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08.12.2013 By: Uni Bielefeld

Would you believe your hand could turn into marble?

Bielefeld neuroscientists present a new bodily illusion


As if one’s hand were made of marble: Bielefeld neuroscientists successfully deceive participants about their body perceptions. Photo: Senna &amp; PariseBielefeld, 12. March 2014. Our body is made of flesh and bones. We know it, and in our daily lives all the senses constantly provide converging information about this simple, factual truth. But is this always the case? A new study by Irene Senna and colleagues, about to be published in PLoS ONE, reports a surprising bodily illusion demonstrating that we can rapidly update our assumptions about the material qualities of our body, based on recent multisensory perceptual experience.

To induce an illusory perception of the material properties of the hand a group of neuroscientist from the University of Bielefeld, the Max-Planck Institute for Biological Cybernetics and the University of Milano-Bicocca, sat volunteers with their hands lying on a table in front of them. They repeatedly gently hit participants' right hand with a small hammer, while replacing the natural sound of the hammer against the skin with the sound of a hammer hitting a piece of marble. Within minutes, the hand started feeling stiffer, heavier, harder, less sensitive, unnatural. Moreover, when approached by a threatening stimulus (a needle moved by the experimenter near their hand) participants showed enhanced Galvanic skin response, thus demonstrating increased physiological arousal.

To perceive our body and the world around us, the brain constantly combines information from different senses with prior knowledge retrieved from memory. However, unlike most bodily properties that frequently change over time (like posture and position), the material of our body never changes, so in principle it would be unnecessary for the brain to constantly try to infer it. This novel bodily illusion, the 'Marble-Hand Illusion', demonstrates that the perceived material of our body, surely the most stable attribute of our bodily self, can be quickly updated through multisensory integration. What is more, this shows that even impact sounds of non-biological materials -like marble and metal- can be consistently attributed to the body, as if its core material could indeed be modified. This surprising perceptual plasticity might help to explain why tools and prostheses can so easily merge into our body schema, in spite of their material.

Original press release


Original publication:
Senna, I., Maravita, A., Bolognini, N., and Parise, C.V. (2014) The Marble-Hand illusion. PLoS ONE.

Contact:
Cesare V. Parise
Max Planck Institute for Biological Cybernetics Tübingen
Bernstein Center for Computational Neuroscience, Tübingen
Cognitive Neuroscience Department and Cognitive Interaction Technology-Center of Excellence, Bielefeld University, Bielefeld
Mobile: +49-176-76418208
Phone: +49-521-1065703
E-mail: cesare.parise(at)uni-bielefeld.de


The Max Planck Institute for Biological Cybernetics works in the elucidation of cognitive processes. It employs about 300 people from more than 40 countries and is located at the Max Planck Campus in Tübingen, Germany. The Max Planck Institute for Biological Cybernetics is one of 80 research institutes that the Max Planck Society for the Advancement of Science maintains in Germany and abroad.


As if one’s hand were made of marble: Bielefeld neuroscientists successfully deceive participants about their body perceptions. Photo: Senna & Parise

As if one’s hand were made of marble: Bielefeld neuroscientists successfully deceive participants about their body perceptions. Photo: Senna & Parise