How to Win at Rock-Paper-Scissors, with Conditional Response

May 4, 2014 6:42 PM

For one reason or another, no one has done a thorough evaluation of rock-paper-scissors. That is, until recently: Zhijian Wang and a group at Zhejiang University in China carried out a study with 360 students recruited from the University. The students were split into 60 groups of six players, and each group played 300 rounds of Rock-Paper-Scissors, with an additional financial incentive to the winners of each group. Winners stuck with with their selected action, while losers cycled through actions (rock, paper, scissors). No word on how well this works with expanded versions of the game (previously).
posted by filthy light thief (23 comments total)

One strategy that I've won with a bunch is to just keep doing the same thing no matter what -- will win you a lot of three out of fives because people will never expect it the third or fourth time. You'd be surprised at how angry people get when they lose to it, too.
posted by empath at 6:51 PM on May 4, 2014 [4 favorites]

Pffft. It involves a simple application of game theory. I've done it myself.
posted by mikeand1 at 7:21 PM on May 4, 2014 [1 favorite]

Except people aren't so logical, thus ruining the basic mixed strategy that is generally applied to the RPS strategy.
posted by filthy light thief at 7:31 PM on May 4, 2014

Saisho wa gu - jyan - ken - POI!
posted by flapjax at midnite at 7:48 PM on May 4, 2014 [1 favorite]

scissors cut paper
paper blows away
stone smashes scissors
and so it goes, another day
but it's all downhill from here
at least that's what Sisyphus said
ah, you're fucked six ways from sunday
with the blues wrapped round your head
posted by flapjax at midnite at 7:50 PM on May 4, 2014 [4 favorites]

Strategy by definition includes taking into account the possible reactions of your opponent, which will vary depending on their assessment of you. Suboptimal strategies can work very well if they take your opponent by surprise. In RPS, tending to stick with your selected action is a very poor strategy if your opponent has read this paper and knows that you have read this paper.

Citation: Luttwak, Strategy
posted by justsomebodythatyouusedtoknow at 8:31 PM on May 4, 2014 [3 favorites]

Stephen Fry can't seem to get the hang of the strategy.
posted by Greg_Ace at 8:40 PM on May 4, 2014 [2 favorites]

good ol rock, nothin beats that
posted by infinitewindow at 8:49 PM on May 4, 2014 [10 favorites]

paper covers rock, bitch
posted by flapjax at midnite at 9:20 PM on May 4, 2014

Meh. All this study shows is how to beat Chinese undergrads at Rock, Paper, Scissors.

It's hardly representative.
posted by notyou at 9:42 PM on May 4, 2014

Isn't this an old thing? I'm sure I've read about it before...
posted by Chuffy at 9:45 PM on May 4, 2014

Okay, this is a bit much.
posted by el io at 9:48 PM on May 4, 2014 [1 favorite]

Kill your opponent and you win.
posted by Pudhoho at 4:34 AM on May 5, 2014

Talk to me for a while and I will probably suggest a starting play for you. Maybe you'll suggest playing it for some reason. I'll indiscriminately throw a few symbols ahead of time to prep you and test your baseline. Then we'll start playing, and chances are I'll throw every single move you make - for fifteen to twenty moves in a row. A three round game takes seven minutes and you are thoroughly frustrated.

I don't play to win, I play to read your pupils and drive you crazy. The only way to win is not to play the game. Note: this does not work with computer based RPS.
posted by Nanukthedog at 5:10 AM on May 5, 2014

Note: this does not work with computer based RPS.

Yeah, the in-game purchases skew the strategy. I blew twenty bucks on spocks and lizards, and I still can't make it past King Hippo.
posted by Slap*Happy at 6:33 AM on May 5, 2014 [1 favorite]

"Nerf paper." -- Rock.

"Paper is fine, L2P." -- Scissors.
posted by Foosnark at 6:34 AM on May 5, 2014 [4 favorites]

Because people are disposed to not repeat moves, a pretty good strategy is usually to just play whatever would lose to the move that your opponent just threw. This strategy would lose to the people disposed to play the same move in streaks, but as this article shows, such people are rare.

But truly winning RPS strategies are way more complicated than this. I've posted this comment before, but it's worth reposting here.

Although a rock-paper-scissors competition seems stupid on first glance because it's all up to random luck, it's really not.

You can see this by considering the RoShamBo programming competition that they used to run at the University of Alberta. Competitors had to program rock-paper-scissors bots that would be entered into a tournament. One might think that a bot that just picked a move at random would be worth entering. But here's the thing: the organizers initially seeded the tournament with a few dummy bots that would not choose moves at random, but choose moves according to an algorithm. If a competing bot could identify them and figure out their strategy, they would be able to reliably defeat the dummy bots and their win percentage would creep up above 50%. And then, once there are bots that run algorithms to try to exploit the non-random bots, they themselves aren't playing completely randomly and their own algorithms can in turn be exploited. Once you've got enough competitors all running algorithmic strategies, you can take the dummy bots out again, and you're left with a field in which a whole bunch of bots that are trying to exploit the strategies of the other bots.

The bot that won the first programming competition had a wonderfully apt name: Iocaine Powder. The source code, and the explanation of the code, is really interesting.
posted by painquale at 6:36 AM on May 5, 2014 [13 favorites]

Okay, this is a bit much.

I think you missed the masterpiece on that site.
posted by painquale at 6:42 AM on May 5, 2014

I always say, "I'm going to play rock" and then play rock. I usually win against new folks and have won more than one single elimination "tournament" with this strategy.
posted by thedward at 7:06 AM on May 5, 2014 [1 favorite]

I like playing "rock" because if you lose your hand is already balled up into a fist
posted by desjardins at 7:22 AM on May 5, 2014 [4 favorites]

I like to say "I'm going to play rock" and then put on a Moby Grape album. I always win.
posted by stupidsexyFlanders at 7:29 AM on May 5, 2014 [2 favorites]

I miss the heady days of childhood RPS when you could unexpectedly choose "MACHINE GUN!" like it meant something.
posted by michaelh at 8:17 AM on May 5, 2014

Lizard. Spock.
posted by Splunge at 10:00 AM on May 5, 2014