We evaluated the hypothesis that postural instability precedes the onset of motion sickness. Subjects standing in a 'moving room' were exposed to nearly global oscillating optical flow. In the experimental condition, the optical oscillations were a complex sum-of-sines between 0.1 and 0.3 Hz, with an excursion of 1.8 cm. This optical motion was of such low frequency and magnitude that it was sometimes not noticed by subjects. However, in two experiments, exposure to the moving room produced significant increases in scores on a standard motion sickness questionnaire. In addition, approximately half of subjects reported motion sickness. Analysis of postural motion during exposure to the moving room revealed increases in postural sway before the onset of subjective motion sickness symptoms. This confirms a key prediction of the postural instability theory of motion sickness.
Bibliographical noteFunding Information:
This research was funded by the Naval Air Warfare Center (contract N61339-94-M-1285), with additional support from the National Science Foundation (SBE-9601351). We extend our gratitude to Sherrie Jones for her support, to Frank Cardullo for design and construction of the moving room, to Mike Gilkey for simulation software and systems integration and to Tjeerd Dijkstra, Tom Sharp, Alexis Salaman, Cynthia Potts, Randy J. Pagulayan, Patricia Comstock and Kartika Houston for help with data reduction and analysis. We also thank Mark Draper for helpful comments on a draft of this article. Portions of the data were presented at a meeting of the International Society for Ecological Psychology, Hartford, CT, March 1996, and at the International Workshop on Motion Sickness: Medical and Human Factors, Marbella, Spain, May 1997.
- Motor control
- Optical flow