Not everyone responds to hypnosis the same way — standardised scales help researchers quantify those differences with surprising consistency.
The Origins of Susceptibility Measurement
The scientific study of hypnotic susceptibility began in earnest with the development of the Stanford Hypnotic Susceptibility Scales (SHSS) by Weitzenhoffer and Hilgard in 1959. These individually administered scales present a series of standardised suggestions — hand lowering, arm immobilisation, auditory hallucination, post-hypnotic amnesia — scored pass/fail. The resulting distribution is remarkably stable: approximately 10–15% of the population scores as highly susceptible, 10–15% as largely insusceptible, and the remainder falling in a normal distribution in between [1]. This finding has been replicated across dozens of studies and multiple decades, suggesting hypnotic susceptibility is a stable trait with measurable psychometric properties.
The Harvard Group Scale and Its Role
The Harvard Group Scale of Hypnotic Susceptibility (HGSHS), adapted from the SHSS by Shor and Orne in 1962, made large-scale susceptibility testing practical by replacing one-on-one administration with a group format using standardised audio recordings. Participants self-score their responses, and studies consistently report high correlations between HGSHS and individually administered SHSS scores [2]. The HGSHS remains the most widely used susceptibility measure in research settings, with norms established across numerous populations. Its limitations include the self-report format, which can inflate scores through demand characteristics, and its focus on behavioural rather than subjective responses to suggestion [3].
What Susceptibility Scores Predict
Susceptibility scores correlate moderately with treatment outcomes for conditions where hypnosis plays a central role, including pain management, irritable bowel syndrome, and anxiety reduction [4]. However, the relationship is not deterministic — many patients with moderate susceptibility scores achieve excellent clinical outcomes, suggesting that therapeutic skill, rapport, and treatment context moderate the relationship between susceptibility and response. Recent research has shifted focus toward the concept of hypnotic suggestibility as a multidimensional construct rather than a single trait, with different suggestion types (cognitive, motor, perceptual) showing only moderate intercorrelations [5]. This has implications for practitioners: a client who scores low on motor suggestions may still respond well to cognitive or perceptual suggestions.
Clinical Relevance for Practitioners
Susceptibility testing in clinical practice is relatively uncommon, but the research strongly suggests that practitioners benefit from understanding the range of client responsiveness. Brief screening measures, such as the Stanford Hypnotic Clinical Scale or the Elkins Hypnotizability Scale, provide clinically useful information in 10–15 minutes without the full administration time of the research scales [6]. Knowledge of a client’s susceptibility profile can guide treatment planning — highly susceptible clients may benefit from direct suggestion approaches, while less susceptible clients may respond better to indirect, permissive techniques or experience-based methods. Crucially, susceptibility is not fixed; training, practice, and context can shift scores modestly, which supports the value of pre-hypnotic preparation and practice sessions [5].
References
- Hilgard, E. R. (1965). Hypnotic susceptibility. Harcourt, Brace & World. 1–131. DOI: 10.1037/11374-000
- Shor, R. E., & Orne, E. C. (1962). Harvard Group Scale of Hypnotic Susceptibility, Form A. Consulting Psychologists Press. 1–56. DOI: 10.1037/t06486-000
- Woody, E. Z., & McConkey, K. M. (2003). What we don’t know about the measurement of hypnotic susceptibility. American Journal of Clinical Hypnosis. 45(4), 293–302. DOI: 10.1080/00029157.2003.10403542
- Milling, L. S., Gervasio, A. H., & Breen, A. C. (2021). Hypnotic susceptibility and treatment outcome: A meta-analytic review. International Journal of Clinical and Experimental Hypnosis. 69(1), 139–167. DOI: 10.1080/00207144.2020.1856645
- Barnier, A. J., Cox, R. E., & McConkey, K. M. (2014). The province of high suggestibility: Achieving high suggestibility in the laboratory and beyond. International Journal of Clinical and Experimental Hypnosis. 62(3), 283–303. DOI: 10.1080/00207144.2014.901079
- Elkins, G. R., Barabasz, A. F., Council, J. R., & Spiegel, D. (2015). Advancing research and practice: The revised APA Division 30 definition of hypnosis. International Journal of Clinical and Experimental Hypnosis. 63(1), 1–9. DOI: 10.1080/00207144.2014.961870