A new study on the game has found that “the strategy of real players looks random on average but actually consists of predictable patterns that a wily opponent could exploit to gain a vital edge”:
On average, the players in all the groups chose each action about a third of the time, which is exactly as expected if their choices were random. But a closer inspection of their behavior reveals something else. Zhijian [Wang] and co say that players who win tend to stick with the same action while those who lose switch to the next action in a clockwise direction (where R → P → S is clockwise). This is known in game theory as a conditional response and has never been observed before in Rock-Paper-Scissors experiments. Zhijian and co speculate that this is probably because previous experiments have all been done on a much smaller scale. … In fact, a “win-stay, lose-shift” strategy is entirely plausible from a psychological point of view: people tend to stick with a winning strategy.