Sakari Kallio
School of Biosciences, University of Skövde, Sweden
Department of Psychology, University of Turku, Finland
Received 25 September 2020, Revised 9 February 2021, Accepted 11 February 2021, Available online 24 February 2021, Version of Record 24 February 2021.
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Abstract
Oakley and colleagues (2021) suggest that a classic scale – HGSHS:A, aiming to measure hypnotic suggestibility – can be used to measure direct verbal suggestibility (DVS). According to the authors, DVS is a trait that can be measured both with and without hypnosis. I find this initiative highly welcome. However, I wish to give several examples why it is time to develop entirely new scales instead. Rather than trying to explain more phenomena with a single scale or concept, researchers should take a cue from research that points to a far more nuanced picture of suggestibility than a construct like DVS allows. There may be no single, unified phenomenon that can be measured with a single scale. The old, time-tested scales should be treated neither as sacred nor final. They require up-to-date, critical analysis of what exactly they measure, with an eye to how they can be further improved.
Keywords
Suggestibility
Automaticity
Hypnosis
Ideomotor suggestion
Introduction
The Harvard Group Scale of Hypnotic Susceptibility Form A (HGSHS:A, Shor & Orne, 1962) has, for almost 60 years, been used as the initial (and still often the only) test when recruiting participants for hypnosis experiments. It has been translated into a number of languages; the latest norms for its use in the United Kingdom were published in 2020 (Oakley et al., 2020). The scale has had an enormous impact on what researchers in the field and participants in hypnosis experiments think that hypnosis is. Despite its ongoing popularity, HGSHS:A has been criticized (e.g., Woody, 1997). Also Acunzo and Terhune (Acunzo & Terhune, Preprint) discuss several of its shortcomings, along with those of other, similar contemporary measures of hypnotic suggestibility: e.g., having binary scoring and single-trial sampling (see also Kirsch et al., 2011).
My comment is two-fold. I will mainly focus on the problems with how the HGSHS:A instructs participants to respond to suggestions along with the kinds of suggestions it includes. Oakley, Walsh, Mehta, Halligan, and Deeley (2021) propose some changes to HGSHS:A; however, at the end of this comment I will point out why these changes do not fix the problems.
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Section snippets
Non-hypnotic suggestibility
By the end of the 19th Century, researchers (e.g., Binet, 1900) had started becoming interested in suggestibility more generally: i.e., without connection to hypnosis. That interest has continued and grown. Gheorghiu et al. (1989) are typical in concluding that the phenomenon of suggestibility finds applications across many areas, including medicine (e.g., via the placebo effect), education, psychotherapy, and marketing.
Unfortunately, too few devices are available to measure waking.
Defining core terms
“Suggestion” has been defined in many ways (for a review, see Gheorghiu, 1989). The following three definitions give an idea of what is meant while revealing why further clarification is sorely needed. McDougall (1908, p. 100) defines “suggestion” as “…a process of communication resulting in the acceptance with conviction of the communicated proposition in the absence of logically adequate grounds for its acceptance”. Sidis (1898) defines “suggestion” as an intrusive idea1
The evolution of HGSHS:A
Development of the currently available scales such as HGSHS:A began in the late 1950s when Andre Weitzenhoffer and Ernst Hilgard developed metrics for hypnotic susceptibility. Their research culminated in the development of three scales in particular, known as the Stanford Hypnotic Susceptibility Scale, Forms A and B (SHSS:A, SHSS:B, Weitzenhoffer & Hilgard, 1959) and the Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C, Weitzenhoffer & Hilgard, 1962). These scales were largely based on
Problems with HGSHS:A
The first problem with HGSHS:A is that the instructions for responding to suggestions are quite ambiguous. In the beginning of the induction, participants are asked to test how it feels to respond to suggestions when not hypnotized (pp. 4–5):
As you know, thinking of a movement and making a movement are closely related. Soon after you think of your head falling forward you will experience a tendency to make the movement.
Several suggestions of the head falling forward are given so that
Conclusion
What has happened to suggestibility closely resembles what has happened to many other constructs in the history of science: the more researchers learn about them, the more complicated they turn out to be. Consider how the construct of memory has come to be understood as a complex cluster of memory systems, some of them working independently of each other (e.g., Bower, 2000).
I have taken up many concerns that I have regarding the Harvard scale in its current form. While noting similar concerns,
Acknowledgements
This research did not receive any grant from funding agencies in the public, commercial, or not-for-profit sectors. I wish to thank Joel Parthemore and Oskar MacGregor for commenting on the manuscript.
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