Duh, HBL and Parker, DE, Mitigating cybersickness in virtual environments, International Encyclopedia of Ergonomics and Human Factors, CRC Press, W Karwowski (ed), USA, pp. 1-3. ISBN 978-0-415-30430-6 (2006) [Research Book Chapter]
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.