4. Can anyone be hypnotized, or only certain people?

4.1. Hypnotizability

Using standardized induction scripts and classical induction techniques, somepeople are found to be markedly more hypnotizable than others. Aside from arequisite minimum intelligence for language and capacity to followinstructions, there are some other stable characteristics that seem to relateto hypnotizability, though they do not appear to relate directly to anythingthat we ordinarily consider personality traits (such as the stereotype ofgullibility and so on).

An exceptionally skillful operator can individualize their approach andthereby reduce the number of 'unhypnotizable' or 'resistant' subjects quite abit, but there are still some people that respond much more easily than othersto hypnotic suggestion, especially with regard to 'deep trance' phenomena.This responsiveness appears to show high test-retest reliability, even aftermany years.

There are 12 standard tests in the SHSS (Stanford Hypnotic SusceptibilityScale) which measure how well a subject conforms to the behavior of aclassically hypnotized person. By these scales, about 5% of people areclassically unhypnotizable, most people show moderate scores, and about 10%are hypnotizable to extreme depths and show the classical deep trancephenomena such as somnambulism, visual and auditory hallucinations, andability to remain deeply in hypnosis with eyes open.

As mentioned, hypnotizability does not appear to show any obvious correlationwith any of the usual personality traits or characteristics. Not only isgullibility not directly correlated, but gender, extraversion/introversion,and neurotic tendencies have also been shown not to correlate well withhypnotizability.

There is some tentative evidence that physiological response to suggestion isinfluenced by certain forms of sensory deprivation or isolation. For example,see Barabasz and Gregson, "Antarctic wintering--over, suggestion and transientolfactory stimulation: EEG evoked potential and electrodermal responses." inBiological Psychology. 9(4):285-95, 1979 Dec.

EEG evoked potential and electrodermal responses to real and suggestedolfactory stimulation were recorded on a team of nine men who wintered -overat Scott Base, Antarctica. Multi-variate analysis of variance findingsindicated some consistent trends despite adverse conditions and markedinter-individual differences. Consistent with studies of secondaryafferentation olfaction-related EEGs were evidenced in the occipital area (O1and O2) as well as the temporal area (T3 and T4). Skin conductance (SC) showedsignificant responses for real and suggested odorants pre and postwintering-over. Suppression of EEG amplitudes for real and suggested stimuliwas evidenced prior to wintering-over. Following wintering-over experiencesuppression of EEG amplitudes for real stimuli showed a decrease whilesuppression increased for suggested stimuli. The implications of thesuggestion findings are discussed in possible explanation of the apparentconflict between different sources of information about human responses toisolation in the Antarctic environment.