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Sana Inoue and Tetsuro Matsuzawa of Kyoto University showed a
computer screen grid of nine numbers to six chimpanzees. The chimps
were previously trained to recognize the ascending nature of the
numbers. They were also shown to nine college students. When
subjects touched one of the numbers, all of the others vanished.
They then had to touch the squares in the order of the numbers that
used to be there.
When the numbers flashed for just four-tenths of a second or less,
one of the chimps beat all of the college students.
Here's the press release from 'Current Biology', a publication
of Cell Press:
Young chimps top adult humans in numerical
memory
Young chimpanzees have an “extraordinary” ability to
remember numerals that is superior to that of human adults,
researchers report in the December 4th issue of Current Biology, a
publication of Cell Press.
“There are still many people,
including many biologists, who believe that humans are superior to
chimpanzees in all cognitive functions,” said Tetsuro
Matsuzawa of Kyoto University. “No one can imagine that
chimpanzees—young chimpanzees at the age of five—have a
better performance in a memory task than humans. Here we show for
the first time that young chimpanzees have an extraordinary working
memory capability for numerical recollection—better than that
of human adults tested in the same apparatus, following the same
procedure.”
Chimpanzee memory has been extensively
studied, the researchers said. The general assumption is that, as
with many other cognitive functions, it is inferior to that of
humans. However, some data have suggested that, in some
circumstances, chimpanzee memory may indeed be superior to human
memory.
In the current study, the researchers
tested three pairs of mother and infant chimpanzees (all of which
had already learned the ascending order of Arabic numerals from 1
to 9) against university students in a memory task of numerals. One
of the mothers, named Ai, was the first chimpanzee who learned to
use Arabic numerals to label sets of real-life objects with the
appropriate number.
In the new test, the chimps or humans were
briefly presented with various numerals from 1 to 9 on a
touch-screen monitor. Those numbers were then replaced with blank
squares, and the test subject had to remember which numeral
appeared in which location and touch the squares in the appropriate
order.
The young chimpanzees could grasp many
numerals at a glance, with no change in performance as the hold
duration—the amount of time that the numbers remained on the
screen—was varied, the researchers found. In general, the
performance of the three young chimpanzees was better than that of
their mothers. Likewise, adult humans were slower than all of the
three young chimpanzees in their response. For human subjects, they
showed that the percentage of correct trials also declined as a
function of the hold duration—the shorter the duration
became, the worse their accuracy was.
Matsuzawa said the chimps’ memory
ability is reminiscent of “eidetic imagery,” a special
ability to retain a detailed and accurate image of a complex scene
or pattern. Such a “photographic memory” is known to be
present in some normal human children, and then the ability
declines with the age, he added.
The researchers said they believe that the
young chimps’ newfound ability to top humans in the numerical
memory task is “just a part of the very flexible intelligence
of young chimpanzees.”
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The researchers include Sana Inoue and
Tetsuro Matsuzawa, of Kyoto University, Japan.
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