What Is Hypnotizability? How It’s Measured and What It Predicts

People differ, sometimes dramatically, in how they respond to hypnotic suggestion. One person’s arm drifts upward as though lifted by a balloon; another feels nothing beyond mild relaxation. Hypnotizability is the name for that difference. It is one of the most studied concepts in hypnosis research, and it matters for anyone reading that research, because it can shape who benefits and how a study’s results should be interpreted.

A working definition

The Society of Psychological Hypnosis (Division 30 of the American Psychological Association) defines hypnotizability as “an individual’s ability to experience suggested alterations in physiology, sensations, emotions, thoughts or behavior during hypnosis” [1]. You will also see the terms hypnotic suggestibility and hypnotic susceptibility. They refer to the same measured quantity, though authors sometimes choose a term to signal a theoretical position.

The definition deliberately says nothing about mechanism. It describes what scales measure, not why people differ.

How it is measured

Hypnotizability is assessed with standardized scales. Most follow the same pattern:

1. A scripted induction, delivered identically to everyone, live or recorded.
2. A series of test suggestions, roughly from easier to harder. Easier items involve movement, such as a hand feeling heavy and lowering. Harder items involve changes in perception or memory, such as not hearing a sound or forgetting part of the session.
3. Scoring, usually by counting how many suggestions the person “passes” against set criteria. Newer scales also ask how real and involuntary each experience felt.

Some scales are given one to one by a trained examiner; others, such as the Harvard Group Scale and the Sussex-Waterloo Scale (SWASH), are designed for groups, which makes screening hundreds of research volunteers practical [3]. Normative data for the Harvard Group Scale from a large UK sample were broadly consistent with earlier Western samples in score distribution and item difficulty [4].

Scores form a continuum. By convention, researchers often label the highest- and lowest-scoring 10–15% of a sample “high” and “low” hypnotizable, with everyone else in the middle [3]. Those bands are a research convenience, not natural types.

The scales have critics. A 2021 review argued that binary pass/fail scoring and testing each suggestion only once discard useful information, that some items use suboptimal suggestion content, and that the classic scales “have outlived their usefulness” for current research questions [2].

What is reasonably well established

People vary markedly. The same review called this variability the most well-established finding in decades of experimental hypnosis research [2].

Scores are stable. In a longitudinal study, 50 people first tested as students were retested on the same Stanford scale 10, 15 and 25 years later. The correlations were .64, .82 and .71, and the median person’s score changed by only one point on the 12-item scale [5]. That is comparable to the stability of other well-studied individual differences.

Broad personality explains little. In a 2025 study of 78 young adults, Big Five personality traits showed no relationship with Harvard Group Scale scores, while daytime sleepiness did [6]. The picture for intelligence is unsettled: a 2025 study of 221 undergraduates found a negative correlation between college entrance test (ACT) scores and hypnotizability, while grades and choice of a science field were unrelated [7]. One study each is not enough to settle either question.

Expectation matters a great deal. In two experiments, responsiveness to suggestion without hypnosis correlated with absorption, fantasy proneness, motivation and expectation, but only expectation predicted it once the others were controlled. Non-hypnotic suggestibility, motivation and expectation together accounted for 53% of the variance in behavioural response to hypnosis [8].

What remains debated

What the scores actually reflect

Different research traditions read the same scores differently. One emphasizes a distinct cognitive capacity. Supporting work includes a brain-imaging study in which 12 high and 12 low hypnotizable adults differed in resting connectivity between the left dorsolateral prefrontal cortex, an executive-control region, and the salience network including the dorsal anterior cingulate cortex, with no differences in brain structure [9]. The sample was small, and a connectivity difference does not establish cause.

Another tradition emphasizes expectations, motivation and the social context of testing, drawing on findings like those above [8]. Many current accounts combine both.

How much the induction adds

People respond to many of the same suggestions without any induction. When suggestibility was measured first without hypnosis and then with it, the induction produced a small but significant increase on average. For a substantial minority of participants, hypnosis decreased suggestibility [8].

Whether it can be trained

In a 1986 study, low and medium scorers received information about cognitive strategies, practice and a video of a model responding successfully. Over half of the initial low scorers and over two-thirds of the medium scorers in that condition scored as highly hypnotizable on two later scales, well above practice-only and control groups [10]. The result is clear; its meaning is not. The study cannot separate a genuine change in experience from people learning what the scales reward, which is part of why the 25-year stability findings and the training findings coexist uneasily.

Does hypnotizability predict who benefits?

In the laboratory, strongly. A meta-analysis of 85 experimental pain studies in 3,632 healthy volunteers found that hypnosis with direct pain-relief suggestions produced clinically meaningful pain reductions of 42% in high and 29% in medium suggestible participants, and minimal benefit in low scorers [11].

In clinics, much less. A meta-analysis of 10 clinical studies with 283 participants found a small-to-medium correlation (r = .24) between hypnotizability and outcome, accounting for 6% of the variance. Smaller studies reported larger effects, and the authors questioned the usefulness of assessing hypnotizability in clinical settings [12].

Claim	Strength of evidence
People differ markedly in response to suggestion	Strong
Scores are stable across years in adults	Moderate to strong; the longest follow-up is one 50-person cohort
Hypnotizability predicts lab pain relief	Strong
Hypnotizability predicts clinical benefit	Weak to modest
Broad personality traits predict scores	Little support
Training produces lasting real change	Mixed; interpretation disputed
A specific brain network underlies it	Preliminary

Why it matters when reading research

• Selection. Some studies recruit only high scorers. Results from highly responsive volunteers may not apply to people in general.
• Moderation. Some trials report whether high and low scorers improved differently. Where a difference appears, it tends to vary by condition and outcome.
• Comparison. Responsive participants may improve partly through expectation. A suitable control group is needed to tell the difference; see Expectation, Placebo and Hypnosis: Why Comparison Groups Matter. For how this fits into trial design generally, see What Is a Randomized Controlled Trial? Reading Hypnosis Research.

What a hypnotizability score does not tell you

A low score does not mean hypnosis can be of no use, and a high score does not guarantee benefit. A score reflects responses to specific test items under specific conditions. It is not a diagnosis.

A score is not a clinical recommendation. Whether hypnosis suits a health problem depends on the condition and the evidence for it, not on a suggestibility test. If you are considering hypnosis for pain, anxiety, sleep or another health concern, discuss it with a qualified clinician, and see a doctor first about new, severe or worsening symptoms.