The Rubber Hand Illusion: A Curious Psychological Effect
The study of the optical illusions It has been of great help to psychology because of what it can reveal about perceptual processes. For example, understanding how our brain works with respect to proprioception, has been very useful for patients who have suffered an amputation. Thanks to techniques such as the mirror box it is possible to reduce your phantom pain and improve your quality of life.
For several decades, science has been interested in these phenomena. And technological advancement has made it possible to acquire new knowledge and better understand what happens in our brain. A group of psychologists from Pennsylvania (United States) discovered a curious illusion, known as the “rubber hand illusion.”
Researchers realized that if we put a rubber hand in front of us and, at the same time, cover one of our arms so that it seems that the rubber hand is part of our body, when someone caresses the rubber hand , we will feel that we are being caressed by the royal hand.
Below you can see how the rubber hand illusion happens:
The rubber hand illusion, more than a simple trick for illusionists
The rubber hand illusion not only became a trick for illusionists, but it was an important discovery because allowed us to understand how sight, touch and proprioception (that is, the sense of body position) combine to create a compelling sense of ownership of the body, one of the foundations of self-awareness.
Body ownership is a term used to describe our sense of physical self and differentiate it from not being a part of us. It is what allows us to know that a hammer we are holding in our hand is not part of our body or, in the case of animals, to know that they should not eat their legs because they belong to their own body.
The discovery of rubber hand illusion has inspired many researchers
For Henrik Ehrsson, a neuropsychologist at the Karolinska Institute in Stockholm (Sweden), “The rubber hand illusion has inspired many researchers, and many studies have attempted to find answers to this phenomenon. Science has wanted to know how the body is perceived by our mind, and how the integration of this information happens.”
Scientists have discovered that the greater the intensity with which the rubber hand illusion is experienced, for example by hitting it forcefully, there is greater activity in the premotor cortex and parietal cortex of the brain. These areas They are responsible for integrating sensory and movement information But of course, stroking the hand is not the same as hitting it. And although the individuals who have carried out experiments with the rubber hand are aware that said hand is not part of their body, the brain regions that are activated by fear and threat, and that correspond to flight, are also They become more active.
What happens to the authentic hand that is hidden?
Another interesting discovery is the one carried out by a group of scientists from the University of Oxford, who wanted to know what happens to the hand that is hidden during the experiment. If the brain reacts to the rubber hand, does it also react to the hand that is hidden? Well, it seems that, just when the brain falsely recognizes the rubber hand as its own, the temperature of the real hand, which is hidden, drops Instead, the rest of the body remains the same.
Furthermore, when the experimenter stimulates the hidden hand, the subject’s brain takes longer to respond than when the other authentic hand is touched. These results seem to show that when the brain thinks that the rubber hand is a real hand, it forgets about the other hand.
This has been really interesting for medicine because it shows that thermal regulation of the body also depends on the brain.
Mirror box therapy: another example of optical illusion
Illusion-based experiments have helped amputee patients who continue to feel pain even though the limb is no longer part of their body, known as “phantom pain.”
The neurologist cbetween the Brain and Cognition of the University of California, San Diego, Vilayanur S. Ramachandran, also became interested in these types of optical illusions to design Mirror Box Therapy, which works to reduce phantom pain.
The mirror box has similarities to the rubber hand illusion In the mirror box, the good hand is placed next to a mirror and moved so that the person thinks they are moving the wrong hand. In this case, the mirror hand acts as the rubber hand and, thanks to this, the pain disappears through visual feedback and by eliminating potentially painful positions. With this technique, it is possible to give feedback to the brain and relieve the pain that the person feels.
If you want to know more about the mirror box, you can read this article: “The phantom limb and mirror box therapy.”
