Hypnotic susceptibility

Hypnotic susceptibility is a measurement of how easily a person can be hypnotized. The are several types of scales used, however the most common are the Harvard Group Scale of Hypnotic Susceptibility and the Stanford Hypnotic Susceptibility Scales. The Harvard Group Scale, as the name implies, is administered predominantly to large groups of people while the Stanford Hypnotic Susceptibility Scale is administerd to individuals. No scale can be seen as completely reliable due to the nature of hypnosis. It has been argued that no person can be hypnotized if they don't want to be, therefore a person who scores very low may not want to be hypnotized making the test scores invalid.

Harvard Group Scale
Ronald Shor and Emily Carota Orne developed the Harvard Group Scale in 1962. It consists of 12 items of progressive difficulty (as defined, psychometrically, by the percentage of subjects in a normative sample that reports experiencing each particular item) and usually takes around forty-five minutes to complete. The items usually consist of motor tasks and cognitive tasks with the motor tasks being easier to complete. The average score is 5 out of 12. The test is self-scored leaving it open to criticism concerning the validity of the scores.

Stanford Scale
The Stanford Scale was developed Andre M. Weitzenhoffer and Ernest R. Hilgard in 1959. The Scale consists of three Forms: A, B, and C. Similar to the Harvard Group Scale, each Form consists of 12 items of progressive difficulty and usually takes fifty minutes to complete. Each form consists of motor and cognitive tasks but vary in their respective intended purpose. The administrator scores each form individually.

Form A
Based upon the scale developed by Joseph Friedlander and Theodore Sarbin (1938), this form was developed to measure susceptibility to hypnosis with items increasing in difficulty in order to yield a score. The higher the score, the more responsive one is to hypnosis. Following a standardized hypnotic induction, the hypnotized individual is given suggestions pertaining to the list below.

Form B
Form B was designed to be used as a follow-up to Form A when doing experiments involving a second session of hypnosis. The items are similar but are changed somewhat (e.g. the use of the opposite hand in a particular item). The changes were made to "prevent memory from the first exerting too great an influence upon the recall of specific tasks..." (pg. 29, Weitzenhoffer & Hilgard 1959).

Form C
Created a few years after Forms A and B, Form C contains some items from Form B, but includes more difficult items for "when subjects are being selected for advanced tests in which knowledge of their capacity to experience more varied items is required" (pgs v-vi Weitzenhoffer & Hilgard 1962). Following a standardized hypnotic induction, the hypnotized individual is given suggestions pertaining to the list below.

In more modern experiments, a scent such as pepperment has been used in place of ammonia for Item 9.

Other scales
These tests are not widely used because they are usually seen as less reliable than the Stanford Scale and Harvard Group Scale. Many professionals think that these tests produce results because they involve concentration and a certain level of concentration is required to be hypnotized.

The eye roll test
The Eye Roll Test is a simple and quick test to loosely determine if a person is susceptible to hypnosis. In this procedure, you are asked to open your eyes wide, then roll them up. Then you have to lower your eyelids without rolling your eyes down. If a person can do this task they are seen to be susceptible to hypnosis. There has been evidence showing that those who perform well on this test also score highly on the Harvard and Stanford scales. There are also many cases where a person can perform this task and score low on other, more reliable tests. This test is usually not viewed as very reliable in the professional psychological/psychiatric community.

Light test
Individuals are asked to stare at a small light in a dark room. Many people think the light is moving and those who see it change direction the most are thought to be suitable for hypnosis.