Study: Primates’ understanding of quantities offers clues to the origins of human counting

Monkey see, monkey count—almost. New research from the University of Rochester shows that while monkeys don’t have words or symbols for numbers like we do, they do understand the basic logic behind counting—and that can show us how humans first learned to count.

The skills that monkeys and other nonhuman animals demonstrate when comparing two different quantities are similar to those of infants and young children. Monkeys and babies alike are able to understand, for example, that if you add three objects to a quantity of four objects, you do not end up with two objects. However, the monkeys in this study showed more than a basic understanding of quantities: they could also keep track of item-by-item changes in quantity. 

“Without a symbol system, monkeys can’t actually count like humans can, but our study shows that they do possess a counting-like logic that resembles humans',” says Jessica Cantlon, lead author on the study and assistant professor in the brain and cognitive sciences at the University of Rochester. “The fact that we see this proto-counting logic in primates shows that it predated counting in evolutionary history, and perhaps it was a critical piece of cognition for the human invention of counting.”

The monkeys in this study watched researchers drop pieces of food into opaque cylinders. The monkeys then chose which cylinder of food they wanted. They chose the larger quantity of food most of the time, showing that they were able to keep track of how much food was dropped into each cylinder as it happened—a basic logic behind human counting.

The paper, titled “The Origins of Counting Algorithms,” was published May 7, 2015, in the journal Psychological Science. It was co-authored by Steven T. Piantadosi, Stephen Ferrigno, Kelly D. Hughes and Allison M. Barnard. 

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