Kasperian Moving Parts

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Ataxia — a new word that means I can’t play Halo?


So, I found this bit of research today….. I’m finding plenty of pages that document that existence of simulator sickness, but haven’t yet found anything that talks about how to combat it. =:/

Still looking….

My newly-purchased Halo PC game just arrived in my mailbox today. I’d like to think that I’ve not just wasted $27.


Unfortunately, a phenomenon exists that may pose a threat to the ultimate usability of this new technology. That phenomenon is referred to as “simulator sickness” and it is a well-documented effect of simulator exposure (Reason and Brand, 1975; Kennedy and Frank, 1983; Kennedy et al., 1989; Casali, 1986). Simulator sickness is similar to motion sickness but can occur without actual physical motion. The cardinal signs resemble those of motion sickness: vomiting, nausea, pallor, and cold sweating. Other symptoms include drowsiness, confusion, difficulty concentrating, fullness of head, blurred vision, and eye strain. Along with the potential discomfort to the individual, there are several operational consequences of simulator sickness: decreased simulator use, compromised training, and ground and flight safety (Crowley, 1987). There are additional effects of simulator exposure: delayed flashbacks and aftereffects (a sudden onset of symptoms) (Baltzley et al., 1989); shifts in dark focus (the physiological resting position of accommodation) (Fowlkes et al., 1993); eye strain (Mon-Williams et al., 1993); and performance changes (Kennedy et al., 1993).

One potentially critical effect of simulator exposure is postural disequilibrium, referred to as ataxia. Baltzley et al. (1989) suggested that unsteadiness and ataxia are the greatest threats to safety because there have been reports of such posteffects lasting longer than 6 hours and, in some cases, longer than 12 hours. Clearly, occurrence of ataxia has the potential for disastrous consequences.

Recent research (Kolasinski, 1996; Knerr et al., 1993; Regan, 1993) has documented that simulator sickness can also occur in conjunction with VR exposure. The potential consequences of such sickness—particularly with widespread use of VR technology—raise important safety and legal issues for both manufacturers and users alike. Thus, simulator sickness (including effects such as ataxia) as it occurs with VR exposure must be understood if the technology is to make its predicted progress over the next decade. To meet this goal, the primary research challenges will be to thoroughly investigate the phenomenon.

Fortunately, simulator sickness in a virtual environment (VE)—or “cybersickness,” as it is called—need not be regarded as an entirely new phenomenon. As already noted, simulator sickness is related to motion sickness, a phenomenon for which a body of literature exists (Reason and Brand, 1975). In addition, a body of literature exists for simulator sickness occurring in military flight simulators and, to a lesser degree, other simulators such as driving simulators (Crampton, 1990). Thus, VR researchers need not entirely reinvent the wheel but can and should draw on the existing literature, at least in the initial stages of investigation.

Much of the sickness literature that may be applicable to VEs is reviewed by Kolasinski (1995). In this report, three major categories of factors that may be related to simulator sickness as it occurs in a VE were identified: factors related to the individual using the system, factors related to the task performed in the VE, and factors related to the VR system itself. Although simulator sickness is not a new phenomenon, a VE may differ in several important respects from the typical simulator. For example, depending on how a VE is defined, such a system is likely to involve some form of direct sensory input, probably through a head-mounted display (HMD), at least. Such devices may pose unique concerns, and current research efforts (Mon-Williams et al., 1993) are examining the effects of HMD use on the visual system. Thus, although research into sickness occurring in VEs can draw on previous simulator sickness research, new research must be conducted specifically in VEs in order to address sickness issues unique to the VR setting. Very little research exists on sickness as it occurs in conjunction with VR exposure. Furthermore, with few exceptions (Regan and Price, 1994), the majority of VR studies currently reported in the literature were not designed to specifically investigate sickness. Instead, most studies investigated the use of VR systems, with sickness examined only as an aside.

Kolasinski (1996) represents one of the first experimental investigations of simulator sickness as it occurs in VEs. The primary focus was to investigate the prediction of sickness based on characteristics associated with an individual using a VR system, but the occurrence of ataxia following exposure also was investigated. This research established that sickness did, in fact, occur. In some cases it was severeone participant vomitedand/or involved lingering or delayed effects. Ataxia, however, was not found.

This latter finding—that ataxia did not occur even though sickness did—supports findings presented by Kennedy et al. (1995), who found that, with repeated exposure to a simulator, sickness decreases over time but ataxia increases. Although their finding has implications for repeated use of VR technology, the finding of Kolasinski (1996) raises some specific issues of importance to the future application of VR technology. Ataxia is a well-documented effect of simulator exposure (Kellogg and Gillingham, 1986; Kennedy et al., 1993), and previous research has suggested that ataxia may also occur in conjunction with VR exposure. Rolland et al. (1995) found degradation in hand-eye coordination and errors in pointing accuracy following the wearing of a see-through HMD—results that demonstrate that negative aftereffects are indeed possible. There have also been anecdotal observations of individuals demonstrating significant ataxia following a 30-minute VR exposure (K.M. Stanney, personal communication, April 9, 1996). Finally, recent research (Kennedy et al., 1996) has concretely established the occurrence of ataxia following VR exposure.

The VE used in conjunction with the anecdotal observations referred to above was a maze, the traversal of which involved both forward and left/right-represented movements. On the other hand, the task employed in Kolasinski (1996)—the computer game Ascent—involved represented movements primarily in the forward direction only. This suggests that the kinematics of the task performed in the VE may have an important effect on the occurrence of ataxia. For example, VR applications involving limited represented movement—such as teleoperation or simple games—may pose limited risks of ataxia, whereas applications involving a high degree of represented movement—such as highly dynamic games—may pose greater risks of ataxia. Clearly, this unresolved issue is a critical one that must be investigated further.

Author: Jason 'vanRijn' Kasper

My name is Jason 'vanRijn' Kasper. I am the ring leader of the amazing Kasper family. I am unashamedly a Christian Nerd. These are our stories....


  1. Findings:

    Although there is debate as to the exact cause or causes of simulator sickness, a primary suspected cause is inconsistent information about body orientation and motion received by the different senses, known as the cue conflict theory. For example, the visual system may perceive that the body is moving rapidly, while the vestibular system perceives that the body is stationary. Inconsistent, non-natural information within a single sense has also been prominent among suggested causes.

    Although a large contingent of researchers believe the cue conflict theory explains simulator sickness, an alternative theory was reviewed as well. Forty factors shown or believed to influence the occurrence or severity of simulator sickness were identified. Future research is proposed.

  2. Simulator sickness was initially documented by Havron and Butler in 1957 in a helicopter trainer (Casali, 1987). It is similar to motion sickness, but can occur without actual motion of the subject. The most common symptoms resemble those of motion sickness: general discomfort, apathy, drowsiness, headache, disorientation, fatigue, pallor, sweating, salivation, stomach awareness, nausea, and vomiting. Postural instability, flashbacks (a sudden recurrence of symptoms), retching, and vomiting have also been known to occur. Although the potential discomfort to the subject alone makes simulator sickness a problem, additional drawbacks include adverse consequences to training and user acceptance.

    Kennedy and Fowlkes (1992) noted that simulator sickness is properly called a syndrome because of the complex signs and symptoms associated with it. They further noted that some people exhibit all the signs and symptoms, others exhibit only a few, and some exhibit no symptoms at all. Additionally, among people who are symptomatic, no single symptom predominates. Because of the variety of symptoms associated with simulator sickness, Kennedy and Fowlkes described it as being polysymptomatic. Although this characteristic makes sickness difficult to measure, the polysymptomatic nature has an advantage in that symptom differences and changes in symptomaticity may be diagnostic (Kennedy & Fowlkes). For example, if more eye strain is suddenly associated with usage of a particular simulator, it might suggest that something is wrong with the visual display.

    Kennedy and Fowlkes (1992) also described simulator sickness as being polygenic since no single factor can be identified as the cause. Instead, as this report will reveal, many factors are involved.

  3. (these are all from that RTF document, by the way…)

    In an analysis of data from 10 U.S. Navy and Marine Corps flight simulators, Kennedy, Lilienthal, Berbaum, Baltzley, and McCauley (1989) found that approximately 20% to 40% of military pilots indicated at least one symptom following simulator exposure. McCauley and Sharkey (1992) pointed out that pilots tend to be less susceptible to motion sickness than the general population due to a self-selection process based on their resistance to motion sickness. Since VE technologies will be aimed at a more general population, such selection against sickness may not occur. Thus, McCauley and Sharkey suggested that sickness may be more common in virtual environments than in simulators.

  4. hmmm….

    As Stone indicated, problems such as binocular convergence, inappropriate accommodative response to blurred images, unequal focusing capability in each eye, and inadequate fixation or pursuit eye movements are all evident in current Liquid Crystal Display (LCD)-based HMDs. These problems are known to contribute to a disorder known as asthenopia, which Stone described as a type of oculomotor instability.

    maybe I should try this on a CRT….

  5. found this….

    As for what gamers who suffer from sim sickness severely can do in the meantime — well, not much. Even Miller of 3D Realms can only offer this: “People who have this problem can easily avoid playing games that have this effect on them.”

    But that’s hardly a solution for an avid gamer like Lastowka. “The games are too much fun not to play,” he says. Like a junkie who knows the risks of his habit to his health, Lastowka has an addiction that’s simply too strong to resist. “Even when I’m lying in bed, dreading how much my head hurts, I still want to play.”

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