Yes, chimpanzees can learn the rules of Rock Paper Scissors. In a study published in 2017 in the journal Primates, researchers at Kyoto University trained seven chimpanzees on a touchscreen version of the game, and five of them learned which option beats which, ending up performing about as well as 4-year-old children.
That headline got shortened in a lot of places to "chimps play Rock Paper Scissors", which is not quite what happened. Here is what the researchers actually did and what it tells us.
The study
The paper is "Learning the rules of the rock-paper-scissors game: chimpanzees versus children" by Jie Gao, Tetsuro Matsuzawa and colleagues, from Kyoto University's Primate Research Institute (Gao was also affiliated with Peking University). It appeared in Primates in 2017, and Kyoto University announced it in August of that year.
The question was not whether a chimp could win a game against a person. It was whether a chimpanzee could learn a circular relationship: A beats B, B beats C, and C beats A. Most things animals learn to rank are linear (bigger beats smaller, more food beats less). Rock Paper Scissors is the simplest well-known example of a loop, which is why it makes a good test. If you want the maths of why that loop matters, see our page on game theory.
How the chimps were trained
Seven chimpanzees of different ages and both sexes sat at a computer touchscreen. The screen showed two hand shapes, and the chimp had to touch the one that wins under the normal rules. A correct choice earned a food reward.
The pairs were taught in stages:
- Paper vs rock (paper wins)
- Rock vs scissors (rock wins)
- Scissors vs paper (scissors wins)
Once each pair was learned, the pairs were mixed together in the same sessions, which is the real test: the chimp now has to remember that paper is the winner in one pair and the loser in another.
What they found
| Result | Detail |
|---|---|
| Chimps that completed training | 5 of 7 |
| Average sessions to complete | About 307 |
| Hardest pair | Scissors vs paper, the third pair, which closes the loop |
| Comparison | Mixed-pair performance similar to 4-year-old children |
The detail I find most interesting is that last pair. The chimps took much longer to learn scissors-beats-paper than the first two relationships. That is the step that turns a straight line into a circle, and it seems to be the genuinely hard part. The researchers read this as difficulty in completing the circular pattern rather than trouble with any single pair.
The children in the comparison group were tested with actual hand gestures rather than a touchscreen, and older children picked the rules up quickly. Four-year-olds were the age group whose performance the chimps matched.
What it does not show
- The chimps were not playing against each other. They were choosing the winning shape from two shown on a screen. There was no bluffing, prediction or strategy, which is what makes the human game interesting (see the psychology of RPS).
- It does not mean chimps "play for fun". The motivation was a food reward.
- It is not a claim that chimps are as smart as children in general. It is one comparison on one kind of rule learning.
Why it matters
Learning a loop rather than a ladder is a building block for more complex reasoning about relationships. Studies like this one help researchers work out which parts of that ability humans share with our closest relatives, and at what age children develop it. Rock Paper Scissors just happens to be a clean, universally understood way to test it.
If you'd like to read more research on the game itself, including how people actually choose their throws, our science of Rock Paper Scissors page collects the studies we have checked. And if you want to test your own grip on the loop, you can play a round against the computer.
FAQ
Did chimpanzees beat humans at Rock Paper Scissors?
No. The chimps never played a match against anyone. They learned which of two shapes wins.
How long did it take the chimps to learn?
The five that completed training needed about 307 sessions on average.
Where was the study published?
In Primates, a Springer journal, in 2017, by researchers at Kyoto University.