If a person hides his own hand and focuses on a rubber hand, he can perceive it as part of his own body under certain conditions. What sounds like a trick could one day use to help patients suffering chronic pain: researchers at the Psychosomatic Medicine and Psychotherapy clinic at the Hospital of the University of LWL in Bochum, Germany, have shown that the pain caused by heat is experienced as less serious thanks to the illusion of rubber hand. They published their findings in the magazine Pain reports Since April 2025.
Heat creates illusion
The illusion of rubber hand occurs when the hidden hand and rubber hand are touched at the same time, for example, with a brush. In the experiment described here, the illusion was not evoked through touch, but through a simultaneous heat and lighting stimulus with red light:
In the first step, the researchers determined the individual pain threshold for heat pain in the 34 participants of the right -hand tests. Then, the participants placed their left hand behind a screen so that they could no longer see it. The hidden hand on the screen was placed in a thermode head, a small plate that can be heated in controlled conditions. Instead of his left hand, a rubber hand was placed in front of the participants, which could illuminate with red light from below. The right hand of the test participants was placed on a sliding control they used during the experiment to continually qualify the heat pain in their left hand.
The researchers carried out several tests in which they heated the thermode at various temperature levels just below the respective pain threshold, exactly in the pain threshold and only Resp. significantly on top. The rubber hand lit up simultaneously with red light. “The heat stimulus in the left hand with simultaneous red lighting of the rubber hand evoked the illusion,” explains the study supervisor, Professor Martin Diers, head of the Clinical and Experimental Research Section of Behavioral Medicine. A survey by 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.
Pain intensity decreases
“We show that the intensity of perceived pain was reduced in the condition of illusion of the rubber hand compared to the condition of control,” says Martin Diers. “We assume that the mechanism behind the illusion of rubber hand is the multisensory integration of visual, tactile information (here noticeptive) and proprioceptive. The results suggest that when people perceive the hand of rubber 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 demonstrated in other studies: a pain stimulus is perceived as less intense if the person can see the relevant part of the body while it occurs. “However, we still do not completely understand the neural base of this phenomenon,” admits Diers.
In the future, findings could be used in pain treatment. A field of conceivable use would be the treatment of complex regional pain syndrome, for example, in which patients typically experience pain and swelling in their hand.