Effects of hypnotizability on performance of a Stroop task and event-related potentials.

The effect of hypnotizability on verbal reaction times and event-related potentials during performance of a Stroop color-naming task was studied. The Stroop stimuli (colored words) were randomly presented to 5 high and 5 low hypnotizable subjects in the right and left peripheral visual fields during both waking state and hypnotic induction conditions. Unlike studies in which the Stroop stimuli were foveally presented to the subjects, the highly hypnotizable subjects did not show prolonged verbal reaction times in either waking or hypnotic conditions. There was a marked deterioration in performance accuracy, however, for highly hypnotizable subjects during hypnosis. Event-related potentials indicated that the highly hypnotizable subjects showed a reduced P3a amplitude and a decreased N2b latency to the visual stimuli in both waking and hypnotic conditions, suggesting a lack of orienting to or disengagement from peripherally occurring stimuli.