What is a hypnotic "trance" ?
2.5. Trance as
distinct from sleep or stupor
I think we can fairly conclude
from the research on hypnosis done so far that 'trance' may in fact have
useful meaning for describing the subjective experience of subjects in
hypnotic situations, but is not explained, or even described, by any one
simple theory yet proposed, either neurological or psychological. All
of the current theories seem to leave aspects unexplained.
Clearly, selective cerebral
inhibition and activation of some kind is involved at various stages of
a hypnotic induction, but not yet in any way we can uniquely distinguish
from other forms of waking response to changing stimuli in other situations.
And certainly hypnotic response does not rely upon the generalized inhibition
found in the action of depressant drugs or in the normal sleep state.
It is a much more highly specific effect, if indeed it truly is distinct
in some way, as subjective data appear to suggest.
The most common neurological
theories of hypnosis over the years as a form of partial sleep have mostly
been based on (1) the superficial resemblance of a classically induced
subject to a near-sleeping person, (2) on the ease with which a deeply
hypnotized subject will fall off to sleep on suggestion or if hypnosis
is not explicitly ended, and (3) because various drugs that induce sleep-like
or stuporous states can produce some of the same characteristics as hypnotic
It has been very consistently
determined that trance itself has nothing at all to do with sleep, and
is much more easily distinguished from a sleeping state physiologically
than from a waking state. Measurements attempted included a number of
famous early experimental studies in the 1930's, on such variables as
EEG measurements, cerebral circulation, heart rate, respiration, basal
metabolism, and various behavioral parameters. Representative of these
experiments comparing hypnosis and sleep was: M.J. Bass, "Differentiation
of the hypnotic trance from normal sleep," Journal of Experimental
Psychology, 1931, 14:382-399.
Though the mentation in hypnosis
often resembles dreaming, it appears much closer to daydreaming in character
than to normal night time dreaming.
Clark Hull, in his 1936 classic
Hypnosis and Suggestibility describes a number of experimental
setups for distinguishing the mental characteristics of sleep from those
of hypnotic trance.
One thing suggested by this
is that if sleep can be viewed as largely a generalized cortical inhibition,
and trance is not in any determinable way identified with sleep, that
trance is not a form of sleep or a stupor. This is also easily determined
by observing the range of activities possible in hypnotized subjects (compared
to waking subjects and those under the influence of depressant drugs).