UC Irvine

With the increasing popularity of virtual reality, people are now experiencing motion sickness during use of head mounted displays (HMDs). This dissertation reviews the major theories on why certain body motions and visual inputs cause sickness. It then details three experiments which measure motion sickness when a person uses an HMD or a monitor to view virtual environments (VEs). In Experiment 1, seated subjects interacted with a VE using a monitor and using an HMD while physiological signals were recorded. We found that subjects reported severe motion sickness while using an HMD but not while viewing images on a monitor. In fact, half of the subjects chose to quit the experiment after six minutes of HMD use and reported feeling nauseous at that time. It was found that stomach activity, blinking, and breathing can be used to estimate post-immersion motion sickness severity and to classify which viewing condition a subject’s data originated from. Experiment 2 tested postural instability theory, which proposes that a person must exhibit body instability before motion sickness can occur. Subjects either stood on a balance board or sat in a chair while they were immersed in a rotating tunnel simulation. They used a game controller to indicate changes in their perceived vertical. A minority of subjects showed significant changes in postural sway compared to a resting baseline. However, these subjects did experience changes in their perceived vertical; the world had tilted in the direction of visual rotation. We found that subjects with less postural sway reported greater sickness, which contradicts postural instability theory. In the final experiment, subjects navigated a virtual space station while wearing an HMD or viewing a monitor and stood on a balance board. While navigating through the VE, subjects were subjected to unexpected visual motion which produced the sensation of being pushed in virtual reality. Results showed that these visual perturbations caused significantly greater postural sway. Yet, motion sickness was reported similarly when subjects wore the HMD regardless of perturbation presence or absence. These results demonstrate clearly that postural instability caused by unexpected visual change is not a prerequisite of motion sickness.