A chart showing how the three game elements interact.
|Players||2 (or more)|
|Skill(s) required||Luck, psychology|
Rock-paper-scissors is a hand game usually played by two people, where players simultaneously form one of three shapes with an outstretched hand. The "rock" beats scissors, the "scissors" beat paper and the "paper" beats rock; if both players throw the same shape, the game is tied. Other names for the game in the English-speaking world include roshambo, and other orderings of the three items.
The game is often used as a choosing method in a way similar to coin flipping, drawing straws, or throwing dice. Unlike truly random selection methods, however, rock-paper-scissors can be played with a degree of skill by recognizing and exploiting non-random behavior in opponents.
Game play 
The players usually count aloud to four, or speak the name of the game (e.g. "Rock Paper Scissors!" or "Ro Sham Bo!"), each time either raising one hand in a fist and swinging it down on the count or holding it behind. On the fourth count (saying, "Shoot!" or "Go!") or on the third count (saying, "Scissors!" or "Bo!"), the players change their hands into one of three gestures, which they then "throw" by extending it towards their opponent. Variations include a version where players use only three counts before throwing their gesture (thus throwing on the count of "Scissors!" or "Bo!", or a version where they shake their hands three times before "throwing." The gestures are (in the three gesture version):
- Rock, represented by a clenched fist
- Scissors, represented by two fingers extended and separated, sometimes coming together
- Paper, represented by an open hand, with the fingers extended and touching, in order to represent a sheet of paper (horizontal)
The objective is to select a gesture which defeats that of the opponent. Gestures are resolved as follows:
- Rock blunts or breaks scissors: rock defeats scissors.
- Scissors cut paper: scissors defeats paper.
- Paper covers, sands or captures rock: paper defeats rock.
If both players choose the same gesture, the game is tied and the players throw again. The game is sometimes played as "best of three".
Asian origin 
The first known mention of the game was in the book Wuzazu (五杂组) by the Chinese Ming Dynasty writer Xie Zhaozhi (谢肇淛; fl. ca. 1600), who wrote that the game dated back to the time of the Chinese Han Dynasty (206 BC – 220 AD). In the book, the game was called shoushiling (手势令; lit "hand command"). Li Rihua's (李日华) book Note of Liuyanzhai (六砚斋笔记) also reveals this game, calling it shoushiling (手势令), huozhitou (豁指头), or huoquan (豁拳).
In Japanese history, the people often played sansukumi-ken, which were ken (fist) games with "the three who are afraid of one another" in the sense that A beats B, B beats C, and C beats A. They originated in China before being imported to Japan, where they became popular in Japanese society. The earliest Japanese sansukumi-ken was a game known as mushi-ken that had been imported directly from China. Mushi-ken constituted a hand game where the "frog" (represented by the thumb) supersede the "snail", the "snail" (represented by the little finger) supersede the "snake", and the "snake" (represented by the index finger) supersede the "frog". Although, the Chinese character for the poisonous centipede—from the original Chinese game—was mistakenly confused with the character for the "snail". Today, the best-known sansukumi-ken is jan-ken, which is a variation of the Chinese games introduced in the 17th century. The game Jan-ken uses the signs of rock, paper, and scissors and is the game that the modern version of rock-paper-scissors directly derives from. The hand-game using gestures in the particular form of the three conflicting elements of rock, paper, and scissors—the most commonly found modern version of the game—originated in the Edo to Meiji period in late 19th century Japan.
By the early 20th century, rock-paper-scissors had spread beyond Asia, especially through increased Japanese contact with the west. Its English-language name is therefore taken from a translation of the names of the three Japanese hand-gestures for rock, paper and scissors: elsewhere in Asia the open-palm gesture represents "cloth" rather than "paper". The shape of the scissors is also adopted from the Japanese style.
Spread beyond Asia 
The game seems to have arrived in Europe in the early 20th century and to have become popular by the late 1920s. In Britain in 1924 it was described in a letter to a newspaper as a hand game, possibly of Mediterranean origin, called "zhot". A reader then wrote in to say that the game "zhot" referred to was evidently Jan-ken-pon, which she had often seen played throughout Japan. Although at this date the game appears to have been new enough to British readers to need explaining, the appearance by 1927 of a popular thriller with the title Scissors Cut Paper, followed by Stone Blunts Scissors(1929), suggests it quickly became popular.
In 1927 a children's magazine in France described it in detail, referring to it as a "jeu Japonais" ("Japanese game"). Its French name, "Chi-fou-mi", is based on the Japanese words for "one, two, three" ("hi, fu, mi").
A New York Times article of 1932 on the Tokyo rush hour describes the rules of the game for the benefit of American readers, suggesting it was not at that time widely known in the U.S.A.
It is impossible to gain an advantage over a truly random opponent. However, by exploiting the weaknesses of nonrandom opponents, it is possible to gain a significant advantage. Indeed, human players tend to be nonrandom. As such, there have been programming competitions for algorithms that play rock-paper-scissors.
In tournament play, some players employ tactics to confuse or trick the other player into making an illegal move, resulting in a loss. One such tactic is to shout the name of one move before throwing another, in order to misdirect and confuse their opponent. During tournaments, players often prepare their sequence of three gestures prior to the tournament's commencement.
As a consequence of rock-paper-scissors programming contests, many strong algorithms have emerged. For example, Iocaine Powder, which won the First International RoShamBo Programming Competition in 1999, uses a heuristically designed compilation of strategies. For each strategy it employs, it also has six metastrategies which defeat second-guessing, triple-guessing, as well as second-guessing the opponent, and so on. The optimal strategy or metastrategy is chosen based on past performance. The main strategies it employs are history matching, frequency analysis, and random guessing. Its strongest strategy, history matching, searches for a sequence in the past that matches the last few moves in order to predict the next move of the algorithm. In frequency analysis, the program simply identifies the most frequently played move. The random guess is a fallback method that is used to prevent a devastating loss in the event that the other strategies fail. More than ten years later, the top performing strategies on an ongoing rock-paper-scissors programming competition similarly use metastrategies. However, there have been some innovations, such as using multiple history matching schemes that each match a different aspect of the history — for example, the opponent's moves, the program's own moves, or a combination of both. There have also been other algorithms based on Markov chains.
Researchers at the University of Tokyo have created a robot hand that has a 100% winning rate playing rock-paper-scissors. Using a high-speed camera, the robot recognizes within one millisecond which shape the human hand is making, then produces the corresponding winning shape.
Instances of use in real-life scenarios 
American case 
In 2006, American federal judge Gregory Presnell from the Middle District of Florida ordered opposing sides in a lengthy court case to settle a trivial (but lengthily debated) point over the appropriate place for a deposition using the game of rock-paper-scissors. The ruling in Avista Management v. Wausau Underwriters stated:
Upon consideration of the Motion – the latest in a series of Gordian knots that the parties have been unable to untangle without enlisting the assistance of the federal courts – it is ORDERED that said Motion is DENIED. Instead, the Court will fashion a new form of alternative dispute resolution, to wit: at 4:00 P.M. on Friday, June 30, 2006, counsel shall convene at a neutral site agreeable to both parties. If counsel cannot agree on a neutral site, they shall meet on the front steps of the Sam M. Gibbons U.S. Courthouse, 801 North Florida Ave., Tampa, Florida 33602. Each lawyer shall be entitled to be accompanied by one paralegal who shall act as an attendant and witness. At that time and location, counsel shall engage in one game of "rock, paper, scissors." The winner of this engagement shall be entitled to select the location for the 30(b)(6) deposition to be held somewhere in Hillsborough County during the period July 11–12, 2006.
The public release of this judicial order, widely circulated among area lawyers, was seemingly intended to shame the respective law firms regarding their litigation conduct by settling the dispute in a farcical manner.
Auction house rock-paper-scissors match 
When Takashi Hashiyama, CEO of a Japanese television equipment manufacturer, decided to auction off the collection of impressionist paintings owned by his corporation, including works by Cézanne, Picasso, and van Gogh, he contacted two leading auction houses, Christie's International and Sotheby's Holdings, seeking their proposals on how they would bring the collection to the market as well as how they would maximize the profits from the sale. Both firms made elaborate proposals, but neither was persuasive enough to get Hashiyama’s business. Unwilling to split up the collection into separate auctions, Hashiyama asked the firms to decide between themselves who would hold the auction, which included Cézanne's Large Trees Under the Jas de Bouffan, worth $12–16 million.
The houses were unable to reach a decision. Hashiyama told the two firms to play rock-paper-scissors to decide who would get the rights to the auction, explaining that "it probably looks strange to others, but I believe this is the best way to decide between two things which are equally good".
The auction houses had a weekend to come up with a choice of move. Christie's went to the 11-year-old twin daughters of the international director of Christie's Impressionist and Modern Art Department Nicholas Maclean, who suggested "scissors" because "Everybody expects you to choose 'rock'." Sotheby's said that they treated it as a game of chance and had no particular strategy for the game, but went with "paper".
Christie's won the match and sold the $20 million collection, with millions of dollars of commission for the auction house.
Rock-paper-scissors in video games 
In many real-time strategy, first-person shooter, and role-playing video games, it is common for a group of possible weapons or unit types to interact in a rock-paper-scissors style, where each selection is strong against a particular choice, but weak against another, emulating the cycles in real world warfare (such as cavalry being strong against archers, archers being strong against pikemen, and pikemen being strong against cavalry). Such game mechanics can make a game somewhat self-balancing, and prevent gameplay from being overwhelmed by a single dominant strategy.
Many card-based video games in Japan use the rock-paper-scissors system as their core fighting system, with the winner of each round being able to carry out their designated attack. Other games use simple variants of rock-paper-scissors as subgames.
Rock-paper-scissors analogs in nature 
Lizard mating strategies 
The common side-blotched lizard (Uta stansburiana) exhibits a rock-paper-scissors pattern in its mating strategies. Of its three color types of males, "orange beats blue, blue beats yellow, and yellow beats orange" in competition for females, which is similar to the rules of rock-paper-scissors.
Some bacteria also exhibit a rock-paper-scissors dynamic when they engage in antibiotic production. The theory for this finding was demonstrated by computer simulation and in the laboratory by Benjamin Kerr, working at Stanford University with Brendan Bohannan. Additional in vitro results demonstrate rock-paper-scissors dynamics in additional species of bacteria. Biologist Benjamin C. Kirkup, Jr. demonstrated that these antibiotics, bacterioicins, were active as Escherichia coli compete with each other in the intestines of mice, and that the rock-paper-scissors dynamics allowed for the continued competition among strains: antibiotic-producers defeat antibiotic-sensitives; antibiotic-resisters multiply and withstand and out-compete the antibiotic-producers, letting antibiotic-sensitives multiply and out-compete others; until antibiotic-producers multiply again.
Rock-paper-scissors is the subject of continued research in bacterial ecology and evolution. It is considered one of the basic applications of game theory and non-linear dynamics to bacteriology. Models of evolution demonstrate how intragenomic competition can lead to rock-paper-scissors dynamics from a relatively general evolutionary model. The general nature of this basic non-transitive model is widely applied in theoretical biology to explore bacterial ecology and evolution.
World Rock Paper Scissors Society sanctioned tournaments 
Starting in 2002, the World Rock Paper Scissors Society standardized a set of rules for international play and has overseen annual International World Championships. These open, competitive championships have been widely attended by players from around the world and have attracted widespread international media attention. WRPS events are noted for their large cash prizes, elaborate staging, and colorful competitors. In 2004, the championships were broadcast on the U.S. television network Fox Sports Net, with the winner being Lee Rammage, who went on to compete in at least one subsequent championship.
|2002||Jason Tharp||United States|
|2006||Bob Cooper||United Kingdom|
UK Rock Paper Scissors Championships 
organised by Wacky Nation
The 5th UK Rock Paper Scissors Championships took place in London on Saturday 22 October 2011. The event was open to 128 individual competitors. There was also a team contest for 16 teams. The 2011 singles tournament was won by Max Deeley and the team contest won by The Big Faces (Andrew Bladon, Jamie Burland, Tom Wilkinson and Captain Joe Kenny).
The 4th UK Championships took place on 13 November 2010, at the Durell Arms in West London. Paul Lewis from Woking beat Ed Blake in the final and collected the £100 first prize and UK title. Richard Daynes Appreciation Society won the team event. 80 competitors took part in the main contest and 10 entries in the team contest.
The 3rd UK Championships took place on 9 June 2009, in Exeter, Devon. Nick Hemley, from Woking, Surrey, won the contest just beating Chris Grimwood.
The 1st UK Championship took place on 13 July 2007, and then again on 14 July 2008, in Rhayader, Powys. Steve Frost of Powys is the current holder of this WRPS sanctioned event.
USARPS Tournaments 
In April 2006, the inaugural USARPS Championship was held in Las Vegas. Following months of regional qualifying tournaments held across the US, 257 players were flown to Las Vegas for a single-elimination tournament at the House of Blues where the winner received $50,000. The tournament was shown on the A&E Network on 12June 2006.
The $50,000 2007 USARPS Tournament took place at the Las Vegas Mandalay Bay in May 2007.
In 2008, Sean "Wicked Fingers" Sears beat out 300 other contestants and walked out of the Mandalay Bay Hotel & Casino with $50,000 after defeating Julie "Bulldog" Crossley in the finals.
The inaugural Budweiser International Rock, Paper, Scissors Federation Championship was held in Beijing, China after the close of the 2008 Summer Olympic Games at Club Bud. A Belfast man won the competition. Sean finished 3rd.
Team Olimpik Rock Paper Scissors Championships 2012 
The international tournament was held in London 2012. UK Champions Team GB (Andrew Bladon, Jamie Burland, Tom Wilkinson and Stephen Preston) went in as overwhelming favorites, but after a "domestic incident" team captain and UK Team Champion Joe Kenny was forced to pull out, allowing Stephen Preston to fill his gloves. Great Britain came a respectable third to achieve the Bronze Medal, while the crowd favorite Vatican City got the Silver and Lapland A took the prestigious Gold Medal. British team captain Tom Wilkinson commented "after a 4-0 whitewash of hot favorites Vatican City we thought we had it. A simple lapse of concentration lost it for us, but we are happy with our bronze medal. We'll come back from this and look to take the title back again next year. The support was immense, and we are thankful of everyone who came out to support us".
National XtremeRPS Competition 2007-2008 
The XtremeRPS National Competition is a US nationwide RPS competition with Preliminary Qualifying contests that started in January 2007 and ended in May 2008, followed by regional finals in June and July 2008. The national finals were to be held in Des Moines, Iowa in August 2008, with a chance to win up to $5,000.
Guinness Book of World Records 
World Series of Rock Paper Scissors 
Former Celebrity Poker Showdown host and USARPS Head Referee Phil Gordon has hosted an annual $500 World Series of Rock Paper Scissors event in conjunction with the World Series of Poker since 2005. The winner of the WSORPS receives an entry into the WSOP Main Event. The event is an annual fundraiser for the "Cancer Research and Prevention Foundation" via Gordon's charity Bad Beat on Cancer. Poker player Annie Duke won the Second Annual World Series of Rock Paper Scissors. The tournament is taped by ESPN and highlights are covered during "The Nuts" section of ESPN's annual WSOP broadcast. 2009 was the fifth year of the tournament.
Players have developed numerous cultural and personal variations on the game, from simply playing the same game with different objects, to expanding into more weapons and rules.
In Japan, a "strip-poker" variant of Rock-paper-scissors is known as 野球拳 (Yakyuken). The loser of each round removes an article of clothing. The game is a minor part of porn culture in Japan, and other Asian countries after the influence of TV variety shows and Soft On Demand.
In the Philippines, the game is called jak-en-poy, from one of the Japanese names of the game, transliterated as jan-ken-pon. In a longer version of the game, a four-line song is sung, with hand gestures displayed at the end of each line: "Jack-en-poy! / Hali-hali-hoy! / Sino'ng matalo, / siya'ng unggoy!" ("Jack-en-poy! / Hali-hali-hoy! / Whoever loses is the monkey!") The person with the most wins at the end of the song, wins the game.
In the Singaporean version of the game, "scissors" is replaced by "bird," represented with the finger tips of five fingers brought together to form a beak. The open palm represents water. Bird beats water (by drinking it); stone beats bird (by hitting it); and stone loses to water (because it sinks in it).
Singapore also has a related hand-game called "ji gu pa," where "ji" refers to the bird gesture, "gu" refers to the stone gesture, and "pa" refers to the water gesture. The game is played by two players using both hands. At the same time, they both say, ji gu pa!" At "pa!" they both show two open-palmed hands. One player then changes his hand gestures while calling his new combination out (e.g., "pa gu!"). At the same time, the other player changes his hand gestures as well. If one of his hand gestures is the same as the other one, that hand is "out" and he puts it behind his back; he is no longer able to play that hand for the rest of the round. The players take turns in this fashion, until one player loses by having both hands sent "out." "Ji gu pa" is most likely a transcription of the Japanese names for the different hand gestures in the original jan-ken game, "choki" (scissors), "guu" (rock) and "paa" (paper).
Additional weapons 
As long as the number of moves is an odd number and that 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. For example, 5-, 7-, 9-, 11-, 15-, 25-, and 101-weapon versions 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 n as 1/n, so the probability of a tie is 1/3 in RPS, 1/5 in RPSLS and 1/101 in RPS101.
Similarly, the French game "pierre, papier, ciseaux, puits" (stone, paper, scissors, well) is unbalanced; both the rock and scissors fall in the well and lose to it, while paper covers both rock and well. This means two "weapons", well and paper, can defeat two moves, while the other two weapons each defeats only one of the other three choices. This version is also played in some areas of Germany; it often adds "the bull " (which drinks the well empty, eats the paper, but gets stabbed by the scissors, and is crushed by the rock). The well is made by forming a circle with the thumb and index finger to show the opening of a stone well; the bull is made by making a fist but extending the little finger and index finger to show the bull's horns. In theory, "unbalanced" games are less random but more psychological, more closely resembling real world conflicts. However, games of this sort are popular more for novelty than for exploring such ideas.
One popular five-weapon expansion is "Rock-paper-scissors-lizard-Spock", 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 of The Times and was later the subject of an episode of the American sitcom The Big Bang Theory in 2008.
The majority of such proposed generalizations are isomorphic to a simple game of modulo arithmetic, where half the differences are wins for player one. For instance, rock-paper-scissors-lizard-spock may be modeled as a game in which each player picks a number from one to five. Subtract the number chosen by player two from the number chosen by player one modulo 5. Player one is the victor if the difference is one or two, and player two is the victor if the difference is three or four. If the difference is zero, the game is a tie.
See also 
- Matching pennies, the binary equivalent.
- Morra (game) - Another hand game for deciding trivial matters
- Simultaneous action selection
- Nontransitive dice
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- "... and paper scissors". London: The Times Online. 11 June 2005. Retrieved 2009-06-09.
- Lorre, Chuck. "The Big Bang Theory Video — Rock, Paper, Scissors, Lizard, Spock — CBS.com" (video). CBS. Retrieved 4 September 2012.
- Alonzo, Suzanne H.; Sinervo, Barry (2001). "Mate choice games, context-dependent good genes, and genetic cycles in the side-blotched lizard, Uta stansburiana". Behavioral Ecology Sociobiology 49 (2-3): 176–186. doi:10.1007/s002650000265.
- Culin, Stewart (1895) Korean Games, With Notes on the Corresponding Games at China and Japan. (evidence of nonexistence of rock-paper-scissors in the West)
- Gomme, Alice Bertha (1894, 1898) The traditional games of England, Scotland, and Ireland, 2 vols. (more evidence of nonexistence of rock-paper-scissors in the West)
- Opie, Iona & Opie, Peter (1969) Children's Games in Street and Playground Oxford University Press, London. (Details some variants on rock-paper-scissors such as 'Man, Earwig, Elephant' in Indonesia, and presents evidence for the existence of 'finger throwing games' in Egypt as early as 2000 B.C.)
- Sinervo, Barry (2001). "Runaway social games, genetic cycles driven by alternative male and female strategies, and the origin of morphs". Genetica. 112-113 (1): 417–434. doi:10.1023/A:1013360426789.
- Sinervo, Barry; Clobert, Jean (2003). "Morphs, Dispersal Behavior, Genetic Similarity, and the Evolution of Cooperation". Science 300 (5627): 1949–1951. doi:10.1126/science.1083109.
- Sinervo, Barry; Lively, C. M. (1996). "The Rock-Paper-Scissors Game and the evolution of alternative male strategies". Nature 380 (6571): 240–243. doi:10.1038/380240a0.
- Sinervo, Barry; Zamudio, K. R. (2001). "The Evolution of Alternative Reproductive Strategies: Fitness Differential, Heritability, and Genetic Correlation Between the Sexes". Journal of Heredity 92 (2): 198–205. doi:10.1093/jhered/92.2.198.
- Sogawa, Tsuneo (2000). "Janken". Monthly Sinica (in Japanese) 11 (5).
- Walker, Douglas & Walker, Graham (2004) The Official Rock Paper Scissors Strategy Guide. Fireside. (strategy, tips and culture from the World Rock Paper Scissors Society).
|Look up じゃんけん in Wiktionary, the free dictionary.|
- Abrams, Michael (2004-07-05). "Throwing for The Gold". Pursuits (Forbes FYI). Retrieved 2007-04-09.
- Hegan, Ken (2004-01-07). "Hand to Hand Combat: Down and dirty at the World Rock Paper Scissors Championship". Rolling Stone Feature Article. Retrieved 2009-03-30.
- Etymological origin of Janken (Japanese)
- About Ken games (Japanese)
- Origins of Janken (Japanese)
- Janken in the world (Japanese)
- A biological example of rock-paper-scissors: Interview with biologist Barry Sinervo on the 7th Avenue Project Radio Show
- Rock Paper Scissors Programming Competition