Matsuzawa, a pioneer in studying the mental abilities of chimps, said even he was surprised. He and colleague Sana Inoue report the results in Tuesday's issue of the journal Current Biology.
One memory test included three 5-year-old chimps who'd been taught the order of Arabic numerals 1 through 9, and a dozen human volunteers.
They saw nine numbers displayed on a computer screen. When they touched the first number, the other eight turned into white squares. The test was to touch all these squares in the order of the numbers that used to be there.
Results showed that the chimps, while no more accurate than the people, could do this faster.
One chimp, Ayumu, did the best. Researchers included him and nine college students in a second test.
This time, five numbers flashed on the screen only briefly before they were replaced by white squares. The challenge, again, was to touch these squares in the proper sequence.
When the numbers were displayed for about seven-tenths of a second, Ayumu and the college students were both able to do this correctly about 80 percent of the time.
But when the numbers were displayed for just four-tenths or two-tenths of a second, the chimp was the champ. The briefer of those times is too short to allow a look around the screen, and in those tests Ayumu still scored about 80 percent, while humans plunged to 40 percent.