Hyperæsthesia
An Encyclopaedia of Occultism (1920)
An actual or apparent exaltation of the perceptive faculties, characteristic of the hypnotic state. hypnotic state. The smallest suggestion, whether given by word, look, gesture, or even breathing or unconscious movement, is instantly seized upon and interpreted by the entranced subject, who for this reason is often termed "sensitive." The phenomenon of hyperæsthesia, observed but wrongly interpreted by the early magnetists and mesmerists, was largely responsible for the so-called clairvoyance , thoughtreading, community of sensation , and other kindred phenomena. The realisation of suggestion and hyperæsthesia was the great achievement of Bertrand and Braid , which brought hypnotism into the domain of scientific fact. The significance of hyperæsthesia in connection with every form of psychic phenomena can hardly be over-estimated . Nor is it met with only in the trance state. It enters into the normal existence to an extent that is but imperfectly understood. Dreams , for instance, frequently reproduce impressions which have been recorded in some obscure stratum of consciousness, while much that we call intuition is made up of inferences subconsciously drawn from indications too subtle to reach the normal consciousness. Hyperæsthesia has been defined above as an actual or apparent exaltation of the perceptive faculties." The reason for this is that modern scientists declare that it is not known whether the senses are actually sharpened or not. Most probably the hyperæsthetic perception is merely a normal perception which by reason of the state of cerebal dissociation operates in a free field. Very slight sense-impressions may be recorded in the brain during normal consciousness, but such is the inhibiting effect of the excitement occasioned by other similar impressions, that they do not reach full consciousness.
What Has Changed in the Last Century
The 1920 Encyclopaedia of Occultism treated hyperæsthesia mainly as a tool for explaining away clairvoyance and thought-reading: the entranced "sensitive" picking up cues from a look, a gesture, even a sitter's breathing. That cue-reading explanation has held up and grown—it is now the standard account of the Clever Hans effect and of ideomotor phenomena like the ouija board and dowsing—but the word itself has migrated out of psychical research into clinical neurology, where hyperesthesia simply means abnormally increased sensitivity of a nerve or sense, alongside terms like allodynia, hyperacusis and photophobia. The entry's own caution proved right: controlled testing has not shown that hypnosis genuinely sharpens the senses, and modern research treats hypnotic response as a matter of suggestion, expectation and attention rather than heightened acuity. Hypnosis meanwhile gained the medical respectability the author wanted for it, endorsed by the British Medical Association in 1955 and the American Medical Association in 1958.
Written for this edition, 2026.