

While it may seem like there is no way to win at rock-paper-scissors above chance level, if you throw in a bit of game theory and psychology, you may well turn those odds in your favor. (And get that extra slice of pie while you are at it.)

Rock-paper-scissors originates in China, dating back centuries before it gained traction in Europe in the late 1920s. The game is meant to produce a one in three chance of winning, a one in three chance of drawing a tie, and a one in three chance of losing. But people do not play at random—they abide by subconscious patterns and tendencies that an opponent can exploit.

To determine how to do this, a group of scientists from Zhejiang University in China studied 360 students in a massive rock-paper-scissors tournament. As an incentive to do well, the winners were paid in direct relation to their number of wins.

The researchers found that players who won a match tend to repeat their winning hand. Losers, however, tend to switch it up. The “one in three” rule was no longer true. If a player lost playing rock, there was a greater than one in three chance of them playing paper the next round. 

To find out more, watch this six-minute video by Numberphile below. For even more fun, play a computer opponent that exploits a person’s game patterns over at The New York Times.



At the University of Tokyo, researchers have created a robot that wins rock-paper-scissors 100% of the time. However, the robot has an unfair advantage: It is equipped with a high-speed camera that recognizes within a millisecond which shape its opponent’s hand is going to make and then, of course, produces the winning hand.


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