How to Win at Rock, Paper, Scissors

Rock, Paper, Scissors is a totally random game, right? Wrong — and here's the proof: The YouTube channel Numberphile recently posted a video that will teach you how to win at Rock, Paper, Scissors almost all the time. True, these strategies aren't totally fool-proof; they will, however, greatly increase your chances of winning, which might just come in handy the next time you challenge someone to a "best of three" game. Also, the video is illustrated with delightful Monty Python-esque animations, and that's awesome. Just sayin'.

Anyway, the video takes its cues from a recent study conducted in China that involved getting 360 students together to play a whole lot of Rock, Paper, Scissors. And I do mean a lot, by the way; we're talking 300 rounds per game (it apparently took up to two hours to complete in some cases. Wowzers). Numberphile host Hannah Fry walks us through not only what the researchers found, but how we can use it to up our chances of winning. Here's the short version; scroll down to watch the whole video. Ready for this? Here we go.

The Experiment:

The researchers who conducted the Chinese study discovered two important findings from their experiment:

  1. People who win tend to repeat their strategy in the next round — that is, they pick whatever option they won with (rock, paper, or scissors) a second time in a row.
  2. Losers, on the other hand, change their strategy, picking a different option than the one with which they lost in the previous round.

With me so far?

The Trick:

Now, here's the trick: You can exploit these two findings depending on which situation you're in at any given time.

If you just lost...

...That means the other person won (duh). If the other person just won, you now know that they're likely to pick the same option a second time — which means you also know exactly what to pick to foil their plan. For example, if you lost to your partner playing rock, you can be relatively certain that they're going to pick rock again in the next round. Knowing this, your choice is obvious: Play paper. Voila!

If you just won...

...You have to start getting sneaky. If your opponent also knows that people who win tend to pick the same strategy during the next round, that means they think they know what you're going to play in the next round — which in turn means you know which strategy they're likely to play against you. So how do you get around this one? Easy: Play what your opponent just played when they lost. So, say you played rock and your opponent played scissors. Your opponent thinks you're going to play rock again, so they'll probably choose paper. But if you choose scissors — the strategy they just played — you'll slice up their paper like buttah.

If you draw...

...There are no tricks. Sorry. Just play your next move as randomly as you possibly can and go from there.

For Further Information:

Is all this sounds kind of familiar to you, you may know a little bit about game theory already. If you want to know more, check out this free course on game theory on Coursera.

Cool, right? Watch the whole video below, and catch more neat-o math stuff over at the Numberphile YouTube channel:

Images: Sharon Drummond/Flickr; Numberphile/YouTube (5)