Background. To a large extent, discussions about dissociative identity disorder (DID) revolve around the way in which identity states (alters) that are thought to be typical for this condition should be interpreted: are they metaphors or are they genuine actors? Recent literature offers some fine examples of studies demonstrating that alters differ in their physiological profile. On the basis of this type of evidence, some authors have concluded that alters are more than just metaphors. Objective: Drawing upon an experimental example, we argue that such a line of reasoning is highly problematic. Method & Results: Our example demonstrates that normal subjects are perfectly able to simulate alters such that these alters are accompanied by different physiological profiles. This is especially true for subjects scoring high on fantasy proneness. Conclusions: Psychobiological research on DID should include normal controls, preferably controls who are fantasy prone. Unless such a strategy is adopted, psychobiological research on alter activity will not be very informative.