The Stanford and Harvard susceptibility scales are structured tools used in hypnosis research to assess how readily a person responds to standardized hypnotic suggestions. They help researchers describe differences in hypnotic responsiveness in a consistent way.
The word susceptibility is traditional in this area, but many researchers now prefer hypnotic suggestibility or hypnotic responsiveness. These terms focus on a person’s responses under particular testing conditions rather than implying a fixed personal weakness or trait.
What does “hypnotic susceptibility” mean?
Hypnotic susceptibility refers to the degree to which a person responds to suggestions presented during a standardized hypnotic procedure. Suggestions may involve experiences such as:
A hand or arm becoming lighter or heavier
A hand moving without deliberate effort
An inability to perform a simple action
A change in perception
Temporary amnesia for selected material
Posthypnotic responses after the formal procedure
A person’s score reflects responses to the specific suggestions used in the test. It does not provide a complete measure of intelligence, character, motivation, mental health, or overall suggestibility in daily life.
Hypnosis research commonly treats responsiveness as measurable but influenced by several factors, including attention, expectations, motivation, cooperation, the testing situation, and the wording and delivery of suggestions.¹
What is the Stanford Hypnotic Susceptibility Scale?
The Stanford Hypnotic Susceptibility Scale, usually abbreviated SHSS, is a family of standardized hypnosis scales developed at Stanford University by André M. Weitzenhoffer and Ernest R. Hilgard.
The best-known forms are:
Stanford Hypnotic Susceptibility Scale, Form A
Stanford Hypnotic Susceptibility Scale, Form B
Stanford Hypnotic Susceptibility Scale, Form C
Each form uses a standardized hypnotic induction followed by a series of suggestions. The examiner scores whether the participant shows the behavioral response defined by the scoring criteria.
The forms differ in emphasis and difficulty:
Form A is generally used as an introductory measure.
Form B samples a broader range of responses.
Form C includes more challenging items and is often used when researchers want a wider spread of scores among people who respond well to easier suggestions.
The Stanford scales are usually administered individually. This allows the examiner to deliver the procedure in a controlled way and to observe each response directly.
How are Stanford scale scores reported?
A Stanford scale score usually represents the number of suggestions to which the participant responds according to the test’s criteria. Higher scores indicate more observable responses on that particular scale.
Scores are often grouped into broad descriptive categories such as low, medium, or high responsiveness. These labels should be interpreted cautiously. They summarize performance on a standardized procedure; they do not define the person.
The exact scoring rules belong to the published test materials and examiner instructions. In research and professional training, the scale should be administered and scored according to those materials rather than improvised from a general description.
What is the Harvard Group Scale of Hypnotic Susceptibility?
The Harvard Group Scale of Hypnotic Susceptibility, Form A, commonly called the Harvard Group Scale or HGSHS:A, is a standardized group-administered measure of hypnotic responsiveness.
It was developed by Ronald E. Shor and Emily Carota Orne for use when testing people together rather than one at a time.¹ The procedure presents a hypnotic induction and a sequence of suggestions to the group. Participants then record or report their responses, while the administrator uses standardized instructions and scoring procedures.
The Harvard Group Scale was designed to make large-scale testing more practical. It is widely used in research settings because many participants can be assessed during one session.
Why is the Harvard scale called a “group scale”?
The name refers to the administration format, not to a different type of hypnosis. Participants receive the procedure in a group, but each person is scored individually based on that person’s responses.
Group administration has practical advantages:
It can save time.
It can make research testing more efficient.
It permits the assessment of several participants under similar conditions.
It also has limitations. The examiner has less opportunity to tailor the procedure to one participant or clarify an individual response in real time. For that reason, the Harvard Group Scale and individually administered Stanford scales are related but not interchangeable measures.
How are the Stanford and Harvard scales alike?
Both types of scale:
Use standardized hypnotic procedures.
Present a series of suggestions.
Score observable or reported responses.
Aim to improve consistency across participants.
Measure responsiveness to the test procedure rather than a person’s worth or general psychological ability.
Both are also research instruments, not diagnostic tests. A score should be understood in the context of the specific scale, instructions, setting, and scoring method used.
How are they different?
The clearest differences involve administration, purpose, and the range of items included.
Feature | Stanford scales | Harvard Group Scale |
|---|---|---|
Typical format | Individual administration | Group administration |
Main purpose | Detailed assessment under individual testing conditions | Efficient assessment of multiple participants |
Administration | Examiner works directly with one participant | Examiner presents the procedure to a group |
Scoring | Based on the participant’s responses to Stanford items | Based on responses to Harvard Group Scale items |
Relationship | A family of forms, including Forms A, B, and C | A separate group-administered scale, commonly Form A |
The scales should not be treated as if they were simply different versions of one identical test. A score from one scale is not automatically interchangeable with a score from another.
Are the Stanford and Harvard scales tests of whether someone can be hypnotized?
They are tests of how a person responds to a particular standardized set of hypnotic suggestions. In that limited sense, they assess hypnotic responsiveness.
However, the phrase “can be hypnotized” can be misleading because it suggests a simple yes-or-no capacity. In practice, people show a range of responses across different suggestions. Someone may respond strongly to some suggestions and less strongly to others.
A score also depends on the testing context. Attention, expectations, willingness to participate, understanding of the instructions, and the relationship with the examiner can all matter.² A low score does not prove that a person is incapable of responding to every form of hypnosis, and a high score does not guarantee a particular response in every setting.
Do the scales measure suggestibility in everyday life?
Not directly.
These scales measure performance during a defined procedure with a particular set of instructions. Everyday suggestibility is broader and may involve social influence, memory, persuasion, expectations, and other processes that are not identical to hypnotic responsiveness.
Some researchers distinguish hypnotic suggestibility from general suggestibility. The distinction is useful because a person’s response to hypnotic suggestions cannot automatically be generalized to how that person responds to advertisements, authority figures, peer pressure, or ordinary conversation.
Do the scales measure whether someone is gullible?
No.
A high score does not mean that a person is gullible, naïve, unintelligent, or easy to manipulate. A low score does not mean that a person is unusually skeptical or resistant in all situations.
Hypnotic responsiveness is a specialized research construct. It involves how a person responds to suggestions under specific conditions, including focused attention and a defined testing procedure. It should not be used as a shorthand judgment about personality.
Does a high score mean a person loses control?
No.
Hypnotic scales assess responses to suggestions, not a general loss of control. Participants typically receive instructions, understand that they are taking part in a procedure, and choose how they respond.
A person may experience a suggested action as unusually automatic or effortless, but that experience does not establish that the person has surrendered control of all behavior. Research and clinical discussions should distinguish a subjective feeling of involuntariness from the broader claim that hypnosis removes personal agency.
Does a low score mean hypnosis does not work for someone?
No. A low score on one scale indicates relatively few scored responses during that particular procedure. It does not establish that the person can never benefit from hypnosis or respond to any suggestion.
Hypnosis may be used for different purposes and in different settings, and research scales are not designed to measure every possible outcome. A person’s response may also vary with the instructions, the relationship with the practitioner, the type of suggestion, and the individual’s expectations and motivation.
It is more accurate to say that a low score indicates lower responsiveness on that specific standardized measure.
Are the scales used in hypnotherapy?
They may be used in research or training, but they are not required for ordinary hypnotherapy.
A clinician generally does not need to assign a Stanford or Harvard score before providing a hypnosis-based intervention. In clinical work, the relevant questions may concern the person’s goals, preferences, safety, symptoms, medical or psychological history, and response to the intervention.
A susceptibility score should not be used by itself to decide whether a person is suitable for treatment, whether treatment will work, or whether a person has a particular diagnosis.
Can someone improve a score with practice?
Scores can be influenced by experience and by the conditions of testing, but claims about improvement need careful interpretation.
Some people become more familiar with hypnotic procedures, more comfortable with responding, or better able to use imagery and focused attention. At the same time, a change in score may reflect practice with the test, differences in administration, changes in expectations, or other factors.
The scales are most useful when researchers follow standardized procedures and interpret results within the limits of the instrument. They are not designed as a personal competition or a permanent ranking.
Are the scales reliable?
Reliability depends on the scale, the administration procedures, the scoring method, and the population being tested. Standardization helps researchers compare responses more consistently, but no psychological measure should be treated as perfectly independent of context.
The Stanford and Harvard scales have been important tools in experimental hypnosis research. Their value comes from providing structured procedures and defined scoring rules, not from offering a complete description of an individual.
Researchers should report which scale and form they used, how it was administered, and how responses were scored. Without that information, a score is difficult to interpret accurately.
Why do researchers use standardized scales?
Standardized scales help researchers:
Define what counts as a response.
Compare participants under similar conditions.
Study individual differences.
Examine relationships between hypnotic responsiveness and other variables.
Replicate procedures across studies.
Select or classify participants for particular research designs.
They also help separate ordinary impressions—such as “this person seemed very relaxed”—from specific, observable response criteria.
What should a score report include?
A useful report should identify:
The exact scale and form
Whether it was administered individually or in a group
The testing instructions and general procedure
The scoring method
The participant’s score
Any relevant limitations or unusual circumstances
A bare label such as “highly hypnotizable” provides less information than a clear description of the measure and score.
What is the main takeaway?
The Stanford and Harvard scales are structured research tools for measuring responses to standardized hypnotic suggestions.
Stanford scales are typically administered individually and include Forms A, B, and C.
The Harvard Group Scale is designed for group administration.
Both assess responses under specific testing conditions.
Neither scale measures intelligence, gullibility, character, mental health, or a general loss of control.
A score should be interpreted as a result on a particular instrument, not as a permanent label.
Used carefully, these scales provide a practical way to study differences in hypnotic responsiveness while keeping interpretation grounded in the limits of the test.
Notes
Ronald E. Shor and Emily Carota Orne, The Harvard Group Scale of Hypnotic Susceptibility, Form A: Manual, Consulting Psychologists Press, 1962.
André M. Weitzenhoffer and Ernest R. Hilgard, Stanford Hypnotic Susceptibility Scale, Forms A and B, Consulting Psychologists Press, 1959.