SMART NEWS

The Ultimate Rock, Paper, Scissor Strategy

60 percent of the time, it works every time

May 2, 2014

05_02_2014_rock paper scissor.jpg — Two contestants compete in the 2006 International World Rock Paper Scissors Championships in Toronto. MARK BLINCH/Reuters/Corbis

In China, a team of researchers tapped 360 students to try to crack the ever-important nut: how do people play Rock, Paper, Scissors? And what's the best strategy?

Based on their study, says the Washington Post, at the population level, Rock, Paper, Scissors strategies follow a relatively simple pattern:

People start by picking each variable (rock, paper or scissors) about one-third of the time. You can’t really game this stage. BUT after the first round:

If a player wins, he will usually stick with the same play.

If a player loses, he will usually switch actions in “a clockwise direction”: rock changes to paper, paper to scissors, scissors to rock.

So that's it. If you know what someone will play next, it's easy to counter and achieve a grand victory.

But wait, what if they know the strategy, too? And they try to predict and out-smart your next move? But then you, knowing that they know, try to preempt their prediction? Then they, knowing you know they know...

Actually, though, if this all sounds too simple, that's because it probably is. People won't just keep riding Paper victory string into the sunset. Instead, says Graham Walker, from the World Rock Paper Scissor society (via this old Mental Floss post), people playing Rock, Paper, Scissors like to think they're being random. They aren't. “People hate being predictable and the perceived hallmark of predictability is to come out with the same throw three times in row,” he says.

When playing with someone who is not experienced at the RPS, look out for double runs or in other words, the same throw twice. When this happens you can safely eliminate that throw and guarantee yourself at worst a stalemate in the next game. So, when you see a two-Scissor run, you know their next move will be Rock or Paper, so Paper is your best move.

The researchers in China weren't just trying to work out the strategy to a schoolyard game, though. They were using Rock, Paper, Scissor as a way to study people's behavior when making decisions in “non-cooperative strategic interactions.” They were testing which of two different broad strategies people use: either trying to play truly randomly, or playing in an evolutionary way with strategies shifting depending on the outcome. (It was the latter.)

Still, though, as good as your strategy may be, you're never going to beat this Rock, Paper, Scissor-playing robot. Sorry.

Colin Schultz | | READ MORE

Colin Schultz is a freelance science writer and editor based in Toronto, Canada. He blogs for Smart News and contributes to the American Geophysical Union. He has a B.Sc. in physical science and philosophy, and a M.A. in journalism.