Measuring Hypnotizability: The Case for Self-Report Depth Scales and Normative Data for the Long Stanford Scale

Abstract

Conventional suggestion-based tests of hypnotizability have been criticized because they confound hypnotic and nonhypnotic suggestibility. One way around this might be to measure hypnotizability in terms of differences in suggestibility before and after hypnotic induction. However, analysis of data from a 1966 classic study by Hilgard and Tart confirms that difference scores are subject to statistical and methodological problems. Simple verbal hypnotic depth scales are presented as a useful alternative. They correlate well with conventional suggestion-based measures and enable the presence of hypnosis to be indexed independently of formal hypnotic induction procedures. Criticisms of depth scales are addressed, and normative data for the Long Stanford Scale of hypnotic depth are presented, along with data lending empirical support for the construct validity of depth reports.

Zusammenfassung

Konventionelle, suggestionsbasierte Tests der Hypnotisierbarkeit sind dafür kritisiert worden, dass sie hypnotische und nichthypnotische Suggestibilität konfundiert messen. Ein möglicher Ausweg besteht darin, Hypnotisierbarkeit als Unterschied in der Suggestibilität vor und nach einer hypnotischen Induktion zu erheben. Allerdings zeigen Daten einer klassischen Studie von Hilgard und Tart, dass Differenzmaße methodische und statistische Probleme mit sich bringen. Einfache verbale Hypnosetiefeskalen werden als nützliche Alternative vorgestellt. Sie korrelieren gut mit konventionellen suggestionsbasierten Maßen und ermöglichen es, das Vorliegen von Hypnose unabhängig von formalen hypnotischen Induktionsverfahren zu erfassen. Kritikpunkte gegenüber Hypnosetiefeskalen werden erörtert, normative Daten für die Langversion der Stanford Scale of Hypnotic Depth angeführt. Außerdem werden Daten vorgestellt, welche die Konstruktvalidität von Hypnosetiefe-Selbstberichten stützen.

Ralf Schmaelzle University of KonstanzKonstanz Germany

Résumé

Les tests d'hypnotisabilité traditionnels fondés sur la suggestion ont été critiqués parce qu'ils confondent la suggestibilité hypnotique avec la suggestibilité non hypnotique. Pour contrer ce problème, on pourrait mesurer l'hypnotisabilité en fonction des différences de suggestibilité entre celles mesurées avant et après l'induction hypnotique. Toutefois, une analyse des données tirées d'une étude classique menée en 1966 par Hilgard et Tart confirme que les écarts sont susceptibles d'entraîner des problèmes statistiques et méthodologiques. Des échelles verbales simples de la profondeur de l'état hypnotique sont présentées comme étant une solution de remplacement pertinente. Elles présentent une forte corrélation avec des mesures traditionnelles fondées sur la suggestion et permettent à l'hypnose d'être classée indépendamment des procédures officielles d'induction hypnotique. Cet article aborde des critiques émises à l'endroit des échelles de profondeur hypnotique, et présente des données normatives en faveur de l'usage de l'échelle de profondeur hypnotique de Long-Stanford, ainsi que des données empiriques appuyant la validité conceptuelle des rapports de profondeur de l'état hypnotique.

Johanne Reynault C. Tr. (STIBC)

Resumen

Las pruebas convencionales de hipnotizabilidad basadas en sugestiones han sido criticadas porque confunden la sugestionabilidad hipnótica de la no hipnótica. Una solución es medir la hipnotizabilidad desde el punto de vista de las diferencias en la sugestionabilidad antes de y después de la inducción hipnótica. Sin embargo, análisis de los datos de un estudio clásico de 1966 por Hilgard y Tart confirman que las diferencias en las puntuaciones están sujetas a problemas metodológicos y estadísticos. Presentamos como una alternativa útil escalas simples de profundidad hipnótica, correlacionadas con las medidas convencionales basadas en sugestiones, y que permiten la evaluación de la presencia de hipnosis independientemente de los procedimientos formales de inducción hipnótica. Respondemos a las críticas de las escalas de profundidad y presentamos datos normativos para La Escala Larga de Stanford (Long Stanford Scale) de profundidad hipnótica, conjuntamente con resultados que prestan apoyo empírico a la validez de constructo de auto-informes de profundidad.

Etzel Cardeña Lund UniversityLund Sweden

We would like to express our appreciation to Charles Tart, whose pioneering work on and advocacy of self-reported depth scales motivated us to write this paper. We would also like to acknowledge the enormous contributions to this area made by the late Andre Weitzenhoffer and Kenneth Bowers. This research was conducted in full accordance with American Psychological Association and British Psychological Society ethical guidelines.

Notes

³ Sheehan and Perry (1976) have queried Hilgard and Tart's (1966) conclusion that their findings are context free. They point out, for example, that, although there was no evidence of subjects “holding back” in the nonhypnotic conditions, a small sample of nonhypnotic control subjects who were brought back for an unanticipated third session with induction failed to show an appreciable gain following induction. Hilgard and Tart note, however, that the samples were small and the results were still in the appropriate direction.

⁴The following phrases were removed from the first paragraph of Barber's (1969) induction procedure because they were deemed unnecessarily leading and intimidating: “As for your will-power—if you want to, you can pay no attention to me . . . but you are only wasting time” and “In that case you will be helping the experiment and not wasting any time” (p. 251).

⁵The construct validity of a test is the extent to which performance on a test fits into a theoretical scheme about the attribute the test is seeking to measure (Cronbach & Meehl, 1955).

⁶The HGSHS:A items were: hand lowering, finger lock, arm rigidity, and moving hands together; each item was scored on a 4-point scale, from not at all . . . to very . . . For the induction group, LSS scores ranged from 0 to 5 (M = 2.15, SD = 1.23) and their HGSHS:A scores from 4 to 11 (M = 8.00, SD = 1.95). For the group without induction, LSS scores ranged from 0 to 1 (one subject scored 1, the rest 0), and their HGSHS:A scores from 4 to 9 (M = 6.15, SD = 1.53). As one might predict, those who received induction scored significantly higher on the HGSHS:A than those who did not, F(1, 38) = 11.16, p < .003.

⁷The SHSS:A items were eye closure, hand lowering, arm immobilization, finger lock, arm rigidity, moving hands together, verbal inhibition, fly hallucination, eye catalepsy, and amnesia. Subjects' LSS depth scores ranged from 0 to 8 (M = 2.25, SD = 2.15) and their SHSS:A scores from 1 to 10 (M = 5.55, SD = 3.14). Scores for total suggestion-amnesia ranged from 1 to 9 (M = 5.30, SD = 2.85). Five subjects passed the amnesia suggestion (25%); and raw amnesia scores ranged from 1 to 6 (M = 4.15, SD = 1.23).