A team of Japanese and Chinese scientists has shown chimpanzees are capable of learning the rules of the game rock-paper-scissors, meaning they can grasp circular relationships and recognize extended patterns. The chimps weren’t simply just throwing random hand signals back at their opponent, either. By the end of their training, they were playing at the same level of skill as a 4-year-old human.
The new study published in the journal Primates explains how researchers from Kyoto University in Japan and Peking University in China were able to train the chimpanzees using a computer program.
The chimpanzees sat in a booth with a touchscreen and were shown two hand signals on the screen. Their task was to guess which hand signal was stronger based on the rules of the game. If they were correct, they would be rewarded with a piece of apple and a chime sound. If wrong, only a buzzer would sound.
After an average of 307 teaching sessions, five of the seven chimpanzees were able to guess the correct option over 90 percent of the time, although two of the chimps couldn't quite get the hang of it. While all the rules stayed the same (scissors beats paper, rock beats scissor, paper beats rock), they were taught to indicate the different symbols using hand positions different to the human game.
Learning these intertwining set of rules and recognition of abstract patterns is another demonstration of how smart chimpanzees really are. It's also helping scientists understand how we develop the ability to pick up on complex patterns and problem-solving.
The research team also taught the game to 38 preschool children, ranging in ages three to six, to compare the learning process of chimpanzees with that of humans. The kids learned the game within just five sessions, considerably faster than the chimps. However, while the older children could master the game fairly easily, the 4-year-old kids were about as good at performing the task as the chimps.
“The ability of the chimpanzees to perform the tasks in the random sessions appeared equal to that of children at 4 years of age, which is the critical time point for developing the ability to solve loop problems using configural methods,” the authors write in the study.
"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," lead researcher Jie Gao added in a statement. "The chimpanzees' performance during the mixed-pair sessions was similar to that of four-year-old children."
