Chimpanzees can learn the rules of the rock, paper, scissors game through training, matching the intellectual ability of children 4 years old or older, researchers at Kyoto University have found.

In a study that could shed light on the evolution of intellectual abilities in animals, a team of researchers led by Tetsuro Matsuzawa at the university’s Primate Research Institute in Aichi Prefecture let seven chimpanzees kept at the institute play the game. The chimpanzees were shown pairs of the three tools on a computer screen and asked to choose the stronger tool in each pair.

When they picked the right answer, such as the paper in the paper-rock pair or rock in the rock-scissors pair, they were given an apple as a reward. The results showed that five of the chimpanzees mastered the game in about 100 days, the researchers said.

The team then tested the game among 38 children aged 2 to 5, investigating at which age they mastered it.

The results showed that children 4 or older learned the game, suggesting the task requires an intellectual ability present in children that age.

The study also showed that chimpanzees learned the rules about the first two pairs presented relatively easily — that rock beats scissors and that scissors beat paper, for example — but had a difficulty learning the “circular rule” of paper beating rock. Such tendency was not found among children, the researchers said.

The study was published Thursday in the online edition of the journal Primates.

“(The chimpanzees) experienced difficulties finalizing the circularity,” the researchers wrote in the paper. “In contrast, children had little difficulty and required the same number of trials to complete all three pairs of tasks.”

They concluded that further studies should examine how age and sex influence the ability of members of various species to learn circular relationships, as well as reasons for chimpanzees’ difficulties in learning such relationships.

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