DescriptionThe Sally-Ann task has become the litmus test to determine if preschoolers possess a theory of mind (ToM). However, despite living in a social world where interacting with multiple agents with distinct mental states is the norm, children are only examined for their ability to track a single agent. Furthermore, researchers have adduced that threeyear- olds’ fail to attribute a mental state to a single agent, but because of limited empirical evidence, the types of error that three-year-olds produced in such tasks remain unknown. In the current studies, a multiple agent false belief task was introduced to examine the underlying nature of children’s errors in a false belief task, children’s working memory capacity in tracking multiple agents, and its developmental trajectory. Three- and four-year-olds were successful in tracking three agents with distinct false beliefs (Study 1). But when the number of agents was increased to four, four-year-olds continued to succeed, while three-year-olds’ performance suffered greatly (Study 2). The only consistent error pattern, found across studies and ages, was their attribution of a true belief to all agents, which suggest that errors children make tend to be biased by the true belief.