Chimp beats humans at photographic memory task

Blogging on Peer-Reviewed Research

Researchers from Kyoto University’s Primate Research Institute report that a young chimp can out-perform university students on a working memory task. (Cognitive psychologists use the term working memory to refer to the temporary storage and manipulation of information.)

The researchers developed a memory test called the limited-hold memory task in order to compare the working memory of their chimps with that of humans. In the task, numbers are displayed on a screen for fractions of a second, before being covered by white squares. The subject is then required to touch the squares in correct numerical order.

In this test, the human subjects – 9 university students – performed progressively worse, as the period of time for which the numerals are displayed decreases from 600 to 210 milliseconds. This is to be expected, as 210 ms is about the frequency of saccadic eye movements; humans cannot scan the screen quickly enough to see all the numbers being displayed.

This was also observed in Ai, a chimp who the researchers had trained, more than 20 years ago, to use numerals to indicate the number of objects beign displayed. Another chimp, however, a 7-year-old named Ayumu, performed consistently well throught the task. The film clip below shows Ayumu performing the task; you can do the task at the same time while watching it, and compare your performance with his.


This study shows that chimps can memorize at a glance the numerals presented on the screen, and that they can do so just as well – and even better – than humans can. Note that the superior performance came from a young chimp, and that the performance of older chimps on the same task was more similar to that of humans.

Now, the Japanese group woud like to determine how long the chimps’ memory trace of the numerals lasts. In one trial, Ayumu was distracted from the task for about 10 seconds, and yet could still recall the numbers on the screen in the correct order.

The researchers believe that their subjects – both chimp and human – used edietic imagery in the task at hand. Also known as photographic memory, this involves generating an accurate mental “snapshot” of a complex scene – in this case, the positions of numerals on a screen – and retaining it for long enough for recall.

They further suggest that humans lost their ability for accurate eidetic imagery during the course of their evolution, such that the brain could accomodate other complex processes such as language. 

Reference:

Inoue, S. & Matsuzawa, T. (2007). Working memory of numerals in chimpanzees. Curr. Biol. 17: R1004-R1005. [Abstract]

8 thoughts on “Chimp beats humans at photographic memory task

  1. Hi Mo,
    There’s a question that occurred to me when I read about this research, and probably you’re in a better position to answer it than others.
    The chimps were apparently taught to recognize the numerals as parts of a sequence, but not as having specific values associated with a given quantity. Obviously, the humans do associate numbers with known quantities.
    So, is any of the time “lost” by the humans due to their processing the numerals as “known values” rather than just as images that are parts of a series?
    While I also think that age is probably a factor, wouldn’t it be better to teach both chimps and humans a series of symbols which have no other associations in order to make valid comparisons?

  2. They’re way, WAY out of line in their conclusions. It’s well-known that young human children have very good iconic memories. Comparing young chimps with adult humans is introducing a confounding factor: age. Or more precisely, maturity or the lack thereof.
    Comparing young chimps with young humans would be MUCH more appropriate.

  3. exactly! For a human college student (um, as opp to a chimp college student) seeing a number would invoke a whole series of language and visual processes that would be perhaps at the cost of eidetic memory, for this experiment and in general human functioning over time (like evolutionary time) It’s the maybe human characteristic of meaning-making vs strictly sensory processing. I’ve seen lots of stuff lately about synethesia, but it’s been a long time since I’ve seen eidetic memory in the headlines. I wonder what fMRIs of the chimps v students would look like as they do this task?

  4. having associations for numbers is plus – it makes it easier to understand symbol and therefore easier to remember (new things are harder to remember, because they need to be processed/analyzed/categorized/understood first)
    also, humans dont get reward, no wonder they perform worse🙂

  5. What I find interesting is how relaxed the chimp seems to be while performing the test. Human subjects give these sorts of tests more focused attention than munching on/dropping sweets. He barely seems to be paying attention at all.

  6. They’re way, WAY out of line in their conclusions. It’s well-known that young human children have very good iconic memories. Comparing young chimps with adult humans is introducing a confounding factor: age. Or more precisely, maturity or the lack thereof.
    Comparing young chimps with young humans would be MUCH more appropriate.
    Posted by: Caledonian | December 3, 2007 10:39 PM
    This was my guess too. Although another factor might be that humans could have neural pathways developed from other parts of the brain that automatically kick in and cause my processing, ( and time), because we are by nature curious in a more deep and profound way than chimps.
    Dave Briggs :~)

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