Summary: A new study shows that the rubber hand illusion can reduce the intensity of pain caused by heat. Researchers found that when participants viewed a rubber hand being illuminated while their hidden hand received a heat stimulus, they reported feeling less pain.
This suggests that integrating visual and sensory cues can influence pain perception. The findings may one day help develop new treatments for chronic pain conditions such as complex regional pain syndrome.
Key Facts:
- Pain Reduction Effect: The rubber hand illusion decreased perceived heat pain intensity.
- Multisensory Integration: Seeing the rubber hand with red light altered pain perception.
- Future Pain Treatments: Findings could inform therapies for chronic pain conditions.
Source: RUB
If a person hides their own hand and focuses on a rubber hand instead, they may perceive it as part of their own body under certain conditions. What sounds like a gimmick could one day be used to help patients who suffer from chronic pain.
Researchers at the Clinic for Psychosomatic Medicine and Psychotherapy at the LWL University Hospital in Bochum, Germany, have shown that pain caused by heat is experienced as less severe thanks to the rubber hand illusion.
They published their findings in the journal PAIN Reports from April 2025.
Heat creates illusion
The rubber hand illusion occurs when the hidden hand and the rubber hand are touched at the same time, for example with a brush. In the experiment outlined here, the illusion was not evoked through touch, but through a heat stimulus and simultaneous illumination with red light:
In the first step, the researchers determined the individual pain threshold for heat pain in all 34 right-handed test participants. The participants then placed their left hand behind a screen so that they could no longer see it.
The hand hidden by the screen was placed on a thermode head, a small plate that can be heated under controlled conditions. Instead of their left hand, a rubber hand was placed in front of the participants, which could be illuminated with red light from below.
The test participants’ right hand was placed on a slider which they used during the experiment to continuously rate the painfulness of the heat on their left hand.
The researchers carried out several test runs in which they heated the thermode to several temperature levels just below the respective pain threshold, exactly at the pain threshold and just resp. significantly above it. The rubber hand was simultaneously illuminated with red light.
“The heat stimulus on the left hand with simultaneous red illumination of the rubber hand evoked the illusion,” explains study supervisor Professor Martin Diers, Head of the Research Section Clinical and Experimental Behavioral Medicine.
A survey of the test participants confirmed these findings after each series of experiments. In the control condition, the researchers conducted the experiment with a rubber hand rotated by 180 degrees.
The intensity of pain decreases
“We showed that the perceived pain intensity was reduced in the rubber hand illusion condition compared to the control condition,” says Martin Diers.
“We assume that the mechanism behind the rubber hand illusion is the multisensory integration of visual, tactile (here nociceptive) and proprioceptive information. The findings suggest that when people perceive the rubber hand as part of their own body, this reduces their perception of pain.”
Another factor could be the phenomenon of visual analgesia, which has also been shown in other studies: A pain stimulus is perceived as less intense if the person can see the relevant part of the body while it is occurring.
“However, we still don’t fully understand the neural basis for this phenomenon,” admits Diers.
In future, the findings could possibly be used in the treatment of pain. One conceivable field of use would be the treatment of complex regional pain syndrome, for example, in which patients typically experience pain and swelling in the hand.
About this pain and neuroscience research news
Author: Meike Driessen
Source: RUB
Contact: Meike Driessen – RUB
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Time Course of the Rubber Hand Illusion Induced Analgesia” by Martin Diers et al. Pain Reports
Abstract
Time Course of the Rubber Hand Illusion Induced Analgesia
Introduction:
Previous investigations on pain modulatory effects of the rubber hand illusion (RHI) yielded mixed results. However, these studies used separate stimuli to induce pain and the RHI. Using a visual-thermal stimulation approach, the illusion-inducing stimulus was simultaneously the pain stimulus which ensured that participants focused entirely on the illusion-inducing stimulus.
Objectives:
In this study, we investigated the time course of pain modulation induced by illusionary body ownership over artificial hands using the visual-thermal RHI and the influence of the stimulation intensity.
Methods:
In a 2 × 4 within-subject design, participants received thermal stimulation on their hidden real left hand, while the rubber hand synchronously lit up red. Four stimulation intensities were used: moderate pain (+0°C), −0.75°C, +0.75°C, and +1.5°C. For control trials, the rubber hand was rotated by 180°. With the right hand, participants provided continuous pain ratings using a slide knob.
Results:
Embodiment ratings were higher in the RHI compared with the control condition. Continuous pain ratings were lower in the RHI condition for all temperature levels except for +0.75°C. Rubber hand illusion–induced pain reduction was observed throughout most of the stimulation interval, absent only at the very beginning and end.
Conclusion:
These findings suggest that visual-thermal induction of the RHI is consistently associated with increased embodiment ratings, regardless of the temperature level presented. The illusion is further accompanied by reduced pain ratings throughout major parts of the stimulation interval. On the whole, these findings speak for the robustness of the effect and the practicality of our visual-thermal stimulation approach.
