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Acta Astronautica 56 (2005) 10251032 www.elsevier.com/locate/actaastro

Summary: Acta Astronautica 56 (2005) 10251032
The relative role of visual and non-visual cues in determining the
perceived direction of "up": Experiments in parabolic flight
H.L. Jenkin, R.T. Dyde, J.E. Zacher, D.C. Zikovitz, M.R. Jenkin, R.S. Allison,
I.P. Howard, L.R. Harris
Centre for Vision Research, York University, Toronto, Ontario, Canada M3J 1P3
Available online 14 March 2005
In order to measure the perceived direction of "up", subjects judged the three-dimensional shape of disks shaded to be
compatible with illumination from particular directions. By finding which shaded disk appeared most convex, we were able
to infer the perceived direction of illumination. This provides an indirect measure of the subject's perception of the direction
of "up". The different cues contributing to this percept were separated by varying the orientation of the subject and the
orientation of the visual background relative to gravity. We also measured the effect of decreasing or increasing gravity
by making these shape judgements throughout all the phases of parabolic flight (0g, 2g and 1g during level flight). The
perceived up direction was modeled by a simple vector sum of "up" defined by vision, the body and gravity. In this model,
the weighting of the visual cue became negligible under microgravity and hypergravity conditions.
2005 Elsevier Ltd. All rights reserved.
Keywords: Perceived orientation; Microgravity; Hypergravity; Idiotropic vector
1. Introduction


Source: Allison, Robert - Department of Computer Science, York University (Toronto)
Harris, Laurence R. - Departments of Biology & Psychology, York University (Toronto)


Collections: Biology and Medicine; Computer Technologies and Information Sciences