You must turn off your ad blocker to use Psych Web; however, we are taking pains to keep advertising minimal and unobtrusive (one ad at the top of each page) so interference to your reading should be minimal.

If you need instructions for turning off common ad-blocking programs, click here.

If you already know how to turn off your ad blocker, just hit the refresh icon or F5 after you do it, to see the page.

Psi man mascot

Phenomena of Hypnosis

The old stereotyped image of a hypnotized person as a glassy-eyed zombie is not accurate. However, it is true that a hypnotized individual may look calm and a little vacant in the eyes.

A good hypnotic subject is somebody who is capable of entering a deep trance, responding to demanding suggestions. This is rare: out of an auditorium full of people, a hypnotists may be able to pick out 4 or 5 good hypnotic subjects by issuing simple suggestions like "A wind is blowing from this side to that side" and watching for people who tilt.

Perhaps less than 1% of people can be deeply hypnotized, able to respond to suggestions to hallucinate. These can be positive hallucinations ("You see a double of myself, standing next to me") or negative halluc­inations ("We are alone in this room; everybody else has vanished").

It is also true that a hypnotized person can lie rigidly between chairs. However, critics of the hypnosis concept point out that lying between chairs can be done by people who are not hypnotized.

An illusionist named The Great Kreskin was famous for doing the chair trick with non-hypnotized students. He simply commanded them to do it.

Kreskin used subjects who were awake and never had been hypnotized. He persuaded them that any determined person could accomplish the chair trick.

Kreskin set up chairs and supported the student as he or she lay between the chairs. Then he would remove the support. The student would remain lying suspended rigidly between the chairs.

The key to such tricks appears is charisma, persuasion, or (to use the conventional term) suggestion. There is no special trance state needed.

Kreskin flatly denied that hypnotism existed. However, in old videos of his performances, it was clear he wove a spell in his own way. He had a forceful personality: what people commonly call charisma.

Kreskin would keep up a constant but articulate chatter. He had a very self-confident manner.

Perhaps hypnosis has more to do with accepting the ideas and commands of a charismatic leader rather than entering a trance state. A person undergoing hypnosis submits trustingly to an authority figure. That may be all that is required for hypnosis-like phenomena to occur.

Post-hypnotic suggestions occur when subjects are instructed under hypnosis to perform a simple act later, after awakening. Typically a pre-arranged signal is used to trigger the behavior. ("When I say the words cold outside, you will suddenly fill very, very cold.")

Finally, the subject can be told to forget the events of hypnosis, leading to post-hypnotic amnesia. If a post-hypnotic suggestion is combined with a suggestion for amnesia, the subject will carry out a suggestion later, after the hypnosis is over, without knowing why.

This works reliably with good hypnotic subjects. However, as a rule, hypnotized people cannot be made to do something that goes against their moral code. It is unlikely, for example, that a person could be given am effective post-hypnotic suggestion to rob a bank.

What are post-hypnotic suggestions? What is post-hypnotic amnesia?

Originally, in the mid-1800s, scientists believed that true hypnosis was marked by amnesia for the events of hypnosis. They thought a person who was gen­uinely hypnotized would never remember what happened under hypnosis.

In the 1880s, hypnosis researchers discovered that was not true. People who had been hypnotized could remember what happened to them under hypnosis.

What did scientists originally believe about hypnosis? What proved to be true?

They simply had to be given new suggestions. They were urged to remember the events of hypnosis. Then they would.

Hypnosis as a Dissociative State

Pierre Janet
Pierre Janet

Ernest R. Hilgard of Stanford University described hypnosis as a dissociative state. The concept of dissociation is like parallel processing. One part of the mind operates independently of the rest.

The concept of dissociation originated with Pierre Janet (Jan-AY) (1859-1947). Janet worked with multiple personality patients. Multiple personality is perhaps the most spectacular example of dissociation.

How did Hilgard describe hypnosis? Why is hypnosis considered a dissociative state?

Hypnosis is much less dramatic than multiple personality, but it contains the essential ingredients of all dissociative states: a person does intelligent actions without normal conscious awareness and does not remember it later (unless prompted by suggestions).

For example, a hypnotized person can be told to feel a poke in the back when he or she hears a particular word. Later the person does not remember this suggestion, but when the special word is uttered, the person jumps as if he or she felt a poke in the back.

Some portion of the mind or cognitive system was separated or dissociated from ordinary awareness. It remembered and executed the instructions.

Hypnosis and Memory

Suggestion can occasionally help memory to a remarkable degree. Numerous crimes have been solved with the aid of hypnosis.

For example, in the case of a 1976 kidnapping incident in Chowchilla, California, an entire bus load of children was taken hostage. By hypnotizing the bus driver, who was not taken captive, police were able to retrieve part of the license number of the kidnapper's van. That was enough to locate the vehicle and rescue the children.

A murder at the Metropolitan Opera House in New York was solved using hypnosis. A young ballerina saw a young man with a cellist before the cellist was murdered. Under hypnosis, she describ­ed the man accurately enough to lead to an arrest, later supported by other evidence.

How has hypnosis aided the solution of crimes?

In other cases, suspects are freed because of hypnosis. A Connect­icut teenager confessed to killing his mother. He was acquitted when hypnotic interviews revealed that a false confession had been forced out of him through clever, manipulative questions.

In a similar incident, a man was accused of pushing a woman onto subway tracks in New York. He was acquitted when hypnosis showed his confession could not be taken seriously (Brody, 1980).

It is important to realize that memories of past events are not like tape recordings. Memories are constructions that depend on imagination and inference. Detail does not prove accuracy.

In one case, a hypnotized witness recalled the license number of a getaway car used in a $2.7 million Brinks robbery. It was the license number of a local college president who had "an iron-clad alibi both for himself and for the car" (Holden, 1980, p.1444).

What are some cautions that must be kept in mind, concerning hypnotically aided memory?

In general, hypnosis lowers the threshold for accepting a memory as genuine. This may enable retrieval of weak memories, as with the successful crime solutions described above. It also increases the likelihood of false positives, illustrated by recall of the college president's license plate.

The Problem of Leading Questions

One of the biggest problems with using hypnosis to guide memory retrieval is the influence of leading questions. Leading questions suggest answers indirectly.

A direct suggestion would be: "You will remember a robber with a moustache." A leading question might be, "Did the robber have a moustache?" The results could be exactly the same. A suggestible person imagines a robber with a moustache.

People under hypnosis are very susceptible to this type of influence. To make things worse, a hypnotized person is likely to insist later (when no longer hypnotized) that the memory is genuine.

What is a "leading question"?

An experiment demonstrated this effect. Laurence and Perry (1983) asked subjects under hypnosis, "Did something wake you last night around 4 a.m.?" Usually their subjects said, "Yes."

The researchers then asked, "Was it a sudden sound?" Again, most subjects under hypnosis said, "Yes." Many went on to describe being awak­ened the night before by a gunshot.

Why? It is a logical to assume, when asked about a loud noise at night, that the noise was a gunshot. Why would anybody ask, except if it was important? What is an important loud noise at night? A gunshot!

When these subjects were interviewed without being hypnotized the next day, most of them insisted the memory was genuine. They reported being awakened by a sudden sound, usually a gunshot, two nights before.

When experimenters told them it was a false memory generated as part of the experiment, some subjects became irritable and refused to believe the experi­menters. They stuck to their insistence that the memory was real.

What was Laurence and Perry's (1983) "loud noise at night" study?

The leading question gets its name from the fact that it directs or leads a person to an answer or conclusion (or mem­ory, in this case). Leading questions are important because they can cause a person to make up an imaginary scene.

The process of making something up and believing it is called confabulation. This is where the word fib (meaning a lie) came from. A confabulation is a fib that a per­son believes.

In Chapter Two (Human Nervous System) we saw evidence that confabulation is a well developed talent in human beings. One of the findings from the split-brain research was that the left hemisphere confabulates immediately and effort­lessly, when asked to explain actions generated by the right hemisphere.

The Laurence and Perry study showed how easy it was to make people confabulate under hypnosis. This is a real problem for law enforcement. When a person believes in a memory, no lie detector test can expose the deception.

What is confabulation? Why can this not be detected with a lie detector?

Controlled research shows that memory errors under hypnosis are common. It is true that subjects receiving a list of words to memorize can recall more, later, if hypnotized during recall.

But they also make more errors, and they are unable to distinguish the errors from the correctly recalled words. Apparently hypnosis reduces the threshold for accepting something as true but does not guarantee accuracy.

What is shown by controlled research on memory under hypnosis?

Because leading questions can stimulate confabulation so easily, they must be carefully avoided during hypnotic interrogations in crime investigations.

Hypnotic sessions must be videotaped, if evidence will be used in a trial. That way, a judge or a jury can verify that no leading questions were asked under hypnosis.

What precautions must be taken, if hypnosis is used in a criminal investigation?

Martin Orne, a specialist who studied confabulation under hypnosis, had a simple recommendation. He said no evidence obtained under hypnosis should be admitted in court cases, unless other forms of evidence corroborate it.


Brody, J. E. (1980, October 14). Hypnosis vs. crime: A powerful weapon–or an abuse. New York Times. pp.C1,C2.

Hilgard, E. R. (1977). Divided Consciousness: Multiple Controls in Human Thought and Action. New York: Wiley.

Holden, C. (1980). Forensic use of hypnosis on the increase. Science, 210, 1443-1444.

Laurence, J. & Perry, C. (1983). Hypnotically Created Memory Among Highly Hypnotizable Subjects. Science, 222, 523-524.

Write to Dr. Dewey at

Don't see what you need? Psych Web has over 1,000 pages, so it may be elsewhere on the site. Do a site-specific Google search using the box below.