The Science of Rock Paper Scissors.

Rock Paper Scissors is often thought of as a game of random chance, but may not be so random after all. According to a study published in Nature and recently reported on by Discover, most humans have a tendency to make moves that are irrational, unconscious, and to some degree, predictable.

In a previous study, researchers pitted students, against each other in 300 games of rock paper scissors and found that players had a tendency to replay winning moves and upgrade losing moves (for instance, switching from paper to scissors after a loss).

This new study took a slightly different approach. The researchers, led by Benjamin James Dyson, pitted players against a computer. Their findings not only backed up the ideas from the previous study, but they showed that human players had a slight preference for rock.

As in the previous study, participants had a tendency to stick with winning moves and switch in the case of a loss or a draw, according to Discover. However, while the initial study analyzed the kinds of moves humans make against humans—a situation in which moves were made with some form of bias on each side—this study looked at the interactions between humans and computers. That is, participants in the previous study might have realized their competitors were playing non-randomly and tried to pick up on their patterns of play, thus altering the moves that were made. In the Nature study, however, humans likely believed the computer was making random moves—andyet, they still employed the same unconscious strategies. Researchers believe the study may have implications outside the realm of a simple game of rock-paper-scissors. In fact, they explain that this form of unconscious, irrational decision-making could have an impact on other higher stakes situations.

“Rock, Paper, Scissors (RPS) represents a unique gaming space in which the predictions of human rational decision-making can be compared with actual performance,” the study explains. “The data reveal the strategic vulnerability of individuals following the experience of negative rather than positive outcome, the tensions between behavioural and cognitive influences on decision making, and underline the dangers of increased behavioural predictability in other recursive, non-cooperative environments such as economics and politics.