Rock Paper Scissors (aka Ro-Sham-Bo, janken, and Scissors, Paper, Stone) is a simple hand game that is played around the world, with many different names and variations. It is commonly used as a way of coming to decisions, and in some cases is even played for sport. The rules require that competing players use one hand to form one of three shapes at an agreed-upon time. The person that plays the strongest “object” is the winner of the game. It’s that easy!

Unless you’re playing for amusement’s sake, some issue will normally be hanging in the balance. Maybe you’re trying to decide who gets the last slice of pizza, or who should be first in line to try out a new waterslide. In most cases, Rock Paper Scissors is played as a means to help make a choice or put an end to a disagreement. The idea is that both players have an equal chance of winning, making the game random but fair.

Additional Weapons

As long as the number of moves is an odd number and each move defeats exactly half of the other moves while being defeated by the other half, any combination of moves will function as a game. 5, 7, 9, 11, 15, 25, and 101-weapon versions of Rock Paper Scissors exist, adding new gestures has the effect of reducing the odds of a tie, while increasing the complexity of the game. The probability of a tie in an odd-number-of-weapons game can be calculated based on the number of weapons nas 1/n, so the probability of a tie is 1/3 in standard rock-paper-scissors, but 1/5 in a version that offered five moves instead of three.

One popular five-weapon expansion is “rock-paper-scissors-Spock-lizard”, invented by Sam Kass and Karen Bryla, which adds “Spock” and “lizard” to the standard three choices. “Spock” is signified with the Star Trek Vulcan salute, while “lizard” is shown by forming the hand into a sock-puppet-like mouth. Spock smashes scissors and vaporizes rock; he is poisoned by lizard and disproven by paper. Lizard poisons Spock and eats paper; it is crushed by rock and decapitated by scissors. This variant was mentioned in a 2005 article in The Times of London and was later the subject of an episode of the American sitcom The Big Bang Theory in 2008 (as rock-paper-scissors-lizard-Spock).