Physiological
Problematics in Immersive Environments
Nicholas Negroponte’s 1995 book Being Digital is perhaps the most widely
read text on the cultural sea change digital technology will necessitate. In it, he briefly describes his optimistic
prospects for virtual reality (VR) technology, noting its history in flight
simulation and other military applications and then speculating on its future
as a general-purpose computing interface.
The imminent VR future, he assures the reader, will allow simulation of
any type of vehicle, learning and information retrieval based on spatial logic
(which is the foundation of NASA’s Dataspace project), entertainment in
unlimited imaginary theme parks, or navigation of the physically inaccessible,
such as the inside of an organism or the Milky Way itself.[1] A number of other writers have pointed out
the real or potential utility of VR. In
addition to simulation and recreation, VR provides avenues for industrial
design and architecture, treatment of phobias, telepresence (working via
robotics in hazardous or otherwise inaccessible environments),
telecollaboration, and medicine.
Regarding the last of these, and in relation to Negroponte’s
predictions, consider the possibilities for bringing together scanning and VR
technologies. A doctor could take a
trip through the patient’s body in real time to diagnose problems. By extension, in the slightly more distant
future, the physician could implement treatment through telecontrol of nanotech
robotics.[2] In describing the applicability of current VR
technology, Negroponte notes only the computational constraints placed on
representing the virtual environment (VE) in a visually realistic fashion.[3] But given his technical expertise, his
omission of problems in the human-factors area can only be seen as
misinformation. The technical
literature in the field of VR clearly demonstrates that technical factors do
not present nearly so great an obstacle to the widespread, general-computing
use of VR as do human factors.[4]
Stanney et al. write: Motion
sickness and other aftereffects (i.e., balance disturbances, visual stress,
altered hand-eye coordination) are an unwanted by-product of VE exposure. …There is concern that continued development
of VE tecnology may be compromised by the presence of these maladies, which are
experienced by a significant proportion of users.[5] We should begin by stipulating the
usage of the term “immersive virtual reality.”
VR, like so many end-of-the-century terms, has been radically overused
and abused. So for our purposes it is
useful to trim the definition down to a few loose necessaries. A virtual reality system is any digital
apparatus that allows the user to move within and interact with a graphically
rendered, though fundamentally binary, three-dimensional space, the VE. Under this description, 3D computer games or
architectural software would be considered VR, even if the interface were
nothing more than a standard keyboard/mouse/monitor combination. This is acceptable so long as we
differentiate between immersive and non-immersive VR. In immersive VR, a variety of technologies are used to place the
participant, cognitively speaking, within the three-dimensional VE. This is achieved primarily through
monopolizing the user’s entire field of view with the imagery of the VE. The technologies that allow this to occur
include surround screens, Cave Automatic Virtual Environment displays (CAVEs,
for short), and, most commonly, head-mounted displays (HMDs). Although most reception interface design has
concentrated on visual immersion; sound, touch, and smell interfaces are all
under development by various researchers.
But most human-factors problems currently under investigation are
centered around the visual interface, so it is there that I wish to focus my
attention. The most common negative symptom of VE
immersion is nausea,
[6] a phenomenon common enough to have earned its own neologism—“cybersickness.” Ironically, nausea is a direct result of one
putatively positive symptom
of VE immersion, false motion. You
need not have participated in an immersive VE to be familiar with the
sensation of false motion. A
very similar psychophysiological response is common among spectators
of Imax films. In both cases, the “hows” of false motion are
the same. In a typical computer
game, television program, or film, the majority of the spectator’s field
of view is dominated by a stable frame of reference. Although the image on the screen may be hyperkinetic, the prominence
of stability on the periphery assures the brain that the body is, in
fact, stationary. However, when
an Imax movie screen or a VR head-mounted display robs the spectator
of that peripheral stability, the center of the brain that processes
visual information understands the signal as an actual bodily movement. The result is false motion, the physical sensation of flying, falling,
etc. (Incidentally, I would
hypothesize that the greater sense of presence that comes with sitting
close to a normal TV or film screen—and thereby allowing visual motion
to cover a greater portion of one’s field of view—is at the root of
children’s propensity to sit a foot from the TV or in the front row
of the movie theater.) The skeptic may reply that other senses also participate
in the overall processing of movement.
That is true; and it is also at the core of cybersickness. But to understand why, we must have an explanatory
model of motion sickness in general. The theory that has been dominant since the mid-60s is described
as the “sensory conflict” model.[7] According to the sensory conflict model of
motion sickness, motion cues from the visual system come into conflict
with those provided by the vestibular system of the inner ear. In normal situations, the information provided
by these two systems is in agreement.
But imagine for example, that you are sitting in the back seat
of a car and reading a book while the car is being driven down a winding
road. Your field of view is populated almost entirely
by stable objects, and the visual apparatus therefore receives no cues
that you are in motion. Meanwhile,
the fluids of your vestibular system are sloshing away, sending copious
data to your brain that you are in motion.
The result is sensory conflict, which manifests itself as nausea. (Why nausea? Although the literature on the response is primarily qualitative,
the predominant theory holds that it is an evolutionary adaptation. Since sensory conflict is one major effect
of the toxins commonly found in spoiled foods, many animals, including
humans, evolved nausea, and by extension vomiting, as a method for expelling
the offending toxins.
[8]) The remedy in this common carsickness scenario
is well known—sit in the front seat and look at the road, thus encouraging
visual/vestibular agreement. In the case of immersive VR (or Imax
cinema, for that matter), the exact opposite neurological inputs occur, but the
result is similar. In VR, the visual
apparatus sends cues to the brain stem telling it the subject is moving, but
the vestibular system sends no (or at least very few) movement cues. Harris et al. write: Consider
the common virtual environment in which an operator equipped with a
head-mounted display is physically limited to the tracking region of the head
tracker and “flies” about an environment using a joystick or some other
pointing device to signal desired motion.
Such a subject is then presented with a wealth of visual cues to self
motion, but the non-visual cues that are found in the real-life version of the
experience are sorely missing. . . . A
virtual environment with only visual cues ignores the physical cues to linear
self motion which are largely signaled by the acceleration-sensitive otolith
division of the vestibular system.[9] The
situation is furthermore exacerbated, not reduced, by improvements of image
quality. Much has been made of the low
level of verisimilitude in most virtual environments, a problem primarily
related to limitations in computing power.
Indeed, R. J. Stone has half-jokingly referred to VR as a form of
sensory deprivation.[10] Regarding VR flight simulation, Regan has
noted, “The literature suggests that simulator sickness problems appear to get
worse as the simulation gets better with technological progress.”[11] That is, the closer a VE approximates
photorealism, the more likely, and the more strongly, the participant will
suffer cybersickness. At any rate,
Regenbrecht et al. are careful to point out that an increased sense of presence
in the VE is not necessarily dependent on visual realism: A
further point can be made by referring to the paradox of experiencing virtual
stimuli as real. By acknowledging the
virtual objects as sharing the environmental space with him or her, the user
projects the perceived (felt) reality of his or her own body onto the virtual
objects. The virtual objects are
experienced as real even if any sense of photorealism is absent.[12] At first, the problem of sensory
conflict may seem like simply another minor technological roadblock. But in fact, it amounts to a profound
obstacle in VR advancement. Consider
that one of the raisons d’etre of VR,
full freedom of movement within the VE, is severely compromised, and not by
something as ephemeral as processing speed or display size, but rather by an
inherent physiological trait of the human sensorium. Of course, significant research is ongoing
in regard to the problem of cybersickness. Potential solutions engage the problem at the sending end (the VR
apparatus) or the receiving end (the human participant), but usually
through some combination of both. The
most obvious strategy would be to nullify sensory conflict by introducing
actual movement to the subject. A
specially designed VR chair or cockpit could move interactively with
the participant’s movement within the VE.
There has been significant success with this model in high-end
aircraft simulation. But the drawbacks of such an approach are just
as obvious. The necessity of
such a cumbersome and costly device would prevent any general-computing
use of VR. Cutting corners does not help the situation
much, as John Vince notes several studies which indicate that anything
less than the full six degrees of freedom (that is, pitch/roll/yaw and
sway/surge/heave) in such devices still results in significant cybersickness
problems.
[13] An alternative would be to somehow decrease
or eliminate the symptoms caused by sensory conflict. This adaptive approach seeks to create immunity
in the VR participant through a progressive series of limited exposures. At first glance, the research supporting adaptation
seems promising. Regan notes,
“adaptation can cause dramatic reduction in symptoms for approximately
95% of all normal individuals, although it is generally accepted that
5% of the population will never acquire immunity to sickness, irrespective
of length of exposure.”
[14] Stanney et al. indicate that dramatic decreases
can be achieved with as few as four exposures.[15] But the drawbacks to adaptation may not be
worth the advantages. Stanney
et al. go on to point out that, “Although such adaptation may sound
advantageous, aftereffects may make individuals maladapted for the return
to the ‘real’ world once VE interaction concludes . . . leaving the
participants ‘miscalibrated for the real world’.”
[16] In a moment I will argue that much of the philosophical
discussions of VR are premature; but here, at least, we have a genuine
postmodern dilemma. The use
of a machine designed to simulate reality causes impairments in the
cognitive abilities that help subjects navigate the non-virtual
world. I must now admit that I have been
using the term “cybersickness” perhaps a bit too specifically, essentially
equating it with nausea. Most
researchers use it more loosely—any negative physiological symptoms associated
with VE exposure are described as variations of cybersickness. Nausea is the most commonly cited and
arresting issue, but other cybersickness symptoms include drowsiness, fatigue,
headache, eye strain, and sopite syndrome, which is “characterized by lowered
arousal or mood during or after VE use.”[17] Furthermore, I have only described one
characteristic type of sensory conflict, but the image processing speed of the
VR system can also cause a conflict akin to traditional motion sickness. Regan explains: There
is the additional problem that can be caused by display update lags. Such lags can induce a conflict for the user
when the time between an action (such as a head movement) and the result
(change in visual scene) becomes discernible.
The visual-vestibular conflict here arises from discrepancies in time
between the actual physical movement, which provides the vestibular cues, and
the movement of the visual field.[18] The
human-factors problems facing immersive VR development are therefore
great. And with only a few exceptions,
technological solutions for cybersickness symptoms do not seem apparent. It is a curious aspect, then, of most
popular and philosophical writing on VR that cybersickness is barely, if at
all, discussed. Whether utopian or
reactionary, these writers seem magnificently unaware of human-factors
problems. Writers of VR literature aimed at a
mass audience are, as might be expected, most guilty of futuristic
naivete. I have already mentioned
Nicholas Negroponte, who’s view of progress in digital technology seems to be
something like, good developments are inevitable due to their inherent
virtue. L. Casey Larijani’s The Virtual Reality Primer, another
leading popular title, spends most of its 206 pages inventorying the VR
application horn of plenty without even once mentioning these serious
human-factors issues. The anthology, Communication in the Age of Virtual Reality,
and Fred Moody’s The Visionary Position likewise
give cybersickness short shrift. In
fairness, I should note John Vince’s Essential
Virtual Reality. Vince is an
important working researcher in the field, and his is the only popular text
that discusses human factors in any depth.
But even here, the author displays a technologically deterministic view,
trusting that these problems will be readily overcome. One might furthermore easily argue that the
predominant notions of immersive VR in the public mind come not from books, but
from media representations and countless unfiltered internet discussions. Johnny
Mnemonic, Lawnmower Man, Star Trek: The Next Generation, Strange Days,
eXistenZ, and The Matrix, among
others, go farther than any books in shaping the public imagination regarding
VR. And if these deal with physical
factors at all, it is to symbolically render the existential dilemmas presented
by the mythology of VR, rather than to point out the technology’s actual
interface shortcomings. More scholarly VR writings in
qualitative, as opposed to technical, veins have also refused to problematise
cybersickness. This seems odd,
considering that this area of the literature is almost uniformly concerned with
rejecting euphoric attitudes toward VR technology. Philosopher Michael Heim, in The
Metaphysics of Virtual Reality, centers his discussion, as the title
suggests, around questions of being posed by VR, but without considering how
cybersickness may figure into those questions.[19] Additionally, Mark Slouka’s War of the Worlds is typical—much ado
about the philosophical problems putatively presented by VR but actually very
little thought based on physiological and psychological research.[20] Probably the broadest text in the humanities
literature is the anthology, The Virtual
Embodied: Presence, Practice, Technology.[21] The contributors discuss VR from a variety
of perspectives, with the balance tipped toward post-structuralism. Once again, physiological factors are
largely ignored. The most
psychologically sophisticated piece in the volume is Max Velmans’ “Physical,
Psychological, and Virtual Realities.”
In it, he, at least, acknowledges the speculative nature of his
argument: It is notoriously
difficult to predict how far new technologies will develop or what their social
impact will be. However, let us suppose
that VR worlds eventually become so convincing that they are no longer clearly
distinguishable from actual worlds (this blurring of imagination into reality
already exists, for some, in vivid dreams).[22] It is not my intention to imply that
the VR literature described above has no worth. We would be in a far worse condition if cultural and existential
questions were not addressed. But it is
difficult not to feel that scholarly examination of the deeper issues in VR is
based too much on naive popular notions of what VR is and will be—the mythology
of VR, not VR as it is. We are addressing
question nine while question four goes unconsidered. The current human-factors problems are too great to be glossed
over in every branch of the literature other than the technical, and the
possible avenues for cultural and philosophical analysis in this more timely,
if less grandiose, area are ripe. [2] In
addition to Negroponte, see especially Frank Biocca and Mark R. Levy, eds., Communication in the Age of Virtual Reality (Hillsdale,
NJ: Lawrence Erlbaum, 1995); L. Casey Larijani, The Virtual Reality Primer (New York: McGraw-Hill, 1996); Fred
Moody, The Visionary Position: The Inside
Story of the Digital Dreamers who are Making Virtual Reality a Reality (New
York: Random House, 1999); and John Vince, Essential
Virtual Reality (London: Springer, 1998). [3] Negroponte, Being Digital, 118. [4] See especially Laurence
Harris et al., “Vestibular Cues and Virtual Environments,” Proceedings of the IEEE 1998 Virtual Reality Annual International
Symposium (Los Alamitos, CA: IEEE, 1998); E. C. Regan, “Some Human Factors
Issues in Immersive Virtual Reality: Fact and Speculation,” Virtual Reality Applications, R. A.
Earnshaw, J. A. Vince, and H. Jones, eds. (London: Academic Press, 1995);
Holger Regenbrecht, Thomas Shubert, and Frank Friemann, “Measuring the Sense of
Presence and its Relations to Fear of Heights in Virtual Environments,” The International Journal of Human-Computer
Interaction, 10/3: 233-49; Kay Stanney et al., “Aftereffects and Sense of
Presence in Virtual Environments: Formulation of a Research and Development
Agenda,” The International Journal of
Human-Computer Interaction, 10/2: 135-87; and Robert Kennedy and Kay
Stanney, “Postural Instability Induced by Virtual Reality Exposure,” The International Journal of Human-Computer
Interaction, 8/1: 25-47. [5] Stanney et al.,
“Aftereffects and Sense of Presence,” 139. [6] Stanney at al.,
“Aftereffects and Sense of Presence,” 139; Regan, “Some Human Factors Issues,”
165. [7] See J.
B. Murray, “Psychophysiological Aspects of Motion Sickness,” Perceptual and Motor Skills, 85/3:
1163-67; Eric Muth et al., “A Psychophysiological Paradigm for the Study of
Nausea,” The Journal of Psychophysiology,
12/1: 56-61; and T. Probst and U. Schmidt, “The Sensory Conflict Concept for
the Generation of Nausea,” The Journal of
Psychophysiology, 12/1: 34-49. [8] Steven
Pinker, How the Mind Works (New York:
Norton, 1997), 264-266. [9] Harris et al.,
“Vestibular Cues and Virtual Environments,” 133. [10] R. J.
Stone, “Virtual Reality—The Serious Side; Where Next, and How?” Proceedings of Virtual Reality 91: Impacts
and Applications (London: Meckler, 1991), 73. [11] Regan, “Some Human
Factors Issues,” 167. [12] Regenbrecht et al.,
“Measuring the Sense of Presence,” 235. [13] Vince, Essential Virtual Reality, 68. [14] Regan, “Some Human
Factors Issues,” 167. [15] Stanney et al.,
“Aftereffects and Sense of Presence,” 140. [16] Stanney et al.,
“Aftereffects and Sense of Presence,” 144. [17] Stanney et al.,
“Aftereffects and Sense of Presence,” 143. [18] Regan, “Some Human
Factors Issues,” 169. [19] Michael H. Heim, The Metaphysics of Virtual Reality
(London: Oxford Univ. Press, 1994).
[20] Mark
Slouka, War of the Worlds: Cyberspace and the High-Tech Assault on
Reality (New York: Basic Books, 1995). [21] John
Wood, ed., The Virtual Embodied: Presence, Practice, Technology (London:
Routledge, 1998). |