Trait phenomenological control predicts experience of mirror synaesthesia and the rubber hand illusion

Abstract

In hypnotic responding, expectancies arising from imaginative suggestion drive striking experiential changes (e.g., hallucinations) - which are experienced as involuntary - according to a normally distributed and stable trait ability (hypnotisability). Such experiences can be triggered by implicit suggestion and occur outside the hypnotic context. In large sample studies (of 156, 404 and 353 participants), we report substantial relationships between hypnotisability and experimental measures of experiential change in mirror-sensory synaesthesia and the rubber hand illusion comparable to relationships between hypnotisability and individual hypnosis scale items. The control of phenomenology to meet expectancies arising from perceived task requirements can account for experiential change in psychological experiments.

Fig. 1. Scatter plots showing linear regression of vicarious pain measures (n = 404 participants) on hypnotisability.

a Total pain responses on hypnotisability, Spearman’s r_s = 0.26, 95% CI [0.17, 0.35]. b Pain intensity on hypnotisability, Spearman’s r_s = 0.27, 95% CI [0.18, 0.36]. Error bars show 95% CI.The centre of credibility intervals is the predicted score. Note: SWASH is an abbreviation of Sussex-Waterloo Scale of Hypnotisability.

Fig. 2. Scatter plots showing linear regression of mirror touch measures on hypnotisability (n = 154 participants).

a Touch to human responses, Spearman’s r_s = 0.19, 95% CI [0.04, 0.34]. b Touch to object responses, Spearman’s r_s = 0.21, 95% CI [0.06, 0.36]. Error bars show 95% CI. The centre of credibility intervals is the predicted score. Note: SWASH is an abbreviation of Sussex-Waterloo Scale of Hypnotisability.

Fig. 3. Scatter plots showing linear regression (n = 353 participants) of synchronous condition rubber hand illusion measures on hypnotisability and expectancies.

a Mean subjective report for location and ownership (S1–S3) on hypnotisability, r_s = 0.26, 95% CI [0.16, 0.37]. b Proprioceptive drift on hypnotisability, r_s = 0.11, 95% CI [0.003, 0.22], (c) subjective report for visual hallucination (S4) on hypnotisability, r_s = 0.31, 95% CI [0.21, 0.43], and (d) synchronous condition mean subjective report for location and ownership (S1–S3) on synchronous condition expectancy. r_s =  0.23, 95% CI [0.13, 0.34]. Error bars show 95% CI. The centre of credibility intervals is the predicted score. Note: SWASH is an abbreviation of Sussex-Waterloo Scale of Hypnotisability.