The Rubber Hand Illusion (RHI), developed by Botvinick and Cohen, is widely used in research to manipulate body perception. This illusion occurs when body ownership through the simultaneous presentation of visual and tactile stimulation targets artificial hands while keeping their natural hands hidden from view. New research investigated the relationship between pain perception and RHI by introducing thermal stimulation to the illusion. The researchers utilized continuous, real-time pain ratings in their investigation to enhance the accuracy of understanding how RHI produces its analgesic effects.
A study group consisting of thirty-four right-handed healthy participants (27 female and seven male with a mean age of 24.03 years) was recruited from Ruhr University Bochum. The research included patient screening to confirm the absence of and with chronic pain disorders, and consent was obtained from participants. A 2 × 4 within-subject experimental design examined normal and inverse rubber hand placement in combination with +0°C, -0.75°C, +0.75°C, +1.5°C temperature levels. During the normal condition, participants viewed the anatomically intact rubber hand, yet the inverse arrangement required a 180° rotation.
Participants placed their left hand on a concealed thermode and used their right hand to adjust a pain rating slider. The rubber hand received illumination during the process of heat application. Participants underwent a slow temperature progression of the thermode until they reported feeling moderate pain between levels 5-7 on the 10-point scale. The research team adjusted heat stimuli at this stage.
The study used synchronized thermal and visual cues that progressively heated up for two seconds before maintaining the peak temperature for five seconds and then restoring baseline levels. The experimental period lasted ten seconds while brief pauses separated each trial from the next. Participants scored their pain intensity continuously throughout stimulation before assessing it through a post-stimulation visual analog scale. Participants used a nine-item questionnaire to evaluate their sense of ownership of the rubber hand. Researchers conducted their statistical investigations through linear mixed models (LMMs) in R (RStudio) to understand how rubber hand orientation and temperature variables, together with time, affected pain and ownership measurements.
Participants showed an average of 43.75°C (±3.71) as their pain threshold, but the stimulated temperature reached 46.11°C (±2.17). Pain ratings showed significant changes based on RHI exposure and temperature and were also influenced by time (p < 0.001), with notable factor interactions. Post hoc analysis revealed that normal rubber hand conditions produced lower pain ratings at most temperature levels and only excluded the +0.75°C point (p = 0.102). The pain reduction started during stimulation and remained consistent, except for temporary disruptions during the initial and final stages.
Participants scored significantly higher on body ownership tests through RHI exposure (p < 0.001) without any impact from different temperature conditions. The experimental findings showed no meaningful influence between RHI exposure and temperature variations (p = 0.911). Temperature acted as the key factor in determining pain intensity differences (p < 0.001), while RHI failed to produce significant variations (p = 0.76), and their combined effect showed no significance (p = 0.274). The results showed that high-temperature levels significantly influenced pain unpleasantness scores (p < 0.001), while RHI failed to show any impact on this rating (p = 0.566).
The experimental design, which combined pain tests with illusion stimuli, helped maintain participants’ focused attention, potentially enhancing the observed analgesic effect. The process of body self-observation causes alterations in pain perception through varying degrees of augmentation or reduction based on situational factors. Research evidence supports the finding that attentional mechanisms influence pain regulation. The normal rubber hand condition produced sustained reductions in pain intensity, thus demonstrating that body ownership acts as an analgesic factor. Test results using inverse hands displaying ownership issues did not reveal similar pain reduction levels when compared to standard conditions.
RHI demonstrated a pain-reducing effect using ongoing pain ratings, but the participants failed to show differences in pain ratings after being stimulated. The difference between real-time feedback and delayed assessments may stem from the experimental control group along with memory-based recall problems. Real-time rating measurements established better pain analysis by demonstrating why ongoing observation should remain a focus in research about pain.
The research findings help explain how bodily ownership behaves when combined with multisensory processing to influence pain experiences in our brains. The RHI resulted in sustained pain relief, which began during most of the stimulation period. Body ownership ratings remained consistent across all temperature conditions which confirmed that the illusion maintained its strong influence. These research discoveries advance the study of RHI as a possible pain treatment approach while demonstrating the necessity of continued studies for its use with chronic pain diseases.
References: Mosch B, Fuchs X, Tu T, Diers M. Time course of the rubber hand illusion–induced analgesia. Pain Rep. 2025;10(2):e1252. doi:10.1097/PR9.0000000000001252
