Body Swap Illusion

Another great find from @spencernobleman:

Now researchers from the Karolinska Institute report that they have induced a “body-swap” illusion, whereby subjects perceived the body of another person as belonging to themselves. Their findings are published today in the open access journal PLoS One. [...]

Normally, the position of one’s body corresponds directly to the way it feels and the way it looks and, as a result, one can identify their own body as belonging to themselves, and also distinguish very easily between the “self” and “non-self” (or objects in the external world).

Under certain circumstances, however, the sense of body ownership can be perturbed, and sometimes this has bizarre consequences. Take, for example, somatoparaphrenia, a condition in which ownership of the left hand or leg is denied, following damage to the right parietal lobe. Often, patients with this condition perceive their limb to belong to, and to be controlled by, another person. Or take hemispatial neglect, a related disorder, which also occurs as a result of brain damage. [...]

Afterwards, the participants were interviewed, so that their perceptual experiences could be established. They reported that in the synchronous condition they had perceived the researcher’s arm as their own, and that they sensed their entire body behind it. Some even spontaneously remarked with comments such as “Your arm felt like it was my arm, and I was behind it”, “I felt that my own body was someone else” or “I was shaking hands with myself!”. Remarkably, they also reported that the sensations evoked when the researcher squeezed their hands seemed to originate from the researcher’s hand and not from their own. This illusion was vivid and robust - it persisted even though their own body was in full view, and regardless of either the sex of the researcher or the shape of their body. Furthermore, the participants exhibited anxiety when a knife was placed just above the researcher’s wrist, but not when it was placed near their own.


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This entry was written by happy thanksgiving, y'all!, posted on January 20, 2009 at 1:34 pm.

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2 Comments

  1. Timothy Obama
    Posted January 20, 2009 at 1:34 pm | Permalink

    Why can the sense of body ownership be manipulated so easily? In a real life situation, identifying one’s own body in space quickly and accurately can be of vital importance. It may therefore rely on memory during any decision-making process, because we have lifelong experience of seeing our own bodies from the first-person perspective, and because our bodies generate typical patterns of sensory signals in from the different modalities (vision, proprioception, and so on). Thus, information from memory is used to generate an estimate of the body’s location in space, and this estimate is continuously refined by the incoming sensory information.

    This refined information is then processed by populations of neurons in the premotor cortex which integrate multisensory cues and map them onto co-ordinates within which the body is at the centre. In the body-swap illusion, these same neuronal populations encode and integrate visual information from a new visual perspective, but because of their egocentric co-ordinates, the individual’s centre of awareness is shifted, so that she perceives her “self” to be located at the new position in space. Consequently, the sense of ownership of one’s own body can be modified simply by altering the perspective from which the body is viewed.

  2. Omega Timothy
    Posted January 20, 2009 at 7:18 pm | Permalink

    http://en.wikipedia.org/wiki/Stations_of_the_cross

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  1. By @tmbchr » BEYOND IDENTITY. An Philosophical Analysis of Transcendent Post-Corporate Consciousness Technologies on January 22, 2009 at 1:28 pm

    [...] mimesis, self-identification and participation mystique through a series of experiments related to swapping in and out or replacement of inputs into the sensory/perceptual system of human and other entities. “In the first experiment, the [...]

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