What makes Rock the most popular in Rock, Paper, Scissors?

In his most recent link roundup, Scott Alexander shared the following visualization from @infobeautiful showing that Rock is the most popular first throw in Rock/Paper/Scissors games:

He writes:

The practical upshot is to start with paper, but what broader lesson should we take from this? Since all options are mathematically identical, any difference in player behavior must come from connotations. Since rock feels strongest, a naive child would choose rock. But since everyone knows that, a slightly smarter person would choose paper. But since everyone knows that, an even smarter person might choose scissors. But since . . . and the lesson of this graph is that when playing the average member of the population, all of this galaxy-brained thinking provides negative value, because in practice most people never leave the naive first level.

It’s a plausible theory… but I give people more credit than this!

Mine is a psychological theory that predicts people to be both smarter and sillier than Scott’s theory, and it’s based on my own experience—because I too am guilty of having favored Rock throughout my life. And not as a deliberate strategy, but just something that sort of naturally happened.

The reason emerges from these two seemingly unrelated observations:

1. I’m not a good random number generator.
2. And most importantly, Rock seems like the default option.

Humans are kind of famously bad at probability. One example I’ve always enjoyed:

Say you flip a fair coin 10 times. What would you guess is the chance of getting at least 3 Heads in a row?

Most of the kids in my high school math class guessed something like a 25% chance. The real answer is just a hair over 50%.

If asked to simulate a sequence of one hundred random coin flips, we’ll do a terrible job of it. Our fake flips will invariably end up too orderly—either without enough streaks, or overcompensated with too many streaks, or messed up in some other way.

As Dostoevsky said, man is a fickle and incongruous creature. Yet that doesn’t make us good at making uniformly random choices between different numbers or any other options. That means when I’m playing repeated games of R/P/S, I’m afraid of being biased towards one option or another; any observable bias might lead me to lose. I’ll typically think to myself, “Alright, better not be predictable. Let’s start off with a purely random choice before I delve into any kind of reverse-psychology on the second choice.” But then I have no way to actually make a random selection among rock, paper, and scissors, and certainly not within the scant few seconds I have before my hand must come down—a hand that, it may be germane to mention, happens to already be in the shape of a rock.

The serial-position effect states that a person tends to remember the first and last items in a series best. This gets broken down into the “recency effect” for last items and “primacy effect” for first items.

Priming is the general idea of how humans can get biased towards certain ways of thinking when we’ve been recently prompted by certain stimuli. Social priming has gotten a bad rep thanks to the replication crisis (also recently discussed by Scott Alexander here), but other types of priming have held robust, like semantic priming. Humans can recognize the word “doctor” faster if they’ve just been exposed to the word “nurse”, for instance.

I suspect that when it comes to titles, the primacy effect holds stronger than the recency effect, and that’s why actors always have their names listed in order of highest billing to lowest (much to comedic effect in posters) or why lawyers will argue over whose surname gets the prized position of first in the names of their firms. In the game of R/P/S, rock gets both the prized position of first, which I posit is enough to prime Rock as more dominant than Paper or Scissors.

My wife has always had the feeling that Scissors is the strongest choice, which makes a sample size of two: China has many different R/P/S variants, and the one my wife knew was 剪刀石头布! (jiǎndāo shítou bù!): Scissors, Rock, Cloth.

What this dominant priority means for me, when I’m trying to make a random selection, is that I end up thinking something like:

Okay, what would be more random—let’s not focus on rock—which would be better between paper or scissors? Scissors or paper?Wait, I shouldn’t just ignore Rock entirely.Heck, me avoiding Rock is probably more expected. Maybe I’ll pick rock, and that’ll be the surprise move.

Those aren’t the thoughts going through my head every time. But it doesn’t take a lot to shift a 1/3 chance to a 1/2, and neither paper nor scissors have any similarly compelling factors to play in their favor (at least in the very first round, among non-professionals, when playing with someone you don’t have history with).

But maybe I’m wrong that my way of thinking is common. Please share your own thoughts in the comments!

(And if you liked this post, maybe you’ll like…)

Subscribe now

Share