Hypnosis

Hypnosis is a human condition involving focused attention (the selective attention/selective inattention hypothesis, SASI), reduced peripheral awareness, and an enhanced capacity to respond to suggestion.

There are competing theories explaining hypnosis and related phenomena. Altered state theories see hypnosis as an altered state of mind or trance, marked by a level of awareness different from the ordinary state of consciousness. In contrast, non-state theories see hypnosis as, variously, a type of placebo effect, a redefinition of an interaction with a therapist or a form of imaginative role enactment.

During hypnosis, a person is said to have heightened focus and concentration and an increased response to suggestions. Hypnosis usually begins with a hypnotic induction involving a series of preliminary instructions and suggestions. The use of hypnosis for therapeutic purposes is referred to as "hypnotherapy", while its use as a form of entertainment for an audience is known as "stage hypnosis", a form of mentalism.

The use of hypnosis as a form of therapy to retrieve and integrate early trauma is controversial within the scientific mainstream. Research indicates that hypnotising an individual may aid the formation of false memories. Medical hypnosis is often considered pseudoscience or quackery.

The words hypnosis and hypnotism both derive from the term neuro-hypnotism (nervous sleep), all of which were coined by Étienne Félix d'Henin de Cuvillers in the 1820s. The term hypnosis is derived from the ancient Greek ὑπνος hypnos, "sleep", and the suffix -ωσις -osis, or from ὑπνόω hypnoō, "put to sleep" (stem of aorist hypnōs-) and the suffix -is. These words were popularised in English by the Scottish surgeon James Braid (to whom they are sometimes wrongly attributed) around 1841. Braid based his practice on that developed by Franz Mesmer and his followers (which was called "Mesmerism" or "animal magnetism"), but differed in his theory as to how the procedure worked.

A person in a state of hypnosis has focused attention, a deeply relaxed physical and mental state, and increased suggestibility.

The hypnotized individual appears to heed only the communications of the hypnotist and typically responds in an uncritical, automatic fashion while ignoring all aspects of the environment other than those pointed out by the hypnotist. In a hypnotic state an individual tends to see, feel, smell, and otherwise perceive in accordance with the hypnotist's suggestions, even though these suggestions may be in apparent contradiction to the actual stimuli present in the environment. The effects of hypnosis are not limited to sensory change; even the subject's memory and awareness of self may be altered by suggestion, and the effects of the suggestions may be extended (post-hypnotically) into the subject's subsequent waking activity.

It could be said that hypnotic suggestion is explicitly intended to make use of the placebo effect. For example, in 1994, Irving Kirsch characterized hypnosis as a "non-deceptive placebo", i.e., a method that openly makes use of suggestion and employs methods to amplify its effects.