Running Head: THE CURSE OF KNOWLEDGE The Curse of Knowledge in Reasoning about False Beliefs

Assessing what others know and believe is critical for accurately understanding human action. Young children find it difficult to reason about false beliefs—beliefs that conflict with reality. The source of this difficulty is a matter of considerable debate. Here we show that if sensitive enough measures are used, adults show deficits in the same kind of false belief task that young children fail on. In particular, we show ‘a curse of knowledge bias’ in false belief reasoning. That is, adults’ own knowledge of an event’s outcome can compromise their ability to reason about another person’s beliefs about that event. We also find that adults’ perception of the plausibility of an event mediates the extent of this bias. These findings shed light on the factors involved in false belief reasoning and are discussed in light of their implications for both adult and child social cognition.