Hypnotism is known under many names, including hypnosis, neurohypnosis, neurypnology, artificial somnambulism, and Braidism. All these terms are used to denote the procedure or the state induced by that procedure, by means of which a hypnotist establishes rapport in a receptive subject, so that the subject is persuaded to experience changes in consciousness, perception, cognition, emotion, volition, and/or motor behaviour in accordance with the hypnotist’s suggestions.
When subjects hypnotize themselves, this is known as autohypnosis. When they are hypnotized by a third person, i.e. a hypnotist, the term heterohypnotism is used. Conceptually as well as phenomenologically, hypnotic states are related to other states of altered consciousness such as rapture, ecstasy, dissociation, trance, and somnambulism.
Historically, the theory of hypnotism was preceded by the theory of animal magnetism or mesmerism.
The terms hypnotism and hypnosis stem from the Greek noun hupnos, which means sleep. It is not clear who introduced them. What we do know is that the term hypnologie appeared in the second edition of Morin’s Dictionnaire Étymologique published in 1809 and that in 1820 various terms with the prefix ‘hypn-‘ figured in the mesmerist works of the French magnetist Baron Etienne Félix d’Hénin de Cuvillers (1755-1841). From 1842 on, the Scottish neurosurgeon James Braid (1796-1860) used the terms neurypnology, neuro-hypnosis, and hypnosis to denote the somnolent state which he considered the physiological correlate of mesmerism.
According to Braid, mesmerists did not establish rapport by means of animal magnetism or any variant thereof, but by inducing a “nervous sleep” which in his opinion differed somewhat from ordinary sleep. His own favourite method for producing this state was through visual fixation on a small bright object held 18 inch above and in front of the eyes, thus forcing the subject into a ‘Braid’s strabismus’. At the time, Braid attributed the efficacy of this manoeuvre to the over-exercising of the eye muscles.
After much experimentation, however, he came to the conclusion that the majority of hypnotic states can be induced without the interference of sleep in any form. Realizing that the term hypnotism was therefore inappropriate, in 1847 he proposed replacing it by monoideism. However, by that time the terms hypnotism and hypnosis had gained such wide acceptance that the term monoideism failed to catch on.
Hypnotic states can be induced in a multitude of ways, including fixation of the subject’s gaze, exposure to movement, colours or sounds, and suggestion. The hypnotic state is commonly divided into three stages: light hypnosis (in which the subject is lethargic, but aware of his or her surroundings), the cataleptic state (characterized by muscular rigidity), and the somnambulistic state (i.e. a deep trance during which the subject tends to be the most compliant to the hypnotist’s suggestions). During the latter stage, in particular, illusions and hallucinations can be induced.
In biomedicine these are referred to as hypnotic or hypnotically induced hallucinations. It is generally held that the perceptual material brought to the surface in this way derives from unconscious or subconscious material. In this sense, hypnotic hallucinations can perhaps best be regarded as release phenomena.
In parapsychology, some hypnotic hallucinations are designated as ‘higher phenomena’. These include clairvoyance, clairaudience, telepathic phenomena, remote viewing, and eyeless vision. A type of hallucination which appears to be largely restricted to the context of hypnotism is the negative hallucination.