Hypnotic suggestion: a musical mathaphor.

Conceptually, hypnotizability has always been associated with the increase in suggestibility produced by hypnosis. In practice, hypnotizability is measured as suggestibility following a hypnotic induction. Our understanding of hypnosis and suggestion has been hampered by this discordance between the conceptual and operational definitions of hypnotizability. For example, despite hundreds of studies purporting to use standardized scales to assess hypnotizability, we know next to nothing about that construct, as it has been defined conceptually. Neither the hypothesis that it is a stable trait nor the hypothesis that it is modifiable have been tested in any study, and correlations between hypnotizability and other psychological or physiological variables have not yet been assessed. Conversely, we have learned much about hypnosis, suggestion, and suggestibility. Suggestibility has been measured on reliable and valid instruments, and we have abundant data on its stability, modifiability, and correlates. Hypnosis enhances suggestibility to a modest degree and increases the effectiveness of psychotherapy.