Game theorists in China say that how most people play this classic game is predictable, and knowing the opponent's next move is possible. 

Game theorists have come up with a winning strategy for the classic dispute-settler Rock-Paper-Scissors, they say.The theorists, who published their results in an arXiv.org open-access paper called, "Social cycling and conditional responses in the Rock-Paper-Scissors game," say an opponent's next move is predictable and therefore can be defeated with a preemptive strike. The game theorosts Zhijian Wang of Zhejiang University, and Bin Xu of Zhejiang Gongshang University, both of Hangzhou, China, believe their findings have implications for decision-making in moments of uncertainty.

Like Us on Facebook

Wang and Xu had 360 students - mostly females, who were the most "enthusiastic" about volunteering - play the game over the course of five sessions on different days between 2010 and 2014. Each player played the game with the same other five players for 300 rounds, and had 40 seconds to choose rock, paper, or scissors. Competitors were not allowed to speak with each other.

Amazingly, all 360 players of 59 of the 60 sessions divided their choices evenly between "rock," "paper," and "scissors." There was one session, though, the researchers found so "exceptional," that they exempted it from their final computations. After the Rock-Paper-Scissors game has proceeded for 72 rounds, the six players all stuck to "rock" for the next 228 rounds. "This population obviously has reached a highly cooperative state," the game theorists wrote.

The Rock-Paper-Scissors game is in a class of games using "mixed-strategy Nash equilibrium," meaning that each player has the same three actions to choose from, with equal probability  - in this case, one third of the time. But Wang and Xu found that players who win one round will invariably repeat that choice the following round.

The loser of the first round can confidently anticipate that the winner will repeat her or his winning play, allowing the loser to adjust his choice accordingly: If the winner won with "rock," the loser can rely on her or him using "rock" the next round. The loser would then be wise to choose "paper." This strategy will work, though, only if the other player doesn't posses that strategy as well.

On the other side of the equation, Wang and Xu found that players who lose will invariably try the next "clockwise" choice: If they lost with "rock;" they'll try "paper;" if they lost with "paper;" they'll try with "scissors;" and if they lost with "scissors;" they'll try to win with "rock." The winner can anticipate those moves as well, and win again.

The game theoriests believe their findings have implications beyond gamesmanship to human decision-making, especially when faced with uncertainty. The tendancy to repeat a winning strategy and shift from a losing strategy may be an approach conditionally ingrained deep within the human psyche, they wrote. "Whether the conditioned response is a basic decision-making mechanism of the human brain or just a consequence of more fundamental neural mechanism is a challenging question for further studies."