Can Any Procedure Be Hypnosis? Exploring the Effect of Framing on Hypnotic Depth and Electrophysiological Correlates of Hypnosis in a Balanced Placebo Design

TL;DR

This study investigates how labeling affects hypnosis experiences and brain activity, finding that framing influences subjective depth but not all brain responses.

Contribution

A novel balanced placebo design to separate the effects of labeling from procedural differences in hypnosis inductions.

Findings

Labeling strongly influenced subjective hypnosis depth, with 'white noise hypnosis' matching conventional inductions.

EEG changes were largely unaffected by labeling, contradicting expectancy theory predictions.

Decreased occipital gamma power emerged as a potential EEG correlate of hypnosis.

Abstract

Expectancy theory of hypnosis posits that any procedure can serve as a hypnotic induction provided it is labeled as “hypnosis”. The present study explored this hypothesis by contrasting the effects of two conventional and two unconventional (placebo) hypnotic inductions on hypnotic experiences and electrophysiological correlates. In a 2 × 2 balanced placebo design, all participants were exposed to four conditions: conventional induction labeled as “hypnosis”, conventional induction labeled as “control”, unconventional induction labeled as “hypnosis”, and unconventional induction labeled as “control”. EEG was recorded from 61 channels. We computed EEG features that were identified in previous studies as correlates of hypnosis or hypnotizability. Consistent with the predictions of expectancy theory, we found that labeling of the procedure was most influential in determining subjective hypnosis depth, and one of the unconventional (placebo) inductions, “white noise hypnosis”, evoked comparable hypnosis depth to the conventional hypnotic inductions. However, contrary to its predictions, “embedded hypnosis”, another unconventional induction, evoked smaller hypnosis depth reports than the other three inductions. Both relaxation and embedded induction procedures showed decreased gamma power in the midline occipital area. Most EEG features we explored were comparable between conventional and unconventional induction conditions, but labeling also seemed to have no effect on EEG changes, which is contrary to the prediction of the expectancy theory. Possible exceptions were a negative effect of conventional induction on functional connectivity between the O1‐Pz channels in the theta band, and a decrease in anterior and posterior alpha power in trials labeled “hypnosis”. However, these effects were inconclusive. Overall, our results provide only partial support for the expectancy theory of hypnosis. The most promising EEG correlate of hypnosis based on our results is decreased occipital gamma power. However, our findings should be considered exploratory. Confirmatory research is required to strengthen our confidence in these effects.

The research plan of this study was registered on the Open Science Framework (https://osf.io/kugdf) before any data collection. The data collection of the first 9 participants was not in accordance with the research plan due to a programming error. The data from these trials was not used in the confirmatory analysis. Consequently, we made changes to the sampling plan and the analysis plan. The altered version of the research plan had been registered at the Open Science Framework (https://osf.io/wvhda) before any new data was collected

Framing is thought to be a key ingredient in inducing hypnosis. This study provides a novel exploration of how procedures framed as “hypnosis” differ from those framed as non‐hypnotic relaxation in electrophysiological activity. Our balanced placebo design separates the effect of labeling from the effect of procedural differences among different unconventional and conventional induction techniques. Our results also verify previous findings about electrophysiological correlates of hypnosis.

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