Hypnosis and lateralized brain functions.

Bilateral EEG measures were obtained on 16 high hypnotizable Ss (scores of greater than 8 on the Harvard Group Scale of Hypnotic Susceptibility, Form A, Shor & E. Orne, 1962), while performing hemisphere-specific tasks during hypnosis and a no-hypnosis control condition. Conditions and tasks were presented in counterbalanced order, and Ss served as their own controls. The data call into question the right hemisphere activation interpretation of lateralized brain function during hypnosis; rather, the data suggest a lack of task appropriate activity during hypnosis. The failure to attend to baseline activity measurements and the use of ratios to evaluate interhemispheric lateralization may contribute to potential misinterpretations of data. It is critical that activity changes of the separate hemispheres be taken into account in the interpretative process.