Objective measurement of simulator sickness and the role of visual-vestibular conflict situations: a study with vestibular-loss (a-reflexive) subjects

Abstract

Simulators, in particular driving simulators, are gaining importance not only for research and development purposes, but also for education, training and even recreation. Progress in computer graphics and performance allow for highly realistic simulator visuals. High-end models are becoming somewhat better at generating acceptable inertial self-motion information, sometimes even providing real (but limited) linear translation in addition to angular movements. Simpler versions do not generate inertial information at all (fixed-base simulators). Here, we present a study on a problem that often occurs with driving simulators, i.e., simulator sickness. This phenomenon closely resembles the classically experienced motion sickness and can make a user abort a simulator run within minutes. We investigated the hypothesis that simulator sickness is caused by a visual-vestibular conflict, comparing susceptibility in normals and in vestibular-loss patients. We studied the psychophysical reactions of subjects, and quantitatively recorded their neurovegetative activity, to improve understanding of the underlying causes of simulator sickness, and to develop an objective measure for monitoring purposes. We used a fixed-base simulator, with an urban circuit with many sharp turns and traffic lights. No vestibular input was received during driving simulation, thus creating numerous visual-vestibular conflict situations. Subjects were asked to indicate continuously their discomfort on a visual-analog scale. We studied 33 normals (19 became sick) and 6 bilateral vestibular-loss subjects (one became truly sick, 2 others somewhat). Sickness correlated strongly with an increase in anxiety (Spielberger STAI). The subjective discomfort readings correlated well with simultaneous neurovegetative data and with a symptom scoring test administered immediately afterwards. There was no clear indication of an age or gender dependence in the normals. The fact that a complete vestibular-loss patient became sick indicates that more parameters may be responsible for simulator sickness than just a visuo-vestibular conflict situation (anxiety, nauseating odours, etc.). - Supported by the European Union (QLK6-CT-2002-00151: EUROKINESIS).