Modulating Agency in Hypnosis: Using Suggestion to Induce Self-Tickling

Agency is the subjective sense of control we have over our actions. According to an influential model, this arises when the predicted sensory effects of movements match actual sensory feedback. Consistent with this, previous research found that mechanically manipulating the sensory consequences of actions creates the illusion that they are externally-produced. Across three experiments, we aimed to develop a hypnotic analogue and clarify specific components of hypnosis that contribute to alterations in agency. We compared different suggestions based on clinical impairments whist varying the hypnotisability of subjects and the presence of a hypnotic induction. We found that suggestions designed to model self-monitoring deficits increased perceived involuntariness of actions; these effects were stronger in high hypnotisable participants and after an induction; and could not be explained by demand characteristics alone. These results highlight the capacity of hypnosis to alter sense of agency and model deficits associated with clinical conditions using hypnosis.

Modulation of a Stable Neurobehavioral Trait Using Repetitive Transcranial Magnetic Stimulation: A Preregistered Randomized Controlled Trial

Hypnotizability, one's ability to experience cognitive, emotional, behavioral, and physical changes in response to suggestions in the context of hypnosis, is a highly stable trait associated with increased functional connectivity between the left dorsolateral prefrontal cortex (L-DLPFC) and dorsal anterior cingulate cortex (dACC). We conducted a preregistered, triple-blinded, randomized controlled trial to test the ability of continuous theta-burst stimulation (cTBS) over a personalized neuroimaging-based L-DLPFC target to temporarily enhance hypnotizability. We tested our hypothesis in 78 patients with fibromyalgia syndrome (FMS), a functional pain disorder for which hypnosis has consistently been shown to be beneficial as a nonpharmacological treatment option. Pre-to-post cTBS change in Hypnotic Induction Profile scores (HIP; a standardized measure of hypnotizability) was significantly greater in the Active versus Sham group. Our findings suggest a causal relationship between L-DLPFC and dACC function and hypnotizability. Dose-response optimization should be further examined to formalize guidelines for future clinical utilization.

Is there a G-factor in Hypnotic Suggestibility? Confirmatory Factor Analysis of the Harvard Group Scale of Hypnotic Suggestibility

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.

The Phenomenological Control Scale: Measuring the capacity for creating illusory nonvolition, hallucination and delusion.

Phenomenological control is the ability to generate experiences to meet expectancies. There are stable trait differences in this ability, as shown by responses to imaginative suggestions of, for example, paralysis, amnesia, and auditory, visual, gustatory and tactile hallucinations. Phenomenological control has primarily been studied within the context of hypnosis, in which suggestions are delivered following a hypnotic induction. Reports of substantial relationships between phenomenological control in a hypnotic context (hypnotisability) and experimental measures (e.g., the rubber hand illusion) suggest the need for a broad investigation of the influence of phenomenological control in psychological experiments. However, hypnosis is not required for successful responding. Because misconceptions about the hypnotic context may influence hypnotisability scores, a non-hypnotic scale which better matches the contextual expectancies of other experiments and avoids the hypnotic context is potentially better suited for such investigation. We present norms for the Phenomenological Control Scale (PCS), an adaptation of the Sussex Waterloo Scale of Hypnotisability (SWASH) which is free of the hypnotic context. Mean scores for the PCS are higher than for SWASH, and the subjective scales of PCS and SWASH show similar reliability. The PCS subjective scale is a reliable tool for measuring trait response to imaginative suggestion (i.e., phenomenological control) outside the context of hypnosis.

The Phenomenological Control Scale: Measuring the Capacity for Creating Illusory Nonvolition, Hallucination and Delusion

Phenomenological control is the ability to generate experiences to meet expectancies. There are stable trait differences in this ability, as shown by responses to imaginative suggestions of, for example, paralysis, amnesia, and auditory, visual, gustatory and tactile hallucinations. Phenomenological control has primarily been studied within the context of hypnosis, in which suggestions are delivered following a hypnotic induction. Reports of substantial relationships between phenomenological control in a hypnotic context (hypnotizability) and experimental measures (e.g., the rubber hand illusion) suggest the need for a broad investigation of the influence of phenomenological control in psychological experiments. However, hypnosis is not required for successful response to imaginative suggestion. Because misconceptions about the hypnotic context may influence hypnotizability scores, a non-hypnotic scale which better matches the contextual expectancies of other experiments and avoids the hypnotic context is potentially better suited for such investigation. We present norms for the Phenomenological Control Scale (PCS), an adaptation of the Sussex Waterloo Scale of Hypnotizability (SWASH) which is free of the hypnotic context. Mean scores for the PCS are higher than for SWASH, and the subjective scales of PCS and SWASH show similar reliability. The PCS subjective scale is a reliable tool for measuring trait response to imaginative suggestion (i.e., phenomenological control) outside the context of hypnosis.

Segregated brain state during hypnosis

Can the brain be shifted into a different state using a simple social cue, as tests on highly hypnotizable subjects would suggest? Demonstrating an altered global brain state is difficult. Brain activation varies greatly during wakefulness and can be voluntarily influenced. We measured the complexity of electrophysiological response to transcranial magnetic stimulation in one ‘hypnotic virtuoso’. Such a measure produces a response arguably outside the subject’s voluntary control and has been proven adequate for discriminating conscious from unconscious brain states. We show that a single-word hypnotic induction robustly shifted global neural connectivity into a state where activity remained sustained but failed to ignite strong, coherent activity in frontoparietal cortices. Changes in perturbational complexity indicate a similar move towards a more segregated state. We interpret these findings to suggest a shift in the underlying state of the brain, likely moderating subsequent hypnotic responding.