Ayumu - A Chimpanzee with Incredible Memory

Ayumu, is an 11-year-old chimpanzee who lives and trains at Kyoto University's Primate Research Institute. In his time there, Ayumu has come to excel at an incredibly difficult — albeit very straightforward — memorization game. If you challenge him to this game, you will lose.

The video below demonstrates Ayumu doing what he does best: a straightforward working-memory challenge. Cognitive psychologists use the term "working memory" to describe the mind's ability to temporarily store and manipulate information. In this case, that information is the position of arabic numerals on a touch-sensitive screen. Ayumu is shown the numbers 1—9 on the computer screen, and given just a fraction of a second to commit their randomized location to memory. Once that fraction of a second is up, the numbers are covered with white squares, at which point Ayumu must select them in numerical order.

Ayumu not only outperformed all the other test subjects, his performance remained more or less consistent for all three time durations. But there's something you should know about these results. In this experiment, Ayumu, his mother, and the university students were only asked to recall the position of five numerals.

How does Ayumu do this?  There are a couple of ideas. The first points to a poorly understood (and poorly defined), controversial phenomenon known as "eidetic imagery," which is characterized by the ability to commit to memory an accurate image of a complex scene or pattern.

Some researchers, most notably psychologist Ralph Norman Haber, believe eidetic imagery may occur in as many as 15 percent of children under 12, but that the ability fades over time, and only rarely presents itself in adults. In the 2007 study examining Ayumu's task performance, lead researcher Tetsuro Matsuzawa claims that Ayumu's working memory capabilities — which were superior to those of adult humans as well as an adult chimp — fit well with what is known about eidetic imagery abilities in humans.

The other explanation boils down to a skill known as subitizing. Subitizing is the ability to glimpse a small number of items and instantly know how many are present. This skill is very different from "enumerating," whereby you determine how many items there are by counting them individually. Generally speaking, humans are capable of subitizing groupings of about four or five items; any more and we fall back on enumerating.

So why do chimpanzees have this ability and human's don't? A common explanation is known as the trade-off hypothesis. Matsuzawa and his colleagues describes the concept in The Mind of the Chimpanzee: Ecological and Experimental Perspectives:

The common ancestor of humans and chimpanzees may have possessed an extraordinary memory capability, much like that exhibited by Ayumu. At a certain point in evolution, because of limitations on brain capacity, the human brain may have acquired new functions in parallel with losing others — such as acquiring language while losing the visuospatial temporal storage ability demonstrated [by Ayumu].

Try the test for yourself: http://games.lumosity.com/chimp.html

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