The origins of belief representation: monkeys fail to automatically represent others' beliefs

Young infants' successful performance on false belief tasks has led several researchers to argue that there may be a core knowledge system for representing the beliefs of other agents, emerging early in human development and constraining automatic belief processing into adulthood. One way to investigate this purported core belief representation system is to examine whether non-human primates share such a system. Although non-human primates have historically performed poorly on false belief tasks that require executive function capacities, little work has explored how primates perform on more automatic measures of belief processing. To get at this issue, we modified Kovács et al. (2010)'s test of automatic belief representation to examine whether one non-human primate species--the rhesus macaque (Macaca mulatta)--is automatically influenced by another agent's beliefs when tracking an object's location. Monkeys saw an event in which a human agent watched an apple move back and forth between two boxes and an outcome in which one box was revealed to be empty. By occluding segments of the apple's movement from either the monkey or the agent, we manipulated both the monkeys' belief (true or false) and agent's belief (true or false) about the final location of the apple. We found that monkeys looked longer at events that violated their own beliefs than at events that were consistent with their beliefs. In contrast to human infants, however, monkeys' expectations were not influenced by another agent's beliefs, suggesting that belief representation may be an aspect of core knowledge unique to humans.