Chimpanzees are human's closest relatives.
Chimpanzees are human’s closest relatives. USAID Africa Bureau/Public Domain

Rock-paper-scissors is a useful tool for deciding who has to do the dishes or which sports team goes first. But the game is also great for testing chimpanzees’ learning abilities. A new study shows chimps can eventually figure out the circular rules—rock beats scissors, scissors beat paper, and paper beats rock—and children can easily pick up the rules starting around age four.

A team of researchers from Kyoto University used a computer program to teach seven chimpanzees and 38 young children how to play rock-paper-scissors, while also tracking how long it took them all to learn the circular rules of the game. The computer introduced the chimps to the rules step-by-step, and while they grasped the first two, it took five of the chimps about 307 computer trials to understand the third rule and the circular connection between all the rules (two of the chimps never quite got it). Interestingly, the report authors note, rats and pigeons also had a hard time learning the third relationship for similar tasks in other studies.

The human children, on the other hand, figured out the three relationships in about six tries, on average. After the kids were taught the rules, they were given the relationships at random and asked which hand gesture won. Kids older than 50 months (just over age four) remembered the relationships and did better than chance, while younger kids were just randomly guessing. And when the chimps were given the relationships at random, they performed just as well as a human four-year-old.