Hypnosis is not an altered brain state?

Hypnosis is not an altered brain state?

Brain Scan
Brain Scan

Copyright © Donald Robertson, 2010.  All rights reserved.

Perhaps surprisingly, it’s not clear where the association between “hypnotic trance” and hypnotism comes from.  James Braid, the founder of hypnotism in the 1840s, never used the word “trance” to explain hypnosis.  Neither did Hippolyte Bernheim, the second most important figure in the early history of hypnotism.  Indeed, the concept of “trance” was generally more associated with Mesmerism, and hypnotists and Mesmerists were fundamentally opposed to each other’s views.  Whereas Mesmerists believed that subjects were influenced by supernatural powers channelled in the form of a “magnetic fluid” by the Mesmerist, hypnotists were skeptics who believed that subjects were responding mainly because of suggestion and imagination.  Modern researchers, as we shall see, are also generally quite skeptical about the idea of “hypnotic trance” and many view hypnosis instead as being primarily a state of heightened expectation and focused attention.

It is sometimes claimed that that people in hypnotic trance produce a higher frequency of “alpha”, or sometimes “theta”, brain waves on electroencephalogram (EEG) brain scans. Michael Heap, one of the UK’s leading psychological researchers in this field warns,

Incidentally, ignore any statements in the popular hypnosis literature to the effect that hypnosis is an “alpha state” or “theta state” or that the right hemisphere is put into one of these states, or that the hypnotist directs suggestions to the unconscious mind in the right hemisphere by sitting on the subject’s left side, or that the hypnotist matches the frequency of his voice with that of the subject’s brainwaves, etc., etc. (Heap, 2006: 6)

Likewise, Steven Jay Lynn and Irving Kirsch, two of the most prolific contemporary researchers in the field of hypnosis, and leading critics of the notion that hypnotism works by inducing an altered state of consciousness or “trance”, write,

The idea that hypnosis involves a trance state may be the most pernicious of popular ideas about hypnosis.  Decades of research have failed to confirm the hypothesis that responses to suggestion are due to an altered state of consciousness, and as a result, this hypothesis has been abandoned by most researchers in the field.  Many knowledgeable scholars either reject the use of the term trance as misleading or use it in a sufficiently broad sense to include such commonplace experiences as being absorbed in an interesting move, conversation, or daydream.  (Lynn & Kirsch, 2006)

Indeed, referring to hypnosis as involving a “trance” actually appears to make people less hypnotisable.  It may foster anxiety about loss of control and encourage subjects to adopt an overly-passive “wait and see” attitude.  By contrast, researchers have generally found that subjects who actively imagine the things being suggested tend to respond better to hypnosis.  For example, Lynn and his colleagues found that when participants in an experimental study were told that it was necessary to enter “trance” to respond to hypnotic suggestions, they became less suggestible instead of more so.

There are some brain imaging correlates of hypnotic responses but they tend to be more complex and “task-specific” than popular psychology books assume.  For example, after reviewing the literature on EEG scans during hypnosis, James E. Horton and Helen J. Crawford, two experts in this area, recently concluded,

Hypnosis is not a unitary state and therefore should show different patterns of EEG activity depending upon the task being experienced. In our evaluation of the literature, enhanced theta is observed during hypnosis when there is task performance or concentrative hypnosis, but not when the highly hypnotisable individuals are passively relaxed, somewhat sleepy and/or more diffuse in their attention. (Horton & Crawford, in Heap et al., 2004: 140)

Similar differences, they note, are well-known from research on meditation, where changes in brain wave activity depend on the kind of meditation being practiced, in particular whether it involves intense concentration or not. These changes are, therefore, probably merely a reflection of the concentration employed rather than anything which could be accurately referred to as a “trance” or “altered state of consciousness.”  Because the neurological and physiological correlates of hypnosis are task-specific, nobody has ever been able to produce a single unambiguous marker of hypnotic trance. In other words, it is currently impossible to point at two brain scans and say, “That one’s definitely in hypnotic trance and that one isn’t.”

Some magazine articles that may be of interest,

This recent Scientific American magazine article by Scott Lilienfeld (2009) summarises research on hypnosis from a sceptical nonstate position.

Scientific American

This older TIME magazine article from the 1970s provides quotes from T.X. Barber outlining some of the key experimental observations which led to the “cognitive-behavioural” theory of hypnosis.

TIME Magazine