In Japan, it’s called Janken; to others, it’s known as roshambo. But whatever you call it, the rules of the hand game rock-paper-scissors are straightforward. On the count of three, both players make one of three shapes: a flat palm represents paper, a fist represents rock, and a hand with two extended fingers represents scissors. Rock beats scissors, scissors beats paper, and paper beats rock – which means that, if chosen at random, every move has an equal chance of winning.

However, a new study has shown that, in practice, players do not pick their moves at random but rather follow hidden patterns. The study was based on the results of a mass tournament held at Zhejiang University in China, where 360 students each played 300 rounds of rock-paper-scissors. Analysis of the resulting data revealed that players tended to repeat winning moves – so if a player plays ‘rock’ and wins, they’re fairly likely to play ‘rock’ again in the next round.

f a player loses, however, they’re likely to switch to a different action – and again, their choices reveal a hidden pattern. The researchers discovered that players tended to cycle through the actions in the order of the game’s name – rock, then paper, then scissors. So if a player plays rock and loses, they’re more likely to play paper in the next round than they are to stick with rock or switch to scissors. Similarly, if they play paper and lose, scissors is their most likely move in the next round.

Of course, these strategies aren’t guaranteed to produce a victory – every person is different, and no one will follow the patterns 100% of the time. However, understanding the psychology involved in this simple game could help players to swing the odds in their favour – something to bear in mind next time you use rock-paper-scissors to decide whose turn it is to wash the dishes!