Rock, Paper, Scissors

Encyclopedia : R : RO : ROC : Rock, Paper, Scissors

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Rock, Paper, Scissors, also known in Japan as Janken, is a hand game most often played by children. It is often used as a selection method in a similar way to coin flipping, Odd or Even, throwing dice or drawing straws to randomly select a person for some purpose, though unlike truly random selections it can be played with skill if the game extends over many sessions, because one can often recognize and exploit the non-random behavior of an opponent.

Various sports may use Rock, Paper, Scissors to determine which team gets the opening play (rather than a coin toss). Similarly, uncertain calls, or even the whole game in case of rain, may be decided by the game. It is also often used as a method for creating appropriately non-biased random results in live action role-playing games, as it requires no equipment.

Game play

Each of the three basic hand-signs ( from left to right: rock, paper and scissors ) beats one of the other two.

The players count together "1...2...Break!", "1 ... 2 ... 3 ... Shoot!", "1 ... 2 ... 3!", "Once ... Twice ... Thrice ... Shoot!" "Rock ... Paper ... Scissors ... Shoot!", "Rock ... Paper ... Scissors ... Says ... Shoot!", "Rock ... Paper ... Scissors!", "Scissors... Paper... Stone!", "Zim... Zam... Zee!", "Scissors... Paper... Rock!" or "Ro ... Sham ... Bo!" while simultaneously bouncing their fists. On "Shoot", "Go", or "Scissors", the players simultaneously change their fists into any of three "objects":

• Rock: a clenched fist.
• Paper : all fingers extended, palm facing downwards, upwards, or sideways.
• Scissors: forefinger and middle finger extended and separated into a "V" shape.

The objective is to defeat the opponent by selecting a weapon which defeats their choice under the following rules:

1. Rock smashes (or breaks or blunts) Scissors (rock wins)
2. Scissors cut Paper (scissors win)
3. Paper covers Rock (paper wins)

If players choose the same weapon, the game is a tie and is played again.

Typically, the game is played in a "best 2 out of 3" match.

Japanese Gameplay

While in essence the same game, the Japanese version, known as Janken, varies slightly.

• clenched fist: is called gu
• flat hand : is called pa
• two-finger V-shape: is called choki

The game begins with both players simultaneously saying the phrase "saisho wa gu", meaning "first is fist" and extending a gu hand to signal the start of the exchange. Then both players slowly pull back their hands while saying "jan ken..." and then on the word "poi" or "pon" (the final word varies by region) "throw" either gu, pa, or choki. The relationships between the three possible throws are the same as in most other versions of the game in other parts of the world.

Should both players make the same throw, the players say "aiko desho" (meaning "it's a tie") and on desho, make another throw. This can be repeated for unlimited ties, should they occur in sequence.

General Strategies

Strategy between human players obviously involves using psychology to attempt to predict or influence opponent behavior. It is considered acceptable to use deceptive speech (e.g. "Good old Rock, nothing beats rock!", A quote from The Simpsons, or "Nah, Rock flies right through Paper!", a quote from Seinfeld) to influence one's opponent.

Mathematically optimal play (according to game theory) is a simple matter of selecting randomly, and so the game may be considered trivial in that sense when played in a way that eliminates psychology, as with a computer program that does not take into account previous throws. But "optimal" in this sense means only "incapable of being defeated more than expected by chance", while it does not imply that the random strategy is best at taking advantage of a suboptimal opponent. In fact, if the opponent is human or a non-random program, it is almost certain that he plays suboptimally and that a modified strategy can exploit that weakness. This is easily demonstrated by Roshambot, a computer program that easily defeats some human players (as does its author Perry Friedman, who won an $800 competition against seven opponents including former world poker champion Phil Hellmuth in August 2001). Poker player Darse Billings of the University of Alberta organizes a computer Rock-Paper-Scissors competition to explore these possibilities, and their application to computer game play in other fields (notably poker, in which exploiting an opponent's non-random behavior is an important part of strategy).

One high-profile strategic opinion came in 2005 from Alice Maclean, age 11. When rival auction houses Christie's and Sotheby's agreed to play rock-paper-scissors to determine the rights to a highly valuable art collection, Maclean's father Nicholas, a Christie's employee, asked her for advice. As later told to reporters, her strategy was summed up thus: "Everybody knows you always start with scissors. Rock is way too obvious, and scissors beats paper." (Christie's won, with scissors.)

Cheating

One of the first tricks learned by a Rock-Paper-Scissors novice is to hold back a throw of paper until the last possible moment to dupe an opponent into believing that one may actually be throwing a rock. Both paper and scissors have this ability; however, unless one is employing a "double-back" strategy, cloaking a paper throw is likely to draw an instinctive paper from one's opponent.

The opening ritual before the actual throws are made ("1… 2… 3… Shoot!" or “Rock, paper, scissors, shoot!”), called "priming", is intended to get both players in sync so as to ensure simultaneous delivery of throws. This can be used to an advantage when two players are meeting for the first time, since it is often unclear as to what the priming speed will be. The tendency is to default to the priming speed of the faster player. This allows the faster priming player the luxury of dictating the flow of play and causes their opponent to dedicate more energy to "catching the prime" rather than concentrating on delivering an effective throw.

A common variation on the opening ritual is to have both players hold their hands behind their backs and reveal their already formed throw after the count of three. The intention is to prevent any sort of timing based cheating. This is often seen among live action role-players.

Among children and immature adults, the "bomb" (thrown the same as a rock, except with the thumb sticking straight up rather than hidden) is employed as a desperate attempt to thwart one's opponent. Needless to say, this maneuver is illegal, and those who employ this tactic are scorned for cheating. However, it could be assumed that scissors could beat bomb in the sense of cutting the fuse. Other variants of this include the finger, volcano, fire, gun, squirrel, and the flagon tri, the latter being an automatic win. However, in certain Live-action Role-playing games, the bomb is a legal move used in particular situations, such as the ultimate level of a skill.

Retribution can be accomplished after a failed throw by punching, slapping, or poking your opponent depending on the move in hand.

Variations

See Rock, Paper, Scissors variations

There are many different variations of Rock, Paper, Scissors which range from simple changes in the names of the objects to increasing the number of players or objects. While interesting, most rule variations suffer from one problem or another, making them less interesting games. Versions of this game are also observed in many different cultures. It is usually known by direct translations of "Rock, Paper, Scissors" although some cultures have slightly different names representing different objects. Minor variation is also observed in the standard game play.

Another variation is known as RPS-25http://www.umop.com/rps25.htm from umop.com, which is an extreme version of the classic game with 25 different gestures instead of just three.

The additions are: Gun, Dynamite, Nuke, Devil, Dragon, Alien, Water, Bowl, Air, Moon, Sponge, Wolf, Cockroach, Tree, Man, Woman, Monkey, Snake, Axe, Fire, and Sun.

There is a very complex set of relationships between these gestures, which almost require a chart to play. Simpler variations include RPS-7,http://www.umop.com/rps7.htm RPS-9,http://www.umop.com/rps9.htm RPS-11,http://www.umop.com/rps11.htm and RPS-15.http://www.umop.com/rps15.htm

A very popular variation is "Rock, Paper, Scissors, Slap". Two people are locked in a perpetual handshake. When Person A wins, Person A turns the hands so Person B's hand is facing up. Person A then slaps Person B's hand.

Multiplayer RPS

When playing with more than two people, all players throw simultaneously. If all three objects are displayed, there is no winner and the game is repeated with all players. If only two symbols are displayed (e.g. half of the players threw paper and half threw scissors), the players showing the losing object are out of the game, and it is repeated with the remaining players until only one winner remains. This is a common method of selecting a starting player among devotees of German-style board games.

Extreme RPS

Extreme RPS uses the same rules as regular RPS except that the winning "weapon" is used to attack the losing player. If you pick rock and lose to paper you get a slap on the upper arm. If you pick paper and lose to scissors you receive a "stinger" on the inside of the elbow where the veins usually come to the surface. A stinger is when you slap with the index and middle fingers. If you pick scissors and lose to rock you get a punch on the upper arm.

Math and non-transitivity

Rock, Paper, Scissors is also often used as an example of the mathematical concept of non-transitivity. A transitive relation R is one for which a R b and b R c implies a R c. A reflexive, antisymmetric, and transitive relation on a set is known as a partial ordering, from which notions of "greater" and "less" follow. A game option which is "greater" than another is closer to being optimal, but such a notion does not exist in Rock, Paper, Scissors: The relation used to determine which throws defeat which is non-transitive. Rock defeats Scissors, and Scissors defeat Paper, but Rock loses to Paper. In fact, Rock-Paper- Scissors could be called "antitransitive" because if A strictly defeats B, and B strictly defeats C, A necessarily loses against C.

History

Rock, Paper, Scissors was invented by the Japanese.^{[[Citing sources citation needed]]}

There is no record of Rock, Paper, Scissors in the West before there was direct contact with Asia.^{[[Citing sources citation needed]]} The Chinese and Koreans use Cloth along with Rock and Scissors, while the Japanese have adopted Paper.Jan Ken Pon - [Some Historical Data]

Pop culture trivia

Because of its widespread use by children and adults, Rock Paper Scissors has received substantial references in popular culture. Seinfeld, The Simpsons, and That 70s Show all poke fun at particular characters' incompetence at understanding the game rules. In other shows, mischievous characters are often able to "win" the game by deploying new objects which beat all the others and are subsequently able to convince their slow-witted competitor that deploying the new object is a legitimate move. In video games, intransitive relationships (like Rock, Paper, Scissors) often appear either in strategy choices or in weapons' abilities.

"Rock is Dead. Long live Paper and Scissors." is a popular t-shirt among young people wishing to express disdain for the lack of quality rock music available.

Federal case

In 2006, 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. He ruled in Avista Management v. Wausau Underwriters:

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 (1) 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.

Evolutionary strategy

Biologist Barry Sinervo from the University of California, Santa Cruz has discovered a Rock-Paper-Scissors evolutionary strategy in the mating behaviour of the side-blotched lizard species Uta stansburiana. Males have either orange, blue or yellow throats and each type follows a fixed, hereditable mating strategy:http://www.biology.ucsc.edu/faculty/sinervo.html

• Orange-throated males are strongest and do not form strong pair bonds; instead, they fight orange-throated males for their females. Yellow-throated males, however, manage to snatch females away from them for mating.
• Yellow-throated males are smallest, and their coloration mimicks females. Under this disguise, they can approach orange-throated males but not the stronger-bonding blue-throated specimens and mate while the orange-throats are engaged in fights.
• Blue-throated males are middle-sized and form strong pair bonds. While they are outcompeted by orange-throated males, they can defend against yellow-throated ones.

The proportion of each male type in a population is similar in the long run, but fluctuates heavily in the short term. For periods of 4-5 years, one strategy predominates, after which it declines in frequency as the strategy that manages to exploit its weakness increases. This corresponds to the stable pattern of the game in the replicator dynamics where the dynamical system follows closed orbits around the mixed strategy Nash equilibrium.

Tournaments

WRPS Sanctioned Tournaments

Starting in 2002, the World Rock Paper Scissors Society (WRPS) standardized a set of rules for international play http://www.worldrps.com/index.php?option=com_content&task=view&id=14&Itemid=31 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.http://www.washingtontimes.com/national/20041210-120729-4008r.htmhttp://www.npr.org/templates/story/story.php?storyId=1477870http://www.cbsnews.com/stories/2003/10/29/earlyshow/contributors/melindamurphy/main580709.shtmlhttp://www.usatoday.com/news/offbeat/2003-10-27-rock-paper_x.htmhttp://www.foxnews.com/story/0,2933,188380,00.htmlhttp://www.voiceoftreason.net/hand-to-hand-combat.html WRPS events are noted for their large cash prizes, elaborate staging, and colourful competitors.http://www.worldrps.com/index.php?option=com_gallery2&Itemid=30 In 2004 the championships were broadcast on the U.S. television network Fox Sports Net.

World Championship results since 2002

Year	Host City	Medal	Champion	Gender	Nationality
2002	Toronto		Pete Lovering	Male	Canadian
			Moe Asem	Male	Canadian
			Dave Ferris	Male	Canadian
2003			Rob Krueger	Male	Canadian
			Marc Rigaux	Male	Canadian
			Patrick Merry	Male	Canadian
2004			Lee Rammage	Male	Canadian
			Heather Birrell	Female	Canadian
			Chris Berggeren	Male	American
2005			Andrew Bergel	Male	Canadian
			Stan Long	Male	American
			Stewart Waldman	Male	American

Tour events

In addition to the International World Championships the WRPS also endorses or sanctions a year-round series of tournaments world wide. "Endorsed" tournaments agree to abide by the WRPS standardized international rules of play and code of conduct, while "Sanctioned" tournaments will net the winner a trip to compete at the International World Championships. Some of the major events of this tour include:

• [Roshambo Winery RPS Championships], Healdsburg, California
• [RPS Keystone Classic], Philadelphia, Pennsylvania
• [RPS Philadelphia City League Championship Series], Philadelphia, Pennsylvania
• [Rocksdam RPS Charity Tournament], Potsdam, New York
• [Atlantic Yards Smackdown], Brooklyn, New York
• [RPS Australian Championships]
• [RPS New Zealand Championships]

USARPS Tournaments

In April 2006, the inaugural USA Rock Paper Scissors League Championship was held in Las Vegas, Nevada.http://www.usarps.com 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 aired on A&E on June 12, 2006.

At the first ever USA Rock Paper Scissors League Championship, "Drill" McGill defeated "Fast Twitch" Twitchel to win the tournament.

Programming Competitions

In Rock Paper Scissors programming competitions,http://www.cs.ualberta.ca/~darse/rsbpc2.html competitors will play hundreds of rounds in order to give them an opportunity to detect patterns in their opponents, less than optimal play which can be exploited.

References

• Sogawa, Tsuneo (2000). "Janken". Monthly Sinica, Vol.11, No.5. (Japanese)
• 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. (ditto)
• Opie, Iona and 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.)
• Alonzo, S.H. and Sinervo, B. (2001). "Mate choice games, context-dependent good genes, and genetic cycles in the side-blotched lizard, Uta stansburiana". Behavioral Ecology Sociobiology Vol.49, pp.176-186
• Sinervo, B., and Lively, C. (1996). "The Rock-Paper-Scissors Game and the evolution of alternative male strategies". Nature Vol.380, pp.240-243
• Walker, Douglas & Graham (2004). "The Official Rock Paper Scissors Strategy Guide" Fireside (RPS strategy, tips and culture from the World Rock Paper Scissors Society).

External links

• [Roshambo Winery's Annual Championships]
• [Play RPS against real people over the internet.]
• [USA Rock Paper Scissors League]
• [Play Rock Paper Scissors Now, RPS Super Challenge]
• [PRPS Format, Rules and Strategy]
• [World Rock Paper Scissors Society]
• [Regional variations on Rock Paper Scissors], from the "Multiculturalpedia"
• [RoShamBo Programming Competition]
• [BombBeatsThemAll], an AIM Rock Paper Scissors bot that allows two people to play RPS over AIM
• [Stanford University's RoshamBot], an artificial intelligence RPS player
• [Skill Extreme's Roshambo multiplayer online game]
• [Free RPS game]
• [Javascript RPS game at CoolToons]
• [stensakspapir.dk - Challenge a friend and watch the match (Flash based)]
• [Article from Forbes FYI]
• [Dr. Barry Sinervo's web page on the lizards' mating strategy]
• [Challenge the world or a friend and play live (Flash Based)]
• [Exasperated judge resorts to child's game]

[ v]·[ d]·[ e]	Topics in game theory
Definitions	Normal form game · Extensive form game · Cooperative game · Information set · Preference
Equilibrium concepts	Nash equilibrium · Subgame perfection · Bayes-Nash · Trembling hand · Correlated equilibrium · Sequential equilibrium · Quasi-perfect equilibrium · Evolutionarily stable strategy
Strategies	Dominant strategies · Mixed strategy · Grim trigger · Tit for Tat
Classes of games	Symmetric game · Perfect information · Dynamic game · Repeated game · Signaling game · Cheap talk · Zero-sum game · Mechanism design
Games	Prisoner's dilemma · Chicken · Stag hunt · Ultimatum game · Coordination game · Matching pennies · Minority game · Rock, Paper, Scissors · Pirate game · Dictator game
Theorems	Minimax theorem · Purification theorems · Folk theorem · Revelation principle · Bishop-Cannings theorem
Related topics	Mathematics · Economics · Behavioral economics · Evolutionary biology · Evolutionary game theory · Population genetics · Behavioral ecology · Adaptive dynamics · List of game theorists

 

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