Smirnova, A. A., Lazareva, O. F., & Zorina, Z. A. (2000).
Use of number by crows: Investigation by matching and oddity learning.
Journal of the Experimental Analysis of Behavior,
73, 163-176.
Hooded crows were trained in two-alternative simultaneous
matching and oddity tasks with stimulus sets of three different
categories: color (black and white), shape (Arabic Numerals 1 and
2, which were used as visual shapes only), and number of elements
(arrays of one and two items). These three sets were used for
training successively and repeatedly; the stimulus set was
changed to the next one after the criterion (80% correct or
better over 30 consecutive trials) was reached with the previous
one. Training was continued until the criterion could be reached
within the first 30 to 50 trials for each of the three training
sets. During partial transfer tests, familiar stimuli (numerals
and arrays in the range from 1 to 2) were paired with novel ones
(numerals and arrays in the range from 3 to 4). At the final
stage of testing only novel stimuli were presented (numerals and
arrays in the range from 5 to 8). Four of 6 birds were able to
transfer in these tests, and their performance was significantly
above chance. Moreover, performance of the birds on the array
stimuli did not differ from their performance on the color or
shape stimuli. They were capable of recognizing the number of
elements in arrays and comparing the stimuli by this attribute.
It was concluded that crows were able to apply the matching (or
oddity) concept to stimuli of numerical category.
Key words: numerical competence, concept formation, matching to
sample, oddity from sample, crows