Abstract
How do we come to come to identify and individuate objects as members of different kinds? Some developmental psychologists have hypothesized that learning language plays a crucial role in the capacity to represent objects as different kinds of entities. If this hypothesis is correct, then non-linguistic animals should lack the capacity to represent objects as kinds. Previous research with rhesus monkeys (Macaca mulatta) and new data with capuchin monkeys (Cebus apella) shows that monkeys can individuate different kinds of objects. Using a searching time measure, we found that monkeys who see one kind of object being hidden search longer when they find a different kind of object. But are monkeys in this task individuating objects as different “kinds”, or simply representing objects with different properties? Here, we explore whether monkeys can individuate different kinds of objects in a task in which the visual properties of the objects don't vary. Again using a searching time measure, we found that capuchin and rhesus monkeys have different expectations about different kinds of objects even when the perceptual features of the objects are held constant. These data are the first of their kind to suggest that language is not necessary to represent kinds.