The long-held belief that man is superior among all species in all cognitive functions has been challenged by a new research, which has found that young chimpanzees can do much better in memory tests than humans.

The research conducted by Japanese scientists says that young chimpanzees have an extraordinary ability to remember numerals and recall them much better than human adults.

"There are still many people, including many biologists, who believe that humans are superior to chimpanzees in all cognitive functions," Tetsuro Matsuzawa of Kyoto University said.

The results of the research published in the latest issue of Current Biology says, "No one can imagine that chimpanzees, young chimpanzees at the age of five, have a better performance in a memory test than humans."

"Here we show for the first time that young chimpanzees have an extraordinary working memory capability for numerical recollection better than that of human adults tested in the same apparatus, following the same procedure," the research said.

One of the mothers, named Ai, was the first chimpanzee who learned to use Arabic numerals to label sets of real-life objects with the appropriate number.

In the new test, the chimps or humans were briefly presented with various numerals from 1 to 9 on a touch-screen monitor.

Those numbers were then replaced with blank squares, and the test subject had to remember which numeral appeared in which location and touch the squares in the appropriate order.

The young chimpanzees could grasp many numerals at a glance, with no change in performance even when the numbers were flashed for just 210 milliseconds, roughly twice as long as a blink of an eye and not enough time for human vision to wander across a screen, the research found.

In general, the performance of the three young chimpanzees was better than that of their mothers. Likewise, adult humans were slower than all of the three young chimpanzees in their response, it said.

For human subjects, they showed that the percentage of correct trials also declined as a function of the hold duration worse their accuracy was.

Matsuzawa said the chimps' "special ability" to retain a detailed and accurate image of a complex scene or pattern.

"Such a photographic memory is known to be present in some normal human children, and then the ability declines with the age," he said.

The researches said they believe that the young chimps' newfound ability to top humans in the numerical memory tasks is "just a part of the very flexible intelligence of young chimpanzees."