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Sensory deprivation causes hallucinations

Posted Nov 06 2009 9:11am

Short periods of sensory deprivation can cause hallucinations, even in people who are not prone to them.

A new study conducted by the University College in London has shown that sensory deprivation can indeed trigger hallucinations. Over 200 people applied to take part in the study and completed a Revised Hallucinations Scale questionnaire, which determines if a person is predisposed to hallucinations. Researchers chose 19 volunteers, based on their scores. Nine were chosen from the subjects who scored in the upper 20 th percentile and 10 were selected from the lower 20 th percentile.

Volunteers were placed in an anechoic chamber. The chamber had thick outer walls, covered with fiberglass on the inside. Over the fiberglass, metallic acoustic panels covered the inside of the chamber. All light and sound were completely blocked inside the chamber, making it impossible for participants to see and they could only hear the noises they made inside the chamber.

Subjects sat on a padded chair inside the soundproofed chamber in complete darkness for 15 minutes. A panic button was installed inside the chamber which would immediately release the participant but none of the subjects used this button. They all remained inside the chamber for the full 15 minutes. Many of the participants reported “hallucinations, a depressed mood or paranoia”.

After they were removed from the chamber, participants completed a Psychotomimetic States Inventory test to determine if they had experienced hallucinations or other symptoms of psychosis. (This test was originally developed to study the effects of recreational drug use.)

The nine volunteers who scored in the upper 20 th percentile on the Revised Hallucinations Scale stated that they experienced something “very special or important” inside the chamber.

Six of the participants reported seeing objects that were not there, five had hallucinations of faces, four reported a heightened sense of smell and two felt there was an evil presence in the chamber with them.

The 10 volunteers who had lower scores on the questionnaire, indicating they were less prone to hallucinations, still reported experiencing hallucinations and delusions, but to a lesser degree than the other group.


Psychologist Oliver Mason, one of the researchers involved in this study, said “the results of the experiment support the idea that hallucinations are produced through what the scientists call faulty source monitoring: the brain misidentifies the source of its own thoughts as arising from outside the body.”

Mason was not surprised by the rather dramatic results after such a short time, saying the psychosis-inducing effect of sensory deprivation is analogous to the effect of drugs such as cannabis and ketamine, especially in those prone to psychoses. The findings may be important because they suggest that mental illness and normality occur on a continuum.

The results of the study are published in the October edition of the Journal of Nervous and Mental Disease.

Source: PhysOrg

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