Author's personal copy 0167-9457/$ - see front matter  2006 Elsevier B.V. All rights reserved. doi:10.1016/j.humov.2006.03.001 Human Movement Science 25 (2006) 800–820 www.elsevier.com/locate/humov ‘Motion sickness preceded by unstable displacements of the center of pressure Cedrick T. Bonnet a , Elise Faugloire a , Michael A. Riley b , Benoît G. Bardy c , Thomas A. StoVregen a,¤ a University of Minnesota, School of Kinesiology, 1900 University Avenue SE, Minneapolis, MN 55455, United States b Department of Psychology, University of Cincinnati, Cincinnati, Ohio, United States c Faculty of Sport Sciences, University of Montpellier 1, Montpellier, France Available online 16 May 2006 Abstract We exposed standing participants to optic Xow in a moving room. Motion sickness was induced by motion that simulated the amplitude and frequency of standing sway. We identiWed instabilities in displacements of the center of pressure among participants who became sick; these instabilities occurred before the onset of subjective motion sickness symptoms. Postural diVerences between Sick and Well participants were observed before exposure to the nauseogenic stimulus. During exposure to the nauseogenic stimulus, sway increased for participants who became sick but also for those who did not. However, at every point during exposure sway was greater for participants who became motion sick. The results reveal that motion sickness is preceded by instabilities in displacements of the center of pressure.  2006 Elsevier B.V. All rights reserved. PsycINFO classiWcation: 2300; 2330; 2320; 2323 Keywords: Motion sickness; Motion perception; Posture; Ecological psychology; Perceptual motor coordination * Corresponding author. Tel.: +1 612 626 1056. E-mail address: tas@umn.edu (T.A. StoVregen).