How do people come to understand their actions as their own? Common sense tells us we know when actions are ours because we have caused them; we are intrinsically informed of what we do by our conscious will. But it turns out people can be mistaken about their own authorship, sometimes because they suffer from schizophrenia, dissociative disorder, or a psychogenic movement disorder--or because they encounter situations that mislead them about the origins of action. In hypnosis, facilitated communication, and coactions such as ouija-board spelling, for example, people can become profoundly mistaken about the sources of their actions. People can come to believe that they have performed actions they did not do, or that they were not the source of actions that were in fact their own. Wegner and Wheatley (1999) proposed a theory of apparent mental causation that accounts for these anomalies by suggesting that people will feel they are the source of action when they think about that action in advance of its occurrence, and alternative sources of the action are not known. This theory calls into question the common sense view that conscious will is the cause of action.