• Jan E Holly and Katharine J Harmon.
• Department of Mathematics, Colby College, 5845 Mayflower Hill, Waterville, ME 04901, USA. jeholly@colby.edu
• Aviat Space Envir Md. 2009 Feb 1; 80 (2): 125134125-34.

IntroductionDuring a coordinated turn, subjects can misperceive tilts. Subjects accelerating in tilting-gondola centrifuges without external visual reference underestimate the roll angle, and underestimate more when backward-facing than when forward-facing. In addition, during centrifuge deceleration, the perception of pitch can include tumble while paradoxically maintaining a fixed perceived pitch angle. The goal of the present research was to test two competing hypotheses: 1) that components of motion are perceived relatively independently and then combined to form a three-dimensional (3-D) perception; and 2) that perception is governed by familiarity of motions as a whole in three dimensions, with components depending more strongly on the overall shape of the motion.MethodsPublished experimental data from existing tilting-gondola centrifuge studies were used. The two hypotheses were implemented formally in computer models, and centrifuge acceleration and deceleration were simulated.ResultsThe second, whole-motion oriented hypothesis better predicted subjects' perceptions, including the forward-backward asymmetry and the paradoxical tumble upon deceleration. The predominant stimulus at the beginning of the motion and the familiarity of centripetal acceleration were important factors.ConclusionThree-dimensional perception is better predicted by taking into account familiarity with the form of 3-D motion.

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