How to always win on rock, paper or scissors?

How to always win on rock, paper or scissors?

The famous childhood game Rock, paper or scissors also known as cachipún, jankenpon, dum-kin-go, yan ken po,chips bun potatoes, hakembo, chin-chan-pu, or kokepon, etc. It is a recent case study that has proven to show that game theory does not always behave as expected.

What is the probability of winning Rock, Paper, or Scissors? It’s simple: one of three. At least that’s what chance predicts. Game theory predicts that if each player picks his next play at random, there are equal chances for both players to win in their next game. However recent studies on this game at Zhejiang University in China (yes, the Chinese study whatever), have shown that there is a psychological mechanic behind the game that would allow players to anticipate their opponent’s movements and give them an advantage to win.

In simple terms the result seems to indicate that The winners tend to keep their winning action, while the losers switch to the next action in the “rock-paper-scissors” order.

To find these patterns, the students set up a rock-paper-scissors tournament with 360 students, who were divided into 6 groups and each played 300 rock-paper-scissors games against the members of their group. The strategy in which the three actions are chosen with equal probabilities in each game, is known as Nash equilibrium, in honor of the American mathematician John Forbes Nash Jr, of which by the way a movie called “a brilliant mind” and I highly recommend it.

Initially, as dictated by Nash equilibrium theory, the tournament researchers observed that each player appeared to choose each of the three alternatives one-third of the time when all their games were added together. However, when a more detailed study of each game was carried out, a pattern of behavior was discovered.

How to win more often?

Game psychology

When players won a game, they tended to repeat their winning rock, scissors, or paper more often than chance predicted (one out of every three times). While the losers tended to change their losing play and in the order of the game “rock -> paper -> scissors”. For example, if someone lost with a stone, they were more likely to play their next game with a paper.

The researchers concluded that the strategy of keeping the winning play, and changing the losing play is known in game theory as an innate response in the human brain. Therefore, if you become aware of this conditioned behavior, you could anticipate your opponent’s possible move. and gain an advantage in the game that would give you more wins.

So you know, if tomorrow you bet 2 out of 3 on rock, paper or scissors with someone, you can use this technique and get something to profit.


  • Scientists from Japan developed a robot that plays rock-paper or scissors and always wins, or so they say, have they used these techniques? Or did they discover an even more foolproof method? No, in reality the robot cheats by looking at our hand with a high-speed shield and determining our move to the millisecond, for it to draw the winning hand.
  • In the series The big-bang theory there is a chapter where a geeky version of this game is shown, complicating its rules with 2 new components: lizard and spock, the rules would now be “The scissors cut the paper, the paper covers the stone , the stone crushes the lizard, the lizard poisons Spock, Spock smashes the scissors, the scissors decapitate the lizard, the lizard eats the paper, the paper refutes Spock, Spock vaporizes the stone, and, as usual … the stone crush the scissors. “

Source: BBC Mundo