How To Use Science To Win At Rock-Paper-Scissors?

Mathematics + Decision Theory + Psychology = Win

Hemanth
Street Science
Published in
4 min readDec 4, 2021

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Rock-Paper-Scissors Game Diagram — A triangle with the three elements written at each vertex.
Image Created by The Walking Temple

Rock-Paper-Scissors is a children’s game. What does it have to do with science? Well, there are branches of science that figure out how games work. One such branch happens to be game theory.

And that’s where our story begins. Game theory researchers have been trying to figure out a winning strategy for the typical rock-paper-scissors game, and have come up with intriguing results.

The results turn out to be surprisingly counterintuitive, yet simple. If you are interested in winning a random game of rock-paper-scissors at a party or two, read along. But remember to credit science if you do indeed end up dominating your friends.

Rock-Paper-Scissors — The Rules

For starters, it makes sense to revisit the rules of the most common version of the game. It involves 2 players, and 3 elements — rock, paper, and scissors. Each player calls one of the three available elements simultaneously. And the stronger element wins over the weaker element. Typically, the cumulative best out of 3 rounds wins.

Rock is superior to scissors, scissors are superior to paper, and paper is superior to rock (illustrated by the triangle in the image above). You’ll notice that no element is outright superior to the other two elements. This is what makes the game fun as winning involves the role of chance.

Science Applies Game Theory

Whenever chance is involved, mathematicians tend to barge into the scene. That is exactly what happened with game theory and rock-paper-scissors. Theoretically, each of the three elements in the game has an equal probability of occurrence (1/3).

Therefore, the rational player should choose one of the three randomly. And this should indeed be the best approach according to classical game theory. But human beings almost never fit the theoretical definition of rationality, and this approach doesn’t describe real-life game behaviour well.

So, researchers tried to apply a bounded rationality model known as evolutionary game theory, where microlearning models are employed. Unfortunately, this didn’t tie…

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