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Winning Algorithms For Rock, Paper, Scissors

timothy posted about 6 months ago | from the win-bets-with-children dept.

AI 65

Celarent Darii (1561999) writes "The probability of winning at Rock-Paper-Scissors is about 1 in 3. However, people do not play entirely randomly, a study has revealed. People tend to follow hidden patterns that can be used to win more games. A short article on the BBC gives hints on the strategies to be used to get a competitive advantage with your Rock-Scissors-Paper nemesis." Remember, these strategies are for use against people, not robots.

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This is useless (2, Funny)

Anonymous Coward | about 6 months ago | (#46907439)

When I play rock, paper, scissors with someone, we just play once unless it's a tie, so there are no patterns.

Re:This is useless (3, Insightful)

wonkey_monkey (2592601) | about 6 months ago | (#46907481)

This may come as a surprise to you, but you're not the only person in existence.

Re:This is useless (1)

Anonymous Coward | about 6 months ago | (#46907527)

This may come as a surprise to you, but you're not the only person in existence.

Thanks, imaginary person, for your imaginary post.

Re:This is useless (0)

Anonymous Coward | about 6 months ago | (#46907727)

There's no hard proof of that.

I can only have faith that you all exist, and I'm not some special snowflake.

Re:This is useless (1)

SpankiMonki (3493987) | about 6 months ago | (#46907507)

And /. only gives me mod points on the weekends...except this time. Dammit!

Telling a Pinocchio? (2)

tepples (727027) | about 6 months ago | (#46907627)

I thought the more common protocol was to win 2, as seen in the arcade game Fist Talks.

Re:This is useless (1)

Caesar Tjalbo (1010523) | about 6 months ago | (#46907803)

When I play rock, paper, scissors with someone, we just play once unless it's a tie, so there are no patterns.

I guess that now that you know there are patterns, you'll play it for hours on end.

Re:This is useless (4, Funny)

Nkwe (604125) | about 6 months ago | (#46907949)

When I play rock, paper, scissors with someone, we just play once unless it's a tie, so there are no patterns.

If you play to the death there are no patterns either.

Re:This is useless (1)

Megane (129182) | about 6 months ago | (#46909983)

So add lizard and Spock.

Re:This is useless (1)

gzuckier (1155781) | about 6 months ago | (#46916437)

I like to play it solitaire, right hand against left hand.

A robot (1)

rossdee (243626) | about 6 months ago | (#46907449)

Could watch you muscle movements and with sharper reflexes pick the winning option

Re:A robot (1)

HybridST (894157) | about 6 months ago | (#46907725)

You mean like this? [bbc.com]

strange odds (0)

Anonymous Coward | about 6 months ago | (#46907455)

When I play RPS, the probability of me winning is usually about 1 in 2!

Re: strange odds (0)

Anonymous Coward | about 6 months ago | (#46907467)

No ties then, I assume...

Re: strange odds (0)

Anonymous Coward | about 6 months ago | (#46915053)

Well, someone ends up winning. When's the last time you saw people throw identical signs and just say "oh, well, it's a tie, we'll have to find some other way to decide who gets to eat the last slice of pizza".

I pick (0)

Anonymous Coward | about 6 months ago | (#46907461)

Graphene

It beats everything but Paper with which it is a tie

Wait. What? (3, Interesting)

typing ape (3640619) | about 6 months ago | (#46907515)

OK, so two people play this game, each has about the same chance of winning, and that chance is 1 in 3? BTW, nowhere in the original article does it state that.

Re: Wait. What? (0)

Anonymous Coward | about 6 months ago | (#46907577)

Because it isn't the case. You win, lose, or tie. Your chances of winning are 1 in 3.

Re: Wait. What? (1)

gzuckier (1155781) | about 6 months ago | (#46916443)

Because it isn't the case. You win, lose, or tie. Your chances of winning are 1 in 3.

Tie goes to the house.

Parent post (0)

Anonymous Coward | about 6 months ago | (#46907625)

has clearly never played rock-paper-scissors before

Re:Wait. What? (4, Funny)

PolygamousRanchKid (1290638) | about 6 months ago | (#46907699)

When you play high stakes Rock, Paper, Scissors in a Casino in Las Vegas, the house wins on a tie. That's how they make their money.

Also note that in Las Vegas, they can boot you for life for trying to "play smart", like just happened to Ben Affleck, for allegedly counting cards.

It doesn't seem fair to me . . . if you are good at math, and can count cards, why shouldn't you be able to use your intellectual skills at a game?

Those Las Vegas Casinos are discriminating against geeks. Someone outta sue.

That's way too much of a house edge (1)

tepples (727027) | about 6 months ago | (#46907743)

When you play high stakes Rock, Paper, Scissors in a Casino in Las Vegas, the house wins on a tie.

Citation needed. The house has far less of an edge in craps, basic strategy blackjack, roulette, or regulated slots.

Re:That's way too much of a house edge (0)

Megane (129182) | about 6 months ago | (#46909993)

Here's your citation. [wikipedia.org]

Coin-op RPS (1)

tepples (727027) | about 6 months ago | (#46910243)

I wasn't quite sure if it was a joke. (Damn you Poe's law!) So here's another citation [wikipedia.org] .

Now here's what brought it up: A local arcade has a coin-operated RPS machine called Fist Talks, and I wondered if casinos had been installing similar RPS machines that pay out. I know blackjack tables don't take pushes unless both the player and dealer bust, which provides the fundamental house edge in blackjack. Every rule that benefits the player (standing below 17, double down 10 and 11, split A-A and 8-8, increased payout for 21 with A-10) serves to moderate this house edge. I just wondered whether casino RPS existed and if so, how it reconciled the game's house edge with state gambling regulations.

Counting cards requires collusion w other players (0)

Anonymous Coward | about 6 months ago | (#46907933)

If counting cards was a completely solo task then a casino may still ask you to leave, as is there right, but they couldn't prove you were counting cards. The problem is that you do not have enough information to count cards in Blackjack on your own. How it is accomplished is through groups of people playing at the same table trying to secretly share information on the state of the deck/shoe. If you were to try and share information between players openly you would quickly find out that it is not allowed, thus trying to break that rule by keeping it secret is considered even worse. That's the real issue that casinos have with card counters. It throws the odds in favor of the player, which is something they cannot allow.

Re:Counting cards requires collusion w other playe (1)

BitZtream (692029) | about 6 months ago | (#46907983)

... No.

Counting cards is fairly simple to take away the house edge, if you can count without using your fingers, its easy. You get the best performance counting when you're there from the start of the shoe, but you don't have to wait for a reshuffle to increase your chances by counting.

Its simple hi/lo/zero.

There are extremely complex methods, but they offer no major advantage to using them, arguably none at all beyond the theory that they are better.

Just because you watched some TV special about the church group doesn't mean it has to be done in a group, See Donald Johnson who has taken more from the casinos as a single player than any group has.

Re:Counting cards requires collusion w other playe (0)

Anonymous Coward | about 6 months ago | (#46908235)

By game odds alone, there is plenty of information from counting cards and changing your bets by yourself. The problem is that a single person using this information becomes quickly obvious to a pitboss or anyone else watching. You need a group of people not to get more information, but to hide the variability in betting in response to information making it harder to get caught counting.

Re:Wait. What? (2)

Anubis IV (1279820) | about 6 months ago | (#46909239)

The New York Times made a Rock-Paper-Scissors Flash-based bot [nytimes.com] a few years back. It's essentially exactly what the summary is talking about, since it learns your patterns and will in short order begin winning against you far more than merely 1-in-3 times. Alternatively, if you play the Veteran version of the bot, it has knowledge of all of the patterns from anyone who has ever played it, and it starts off beating you right from the start. If you could smuggle that into the casino, I'd be willing to bet that you could increase your winnings rather significantly

Re:Wait. What? (1)

Megane (129182) | about 6 months ago | (#46910001)

Or you could remember that you were in a casino and borrow a six-sided die in case the other guy was using a bot.

Will they fucking let this go already? (1)

Anonymous Coward | about 6 months ago | (#46907517)

We got it, brains are pattern-based machines at thus have a hard time generating pattern-less random sequences.
Can we now leave this trivial game alone and do some real science please?

Re:Will they fucking let this go already? (1)

camperdave (969942) | about 6 months ago | (#46907797)

We got it, brains are pattern-based machines at thus have a hard time generating pattern-less random sequences. Can we now leave this trivial game alone and do some real science please?

Exactly. Now as to the algorithmic approaches for winning Rock-Paper-Scissors-Lizard-Spock...

Re:Will they fucking let this go already? (1)

smallfries (601545) | about 6 months ago | (#46908277)

Play Lizard 100% of the time.

Re:Will they fucking let this go already? (1)

narcc (412956) | about 6 months ago | (#46908299)

Oh, no! Someone is doing something that you think is a waste of time!

The horror!

I think it needs updating (0)

Anonymous Coward | about 6 months ago | (#46907589)

It should be Space Elevator - Nanotechnology - Private Space Colonies

Lizard Spock (0)

Anonymous Coward | about 6 months ago | (#46907649)

How does this not cover Rock-Paper-Scissors-Lizard-Spock which many geeks have adopted recently thanks to its popularization on The Big Bang Theory.

Re:Lizard Spock (1)

tepples (727027) | about 6 months ago | (#46907733)

The majority of people aren't geeks. The study was able to find 360 people in China familiar with RPS, which would probably have been a lot harder for the pentagram versions. Does Chinese TV even show The Big Bang Theory?

Re:Lizard Spock (1)

Megane (129182) | about 6 months ago | (#46910007)

Does Chinese TV even show The Big Bang Theory?

Well, at least they know about it. [slashdot.org]

rock, paper, scissors, lizard, spock (0)

Anonymous Coward | about 6 months ago | (#46907763)

but will help me beat Sheldon at rock, paper, scissors, lizard, spock

The brain evolved... (0)

blahplusplus (757119) | about 6 months ago | (#46907779)

... to survive, find mates and have kids. Everything else we got is extra. No one should expect the brain to do much more than what it was originally selected to do.

Only most of the time? (1)

edibobb (113989) | about 6 months ago | (#46907799)

Here's how to win all the time: http://www.k2.t.u-tokyo.ac.jp/... [u-tokyo.ac.jp]

Slashdot thinks I type too fast, so they won't take this comment until I wait a while. I can only guess that they want more drivel to fill the white space on the page.

Re:Only most of the time? (2)

alexhs (877055) | about 6 months ago | (#46907997)

It's because you are typing too fast, if you had taken the time to follow all the links in TFS, you wouldn't have posted :)

But who RTFAs anyway, right ? :)

Obligatory (3, Funny)

QilessQi (2044624) | about 6 months ago | (#46907981)

Lisa's Brain: Poor predictable Bart. Always takes 'rock'.
Bart's Brain: Good ol' 'rock'. Nothin' beats that!
Bart: Rock!
Lisa: Paper.
Bart: D'oh!

Re:Obligatory (1)

gzuckier (1155781) | about 6 months ago | (#46916455)

Rock rips through paper because of gravity. Rock wins always!

Well, I don't know.. (2)

hyfe (641811) | about 6 months ago | (#46908005)

Well, I don't know. Let's get a game started to test this..

Rock!

Re:Well, I don't know.. (0)

Anonymous Coward | about 6 months ago | (#46908237)

Banana!

Wait, gimmie a sec...

Re:Well, I don't know.. (0)

Anonymous Coward | about 6 months ago | (#46908321)

A-bomb!

Always wins.

Re:Well, I don't know.. (0)

Anonymous Coward | about 6 months ago | (#46910295)

Black hole!

You lose.

Re:Well, I don't know.. (1)

spitzak (4019) | about 6 months ago | (#46909459)

Scissors! Oh rats...

Friend of Mine and I Play (2)

Greyfox (87712) | about 6 months ago | (#46908123)

A friend of mine and I play to determine exit order on the aircraft. I've beaten him 4 out of the last 5 times we've done it playing rock. Next time we play I'm going to point that out to him in advance and then the head games begin! Will I play rock again, because it's the predictable move, or am I just setting him up to throw paper because I'm planning to throw scissors?

Re:Friend of Mine and I Play (1)

nblender (741424) | about 6 months ago | (#46912303)

Same here. I'm one step ahead of you. My friend and I play for "who has to go deal with the stupid user"... Last time we played, he said "wow. When you said you always pick rock, you really meant you _always_ pick rock"...

He's not a stupid man... So he could be setting me up anticipating that I will play scissors next so I should pick paper...

Good thing there's no iocane powder involved.

Win-stay lose-switch strategy (1)

140Mandak262Jamuna (970587) | about 6 months ago | (#46908247)

This strategy "win-stay lose-switch" is an very important and significant finding in game theory and evolution. The tournament of algorithms conducted in U Mich in late 1980s was a breakthrough in explaining the evolution of cooperation and altruism. But its winning strategy tit-for-tat was indistinguishable from "always-cooperate". So any mutant that does not follow "always-cooperate" would gain a very strong foot hold. This strategy was not evolutionarily stable strategy, ESS.

The win-stay lose-switch strategy would do very badly in any population dominated by non cooperative members. But once tit-for-tat has established a beachhead, and driven the bad actors out of the population, win-stay lose-switch strategy would keep the cheaters to a minimum. This strategy is probably wired into us.

Re:Win-stay lose-switch strategy (0)

Anonymous Coward | about 6 months ago | (#46908335)

"win-stay lose-switch" is also the reason most people never get rich of the stock market.

Re:Win-stay lose-switch strategy (1)

dinfinity (2300094) | about 6 months ago | (#46908657)

Of course it is. That's how a neural network works.
It's hardly surprising that humans are terrible RNGs. It is, however, a good thing to keep in the back of your mind when in a competitive situation where that is relevant.

Doesn't everybody knows that already? (1)

godrik (1287354) | about 6 months ago | (#46908667)

(obvisouly I did not RTFA.)

When I took Simulations in gradschool 10 years ago, one of our assignment was to train a markov chain to predict the player next move at rock-paper-scissors. Using simply as state "lastmove, lastoutcome" is enough to learn what humans (read the students of the class) do.

Re:Doesn't everybody knows that already? (0)

Anonymous Coward | about 6 months ago | (#46909049)

I wrote one in Turbo Pascal in high school. It tracked patterns of 5 moves, so it took longer to train, but got really good at beating everybody in my class.

Am I missing something? (1)

Solandri (704621) | about 6 months ago | (#46908989)

If the winner tends to stick with the same hand, while the loser tends to switch, doesn't that imply the loser will tend to win the next round? I mean, the only way the winner can win the next round by sticking with the same hand is if the loser also sticks with the same hand.

Re:Am I missing something? (1)

DietFluffy (150048) | about 6 months ago | (#46909777)

that's what people tend to do, not the winning strategy. use the trend to your advantage. for example, if someone just beat your scissor with rock, he will tend to play rock again, so you should play paper next. whereas you might've been half-tempted to play rock also

Down here (1)

DarrylKegger (766904) | about 6 months ago | (#46909707)

we tend to call it paper-scissors-rock, so...

Best 2 out of 3 (1)

penguinoid (724646) | about 6 months ago | (#46909711)

Next time I play, I'll suggest playing best 2 out of 3 so as to be able to use this tactic.

Maybe... (1)

jtgd (807477) | about 6 months ago | (#46910847)

They say that the person chooses the next in sequence by the name of the game, but that may not be why. Perhaps when they lose they choose the pattern that beats the pattern they just used. It still results in the same sequence, R>P>S, but for a different reason.

Not truly random (1)

HalAtWork (926717) | about 6 months ago | (#46911419)

FTA:

When players won a round, they tended to repeat their winning rock, paper or scissors more often than would be expected at random (one in three).

If it was truly random then anything could happen, including a game where the opponent only chooses scissors the entire time.

Probabilities... (0)

Anonymous Coward | about 6 months ago | (#46912269)

Let me correct that for you:
"The probability of winning at Rock-Paper-Scissors is about 1 in"... 2

Someone needs to go back to statistics 101...

Re:Probabilities... (1)

Smerta (1855348) | about 6 months ago | (#46912717)

Ouch. Muphry's law (not a typo - http://en.wikipedia.org/wiki/M... [wikipedia.org] ) strikes again.

There are 3 equally possible outcomes: win, tie (same choice), lose.

Did they consult Dr. Sheldon Cooper? (1)

sethrosen (2737555) | about 6 months ago | (#46912795)

I'm sure Dr. Cooper would have told them the winning algorithm for Rock-Paper-Scissors-Lizard-Spock.
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