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Updated: Aug 18, 2026

Assessment of Static Graviceptive Perception in the Roll-Plane using the Subjective Visual Vertical Paradigm
Published on: April 28, 2020
Influence of the gravitational vertical on geometric visual illusions
Gilles Clément1, Jennie Eckardt
1Centre National de la Recherche Scientifique, Centre de Recherche Cerveau et Cognition, Toulouse Cedex, France. gilles.clement@cerco.ups-tlse.fr
Abstract:
The occurrence of geometric orientation illusions and the perception of ambiguous figures were analyzed in 24 subjects during static body tilt relative to gravity on Earth. Results showed that illusions such as the Rock's diamond/square, the Ponzo illusion, and orientation contrast illusions occurred less frequently, and that depth reversal of ambiguous figures took more time when subjects were lying on their side or supine compared to upright, thus suggesting that the gravitational reference plays a significant role in these "visual" illusions. The structure of images, our representation of the environment, and orientation relative to gravity are all integral parts in interpreting visual images. In a weightless environment where no gravitational reference can be used, it is expected that similar alterations in visual perception will occur.
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