For the past several years, Jessica Cantlon has been working to understand how humans develop the concept of numbers, from simple counting to complex mathematical reasoning. Early in her career at the University of Rochester, the assistant professor of brain and cognitive sciences began studying primates in her search for the origins of numeric understanding.
In 2013, she, PhD candidate Steve Ferrigno, and colleagues at Rochester and the Seneca Park Zoo made a surprising discovery: in an experiment using varying quantities of peanuts, baboons (even as young as one year of age) clearly showed an ability to distinguish between large and small quantities of objects.
But the finding raised another question. To what extent might that ability be influenced by other dimensions of those objects—such as their relative surface area—in addition to their number?
This month Cantlon, Ferrigno, and two additional coauthors—Steven Piantadosi, an assistant professor of brain and cognitive science at Rochester, and Julian Jara-Ettinger, a postdoctoral researcher in brain and cognitive sciences at MIT—are publishing the results of a new study suggesting that primates do, in fact, have the ability to distinguish large and small quantities of objects, irrespective of the surface area they appear to occupy.
To test the relative importance of numerical quantities versus surface area, researchers presented subjects with dot arrays, varying in both the number of dots and the relative surface area they occupied. For each array the subjects then selected one of two icons to categorize the array as a large or small quantity.
To keep the task the same across groups, no verbal description of the categories was provided; instead, subjects learned from nonverbal demonstration by the experimenters, and trial and error feedback.
The tests with primates and children and adults in the United States were conducted with touch screen monitors; Tsimane’ adults, who have limited exposure to such devices, were tested with laminated printouts.
Cantlon says the study shows “that the initial step toward becoming mathematically sophisticated likely had to do with focusing in on the number of objects, not just total mass or size.” In a broader sense, she adds, it shows “how humans got to be the way they are.
“This is about understanding human origins and how humans evolved thought processes that are mathematically sophisticated.”
Source: University of Rochester