Neurobiologist Margaret Livingstone of Harvard Medical School and her colleagues taught three rhesus macaques numbers zero through nine and letters with values zero through 25.
When given a choice between two symbols the monkeys generally chose the larger number. They were then given more drops of water, juice, or soda as a reward.
Researchers then wanted to know if monkeys could add numbers. The monkeys then were given a choice between a sum and a symbol. Science Mag reports that within four months the monkeys learned how it worked and were able to add the two symbols and compare that number to a single symbol.
