A nonhuman primate’s expectations about object motion and destination: The importance of self-propelled movement and animacy

Human infants have considerable understanding of why objects move and what causes them to take one trajectory over another. Here, we explore the possibility that this capacity is shared with other nonhumans and present results from preferential looking time tests with a New World monkey, the cotton-top tamarin. Experiments examined whether individuals form different expectations about an object’s potential capacity to change locations. Test objects were: 1) selfpropelled, moving, animate; 2) self-propelled, moving, inanimate; 3) non-self-propelled, moving due to an external agent, inanimate; 4) non-self-propelled, motionless, inanimate. When category 1 objects, either a live mouse or frog, emerged from behind an occluder in a novel location, this did not affect looking time; subjects appeared to expect such changes. In contrast, when the other objects emerged in a novel location following occlusion from view, subjects looked longer than when the object emerged in the location seen prior to occlusion; such locational changes were apparently not expected. Some feature other than self-propelled motion accounts for the tamarins’ looking time responses and at least one candidate feature is whether the object is animate or inanimate. © Blackwell Publishers Ltd. 1998, 108 Cowley Road, Oxford OX4 1JF, UK and 350 Main Street, Malden, MA 02148, USA Developmental Science 1:1 pp 31–37 Address for correspondence: Departments of Anthropology and Psychology, Program in Neurosciences Harvard University, 11 Divinity Avenue, Cambridge, MA 02138, USA press; Santos, 1997; Uller, 1997). The logic underlying this procedure is that if an observed event violates knowledge from a given domain, then the observer should show greater interest in the event as evidenced by his or her heightened attention to it, relative to an event that does not violate expectancy. The power of the technique is that it provides a tool to investigate cognitive abilities across species in the absence of training by reinforcement or punishment.