December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
The full-body illusion changes visual depth perception
Author Affiliations & Notes
  • Manuel Bayer
    Heinrich Heine University Düsseldorf, Germany
  • Sophie Betka
    Swiss Federal Institute of Technology in Lausanne, Switzerland
  • Bruno Herbelin
    Swiss Federal Institute of Technology in Lausanne, Switzerland
  • Olaf Blanke
    Swiss Federal Institute of Technology in Lausanne, Switzerland
  • Eckart Zimmermann
    Heinrich Heine University Düsseldorf, Germany
  • Footnotes
    Acknowledgements  Supported by European Research Council (project moreSense grant agreement n. 757184).
Journal of Vision December 2022, Vol.22, 3581. doi:
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      Manuel Bayer, Sophie Betka, Bruno Herbelin, Olaf Blanke, Eckart Zimmermann; The full-body illusion changes visual depth perception. Journal of Vision 2022;22(14):3581.

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      © ARVO (1962-2015); The Authors (2016-present)

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In this study, we asked whether space perception is embodied. To dissociate real and apparent body position, we used the full-body illusion (FBI). In the FBI subjects see an avatar being stroked simultaneously to stroking that they experience on their real physical back. Under the illusion, subjects report a forward drift in self-location (compatible with drifts reported in out-of-body experiences). We investigated whether this illusion-induced forward drift in self-location affects where subjects see objects in depth. In localization trials, participants saw a single sphere, presented briefly in front of them, either on the left or on the right side. They were asked to estimate the distance of the sphere with a verbal response. After induction of the illusion, spheres presented on the left side were perceived as further in depth. Spheres on the right side however were perceived veridically. The asymmetric manifestation of the spatial distortion on the left side allowed us to apply a psychometric measurement in which subjects compared the position of a probe against a reference sphere. Two spheres were briefly presented simultaneously and participants had to decide in a 2AFC task which of the two they perceived closer to themselves. After the induction of the FBI, we found a significant misestimation of the relative depth of the spheres. Our results suggest that the FBI distorts space perception. This result reinforces claims that depth perception is embodied. In our study, changes in the felt position of the body in space (the bodily self) - as induced by the FBI - modified where subjects saw objects in depth. We conclude that the felt position of the body is taken into account when localizing objects in space.


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