 First-person memory markers play a vital role in enabling rememberers to cope with two problems posed by the interaction between memory and imagination. The source problem, arises because subjects remember not only information deriving from experience but also information deriving from a variety of other sources, including imagination. For example, one might imagine an event and later remember the imagined event. Hence, when one remembers, one is faced with the problem of determining whether the information that one remembers derives from experience or, rather, from another source. Subjects appear to cope with this problem by relying on a form of metamemory known as “source monitoring” (Johnson 1997), in which they employ a variety of content-based markers to determine whether or not they are remembering on the basis of experience. For example, memories deriving from experience tend to be more detailed and to include no information about the cognitive operations that produced them, whereas memories deriving from imagination tend to be less detailed and to include information about the cognitive operations that produced them.