SETI bioastro: Numbers and Counting in a Chimpanzee

From: Larry Klaes (
Date: Tue Apr 25 2000 - 08:01:24 PDT

Cognitive Science:

Numbers and Counting in a Chimpanzee

A chimpanzee that has learned to use Arabic numerals to represent
numbers of items, and that can count from 0 to 9 items, is now
shown to remember the correct sequence of any 5 numbers selected
from the range 0 to 9.



In this context, let us define "animals" as all living multi-
cellular creatures other than humans that are not plants. In
recent decades it has become apparent that the cognitive skills
of many animals, especially non-human primates, are greater than
previously suspected. Part of the problem in research on
cognition in animals has been the intrinsic difficulty in
communicating with or testing animals, a difficulty that makes
the outcome of a cognitive experiment heavily dependent on the
ingenuity of the experimental approach. Another problem is that
when investigating the non-human primates, the animals whose
cognitive skills are closest to that of humans, one cannot do
experiments on large populations because such populations either
do not exist or are prohibitively expensive to maintain. The
result is that in the area of primate cognitive research reported
experiments are often "anecdotal", i.e., experiments involving
only a few or even a single animal subject. But anecdotal
evidence can often be of great significance and have startling
implications: a report, even in a single animal, of important
abstract abilities, numeric or conceptual, is worthy of
attention, if only because it may destroy old myths and point to
new directions in methodology. In 1985, T. Matsuzawa reported
experiments with a female chimpanzee that had learned to use
Arabic numerals to represent numbers of items. This animal (which
is still alive and whose name is "Ai") can count from 0 to 9
items, which she demonstrates by touching the appropriate number
on a touch-sensitive monitor. Ai can also order the numbers from
0 to 9 in sequence.

... ... N. Kawai and T. Matsuzawa (Primate Research Institute
Kyoto, JP) now report an investigation of Ai's memory span by
testing her skill in numerical tasks, the authors making the
following points:

     1) The authors point out that humans can easily memorize
strings of codes such as phone numbers and postal codes if they
consist of up to 7 items, but above this number of items, humans
find memorization more difficult. This "magic number 7" effect,
as it is known in human information processing, represents an
apparent limit for the number of items that can be handled
simultaneously by the human brain.

     2) The authors report that the chimpanzee Ai can remember
the correct sequence of any 5 numbers selected from the range 0
to 9.

     3) The authors relate that in one testing session, after
choosing the first correct number in a sequence (all other
numbers still masked), "a fight broke out among a group of
chimpanzees outside the room, accompanied by loud screaming. Ai
abandoned her task and paid attention to the fight for about 20
seconds, after which she returned to the screen and completed the
trial without error."

     4) The authors conclude: "Ai's performance shows that
chimpanzees can remember the sequence of at least 5 numbers, the
same as (or even more than) preschool children. Our study and
others demonstrate the rudimentary form of numerical competence
in non-human primates."

N. Kawai and T. Matsuzawa: Numerical memory span in a chimpanzee.
(Nature 6 Jan 2000 403:39)

QY: Tetsuro Matzuzawa []

Summary by SCIENCE-WEEK 21Apr00

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