Hallucinations from a cognitive perspective.

Although the phenomenological diversity of hallucinations has been well documented, experimental investigations into their cognitive underpinnings have not yet reflected this complexity. Our goal in this review is to contrast the restricted set of experimental conditions that have been utilized in source-monitoring studies of hallucinations with their documented phenomenological diversity. In particular, we initially focus on the theoretical distinction between origin and source that has been recognized at the level of phenomenology, and then review the source-monitoring literature within this theoretical framework. In addition, we touch on several other aspects of the phenomenological diversity of hallucinations that have not yet been sufficiently investigated experimentally--namely, intentionality, affect, and motivational factors. Finally, we list other methodological problems that may have led to inconsistencies in the literature. We conclude with concrete recommendations for future source-monitoring investigations of hallucinations.