Alex, an African grey parrot who died 5 years ago and was known for his ability to use English words, also understood a great deal about numbers. In a new
study in this month's Cognition, scientists show that
Alex correctly inferred the relationship between cardinal and ordinal numbers, an ability that has not previously been found in any species other than humans. After learning the cardinal numbers—or exact values—of one to six,
Alex was taught the ordinal values (the position of a number in a list) of seven and eight—that is, he learned that six is less than seven, and seven is
less than eight. He was never taught the cardinal values of seven and eight—but when tested on this, he passed with flying colors, apparently inferring,
for instance, that the sound "seven" meant six plus one. In the video above of one of these experiments, comparative psychologist Irene Pepperberg of
Harvard University asks Alex to pick out the set of colored blocks that equal the number seven. Play the video to hear his answer.
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