Cut, Crush, and Cover: The Strategies of Rock-Paper-Scissors

Rock-Paper-Scissors is one of those games that is so ubiquitous that it’s hard to imagine a world without it. As a tool for making random decisions, it ranks up there with flipping a coin or shaking a magic 8 ball. The difference, however, is that there is no World Championship of Flipping Coins. Despite it’s simplicity, Rock-Paper-Scissors has turned out to have enormous depth. I believe that game designers can learn a lot from studying this classic game.

Cutting-Edge Strategy

Rock-Paper-Scissors, also known as Roshambo,  is a very simple game that involves two players making a simultaneous choice. Usually there is a countdown, and at the end of the countdown each player makes a shape with their hands to show their choice. The three choices are – Rock (a fist) which crushes Scissors (two fingers in a V shape), which cuts Paper (a flat hand with fingers together), which in turn covers rock.

At first, this game may seem entirely random. It is impossible to really know what your opponent will pick, so really you are just guessing. If this were the case, each player should have only three options, each with an even probability. They either win, lose, or draw. There is not real way to control which.

The first, and probably most obvious strategy for this game is try simply choose your option randomly. This strategy would be totally fair, and would be impossible for your opponent to exploit. The problems with this strategy are two-fold. Firstly, the best case scenario is that you win exactly 50% of the time, which is quite low for a supposedly optimal strategy.

The second problem is that humans are incredibly bad at actually being random. The human brain is incredibly good at picking up on patterns, and the smallest thing  can influence a supposedly random decision one way or another. A great example of this is pitching in baseball. Pitchers want to keep their pitches as random as possible in order to keep the batter guessing, but this still usually results in a pattern of pitch behavior that be predicted.

The batter may never have 100% certainty what the pitcher is going to throw, but they can have a reasonable guess. The pitcher, in turn, knows that the batter is trying to predict their throw, and modifies their behavior in order to “stump” them. In the pursuit of randomness, they are really taking a huge number of different factors into account which can influence the decision.

In order to get around this, one method is to use some real-world reference as a pseudo-random number generator. Instead of making the decision themselves, players can use information such as the time, the weather, the opponent’s Jersey number, the current score, or some combination thereof to make their choice. Decisions made this way, while not truly random, are random in the sense that the player has no control over the outcome and therefore cannot be predicted.

As mentioned before, however, even if players are able to perfect this random strategy it is still not really worth it. A better strategy would be to acknowledge the physical and psychological factors that influence the game, and use them to your advantage.

For starters, Rock-Paper-Scissors involves a physical action that can be used to predict the opponent’s decision. In 2015, a group of Japanese researchers made a robot that has a 100% win rate at rock-paper-scissors (1). This robot doesn’t actually win by predicting the opponent’s choice, but instead carefully watches the player’s hand as they are making their choice and forms the winning response. Observant human players may also be able to use this type of strategy to their advantage, although it is unlikely any human will have a quick enough reaction speed to match the robot.

You can also take advantage of the numbers. Because human players aren’t totally random, they don’t actually throw all three signs with the exact same frequency. According to tournament statistics Rock is the most common sign, with a little over 35%, Paper is only slightly behind, and Scissors lags at under 30%. Just based on these numbers, if you didn’t know anything else your best first throw would probably be Paper, because it gives you less than a 30% chance of losing.

Another strategy which actually involves predicting your opponent’s pick is to take advantage of the psychological factors associated with each choice. Rock, for example, is considered more aggressive, while paper is seen as more passive. Because of this, paper would be a good choice against an inexperienced angry or masculine player, who is more likely to choose rock (2).

Something else that players should keep in mind is that, although people are terrible at producing random results, most players will try to mimic randomness. Because of this, inexperienced players tend to not throw the same sign more than twice in a row, because this is seen as “not random”. The counter to this strategy is to throw the sign that would lose to the repeated sign – if they don’t throw it again, then you can’t lose.

One Chinese study analyzed the behavior of Rock-Paper-Scissors players and came up with a different strategy. They observed that if a player wins a round, they are more likely to pick the same option again. If they lost the round (or draw), they are more likely to move their option to whatever would have beaten their previous option. This means that if a player loses while choosing Rock, their next choice is more likely to be Paper. This means that your next pick should be Scissors!

Of course, these strategies will have to be adjusted based on the skill level of your opponent. Based on everything above, it appears as if Rock would be the most common opening move for a beginner, so if you are playing a beginner you should probably throw paper. If your opponent is a little more skilled, however, they might expect you to be the beginner, which means that they will throw Paper to cover your rock. In this case, you clearly must go Scissors!

Finally, there are the mind games. Suppose, for example, that before you choose your option you declare to your opponent what you are about to pick. Your opponent will clearly not expect you to follow through on your declaration, and will pick anything BUT the option that beats yours. The next time you do this, your opponent will expect you to switch it up – there’s no way you would follow through twice in a row. Eventually your opponent will catch on to your trick, and expect you to follow through. Once this happens, you know exactly what they are going to throw!

Covering Bases

We have covered a lot of different strategies for winning at Rock-Paper-Scissors here, and at this point you may be asking “What’s the point”? If you were planning to compete in a RPS tournament, then you probably already have your own strategies and techniques. If you aren’t, then this knowledge may not seem like it really matters.

However, the truth is that many of these strategies apply to more than just Rock-Paper-Scissors. At their essence, many games can be broken down into an RPS type structure. Real-Time Strategy Games, Trading Card Games and even Fighting games can often be thought of in terms of these same tactics. However, that is a large enough topic that I believe it deserves it’s own article.

Until Next Week!

That’s all I have for this week! If you liked this article, and would like to see more like it in the future, be sure to subscribe to the blog on Facebook, Twitter, or here on WordPress so you will always know when I post a new article.  If you didn’t like this article, let me know what I could be doing better in the comments below! And join me next time, where we will see what Rock-Paper-Scissors can teach us about other games!