Hypnosis and Memory

In TV shows or movies, there are scenes in which people are given a suggestion that they would not remember a certain thing (such as a person's name or an incident, either during the session itself (hypnotic amnesia) or at the end of hypnosis (posthypnotic amnesia). A reversal cue could also be given, a phrase such as "You will now remember everything"; once the person hears this, their state of amnesia ends.

According to research, around 25% of hypnotised college students could be led to experience amnesia. Although researchers agree that hypnotic and posthypnotic amnesia occur, they do still debate the causes. Some feel that it's a result of voluntary attempts in avoidance of thought on certain information, while others believe it to be caused by an altered state of conscientiousness which weakens normal memory systems.

Memory Enhancement

In contrast to producing the effect of forgetting, can hypnosis enhance memory?

Law enforcement agencies sometimes use hypnosis in aid of eyewitnesses to a crime. In a famous case in California which occurred in 1977, a bus carrying 26 children and its driver disappeared without a trace. The victims, buried underground in an abandoned trailer truck by three kidnappers, were later found alive. After the rescue, an expert hypnotised the bus driver and asked him to recall the ordeal. The driver formed a vivid image of the kidnappers' white van and could "read" all but one digit of the vans licence plate. The information helped track down the kidnappers.

Despite occasional success stories such as this, controlled experiments find that hypnosis is unable to improve memory. In some experiments, participants watch videotapes of simulated bank robberies or other crimes. Next, while hypnotised or not, they are questioned by police investigators or criminal lawyers. Hypnotised individuals tend to remember better than non-hypnotised individuals in some studies, but not all. There have been experiments where hypnotised participants had performed much poorly than non-hypnotised people; they had recalled more information, but much of it was inaccurate.

Another concern regarding this is that some memories recalled under hypnosis maybe pseudomemories—false memories created during hypnosis by statements or leading suggestions made by the examiner. In some experiments, hypnotised and non-hypnotised participants are intentionally exposed to false information about an event (e.g.: about a bank robbery). Later, once the hypnotised subjects are brought out of their hypnosis, they are questioned. Highly suggestible individuals that have been hypnotised are the ones most likely to report the false information as being a true memory and often tend to be confident of the accuracy of their memories.

Although some psychologists are exploring ways to minimise hypnosis-induced memory errors, at present, many courts have banned or limited testimonies obtained under the influence of hypnosis. The increased suggestibility of hypnotised individuals makes them particularly susceptible to memory distortion caused by leading questions, and they may come to believe things that never occurred in the first place. Similarly, if a therapist uses hypnosis to help patients recall long-forgotten memories of sexual abuse, what shall we conclude? Are the memories real, or are they pseudomemories created during therapy sessions?

Disassociation

What is hypnosis ad how does it produce its effects?

Several researchers propose theories that view hypnosis as an altered state involving a disassociation of consciousness. Ernest Hilgard proposed that hypnosis creates a division of awareness in which the person simultaneously experiences two streams of consciousness that are cut off from each another. One stream responds to hypnotic suggestions, while the other—the part of consciousness which monitors behaviour—remains in the background, but is aware of everything that goes on. Hilgard reefers to this second part of consciousness as the Hidden Observer.

Suppose a hypnotised subject is given a suggestion that she wouldn't feel pain. Her arm is lowered into a tub of ice-cold water for 45 seconds and every few minutes, she reports the amount of pain. In contrast to unhypnotised subjects, who find this experience moderately painful, she would probably report feeling less pain. But suppose the procedure is done differently. Before lowering the subject's arm, the hypnotist says, "Perhaps there is another part of you that is more aware than your hypnotised part. If so, would that part of you report the amount of pain."

In this case, the subject's other stream of consciousness, the Hidden Observer, would report a higher level of pain.

For Hilgard, this disassociation explained the reason behind the involuntary automatic behaviour that occurs under hypnosis. Given the suggestion "Your arm will start to feel lighter and will begin to rise," the subject intentionally raises his or her arm, but only the Hidden Observer is aware of this. The mainstream of consciousness that responds to the command is blocked from this awareness and perceives that the arm is rising all by itself.

Studies on Hypnosis

Hypnosis is a state of heightened suggestibility, in which certain individuals can experience imagined situations that seem real. There is great interest in hypnosis several therapists use to treat mental illnesses with it. Some Psychology PhD programmes tend to offer courses in hypnosis. Scientists who explore whether hypnosis is a unique state of altered consciousness tend to put the claims about it through several tests.

Hypnotic Behaviour

Hypnotic Induction is the process by which a person (a researcher or a hypnotist) leads another, the subject, into a state of hypnosis. A hypnotist may request the subject to sit down and gaze at an object on the wall, or something like a pendant in his hand. He then may suggest that the subject's eyes are getting heavy. The goal of this test is to relax the subject while increasing their concentration.

Contrary to popular belief, a person can't be hypnotised against their will. Even when people want to be hypnotized, they differ in susceptibility to hypnotic suggestions. Hypnotic susceptibility scales contain a standard series of pass/fail suggestions being read to a subject after hypnotic induction. The subject's score is based on the number of passes. Some subjects tend to be completely non-responsive; some pass all while the rest fall in between.

Does hypnosis alter one's behaviour and psychological function? Some claim it does.

Involuntary Control

Hypnotised individuals subjectively experience their actions as involuntary ones; they believe they're controlled by a mysterious force rather than their conscious control.

If behaviour seems to be involuntary under hypnosis, can it be used to perform harmful acts? According to Martin Orne and Fredrick Evans, hypnotised subjects were able to be made to dip their hands briefly in a solution of foaming liquid, which as made to believe was acid, and throw on another person's face.

This might be an example of the power of hypnosis in getting people to act against their will. However, in another controlled group that Orne and Fredrick tested on, the subjects were asked to simply pretend to be hypnotised. These subjects were just as likely as the earlier group to dip their hands in the solution and throw it at another.

In another experiment, researchers induced hundreds of adults to keep giving what they believed to be hundreds of  painful electric shocks to an innocent man with a heart condition, while he begged them to stop. None of the subjects were hypnotised; they were simply following the researchers' orders. This shows that contrary to popular beliefs, hypnosis does not involve a unique power to get people to behave against their will. A legitimate authority figure can induce people to commit out of character, dangerous acts with or without being hypnotised.

Amazing Feats

Have you seen or heard of stage hypnotists who gets an audience member to perform an amazing physical feat such as the 'human plank'? The subject, usually a male, is hypnotised and lies  outstretched between two chairs. He is told that his body is rigid and then, amazingly, another person stands on his legs and chest.

Similarly, psychology can have striking effects. Consider the classic experiment which involved 13 people allergic to the toxic leaves of a certain tree. Five of the test subjects were hypnotised while being blindfolded and were told that a leaf from a harmless tree they weren't allergic to was touching one of their arms, when, in fact, it was toxic. But four of five hypnotised subjects had no allergic reaction. For the next  step, the other arm of the hypnotised subjects were rubbed with a leaf from a harmless tree and he or she was falsely informed of the leaf being toxic. All five of them reacted to the harmless leaf with an allergic reaction.

Should the human plank, as well as the unusual responses of the allergic subjects, be attributed to the unique powers of hypnosis? Here is why a healthy dose of critical thinking may be of importance.

Pain Tolerance

Scottish surgeon James Esdaile performed more than 300 major operations in the mid-1800s using  hypnosis as the sole anaesthetic. According to experiments, an increase in pain tolerance, which wasn't due to the Placebo Effect, was confirmed.

For patients who experience chronic pain, hypnosis can produce relief lasting for months, or even years. Brain imaging research has revealed that hypnosis modifies a person's neural activity in areas that process painful stimuli, but non-hypnotic techniques such as mental imagery and performing distracting cognitive tasks also alter neural functioning and reduce pain.

We do not know exactly how hypnosis produces painkilling effects. It may influence the release of endorphins, decrease a patient's fear of pain, distract patients of their pain, or somehow help them in separating the pain from the conscious experience.