Do rhesus monkeys (Macaca mulatta) represent others' knowledge and beliefs?
Laurie Santos
Yale University, USA
I will present the results of several studies using non-verbal theory of mind (ToM) tasks to explore what rhesus monkeys (Macaca mulatta) know about the minds of others in the absence of training. Building on work by Hare, Call, and Tomasello using competitive tasks with chimpanzees, we explore mental state understanding in a free-ranging population of rhesus monkeys living on the island of Cayo Santiago, Puerto Rico. In our first set of studies, we observe that rhesus monkeys, like chimpanzees, understand what others see, hear, and know. These results from competitive tasks suggest that rhesus monkeys understand more about the minds of others than previously thought. In our second set of studies, we explore whether monkeys have a similar understanding of others? beliefs. We presented macaques with a looking-time measure of false belief understanding, one that had recently been developed for use with fifteen month-old human infants. Like human infants, monkeys look longer when a human experimenter fails to act in accord with his true beliefs. In contrast to infants, however, monkeys appear to make no prediction about where a human experimenter will act when he has a false belief. This pattern of results is consistent with the view that monkeys can represent the knowledge and ignorance of others, but not their beliefs. The capacity to represent beliefs may therefore be a unique hallmark of human cognition.