Can We Shake Hands with Our Own Body?

If we want to understand why our centre of awareness, or sense of ‘self’, is located inside our body, illusions of bodily self-perception could be invaluable. The study of illusions is a classical approach adopted in psychology to learn more about the basic processes that underlie normal perception. Indeed, some important initial insights into the mechanisms underlying self-perception of one's own body have been gained through illusions.

One such is the so called ‘Rubber Hand Illusion’ where people have the experience that a prosthetic hand is actually their own hand. In this illusion, synchronous touches applied to a rubber hand in full view of the participant, and the real hand, which is hidden behind a screen, produce the sensations that the touch originates from the rubber hand and a feeling of ownership of the artificial hand. This suggests that the temporal and spatial patterns of visual and somatosensory signals play an important role in how we come to experience that a limb is part of our own body,,,.

Another important factor in determining how we perceive our own body is the adoption of the first person perspective,. When we look at ourselves directly, our limbs and body always present themselves in certain orientations because our eyes are fixed to our skull.

By changing the visual perspective, it is possible to induce the feeling of being in a different place,, or, even, illusory ‘out-of-body experiences’ where people seem to lose ownership of their own body when observing it from the point of view of another person (which we refer to as the third person perspective).

On the basis of this previous knowledge, we hypothesized that it would be possible to induce illusions of owning an entire body other than one's own by the experimental manipulation of the visual perspective in conjunction with correlated visual and sensory signals being supplied to the respondent's body. Our experiments reveal that healthy volunteers can indeed experience other people's bodies, as well as artificial bodies, as being their own.

This effect is so robust that, while experiencing being in another person's body, a participant can face his or her biological body and shake hands with it without breaking the illusion. The existence of this illusion (and the identification of the factors triggering it) represents a major advance because it informs us about the processes that make us feel that we own our body in its entirety.