Quality of hallucinatory experiences: differences between a clinical and a non-clinical sample

In this study, we asked people from two samples (a clinical one, consisting of patients with schizophrenia, and a non-clinical one, including university students) to complete the Revised Hallucination Scale (RHS) as a self-questionnaire. When the participants responded positively to an item, they were encouraged to provide further detailed descriptions (i.e., examples of their own experiences) concerning that item. We found that the kinds of descriptions provided by the two groups were very different. We suggest that it is not advisable to explore the presence of hallucinations in non-clinical samples using research protocols based exclusively on yes-or-no answers to questionnaires like the RHS. Hallucinatory or hallucinatory-like experiences cannot be reliably and validly assessed without a precise characterization of the phenomenal quality of the experience.