Body Transfer in Virtual Reality. How modifying the body in virtual reality can help in clinical treatment

Would you like to experience owning the body of another person? Perhaps the body of a person of another sex, age, size? Then this is the opportunity for you: body swapping in virtual reality!

To give you an idea of how this may look, you can watch this short video.

From reality to virtuality

Virtual reality is a simulation that creates a virtual environment as convincingly as possible. Often the virtual environment resembles a real one. Usually, this is done with the help of a head-mounted display (see image 1), body tracking and other sensory input devices. All the sensory data is integrated in order to generate a virtual environment that a user can engage with.

The person wearing the virtual reality headset is able to move freely and control stimuli in the simulated environment. There is an almost real-time response of the system to interaction with realistically shaded and textured 3D-objects, which creates a lifelike experience for the user. The aim of this technique is to create a sense of immersion so that one is under the impression of being physically present in the virtual world like normally being present in the real world.

You may have experienced a similar feeling when watching a movie in the cinema or playing a video game on the computer. However this experience is only a fraction of what to expect from immersive virtual reality. By relating the experience to an individual’s own body and how it is represented in the brain, the impact can be even greater.

A person experiencing virtual reality with the help of a head-mounted display   PixaBay (CC0 1.0)

Switching bodies – body transfer illusion

As you might know a body transfer illusion can be created by multisensory integration via synchronously visual and tactile stimulation of a person’s body part and a corresponding fake body part.

This illusion can easily be extended to virtual reality. In virtual reality, tactile stimulation on a person’s hidden real body part and synchronous stimulation on the observed virtual body part can induce the embodiment of the virtual body part. Additionally, the illusion can be evoked by simultaneous movements of the virtual and real body part. This is achieved by tracking the movements of the real body and transferring them to the virtual body that is seen through the head-mounted display.

More importantly, in virtual reality illusory ownership over an entire virtual body can be induced. The full body illusion works best when having a first person perspective on the virtual body which means seeing the virtual body when looking down at oneself. Thus, the body is seen in a similar way to physical reality, creating an immersive experience in the virtual world and the feeling of ownership over an entire virtual body. This implies the feeling of the virtual body belonging to oneself and the perception of bodily sensations that are unique to this body.

Pixabay (CC0 1.0)

I’m sure you will have already come up with numerous ideas of what you would try to do in a virtual reality setting which allows for a body swap. Indeed, there are lots of situations to experience under the body ownership illusion in virtual reality. However, what most people do not think about is how this can help in treating certain disorders.

How virtual reality can improve clinical therapy

As virtual reality offers a controlled environment that is as lifelike as possible, it is very useful for research in neuroscience and clinical therapy. This technology can manipulate perception and consciousness, and therefore helps to study effects of body awareness and body representation.

Specifically, the virtual body ownership illusion can help in treating eating disorders such as anorexia nervosa and bulimia nervosa. In these disorders patients have a disturbed body representation which is accompanied by body dissatisfaction. Usually, these patients are underweight, but overestimate their body size and have a negative feeling about their body. Multisensory body illusions are able to alter this misperception and result in an updated and improved experience of the own body.

Virtual bodies can be modified regarding the shape and size of a physical body that serves as reference. For example, a body ownership illusion that is induced over a mannequin body that is slimmer than the actual body size of a healthy participant significantly decreases the perceived real body width and at the same time increases body satisfaction. This proposes a causal link between body perception and body satisfaction. As a result, illusory changes in body size via virtual reality can be used in clinical therapy.

Patients of eating disorders often overestimate their body size which leads to body dissatisfaction Public Domain Pictures (CC0 1.0)

In anorexia nervosa patients, a decrease in overestimation of size of body parts such as shoulders, abdomen and hips was observed after experiencing a full body illusion over a body with healthy body mass index. This improvement of body image disturbance shows that the experience of body size is flexible and can be changed, even for emotionally relevant body parts.

Furthermore, the virtual body swap has enduring implications for the body experience. A change in the memory of one’s own body can be induced. This means that participants in the illusory experience of a skinny body report a decreased estimation of body measures of their real body. Thus, there was an update of the long-term representation of their bodies. For the application in clinical therapy of eating disorders, this is a promising result.

Reducing prejudices by altering social cognition

Beyond clinical research, there are already some studies trying to investigate how social cognition might be affected by experiencing the embodiment of another body. The results suggest that bodily illusions which led to the feeling of ownership over a body that differed to the own body with respect to gender, age or race significantly reduced the implicit biases against the specific outgroup that was investigated.

The body ownership illusion in virtual reality can alter social cognition in order to reduce prejudices. PixaBay (CC0 1.0)

The changes of perceptual and affective body representations are a result of body ownership illusions and are related to the studies regarding eating disorders. Due to a perceived increase in physical similarity between the self and outgroup members, the implicit bias against the outgroup members is reduced. Positive self-associations are now linked to associations with the outgroup members which lead to positive concepts being related to the outgroup. Thus, prejudices and stereotypes could be weakened with the experience of body ownership illusions.

What else is possible with virtual body ownership illusions?

As we have seen, virtual reality really is able to affect our cognition. Not only can body representations be altered, but empathy towards outgroups can also be increased. However, the body transfer illusion can also be used in some other fascinating settings.

For example, body swapping might be a really enjoyable feature in virtual reality videogames. Visual and tactile feedback from a first person perspective in a virtual environment offers multiple new possibilities for gaming adventures.

Or think about the embodiment of additional body parts like three arms or four legs. Wouldn’t it be weird what you could do simultaneously with that many limbs? And how would it feel to own an arm that is twice as long as your usual arm? Some of these questions are answered by research in the field of phantom limb pain. Here the sensations belonging to a non-existing body part, the phantom limb, are investigated.

The most popular thought may well be that of multi-destination beaming. Virtual reality might enable the embodiment of multiple bodies at different locations. As for my part, the experience to inhabit multiple bodies and being able to switch between them sounds great.

All these imaginations could come true through body ownership illusions in virtual reality. They can help in understanding the brain and its body representations and be used in clinical treatment of certain disorders.

Last but not least I recommend watching this entertaining video and checking out this research project on the topic outlined above.


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