Visually induced motion sickness, or “cybersickness”, has been well documented in all kinds of vehicular simulators and in many virtual environments. It probably occurs in all virtual environments. Cybersickness has many known determinants, including (a short list) field-of-view, flicker, transport delays, duration of exposure, gender, and susceptibility to motion sickness. Since many of these determinants can be controlled, a major objective in designing virtual environments is to hold cybersickness below a specified level a specified proportion of the time. More than 20 years ago C. W. Simon presented a research strategy based on fractional factorial experiments that was capable in principle of realizing this objective. With one notable exception, however, this strategy was not adopted by the human factors community. The main reason was that implementing Simon's strategy was a major undertaking, very time-consuming, and very costly. In addition, many investigators were not satisfied that Simon had adequately addressed issues of statistical reliability. The present paper proposes a modified Simonian approach to the same objective (holding cybersickness below specified standards) with some loss in the range of application but a greatly reduced commitment of resources.

Although simulator sickness is known to increase with protracted exposure and to diminish with repeated sessions, limited systematic research has been performed in these areas. This study reviewed the few studies with sufficient information available to determine the effect that exposure duration and repeated exposure have on motion sickness. This evaluation confirmed that longer exposures produce more symptoms and that total sickness subsides over repeated exposures. Additional evaluation was performed to investigate the precise form of this relationship and to determine whether the same form was generalizable across varied simulator environments. The results indicated that exposure duration and repeated exposures are significantly linearly related to sickness outcomes (duration being positively related and repetition negatively related to total sickness). This was true over diverse systems and large subject pools. This result verified the generalizability of the relationships among sickness, exposure duration, and repeated exposures. Additional research is indicated to determine the optimal length of a single exposure and the optimal intersession interval to facilitate adaptation.

Virtual environments are envisioned as being systems that will enhance the communication between humans and computers. If virtual systems are to be effective and well received by their users, considerable human-factors research needs to be accomplished. This paper provides an overview of many of these human-factors issues, including human performance efficiency in virtual worlds (which is likely influenced by task characteristics, user characteristics, human sensory and motor physiology, multimodal interaction, and the potential need for new design metaphors); health and safety issues (of which cybersickness and deleterious physiological aftereffects may pose the most concern); and the social impact of the technology. The challenges each of these factors present to the effective design of virtual environments and systematic approaches to the resolution of each of these issues are discussed.

The widespread use of virtual environment (VE) systems in a variety of applications has serious implications for the user. Users with access to these sophisticated interactive “immersions” in multisensory, three-dimensional (3D) synthetic environments have been shown to experience motion sickness-like symptoms (i.e., eyestrain, ataxia, fatigue, drowsiness) and aftereffects such as visual flashbacks, disorientation, and balance disturbances occasionally occurring up to 12 hours after VE exposure. This is a significant health and safety concern. Technical improvements of VE systems need to be initiated to reduce these potential aftereffects that could result in adverse legal, economic, individual, and social consequences. Many different types of symptoms have been reported that appear to make up the cybersickness syndrome. From our extensive database of virtual environment and flight simulator exposures, we offer examples of these symptoms profiles along with suspected mechanisms and origins. We discuss these issues as well as various assessment techniques and methods used to determine the presence of VE sickness in individuals.

Flight simulators are examples of virtual environment (VE) systems that often give rise to a form of discomfort resembling classical motion sickness. The major difference between simulator sickness and other forms of motion sickness is that the former exhibits more oculomotor-related symptoms and far less actual vomiting. VEs of the future are likely to include more compellingly realistic visual display systems, and these systems can also be expected to produce adverse symptoms. The implications of simulator sickness for future uses of VEs include adverse consequences for users' safety and health, user acceptance, training effectiveness, and overall system performance. Based on data from a factor analysis of over 1000 Navy and Marine Corps pilot simulation exposures, a new scoring procedure for simulator sickness has recently been developed (Lane & Kennedy, 1988; Kennedy, Lane, Berbaum, & Lilienthal, 1992). The factor analytic scoring key provides subscales for oculomotor stress (eyestrain), nausea, and disorientation. Simulators are being examined in terms of these factor profiles to identify causes of simulator sickness. This approach could also be used in evaluating motion sickness-like symptomatology that occurs in connection with the use of VEs. This paper describes the use of the multifactor scoring of the Simulator Sickness Questionnaire (SSQ) in diagnosing sources of simulator sickness in individual simulators. Reanalysis by this new methodology was employed to standardize existing simulator sickness survey data and to determine whether relationships existed that were missed by the more traditional scoring approaches.