Ayumu, the Chimpanzee: Background information when reading Animal Wise

Ayumu, the Chimpanzee

This article relates to Animal Wise

In Virginia Morell's Animal Wise, the reader learns many surprising things about a chimpanzee's skills. The book features one chimpanzee in Japan, Ayumu, who was has been extremely successful at sequence-memory tests. Ayumu lives with his mother Ai at the University of Kyoto's Primate Research Institute, headed by Professor Tetsuro Matsuzawa. In a test, the chimpanzee was shown a randomly distributed sequence of numerals over milliseconds, a blink of an eye, on a touchscreen. Then the numbers were hidden behind white blocks and Ayumu was expected to remember the location of the numerals and touch the white blocks in the correct ascending order. As the video of the experiment below, shows, the quickness and precision of Ayumu's responses were extremely impressive.

This same experiment has been conducted numerous times on Ayumu, his mom and on human subjects. As part of the study, the time between when the subject is shown the numbers, and then covered up, was changed. The results were then been tallied. In the case of Ai and the human subjects, if the time spent viewing the numbers was decreased, the corresponding memory recall also dropped off steeply. This was found to be not the case with Ayumu who has shown that he can recall up to nine numbers in the right sequence even when shown these nine numbers for only 210 milliseconds (that's less than the blink of an eye).

Understandably, the video showing Ayumu doing his experiment became wildly popular and even lead scientists to conclude that chimpanzees' working memory might be more powerful than humans'.

The experiment has been quite controversial however. Apparently Ayumu had had significant hours of practice before the test whereas the human subjects had not. What's more when humans were allowed to practice even a little bit, they scored equally well. In the book, Morell calls the Ayumu study puzzling to academia but she does not review the associated controversy in depth.

Controversies aside, what factors explain Ayumu's fantastic memory recall? Professor Matsuzawa has said that it can be attributed to something called "eidetic" memory. The chimpanzees seem to use this eidetic or photographic memory to take mental images, like snapshots, of the surrounding world. Of course if all chimpanzees have eidetic memory, it does not explain why only Ayumu and not his mother, Ai, could perform astoundingly well at the experiment.

Chimps are also thought to be better at a skill called subitizing. This is a method that helps you figure out in one glance how many of a specific object there are in a bunch of different items. Say you had a grouping of five bananas, four apples and three oranges. In one visual scan, humans can tell there are five bananas. It is speculated that the upper limit for humans is five, whereas chimpanzees can subitize groups of even six or more. Finally some have suggested that Ayumu might have a form of synesthesia in which numbers and letters come across as colored. So he might be punching a sequence of specific colors instead of what looks like a random bunch of white digits. These theories might explain why Ayumu can quickly do visual scans and produce remarkable results.

Filed under Nature and the Environment

This "beyond the book article" relates to Animal Wise. It originally ran in April 2013 and has been updated for the March 2014 paperback edition. Go to magazine.