December 4, 2007
Observatory
Chimps Exhibit Superior Memory, Outshining Humans
By HENRY FOUNTAIN

Spend even a little time around chimpanzees, and you begin to realize how intelligent they are. But can they outshine humans in brain power? Most humans would scoff at that.

But researchers have shown that young chimps outperform adult humans in a memory test, a Concentration-like game using numerals on a computer screen.

“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.

As Ai demonstrates, adult chimps lose the ability, too. Dr. Matsuzawa suggested that as the chimps age, their memory capability is otherwise occupied.