Rock-paper-scissors-lizard-Spock is a five-gesture expansion of the classic selection method game rock-paper-scissors. It operates on the same basic principle, but includes two additional weapons: the lizard (formed by the hand as a sock-puppet-like mouth) and Spock (formed by the Star Trek Vulcan salute). This reduces the chances of a round ending in a tie. The game was invented by Sam Kass with Karen Bryla, as "Rock Paper Scissors Spock Lizard".
The game was mentioned in three episodes of The Big Bang Theory. According to an interview with Kass, the series producers did not ask for permission to use the game, but he was later referenced in an episode in the fifth season. It has been used to understand the transitivity of climate change policy choice.
The rules of Rock-paper-scissors-lizard-Spock are:
- Scissors cut paper
- Paper covers rock
- Rock crushes lizard
- Lizard poisons Spock
- Spock smashes (or melts) scissors
- Scissors decapitate lizard
- Lizard eats paper
- Paper disproves Spock
- Spock vaporizes rock
- Rock breaks scissors
There are ten possible pairings of the five gestures; each gesture beats two of the other gestures and is beaten by the remaining two.
One way to remember the rules is to remember the standard "rock-paper-scissors" ordering, where each gesture defeats the one before it, and is defeated by the one after. But then add the two novel gestures near the word they approximately rhyme with:
In this expanded list, each gesture is defeated by the following two options, and defeats the preceding two.
Since the Spock gesture is known to be notoriously difficult for some people to perform, some players may be disadvantaged while playing this variant. The fingers must be moved quickly into the final position from a closed fist, which means that many people will not be able to use Spock, thus cutting down their options.
- "... and paper scissors". The Times. June 11, 2005. Archived from the original on May 31, 2010. Retrieved 2010-11-04.
- "Rock Paper Scissors Spock Lizard". Sam Kass. Retrieved 2010-11-04.
- The True Story behind RPS, Lizard, Spock http://h30565.www3.hp.com/t5/Feature-Articles/The-Real-Story-and-Some-of-the-Math-Behind-the-Famous-Rock-Paper/ba-p/3551
- Rock Paper Scissors Lizard Spock and Global Warming Policy The Space Review January 21, 2013.
- Geek Dice by Alien Lab http://www.kickstarter.com/projects/geekdice/geek-dice