Are You Suggesting That’s My Hand? The Relation Between Hypnotic Suggestibility and the Rubber Hand Illusion

Abstract

Abstract. Hypnotic suggestibility (HS) is the ability to respond automatically to suggestions and to experience alterations in perception and behaviour. Hypnotically suggestible participants are also better able to focus and sustain their attention on an experimental stimulus. The present study explores the relation between HS and susceptibility to the rubber hand illusion (RHI). Based on previous research with visual illusions, it was predicted that higher HS would lead to a stronger RHI illusion. Two behavioural output measures of the RHI, an implicit (proprioceptive drift) and an explicit (RHI questionnaire) measure were correlated against HS scores. Hypnotic suggestibility correlated positively with the implicit RHI measure contributing to 30% of the variation. However, there was no relation between HS and the explicit RHI questionnaire measure, or with compliance control items. High hypnotic suggestibility may facilitate, via attentional mechanisms, the multisensory integration of visuoproprioceptive inputs that leads to greater perceptual mislocalisation of a participant's hand. These results may provide insight into the multisensory brain mechanisms involved in our sense of embodiment.

Individual Differences in the Rubber Hand Illusion Are Related to Sensory Suggestibility

“…Our observations contrast with a recent study [11] in which proprioceptive drift was found to positively correlate with another type of suggestibility—hypnotic suggestibility (i.e., the ability to experience suggested sensations, emotions, and thoughts during hypnotic induction) [11]. Sensory and hypnotic suggestibility involve different cognitive processes, however: the former requires an imagery ability related to a non-existent, but suggested, sensation [23], whereas the latter also involves heightened attentional focus and the ability to ignore sources of interference during hypnotic induction [11].…”

“…One could argue that highly suggestible individuals are generally more compliant and tend to rate questionnaire statements higher [11]. Although we cannot completely exclude this factor, we believe that compliance alone cannot explain our findings.…”

“…Participants rated their agreement or disagreement with each statement on a numeric rating scale ranging from 0 ("I totally disagree") to 10 ("I totally agree"). The first three statements (“Illusion-related statements”) are most frequently endorsed after synchronous stimulation and are considered as being the ones most sensitive to capture the illusory embodiment of the rubber hand [11]. In detail, statement 1 (S1) refers to an illusory localization of touch on the rubber hand, S2 refers to a causal link between vision and touch, and S3 is more directly related to an illusory feeling of ownership.…”

“…The illusion is commonly assessed by means of implicit and explicit measures that capture distinct, albeit related, aspects of the participant’s experience of the RHI [11]. The implicit measure is proprioceptive drift, which refers to a shift in the perceived position of one’s own hand towards the rubber hand [9, 12].…”

“…With regard to the RHI, the artificial hand can be thought of as a suggestive stimulus [11] and the context appears to be characterized by the ambiguity and uncertainty of the source of information. Namely, synchronous stimulation of both the visible rubber hand and the hidden real hand creates perceptual ambiguity: tactile stimulation is felt on the real hand, but, at the same time, the visual information indicates that it is coming from the rubber hand.…”