Disgust and the rubber hand illusion: a registered replication report of Jalal, Krishnakumar, and Ramachandran (2015)

Abstract

Heightened experience of disgust is a feature of obsessive-compulsive disorder (OCD), particularly contamination-related OCD (C-OCD). Previous studies of the rubber hand illusion (RHI) reported that the sense of body ownership is related to the interaction between vision, touch, and proprioception. One recent study demonstrated a link between the RHI and disgust, suggesting that there is an interaction between these three perceptual modalities and disgust (Jalal et al., PLOS ONE 10:e0139159, 2015). However, there have been no direct replications of this initial study. We therefore performed a direct replication of Jalal et al.’s (PLOS ONE 10:e0139159, 2015) study. We examined 133 participants (based on a power analysis) to determine whether placing contamination-related stimuli on a rubber hand causes OCD-like disgust among healthy participants experiencing the RHI. That is, we tested whether Japanese participants experience more intense disgust when the rubber hand and the participant’s hidden hand are stroked synchronously than when stroked asynchronously, in order to replicate and examine the cross-cultural validity of this effect. The main finding of the original study by Jalal and colleagues was successfully replicated in a large sample. Some inconsistencies in one of the control procedures exploring coldness sensations during the RHI were found, which could possibly be due to cross-cultural differences or the improved statistical power of the present study. Based on the present replication study, we conclude that an intervention using the RHI as proposed by Jalal et al. (PLOS ONE 10:e0139159, 2015) might potentially be useful for the treatment of OCD following replications in clinical OCD populations.Preregistration details: This study was preregistered with Cognitive Research: Principles and Implications. The Authors’ protocol received in-principle acceptance on 31 March 2017. The preregistered protocol is available here: 10.6084/m9.figshare.6217295.

“Fake it till You Make it”! Contaminating Rubber Hands (“Multisensory Stimulation Therapy”) to Treat Obsessive-Compulsive Disorder

“…To our astonishment, participants reported disgust sensations-as if arising from the rubber hand! This finding with potential clinical utility (discussed in more detail below) has since been replicated in a large Japanese sample, suggesting the effect is both robust and cross-culturally reliable (Nitta et al, 2018).…”

“…The formulation of the initial hypothesis that contaminating the fake hand during the RHI results in greater contamination sensations than does asynchronous stroking in OCD, specifically 5 min after beginning the stroking, was based on prior work in healthy volunteers (Jalal et al, 2015; see also Nitta et al, 2018). Evidently, in this study, as the RHI triggered greater contamination reactions than did the control procedure, not 5 min but instead 10 min after stroking began (consistent with the overall hypothesis, but not the timeline in which the two conditions were differentiated), our study design was unable to capture any habituation effects.…”

“…In this study, we assessed the RHI with a subjective intensity measure in addition to the onset rating. Although a single-item intensity measure is limited compared to embodiment questionnaires (Botvinick and Cohen, 1998;Peled et al, 2000), it has proven reliable in studies by us (Jalal et al, 2015; see also Armel and Ramachandran, 2003) and others (Lev-Ari et al, 2015;Lev-Ari and Hirschmann, 2016;Nitta et al, 2018). Future research examining multisensory integration in OCD should include additional measures such as questionnaires and the objective ''proprioceptive drift'' test (e.g., Botvinick and Cohen, 1998;Tsakiris and Haggard, 2005;Longo et al, 2008;Marotta et al, 2016).…”

“…As noted, we have shown that contaminating the fake hand during the RHI provokes OCD-like disgust reactions in healthy volunteers (Jalal et al, 2015): in this study, 81% of participants reported greater disgust during synchronous stroking vs. the asynchronous control condition, and, on overage, those undergoing the RHI reported significantly higher levels of disgust. In a ''direct replication study,' ' Nitta et al (2018) likewise showed that such ''exposure'' during the RHI triggered greater disgust reactions than asynchronous stroking in healthy individuals from Japan.…”

“…If contaminating the fake hand during the RHI (5 min after initiating stroking) provokes greater disgust than asynchronous stroking in healthy individuals (Jalal et al, 2015;Nitta et al, 2018)-given the role of disgust in OCD-this should also hold for patients with contamination obsessions. Moreover, considering that ERP targets both anxiety and washing urges (Rachman, 2004), RHI exposure should likewise evoke such contamination sensations overall (i.e., in addition to disgust).…”