Harvard Mental Health Letter

Exploring the mysteries of hypnosis

The brain basis of the hypnotic state remains a matter of conjecture.

The term "hypnosis," invented in the 19th century, is derived from the Greek word for sleep, but the derivation is misleading. People undergoing hypnosis are often physically relaxed, and they may be told to close their eyes to enter a hypnotic state, but they remain fully awake and alert. Yet the way that the brain processes information during hypnosis does suggest an alteration in consciousness that researchers are still trying to understand.

A hypnotic state involves three related features: absorption or selective attention, suggestibility, and dissociation. Selective attention is a tendency to focus narrowly, noting certain aspects of experience while becoming oblivious to others. Suggestibility is high responsiveness to social and other environmental cues, including the instructions of a hypnotist. Dissociation is an apparent loss of the unity and continuity of consciousness — a seemingly divided awareness or the capacity to shut out certain perceptions and memories.

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