Is the rubber hand illusion associated with somatic symptom reporting?

Abstract

Current approaches to somatic symptom perception conceptualize somatic symptoms partly as somato-visceral or body illusions evoked by an interaction between bottom-up (sensory) and top-down (expectations, attention) processes. Similar processes of multisensory integration are assumed to contribute to the rubber hand illusion (RHI). Findings concerning the strength and direction of associations between these two phenomena, symptom perception and the RHI, are equivocal. Individuals of a non-clinical sample (N = 63; 56% females; M_age = 20.4; SD = 1.6) completed the Patient Health Questionnaire Somatic Symptom Scale (PHQ-15) and participated in an experiment that evoked the RHI. In repeated measures analyses of variance with the PHQ-15 score as covariate, no significant interaction effects between the PHQ-15 score and indicators of the RHI, i.e., proprioceptive drift (F(1,61) < 0.001 p = 0.993, partial η² < 0.001; BF₁₀ = 0.307), felt body ownership(F(1,59) = 0.043, p = 0.836, partial η² = 0,001; BF₁₀ = 0.501), and felt body disownership (F(1,59) = 0.148, p = 0.702, partial η² = 0.002; BF₁₀ = 1.972) were found. Overall, frequentist and Bayesian analysis indicated that the support for a possible association between the PHQ-15 and indicators of the RHI remains inconclusive, i.e., neither the null nor the alternative hypotheses were sufficiently supported. At least in this non-clinical sample, the association between somatic symptom distress and the strength of the RHI appears so weak (perhaps non-existing), that both phenomena (somatic symptom distress and the RHI) appear distinct and largely unrelated.