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Primate Research Institute, Kyoto University
Biro / Poster
The concept of number in the chimpanzee (Pan troglodytes): The introduction of "Zero"
Dora Biro and Tetsuro Matsuzawa, Department of Zoology, University of Oxford and Primate Research Institute Kyoto University
A number of studies have demonstrated numerical competence in
non-human subjects, including rats, pigeons, monkeys, and a parrot. Chimpanzees (Pan
troglodytes) have a long history as participants in such studies, past experiments
having revealed a variety of counting and other numerical abilities long considered unique
to humans. Here we report the introduction of "zero" in three different
numerical tasks, with special emphasis on the distinct phases of acquisition that became
apparent. Our subject was a 21-year-old female chimpanzee, named Ai, with prior training
in a variety of symbolic tasks, including the recognition and productive as well as
receptive use of Arabic numerals 1-9 as applied to everyday objects and computer-generated
stimuli (Matsuzawa, 1985; Murofushi, 1997; Biro & Matsuzawa, 1999). "Zero"
was introduced in the following three tasks. (1) Productive use: subject was required to
label a collection of white dots appearing on a computer screen by selecting, from among a
set of alternatives, the numeral corresponding to the total number of dots. (2) Receptive
use: subject was required to select a set of white dots whose total corresponded to a
sample numeral appearing on screen. (3) Ordering: subject was required to select numerals
presented to her on a computer screen in an ascending order.
Matsuzawa, T. (1985, May 2-8). Use of numbers by a chimpanzee. Nature, 315, 57-59.