Psychophysiological evidence for a state theory of hypnosis and susceptibility.

Psychophysiological evidence is presented of altered cerebral organisation under hypnosis. Bilateral electrodermal activity was examined to tones presented simultaneously with the induction of hypnosis. Susceptibility was monitored throughout. Two control conditions were devised, one for division of attention and another for relaxation. In addition there was a familiarisation session which permitted groups to be equated for rates of habituation. Both faster and slower habituation were found under hypnosis but the direction of change related to susceptibility; Susceptible subjects showed a reduction in orienting responses and Unsusceptible subjects an increase in responses. Susceptible subjects also had lower tonic levels of activity and fewer nonspecific responses during the induction prior to the tones. Neither relaxation nor listening to a story altered habituation systematically. Under hypnosis there was a reversal in lateral asymmetries in orienting response amplitudes in Susceptible subjects suggesting a shift in hemispheric influences from left to right.