Can Hypnotic Susceptibility be Explained by Bifactor Models? Structural Equation Modeling of the Harvard Group Scale of Hypnotic Susceptibility - Form A

Abstract

Individuals differ in their responsiveness to (post-)hypnotic suggestions. However, defining and measuring hypnotizability is contentious because standardized scales, such as the Harvard group scale (HGSHS:A), measure a mixture of general-suggestibility and its increase due to hypnotic induction (hypnotic-suggestibility). Exploratory factor analysis (FA) of standardized scales found them to be heterogeneous; however, the number and nature of latent factors are debated. We applied Confirmatory FA to HGSHS:A scores of 477 volunteers and tested several theory-driven models. Scores were best explained by a bifactor model consisting of a G-factor, tapping into hypnotizability, and three grouping factors, measuring specific suggestibilities, each requiring a unique combination of three top-down cognitive functions: cognitive-simulation, sensory-adaptation, and problem-solving. Structural equation modeling revealed that the simulation-adaptation factor (requiring cognitive-simulation and sensory-adaptation), predicts the other suggestibility factors. These results demonstrate the multifaceted structure of hypnotic-suggestibility and underscore the desideratum for developing a more differentiated scale, focusing on simulation-adaption suggestions.