Young chimpanzees were able to outperform university students in short-term memory tests, a team of Japanese researchers reported Monday.

Scientists from the Primate Research Institute at Kyoto University taught three five-year-old chimpanzees and their mothers the sequence of the numbers one through nine, then matched them up against human adults in two short-term memory tests. In both cases, the chimps won.

Five-year old chimpanzee Ayumu beat university students at a short-term memory test.
(Current Biology)

"Our study shows that young chimpanzees have an extraordinary working memory capability for numerical recollection, better than that of human adults," reported Tetsuro Matsuzawa and Sana Inoue in the Dec. 4 issue of the journal Current Biology.  

Matsuzawa said the findings challenged the assumption of many scientists that "humans are superior to chimpanzees in all cognitive functions."

"No one can imagine that chimpanzees — young chimpanzees at the age of five — have a better performance in a memory task than humans," he said in a statement.

Using a touch-screen monitor, the pair began teaching the chimps numbers at the age of four. When the chimps turned five, they introduced the memory tests.

In the first test, the chimps faced off against a dozen human volunteers in a race to order the numbers one through nine based on memory, as the numbers were replaced with white squares when the first number was touched.

The chimps, while not any more accurate than the humans, were faster.

The second test took the fastest and most accurate chimp, Ayumu, and matched him up against nine university students. Again, the challenge was to put the numbers in order, but in this test the numbers flashed for a limited time, ranging from 210 to 650 milliseconds, then were replaced by white squares.

When the numbers were displayed for about seven-tenths of a second, the chimp and the college students had comparable success rates at about 80 per cent. When the display time was shorter, Ayumu trounced the students. The chimp maintained his 80 per cent success rate, while the students were only able to complete the task about 40 per cent of the time.

"The limited-hold memory task provided a means of performing an objective comparison between the two species under exactly identical conditions," the report explained. "Our present study shows that young chimpanzees can quickly grasp many numerals at a glance, with no decline in performance as the hold duration is varied."

The chimp's edge may have come from his youth, the researchers said. They linked Ayumu's ability to memorize complex patterns to a comparable phenomenon in human children, called eidetic imagery. The ability is known to decline with age in humans, which may also be the case with chimps, as the five-year-olds outperformed their mothers.

Matsuzawa said the chimps may also have had more success at the memory tests because human ancestors lost much of the ability to memorize at a glance in order to make room for language skills.

With files from the Associated Press