If you keep losing at rock paper scissors, here’s a depressing tidbit: chimps, regardless of age and sex, have shown that they can learn and play the game.

It’s not the most complicated game out there, I’ll agree, but it’s still pretty impressive! The team, led by Jie Gao of Kyoto University in Japan and Peking University in China, report that although it might take them a bit longer than it would a human, chimps are perfectly capable of mastering the game up to a young child’s level.

Rock paper scissor chimp

Gao’s team set out to find whether chimpanzees (Pan troglodytes) have the ability to notice and understand extended patterns. Rock-paper-scissors is a really good way to see if they can: the rules are pretty simple and constant but become non-linear during play, meaning the chimps have to understand the rules and how pairings of two signs function in order to play.

Circular (non-linear) relationships are a bit more difficult to grapple with than your regular, run of the mill linear relationships. In the latter, the state of an initial object A will dictate the outcome of object B. But in a circular relationship, the state of A dictates the outcome of B, which in turn changes A. They’re harder to work with because a brain would need to keep constant tabs on the objects involved in the relationship to be able to predict an outcome.

Successfully doing so with rock-paper-scissors would suggest that chimps’ brains can process and understand the relationship network formed between the signs, update what they already know, and solve problems. Which would mean that they’re pretty smart as far as animals go. Smarter than believed up to now, despite proving themselves to be pretty smart in the past.

For the trials, the team worked with seven chimpanzees from the Primate Research Institute at Kyoto University, of both sexes and different ages. Through a computer touchscreen, they were trained to pick the strongest of two options they were presented with. First, the team thought them the rock-paper pairing, then rock-scissors, and finally scissors-paper. After the chimps showed that they understand how the pairs fit together, all pairings were randomly displayed on the screen for them to pick. Five of the seven chimps completed the training, each with about 307 sessions under his or her belt.

The results showed that the chimps were able to learn the circular pattern that the game is based on. However, it took them significantly longer to learn the third (scissor-paper) pair than the others — suggesting that they had trouble re-learning what they were thought about the two signs previously, i.e. that they had some difficulty actually closing the loop on the game’s circular relationship.

As a control, the team then thought the game to 38 preschool children (aged three to six) in order to compare how fast the two groups learned. The kids had a breeze grasping the game, and needed an average of only five sessions to do so. Performance varied quite a lot by age, however. The team notes that children under 50 months (about four years) tended to play the game more with luck rather than skill. The older the child, however, the more accurate his or her response when randomly presented with all three pairs.

“This suggests that children acquire the ability to learn a circular relationship and to solve a transverse patterning problem around the age of four years,” says Gao.

“The chimpanzees’ performance during the mixed-pair sessions was similar to that of four-year-old children.”

Gao hopes the findings will inspire future studies into how age and sex influence the ability of members of various species to learn circular relationships.

The paper “Learning the rules of the rock–paper–scissors game: chimpanzees versus children” has been published in the journal Primates.

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