Hypnotic Olfactory Hallucinations

Olfactory hallucinations (smelling odors that are not present) are intrusive and disruptive yet challenging to investigate because they cannot be produced on demand. In this study, the authors attempted to model olfactory hallucinations using hypnotic suggestions. We gave some subjects a suggestion to smell an odor in the absence of a real odor (positive hallucination) and gave others a suggestion to smell nothing in the presence of a real odor (negative hallucination). High hypnotizable individuals who received the positive hallucination reported intense smells whereas those who received the negative hallucination reported a reduction in intensity. These suggestions also influenced later recall about frequency of odor presentation. Findings are discussed in terms of reality monitoring and differences between positive and negative hallucinations.

A Hypnotic Analogue of Clinical Confabulation

Confabulation—fabricated or distorted memories about oneself—occurs in many disorders, but there is no reliable technique for investigating it in the laboratory. The authors used hypnosis to model clinical confabulation by giving subjects a suggestion for either (a) amnesia for everything that had happened since they started university, (b) amnesia for university plus an instruction to fill in memory gaps, or (c) confusion about the temporal order of university events. They then indexed different types of memory on a confabulation battery. The amnesia suggestion produced the most confabulation, especially for personal semantic information. Notably, subjects confabulated by making temporal confusions. The authors discuss the theoretical implications of this first attempt to model clinical confabulation and the potential utility of such analogues.