title: Visual capture and the experience of having two bodies - Evidence from two different virtual reality techniques.
abstract: In neurology and psychiatry the detailed study of illusory own body perceptions has suggested close links between bodily processing and self-consciousness. One such illusory own body perception is heautoscopy where patients have the sensation of being reduplicated and to exist at two or even more locations. In previous experiments, using a video head-mounted display, self-location and self-identification were manipulated by applying conflicting visuo-tactile information. Yet the experienced singularity of the self was not affected, i.e., participants did not experience having multiple bodies or selves. In two experiments presented in this paper, we investigated self-location and self-identification while participants saw two virtual bodies (video-generated in study 1 and 3D computer generated in study 2) that were stroked either synchronously or asynchronously with their own body. In both experiments, we report that self-identification with two virtual bodies was stronger during synchronous stroking. Furthermore, in the video generated setup with synchronous stroking participants reported a greater feeling of having multiple bodies than in the control conditions. In study 1, but not in study 2, we report that self-location - measured by anterior posterior drift - was significantly shifted towards the two bodies in the synchronous condition only. Self-identification with two bodies, the sensation of having multiple bodies, and the changes in self-location show that the experienced singularity of the self can be studied experimentally. We discuss our data with respect to ownership for supernumerary hands and heautoscopy. We finally compare the effects of the video and 3D computer generated head-mounted display technology and discuss the possible benefits of using either technology to induce changes in illusory self-identification with a virtual body.
authors.affiliation: Center for Neuroprosthetics, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland ; Laboratory of Cognitive Neuroscience, Brain Mind Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland ; Department of Neurology, University Hospital Geneva, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Heydrich
authors.affiliation: Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics Tübingen, Germany.
authors.forename: Trevor J
authors.initials: TJ
authors.lastname: Dodds
authors.affiliation: Laboratory of Cognitive Neuroscience, Brain Mind Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland.
authors.forename: Jane E
authors.initials: JE
authors.lastname: Aspell
authors.affiliation: Center for Neuroprosthetics, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland ; Laboratory of Cognitive Neuroscience, Brain Mind Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland.
authors.forename: Bruno
authors.initials: B
authors.lastname: Herbelin
authors.affiliation: Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics Tübingen, Germany ; Department of Brain and Cognitive Engineering, Korea University Seoul, South Korea.
authors.forename: Heinrich H
authors.initials: HH
authors.lastname: Bülthoff
authors.affiliation: Human Perception, Cognition and Action, Max Planck Institute for Biological Cybernetics Tübingen, Germany.
authors.forename: Betty J
authors.initials: BJ
authors.lastname: Mohler
authors.affiliation: Center for Neuroprosthetics, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland ; Laboratory of Cognitive Neuroscience, Brain Mind Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland ; Department of Neurology, University Hospital Geneva, Switzerland.
authors.forename: Olaf
authors.initials: O
authors.lastname: Blanke
keywords: full body illusion; heautoscopy; ownership; self consciousness; virtual reality