ABSTRACT
Cybersickness, or so-called simulator sickness, is one of the major problems for virtual reality and simulator systems. It has been discussed over many years since the initial development of virtual reality systems. The phenomenon of cybersickness is similar to motion sickness. Symptoms include nausea, ataxia, disorientation, and so on. There are two principle theories to explain cybersickness. The sensory conflict/cue conflict theory (Reason and Brand 1975) is the most widely accepted. Users in virtual environments may feel self-motion due to movement of the visual scene (often called vection) while their inertial receptors report that they are stationary. This theory suggests that the conflicts between the visual and inertial motion cues may result in simulator sickness. Prothero et al. (1998) proposed a “rest frame hypothesis” to refine the sensory conflict theory to explain the ontology of cybersickness. Based on the rest frame hypothesis, they suggested that users report cybersickness in virtual environments because of conflicting rest frames implied by visual and inertial motion cues. Riccio and Stoffregen (1991) proposed postural instability theory, which provided a different view. They suggested that maintenance of postural stability is one of the major goals of animals based on an ecological psychology point of view. If animals go into environments for which they have not learned strategies to maintain their balance, motion sickness-like symptoms may be due to the resulting balance disturbance. Microgravity environments, cyberspace, and virtual environments are new environments for most animals and people. People exhibit symptoms such as postural disturbance, nausea, and disorientation before learning postural stability strategies to cope in these new environments.
