Researchers at the Primate Research Institute at Kyoto University claim young chimpanzees score better in a numeral memory test than adult humans:
“We were very surprised to find this,” Tetsuro Matsuzawa of the Primate Research Institute at Kyoto University said. “But it’s a very concrete, simple fact. Young chimps are superior to human adults in a memory task.”
Dr. Matsuzawa and a colleague, Sana Inoue, first trained chimps to recognize the numerals 1 through 9 in sequence. Ai, the first chimp trained, an adult female was found with a memory capability equal to that of adult humans.
When the researchers went to see if there was a difference with chimps younger than 6, the animals had a touch screen where scattered numerals appeared for up to two-thirds of a second and were then masked by white squares. With the shortest exposure time, about a fifth of a second, the chimps had an 80 percent accuracy rate, compared with adult humans’ 40 percent. The findings are described in Current Biology.
Dr. Matsuzawa said the ability reminded him of the phenomenon called eidetic imagery, in which a person memorizes details of a complex scene at a glance. This so-called photographic memory is present in a very small number of children, and is often associated with autism.
Dr. Matsuzawa speculated that perhaps somewhere back in common evolution, humans and chimps had this ability. But humans lost it because they gained something else, communicating through a complex language.