Friday, May 30, 2014
Friday, May 2, 2014
A group of researchers from Chinese universities have written a paper about the role of psychology in winning (or losing) at rock-paper-scissors. After studying how players change or keep their strategies during multiple-round sessions, they figured out a basic rule that people tend to play by that could potentially be exploited.
The researchers took 360 students, broke them into groups of six, and had them play 300 rounds of rock-paper-scissors in random pairings. The students received small amounts of money each time they won a round. As they played, the researchers observed how the players rotated through the three play options as they won or lost.
What they found was that "if a player wins over her opponent in one play, her probability of repeating the same action in the next play is considerably higher than her probabilities of shifting actions." If a player has lost two or more times, she is likely to shift her play, and more likely to shift to the play that will beat the one that has just beaten her than the same one her opponent just used to beat her. For instance, if Megan loses by playing scissors to Casey's rock, Megan is most likely to switch to paper, which would beat Casey's rock. Per the research, this is a sound strategy, since Casey is likely to keep playing the hand that has been winning. The authors refer to this as the "win-stay, lose-shift" strategy.
Therefore, this is the best way to win at rock-paper-scissors: if you lose the first round, switch to the thing that beats the thing your opponent just played. If you win, don't keep playing the same thing, but instead switch to the thing that would beat the thing that you just played. In other words, play the hand your losing opponent just played. To wit: you win a round with rock against someone else's scissors. They are about to switch to paper. You should switch to scissors. Got it? Good.
This should work unless your opponent has read this article, in which case, you both are in trouble, because you're now living on a plane of RPS strategy the likes of which we can only imagine.