Chimpanzee Memory

At the Primate Research Institute in Japan, Ai is a chimpanzee in her thirties who has been involved in cognition research for decades. She’s well-known for learning to use our familiar numerals (1, 2, 3…) to appropriately label sets of objects (5 bananas, etc.), and she’s done some other really cool things with numerals and numbers.

What I didn’t know until recently is that she has a son, Ayumu, and he too is becoming quite the research superstar. A recent study demonstrated his talent for remembering an array of randomly mixed numerals on a computer screen, after they were very briefly flashed to him and then masked by white boxes. He had to touch each of the hidden numerals in order without a single mistake in order for a trial to be considered a success. This seems to show a pretty impressive working memory for visuo-spatial layouts, but does that mean Ayumu has something like eidetic memory (“photographic memory”)?

I don’t have the full article. However, previous studies with other chimps (including Biro and Matsuzawa’s 1999 study with his mother Ai) have shown that they “queue up” action sequences in a task like this, such that if the targets change/move in the middle of a trial, their fingers still briefly travel toward where the right answer would have been. Perhaps this is a demonstration of a pre-planned motor sequence, rather than anything like photographic memory.

One way to test this might be to remove one or more of the number locations completely (including the white box masking where it originally was flashed). If the chimp has a photograph-like visual of the layout in memory, then he should be able to continue the sequence by skipping over the missing numeral. But if he has pre-planned his actions in advance (as mother Ai did for a set of 3, 4 or 5 numerals), then his finger should still move to where the missing numeral disappeared.

Either way, if the task sounds easy, try it for yourself. (even with only 5 numerals, it’s pretty tough at first). The study compared college students’ performance to that of Ayumu, and the chimp won. Note that without access to the paper, it’s hard to know if the setup was truly the same. Ayumu almost certainly had a lot more practice than the college students (but then this is necessary to teach him what the task is, whereas humans can have instructions explained to them). Also, Ayumu’s numerals aren’t masked until he touches the first one (usually very quickly), but the college students’ might have been masked immediately after flashing (as the website demo with fewer numerals does).

At any rate, the experiment is a very impressive demonstration of a larger memory span than has been seen before in a setup like this. However that information is stored, it’s cool that he can do it.

[Thanks to for the game link]

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