Rock, paper, scissors is usually treated as a coin toss with extra steps. Three choices, each beats one and loses to one, so it must all come out even.
In theory that is right. In practice it is a game about people, and people have habits. Our version, Throw Down, is first to three, which is just long enough for habits to show.
What the theory says
Game theory gives a clear answer. If you choose rock, paper and scissors with equal chance, completely at random, nobody can gain an edge over you. Whatever your opponent does, they win a third of the time, lose a third and draw a third.
That is the safe way to play. It cannot be beaten.
It also cannot win. A random player takes no advantage of an opponent's mistakes. Against someone who throws rock every time, the random player still only wins a third.
So there are two ways to play. Be random and be safe. Or try to read your opponent, and accept that they may be reading you.
Being random is hard
Ask someone to write down a "random" sequence of throws and it will not be random at all. People avoid repeats, because three rocks in a row does not look random to them, even though a real random sequence has plenty of runs. They cycle through the options too evenly. They fall into rhythms.
This is why reading people works.
What a study of real players found
In 2014 researchers at Zhejiang University in China published a study of several hundred students playing hundreds of rounds each. Across the whole group, the three throws were used about equally often. But round by round, a pattern showed up.
Winners tended to stay. A player who had just won was more likely than chance to throw the same thing again.
Losers tended to shift. A player who had just lost was more likely to change to something else.
The researchers described it as a kind of "win-stay, lose-shift" habit. It makes sense. If something worked, do it again. If it did not, try something else.
Turning that into throws
If your opponent follows the pattern, you can stay a step ahead.
After you win: your opponent lost, and is likely to switch. A common piece of advice is that they often go to whatever would have beaten your winning throw. If your rock beat their scissors, they may come back with paper. So throw scissors.
After you lose: your opponent won, and may repeat. If their paper beat your rock, expect paper again, and throw scissors.
After a draw: less clear. Many people change after a tie.
In both cases you are doing the same thing: guessing their next throw from the last result, and answering that. Try it for a few matches and keep count.
Other habits people report
These come from long experience of the game more than from careful study, so treat them as hints.
- Rock first. Inexperienced players are often said to open with rock. If so, paper is a good opening throw.
- No triples. Few people will throw the same thing three times running. After two scissors, a third is unlikely, which means rock is a safe play.
- Announced throws. If someone tells you what they will throw, most people then do not throw it.
The catch
All of this works only against someone who is not thinking about it. If your opponent has read the same things, they will expect your scissors and throw rock.
Then you are in a spiral. I think that you think that I think. At the bottom of the spiral is the random strategy again, which is where game theory said we would end up.
In a first-to-three match, there is room for one or two of these reads and not much more. A sensible plan is to play the pattern once or twice, and if your opponent seems to be ahead of you, go back to choosing without thinking.
A way to be random
If you want to be unreadable, do not trust your own head. Use something outside it. Look at the seconds on a clock: if the last digit is 1, 2 or 3, rock. 4, 5 or 6, paper. 7, 8 or 9, scissors. On zero, look again.
It is a little joyless. But it cannot be beaten.
The same idea in Odds and Evens
Odds and Evens is an even simpler guessing game. Both players pick a number from one to five. One player wants the total to be odd and the other wants it even.
Only one thing matters about your number: whether it is odd or even. And the choices are lopsided. Three of the five numbers are odd. Someone tapping without thought will pick an odd number more often than an even one.
So if your opponent seems to be choosing carelessly, assume they will go odd. The Even player should answer with an odd number, since two odds make an even. The Odd player should pick an even one.
Why we like these games
They are tiny, and they are entirely about the person opposite you. That is something a computer opponent cannot give you, and it is the reason every game on TwoSide needs two people in the same room.
For HTML5 games you can finish in a minute, they tell you a surprising amount about how your friends think.