Chimps Have Better Memories than Humans

My commentary is below the story.

by Yomiuri Shimbun
KYOTO (AP)

Young chimpanzees scored better results than humans in a memory recall test, according to a group of researchers at Kyoto University's Primate Research Institute.

The test involved recalling the locations of groups of numbers flashed onto a computer screen.

The researchers led by Tetsuro Matsuzawa also found that young chimps performed better than mature chimps. Matsuzawa speculated that humans might have lost this kind of short-term memory recall to make room for other information--such as language--as a result of evolutionary processes or aging. The results of the research appear in the journal Current Biology.

Before the test, three pairs of 4-year-old chimps and their mothers were trained to recognize the sequence of numbers from one to nine on a computer display over a period of six months. When the young chimps reached the age of 5-1/2, they were introduced to a computer touch-screen upon which randomly located numbers flashed up once before being hidden. The task for the examinees was to point at the hidden numbers in ascending order from smallest to largest.

Ayumu, a male chimpanzee, was the most successful performer, correctly locating all nine numbers, which were flashed onto the computer screen for 0.7 second. Nine university students who were pitted against the chimps failed to locate the numbers correctly.

In another test, five numbers were flashed onto the computer screen for 0.65 second. Young chimps and students scored similarly with about 80 percent. The chimps' mothers registered about 50 percent.

But when the numbers were displayed for only 0.21 seconds, which is not enough time for the eyes to scan the screen for the scattered numbers, the percentage of correct answers for the young chimps remained at about 80 percent, while that for the students halved to 40 percent. The percentage for the older chimps dropped sharply to 20 percent.

Regarding the degradation of this kind of memory, Matsuzawa said: "The brain's capacity is limited. To obtain new abilities, it might be necessary to give up old ones."

******* A primate psychologist's perspective *******

I have not yet read the research article, so my thoughts are off the cuff. First off, Tetsuro Matsuzawa has been training chimps at the ape lab in Kyoto for a long time. He's got a lot of practice getting them to hunt and peck numbers and other symbols on a touch-sensitive monitor.

The work is interesting, but I think it's important to reiterate that this research is about the capacity of short-term memory rather than numerical competence. These chimps are not counting; they probably do not know that the symbol "9" means nine items, such as pieces of candy or grapes they are accustomed to getting during training.

The capacity of short-term perceptually based memory in humans is about 7-9 items, so the chimps are performing at a level we'd expect from humans. One reason why they score better than people on the test is that the chimps might just be more familiar with the procedure and equipment. They've had 6 months to practice whereas the human participants in this experiment might not have had much more than a few minutes to figure it out.

As far as the conclusions the APA writer attributes to Matsuzawa, that he "speculated that humans might have lost this kind of short-term memory recall to make room for other information--such as language--as a result of evolutionary processes or aging," that sounds plausible on the surface, but I'd have to see the methodology of the research to be convinced there's something there.

As soon as I read the research article, I'll be back with more in depth comments on the methodology. Until then I'll just have to grump one more time about Why it is that news stories gloss over the methods. Oh yeah, that's right - it's because journalists don't learn how to do science in "J school" so they don't realize the methods are actually the most important element of the research they report. Grrr.