Kinetosis / Motion Sickness A new Approach for Adaptation in Virtual

Transcription

Kinetosis / Motion Sickness
A new Approach for Adaptation in
Virtual Reality
DIPLOMARBEIT
zur Erlangung des akademischen Grades
Diplom-Ingenieurin
im Rahmen des Studiums
Medizinische Informatik
eingereicht von
Petra Kölndorfer
Matrikelnummer 0126687
an der
Fakultät für Informatik der Technischen Universität Wien
Betreuung:
Betreuer: Univ. Ass. Mag. Dr. Hannes Kaufmann
Wien, April 2009
Unterschrift Verfasserin
Unterschrift Betreuer
Technische Universität Wien
A-1040 Wien
Karlsplatz 13
Tel. +43/(0)1/58801-0
http://www.tuwien.ac.at
ii
Petra Kölndorfer
Grundsteingasse 42/2/20
1160 Wien
“Hiermit erkläre ich, dass ich diese Arbeit selbständig verfasst habe, dass ich die
verwendeten Quellen und Hilfsmittel vollständig angegeben habe und dass ich die
Stellen der Arbeit – einschließlich Tabellen, Karten und Abbildungen –, die anderen
Werken oder dem Internet im Wortlaut oder dem Sinn nach entnommen sind, auf
jeden Fall unter Angabe der Quelle als Entlehnung kenntlich gemacht habe.”
Wien, April 2009
Unterschrift
iii
Abstract
Kinetosis is the medical expression for motion sickness. It comes from the Greek
word “kinein” which means “to move”. In this master’s thesis the effects of motion
sickness and cybersickness are described. This topic is first discussed on the basis
of existing works in which former approaches are demonstrated. Motion sickness
occurs when the information of all parts of the equilibrium organ - ears, muscles
and eyes - do not send consistent information to the brain. There exist three main
theories which all try to describe the mechanism of becoming motion or cybersick.
Besides this there are also other factors which cause cybersickness. The symptoms
of the illness are very different and there are many of them, for example eye strain,
headache and nausea. The first part of the thesis describes these medical foundations
in detail.
The practical part of this work tests the hypothesis if a short time training programme is useful for people who suffer from cybersickness. To prove this a virtual
environment was built to train test persons within four days. The training itself
required them to watch a replay of a racing game for up to 25 minutes per session.
On each of the four days exactly one session was held. A questionnaire was created
to quantify the results of this training. The sickness scores were analyzed and due
to this data the conclusion was drawn. At the end a small outlook to the future of
cybersickness research is given.
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Zusammenfassung
Kinetose ist der medizinische Begriff für Bewegungskrankheit. Es stammt aus
dem Griechischen und bedeutet so viel wie “sich bewegen”. In dieser Diplomarbeit sind die Effekte der Bewegungskrankheit und von Cybersickness beschrieben.
Dieses Thema wird auf Basis von bestehenden Arbeiten diskutiert, in denen frühere
Ansätze zu diesem Thema aufgzeigt werden. Kinetose entsteht, wenn die Informationen, die alle Teile des Gleichgewichtsorgans - Ohren, Muskeln und Augen zum Gehirn senden, inkonsistent sind. Es existieren drei Haupttheorien über dieses
Thema, die alle versuchen die genauen Mechanismen dieser Krankheit zu ergründen.
Neben diesen Theorien gibt es auch noch andere Faktoren, die Cybersickness hervorrufen. Die Symptome dieser Krankheit sind sehr verschieden und es gibt viele
von ihnen, zum Beispiel angestrengte Augen, Kopfschmerzen oder Übelkeit.
Der praktische Teil dieser Arbeit stellt die Hypothese auf, dass Adaption in kurzer
Zeit möglich ist. Um diese These zu überprüfen, wurde eine virtuelle Umgebung
erstellt, in der die Testpersonen vier Tage trainiert wurden. Das Training bestand
daraus, dass die Personen ein maximal 25 Minuten langes Replay von einem Autorennspiel anschauen mussten. An jedem der vier Tage war eine Sitzung. Ein
Fragebogen wurde erstellt, der die Ergebnisse quantifizieren soll. Die daraus entstandenen Sickness Scores wurden analysiert und aufgrund dieser Daten wurde eine
Schlussfolgerung gezogen. Am Ende gibt es einen kleinen Exkurs zu zukünftigen
Forschungsfeldern.
Each thing is happening twice:
at first in the heads, virtually,
and the second time in action,
in reality.
If it doesn’t happen in the heads,
it will not happen in reality.
– P.Z.
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Acknowledgments
At the end of an student’s life always stays a master’s thesis. This moment is a
very exciting one. You know that you go straight forward to the home straight,
the end of your university life and your student’s life. And it is a very difficult
moment, because writing a master’s thesis is really hard work. You need really
good management skills and steadiness to sit before your computer for hours and
write one page after another. At this phase of your life you need really support from
all the people around you.
First of all, I want to thank my parents, who always support my view of life and
let me do, what I want to do and give me all the freedom a young person needs,
not only in financial issues. They give me the wings to fly to explore my own way
and my own sight of view. They made me a self confident person who can challenge
with the life so far.
On next place I will thank my boyfriend Martin, who understands me and pushes
me through my master’s thesis, because sometimes my motivation was lost in darkness and hopelessness. He gave me that kind of pressure I need to finish all my
tasks and arrangements and let me know that the stands behind me. And I thank
him for all his good advices he gives me in several belongings.
Apart from these people who gave me emotional and financial support, I will
thank my colleagues at work who also support me in some different ways. I also
thank Hannes Kaufmann not just accept my topic for this thesis but also for his
support during some problems with the labor. In the same breath I thank the tutors
at the institute, Christoph and Mathis, who always gave me the opportunity to use
the labor whenever I want and helped me with technical problems.
Last but not least I thank all my test persons who have dipped to my Virtual
Reality. They have all my gratefulness and I take my hat before them. Especially
I thank Daniel who was a really good test person and I have promised to mention
him here. He gave me good support and helped me through this study with his
jocularity. I will miss him for this.
Contents
1 Introduction
1
2 Medical Foundations
5
2.1
2.2
2.3
2.4
The anatomy of the equilibrium organs . . . . . . . . . . . . . . . .
5
2.1.1
The inner ear . . . . . . . . . . . . . . . . . . . . . . . . . .
6
2.1.2
The organ of equilibrium . . . . . . . . . . . . . . . . . . . .
8
Motion sickness - A short description . . . . . . . . . . . . . . . . .
9
2.2.1
The sensory conflict theory . . . . . . . . . . . . . . . . . . .
10
2.2.2
The poison theory . . . . . . . . . . . . . . . . . . . . . . .
13
2.2.3
The postural instability theory
. . . . . . . . . . . . . . . .
14
What is cybersickness? . . . . . . . . . . . . . . . . . . . . . . . . .
15
2.3.1
Other factors causing cybersickness . . . . . . . . . . . . . .
15
The symptoms of motion sickness . . . . . . . . . . . . . . . . . . .
17
3 Related Work
19
3.1
Cause and effect of kinetosis in virtual reality . . . . . . . . . . . .
19
3.2
Connection between virtual reality (VR) and motion sickness . . . .
21
3.3
Adaptation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22
3.4
A question of histamine? . . . . . . . . . . . . . . . . . . . . . . . .
23
4 Evaluation Design
4.1
4.2
25
Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25
4.1.1
Configuration . . . . . . . . . . . . . . . . . . . . . . . . . .
26
Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
4.2.1
28
The game . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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CONTENTS
4.3
4.4
4.5
Building the tracks . . . . . . . . . . . . . . . . . . . . . . . . . . .
Test Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Questionnaire . . . . . . . . . . . . . . . . . . . . . . . . . . .
31
32
33
5 Results
5.1 Gender specific differences . . . . . . . . . . . . . . . . . . . . . . .
5.2 Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3 Additional information . . . . . . . . . . . . . . . . . . . . . . . . .
37
37
40
47
6 Conclusions
6.1 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
53
55
List of Figures
57
List of Tables
58
References
61
Chapter 1
Introduction
In this thesis, the problem of kinetosis is discussed. But is kinetosis - also known as
motion sickness - a real or rather a serious problem? For most people it is. 20% of
the people who drive in a car get sick. A study in virtual reality (VR) shows that
61% of the test persons become motion sick [RP94]. Because of these numbers and
the fact that there is no cure for this, I decided to write a work about this topic.
Especially older persons often explain that they became sick when they first
drove in a car - often seen in the 1920’s. That happens when someone makes a
direction change which is unusual for the person. The problem is not new and not a
cause of the motorization of our world. In former times people became motion sick
when they were on a ship or on a camel. In present-day there are cars, buses, planes,
simulators, virtual reality in computer games, 3D-cinema and CAVEs1 . Astronauts
and cosmonauts also become sick when they fly into space, approximately 60%
[BEN02]. That is then called space adaption syndrome or space sickness.
Primarily, kinetosis is not a great medical problem but a personal. People who
suffer from kinetosis have a limited quality of life. And there is little which can be
done for them. They have got pills and chewing gums, arm bracelets with magnetic
stones and more of such things. If at all, they only help a short time.
For this reason, and my personal experience with this illness and the limited
1
Cave Automatic Virtual Environment
1
2
CHAPTER 1. INTRODUCTION
possibilities of the medicine to help, I looked for a new approach to help these
people and maybe improve their condition. One day I took part in the lecture
from Mag. Dr. Hannes Kaufmann and he spoke about cybersickness and the wide
range of its problems for applications in virtual reality. People are often not able
to participate in these virtual realities because they have really strong problems
with their cognition and well-being during a session in these “unreal places”. And
because of this lecture I decided to take the opportunity to soften these effects.
Therefore the aim of this thesis is to find out if there is the possibility to make a
short time training programme for those who suffer from cybersickness. It should be
possible to train them in short time as it is not practical to exercise several months
only to endure one session in multiple virtual environments. Several works about
doing long term training exist but we test our hypothesis if an adaptation in virtual
reality is also possible in short time.
This is important because computer games become more and more realistic and
people have yet problems to play these games. Especially in first-person shooters
the problem of motion sickness occurs. First-person shooters are games in which
you have a first person perspective and it looks like the gamer looks through the
eyes of the protagonist of the game. The viewing angle is the main problem here
because it looks like you are acting but in reality you sit on your chair and you only
move your hands.
Furthermore this problem also occurs in other areas of life, for example in simulators for pilots. These and similar professions work with simulators and therefore
they are prone to become sick. Another example for simulators is the simulation
of medical surgeries. Here the students can train a certain surgery in a virtual environment. The advantage of this is that students do not harm someone and they
could train very often. However, no student will not make a training in a virtual
environment when they become sick.
Another part is that cinemas explore the more or less new interest to display
movies in 3-D. IMAX2 for example do this at least for over 20 years. Now also
2
IMAX (short for Image MAXimum) is a motion picture film format and projection standard
created by Canada’s IMAX Corporation.
3
“normal” cinemas do this and broadcast movies in 3-D to give the people the opportunity to see something more realistic. Especially for nature documentations
this technique is used. Seeing something like that one can see it as being very realistic but after a while you feel a little bit uncomfortable because of the effect of
cybersickness.
And for all this things of our modern life it is important to know more about
motion sickness and its triggers. In the future it there will exist more and more
virtual environments (VE), for example in museums and in cinemas. In addition
persons will not invest money in a technology which makes a certain part of them
sick.
4
CHAPTER 1. INTRODUCTION
Chapter 2
Medical Foundations
Someone who suffers from kinetosis1 , also known as motion sickness, is not able to
convert moving signals into correct information. But this does not imply that the
equilibrium organ is malfunctioning, it is more likely that the organ is overreacting.
The chapter starts with a short discourse in the area of medicine. In section 2.1, a
short description of the ear and the equilibrium organs is given and to understand
which physical things happen when kinetosis occurs. The next section deals with
the issue of what motion sickness is (section 2.2) and which effects (section 2.4)
occur.
2.1
The anatomy of the equilibrium organs
The inner ear is the part of the body which provides the sense of balance. Because
of this the description of the external ear is not a part of this work. The focus lies
on the build of the inner ear, especially the cochlea and the semicircular canals.
1
from the Greek word κινιν/ kinein = to move
5
6
CHAPTER 2. MEDICAL FOUNDATIONS
2.1.1
The inner ear
To describe the anatomy of the inner ear, two books were used (Lippert [Lip00] and
Boenninghaus [BL05]). These two are considered medical standard works, especially
Lippert.
The inner ear is also called ”labyrinth” because of its complexity. It is sunk into
the skull and is divided into two main sections:
• Labyrinthus cochlearis (cochlea labyrinth): hearing organ
• Labyrinthus vestibularis (vestibule labyrinth): organ of equilibrium. The vestibule
labyrinth lies laterally behind the cochlea labyrinth.
The inner ear is totally surrounded by bones, as you can see in figure 2.1.
Figure 2.1: The inner ear and its location in the head (top view, the nose is above)
2.1. THE ANATOMY OF THE EQUILIBRIUM ORGANS
7
In figure 2.2 you can see a draft about the inner ear. You can see the cochlea,
the three semicircular canals and the three nerve cords. To make things easier a
simplified sketch is also pictured here in figure 2.32 .
Figure 2.2: The inner ear
Cochlea The cochlea contains the hearing organ. The bony cochlea, which
looks like a snail shell (figure 2.2), is winding two and a half times around the axis
(Modiolus), which contains the nerves and vessels. It is filled with perilymph and
is divided into two floors.
Vestibule The bony vestibule lies between the cochlea and the semicircular
canals and is filled with perilymph. Perilymph is an extracellular fluid. It is located
within the cochlea.
2
http://en.wikipedia.org/wiki/Semicircular_canal
8
Figure 2.3: The inner ear (simplified)
Semicircular canals The semicircular bony canals stand in the three main
axis of the room. The membranous canals lie in the bony canals and are surrounded by perilymph. They contain endolymph, which is a fluid in the membranous labyrinth of the inner ear. The sensory cells are located in the ampulla. The
sensory cells stand, surrounded by supporting cells, on the crista ampullaris. The
sensory cell hairs (per cell circa 50 stereocilia and one kinocilium) extend into the
cupule.
2.1.2
The organ of equilibrium
The organ of balance is classified into:
• The two otolithic organs (saccule and utricule) with the sensory area (macule)
to register linear accelerations
• The three semicircular canals (Ductus semicircularis anterior + posterior +
lateralis) to register angular accelerations
• A pressure compensation canal (Ductus endolymphaticus)
2.2. MOTION SICKNESS - A SHORT DESCRIPTION
9
Otolithic organs The sensory cell hairs of the balance cells are embedded
into a gelatin layer. On these lie granules of calcium carbonate. These granules
bow the sensory cells according to the gravity sideways and activate the sensory
cells. One sensory area stands horizontal and one vertical.
Semicircular canals The semicircular canals are filled with endolymph. Due
to the characteristics of fluids, when acted upon from a still state (inside a tube) the
liquid will first flow in a backwards direction. On motion of the head the endolymph
bears against a gelatin cupule. The gelatin cupule is then activated in the opposite
direction by the body’s movement. This causes movement of the crista ampullaris,
the sensory organ of the semicircular canal.
The sensory organ is not activated because of the motion itself but at the change
of the velocity (acceleration or deceleration). The amount of the avocation of the
gelatin cupule relates to the speed of the acceleration. The direction is a combination
of the aroused sensory cells of the six semicircular canals of the human body - three
on each side.
The semicircular canals stand orthogonal together according to the three dimensions of the space.
A schemata of the equilibrium organ is shown in figure 2.4
2.2
Motion sickness - A short description
In this section we put our focus on the question, what motion sickness means.
Motion sickness, with its sub-categories sea sickness, car sickness, air sickness, and
the special cases cybersickness, simulator sickness and space sickness, is a response
of the body to the moving environment.
Motion sickness is not a problem of modern times. The problem occurs since
humans are going upright. Reports exist from the ancient world, for example about
Seneca (Roman rhetorician and writer, ca. 54 BC – ca. 39 AD) who heavily suffered
from sea sickness. Some say, that the soldiers of Scipio in the Second Punic War
10
Figure 2.4: The equilibrium organ
(referred to as ”The War Against Hannibal” by the Romans) (218 to 201 BC) also
suffered from sea sickness, so he had to disarrange the battle. Also Napoleon met
this fate with his soldiers after a ride on a ship.
Kinetosis is not a pathological disease, but a physiological reaction of an external
stimulus. Like in [JJL00] described, three main theories exists:
• The sensory conflict theory
• The poison theory
• The postural instability theory
2.2.1
The sensory conflict theory
This theory is one of the oldest and well accepted ones. It says, that the information which we get from our visual senses and the information, which we get from
our vestibular system (inner ear), the inner muscular system and the gravity, do
11
not correlate with each other and so the person gets ill. The vestibular system is
explained in section 2.1.
[BEN02] is calling this theory “Neural Mismatch Theory” and divided it into
two types:
• Visual-Vestibular Mismatch
• Intravestibular (Canal-Otolith) Mismatch
These two types also have respectively three sub-categories. Figure 2.5 shows
a heuristic model of the sensory conflict which describes the mechanism of motion
sickness.
Figure 2.5: A heuristic model of motor control, motion detection, and motion sickness based on the neural mismatch theory [BEN02].
1. Visual-Vestibular Mismatch
12
Type 1 The vestibular organs and the muscle system do not get the same
information. This happens when for example a person is on a ship and is
observing the waves. The eye gets another information as the vestibular
organs receive, because the waves are wilder than it feels on the ship.
Type 2a This type occurs, when the eyes recognize a movement, but in reality the body does not move. This type is often seen, when someone
watches a film in a 3D-cinema. This type leads us to the phenomenon of
the simulator sickness.
Type 2b The information about what someone sees and what he feels do not
match together. It occurs, when a person sits in a car and cannot see
outside this car. The vestibular system and the muscular system send a
motion, but the eyes do not recognize this. So the person gets ill after
a while. This type always happens on passive means of transportation,
when people do not drive themselves.
Figure 2.6 shows an assembly of the neural mismatch theory and its subcategories.
2. Intravestibular (Canal-Otolith) Mismatch
Type 1 This type occurs, when the Coriolis effect appears. Coriolis or crosscoupled stimulation happens when someone is in motion and he shifts his
head in a direction. The information which the semicircular canal and
the otolith organs get, is that the body is moving but within another
force. Both of them get different information which is the reason why
the brain gets confused. An example of the Coriolis effect is a pirouette
that a ballet dancer is making. Without training we get dizzy and sick
after a while.
Type 2a When in space, the body loses information about gravity. Because
of this, astronauts get space sick with the described symptoms (in section
2.4). In weightlessness the canals correctly recognize movements of the
head, but the information about accelerations is missing. This is the
reason why the mismatch occurs.
Type 2b This type is the opposite of type 2a.
13
Figure 2.6: Classification of neural mismatch in provocative environments[BEN02]
2.2.2
The poison theory
The theory is based on whether the body misreads the signals which come from the
brain. The brain thinks that the organism was poisoned and now it runs an old
evolutionary programme to get the poison out of the organism, as many poisons have
the same effects on the body as motion sickness does [JJL00]. The coordination of
the visual, vestibular and other sensory input systems take part in this programme.
This is not the whole explanation for getting cybersick because some people get sick
in a VE and others do not. So it has a few flaws.
14
2.2.3
The postural instability theory
[JJL00] also describes a theory, which is called the postural instability theory. Postural instability means that you feel unsteady, dizzy or spinning. In some other
diseases it is also called balance disorder, for example at Ménière’s disease. This
theory was investigated by Riccio and Stoffregen. They say that humans try to
provide stability in the environment.
“Postural Stability is defined as the state in which uncontrolled movements of the perception and action systems are minimized.” [RS91]
A example for this is walking on ice. You go different on ice than on solid streets,
because the usual walking pattern does not work on ice and if you try this you will
fall down. The theory also states that instability can cause motion sickness and
cybersickness. The symptoms get more severe due the duration of the instability.
Riccio and Stoffregen [RS91] also claim that there are several environmental
situations which cause sickness symptoms. They define 4 categories:
• Low-frequency vibration
• Weightlessness
• Changing relationships between the gravitoinertial force vector and the surface
of support
• Altered specificity
For cybersickness only the last category - altered specificity - is important.
In VEs accelerations and rotations are only optically specified but some humans
may use muscular force to resist these motions. Hence they put themselves into
postural instability although there is no physical impact.
This theory is also the opposite of the sensory conflict theory because the authors
say that the sensory conflict does not explain all the factors which lead to motion
sickness.
2.3. WHAT IS CYBERSICKNESS?
2.3
15
What is cybersickness?
But what is cybersickness exactly? Is it the same as the other motion sickness
types? Or is it something completely different? It depends on where the line is
drawn.
For most scientists cybersickness and motion sickness are two complete different
things, for example in [JJL00]. It may have similar symptoms but different triggers.
They say that simulator sickness is different because the information of the inner
ear is completely absent. There is no motion attraction of the muscular cells and
also no attraction of the inner ear.
Others say that motion sickness and cybersickness are the same, because they
have the same triggers and the same symptoms. Persons suffering from one of these
diseases also suffer from the others too. There is no division between these two
illnesses. Although no movements are done in a VR, the inner ear and the muscle
cells nonetheless send information to the brain.
In this work the supposition is made that cybersickness and motion sickness are
the same. The reason for this decision was that the symptoms and the triggers are
quite similar and that motion cells are always firing and vection is always registered
in the brain. The brain is still working despite of the fact we are still sitting before
a screen or a in simulator. There are always small movements that are registered by
the ear, the muscles and the eyes although we do not notice this. And our opinion
is that if someone gets ill in a car he or she will also get ill in a simulator with a
high percentage.
2.3.1
Other factors causing cybersickness
In the case of cybersickness people sit still before a screen or they are moving with
a head-worn display. This difference is important for factors which cause sickness
symptoms. Some of this factors only take place when a person sits still and others
only when a head-mounted display is in use. Therefore we can see that it is not so
easy to identify the exact triggers for this suffering.
16
There are other factors which can cause cybersickness, which are not part of one
of the upper three theories and are also described in [JJL00]. There are factors which
are triggered by technological issues and some which are triggered by individual
behavior.
The technological issues are:
Position Tracking Error This is the error by the tracking system if the position
of the head (for example with a head-worn display) and the position on the
screen do not correlate.
Lag Lag describes the phenomenon in computing when a computer freezes and
continues some time later, for example when clicking on a mouse button. This
can also occur in a VR because a computer does the various calculations which
are necessary to coordinate a head-mounted display through an environment.
This effect is seen when the head was moved and the movement is shown a
few seconds later.
Flicker This is the disturbance of the screen when the refresh rate is too low. A
refresh rate of 30Hz is acceptable.
On the other hand individual factors play a great role in becoming cybersick
and motion sick; the complexity of the human organism should not be underrated.
The individual factors are as follows:
Gender Women are more prone than men because they have a wider field of view
and this causes more cybersickness symptoms. Women have physiological a
wider field of view, at least 1% in every direction.
Age Between 2 and 12 years one suffers more than when being older. People over
50 usually do not suffer anymore from this.
Illness A person who is ill, has stress, is tired or something like this is more prone
to motion sickness.
2.4. THE SYMPTOMS OF MOTION SICKNESS
17
Position in the simulator It is also important where you are arranged in the simulator. Usually a person is sitting or standing but sitting causes less symptoms
than standing because of the postural instability.
2.4
The symptoms of motion sickness
The symptoms of motion sickness vary from a minimal discomfort to high consequences for the human body.
There are a number of symptoms that can occur due to cybersickness and motion
sickness. Common symptoms are:
• Eye strain
• Headache
• Pallor
• Sweating
• Dryness of mouth
• Fullness of stomach
• Disorientation
• Vertigo
• Ataxia
• Nausea
• Vomiting
One of the problems with motion sickness and cybersickness is that the symptoms can occur longer times. The so-called aftereffects can last for hours and in rare
cases they last for days. But although motion sickness and cybersickness produce
the same symptoms they are not necessarily the same. Circumstances which lead
to motion sickness, do not necessarily lead to cybersickness and vice versa.
18
Chapter 3
Related Work
In the last fifty years there were a few approaches to explore kinetosis and all
its characteristics. Many theories exist under which conditions motion sickness
and its symptoms appear. NASA, air forces from miscellaneous countries, medics,
scientists and designers of virtual environments have recognized the problem of
motion sickness and made various studies about the phenomenon. In this chapter,
we introduce a small excerpt of these studies.
There exist three relevant areas of research:
1. Cause and effect of kinetosis in virtual reality
2. Connection between virtual reality (VR) and motion sickness
3. Adaptation
3.1
Cause and effect of kinetosis in virtual reality
In [UYS04] Ujike et al. focused on 3 factors, which cause cybersickness:
1. How a moving image is presented,
19
20
CHAPTER 3. RELATED WORK
2. Who watches a moving image,
3. What is presented as moving image.
They made 3 experiments to induce cybersickness of the subjects:
“EXPERIMENT 1: In this experiment, we examined the effects of image types, random dots and ordinary scene, on visually-induced motion
sickness during virtual rotation along yaw, pitch and roll axes.
EXPERIMENT 2: This experiment examined effects of virtual speed of
rotation along each of the three axes: yaw, pitch and roll.
EXPERIMENT 3: This experiment investigated the correlation between
the sickness scores and torsional eye movements during virtual roll motion, to examine the eye movement as an objective indicator.”
The result of these experiments was, that only virtual roll motion produces
cybersickness effectively. Additionally they found out that
“The sickness-related subjective score was the highest among virtual
rotation of different three axes, (i.e., yaw, pitch and roll), regardless
of types of visual image, such as random dots or ordinary scene, and
regardless of different speed of those virtual rotation.”
Another work deals with the problem of balance disturbances [KL95]. The
method was the following: A simulator was used, in which a 6-DOF (degrees of
freedom) motion based system was integrated. The hardware was a Wide Field of
View (WOF) projection dome. They also performed experiments with and without
dosages of alcohol, because this condition made a big difference if simulator sickness
occurs or not. This work shows that alcohol makes the symptoms more severe.
Some scientists made experiments by measuring electrocardiogram, blood pressure and respiration to quantify the regulation system of the human body [KYJB04].
In [JJL00] the author describes very detailed the process of how kinetosis occurs
and which effects it has on the human body and how the system is reacting. He also
3.2. CONNECTION BETWEEN VIRTUAL REALITY (VR) AND MOTION SICKNESS21
specifies the medical issues and circumstances about the inner ear and the vestibule
system. Benson [BEN02] made a very extensive, similar-sounding work.
3.2
Connection between virtual reality (VR) and
motion sickness
Another paper shows that scene oscillation is the most common cause if sea sickness
[SL99]. Oscillation is the repetitive variation, typically in time, of some measure
about a central value (often a point of equilibrium) or between two or more different states. Scene oscillation therefore means that the screen image on which
somebody looks is flickering. With this knowledge they hypothesized that a virtual
environment without scene oscillation produces lower simulator sickness.
The idea, that certain frequency ranges cause simulator sickness, is described in
[PDPF01]. They found out that lower frequencies cause higher simulator sickness
rates than higher ones because low frequencies conflict with the motion stimuli.
Other scientists, Arns et al, Reason and Brand [AC05] describe the relationship
between age and cybersickness. They found out that
”...motion sickness susceptibility was greatest between the ages of 2 to
approximately 12 years old, decreased rapidly from 12 to 21 years of age,
then more slowly until 50.”
In 2003, a high percentage of students from a Japanese junior high school became motion sick while watching a 20 minutes video. This video was filmed with
a hand-held video camera and includes vibration and image motion. Because of
this incidence a study [Uji07] was made in which the influence of larger and smaller
displays were examined. The result was, that larger displays produce higher Simulator Sickness Questionnaire (SSQ) scores than smaller ones. The same effect about
visual displays is shown in [SMM+ 06], which describes the phenomenon of larger
displays and greater visual angle and increasing VIMS (Visually Induced Motion
Sickness).
22
3.3
Adaptation
Other papers describe the effect of adaptation. One example of these papers is
[Cor93]. The author lays his focus on the problem of the space adaption syndrome
and someone‘s ability to adapt. He found out, that everyone has a different ability
to adapt to different conditions. That knowledge was not new, but he was the first
to proof it. He also claimed, that “bad” simulators caused more disorientation and
nausea but also lots more of visuomotor disturbances.
In [LL04] Lucertini identified that three factors (sensitivity, adaptability, retentivity) are the baseline for studies on motion sickness. His method was using a
Coriolis Stress Test (CST). The test persons had to throw their heads forward and
backwards with eyes closed. This exercise induces the Coriolis effect1 . The aim
was to create a rehabilitation programme for student pilots. The result of this programme was that the students have lower effects on motion sickness after performing
the CST regularly.
Simulator sickness in gaming is another research area. In [HPTN06] is described
how motion sickness can occur when playing computer games. The aim of the
authors was to compare different displays and their role in getting motion sick
during game playing. They wanted to compare
“... the simulator sickness produced by an ordinary display, a head-worn
virtual display and ahead-worn virtual display with stereoscopic game.”
The results showed that the sickness symptoms grew with the factor of the stereoscopic depth with the head-worn displays. Without stereoscopic depth at all the
symptoms were nearly the same as playing the game on a monitor.
1
The Coriolis effect is part of fictitious force, also called pseudo force. Through the movement
of the earth a moving object is always redirected to the right side, when we are on the northern
hemisphere and vice versa on the southern hemisphere. This distracting force is called Coriolis
effect, which is named after its discoverer Gaspard Gustave de Coriolis. It is a visible force, for
example railway rails wear away on one side stronger than on the other side. It also has effects on
the weather.
3.4. A QUESTION OF HISTAMINE?
23
Another author [Art96] describes the phenomenon of vection. He says, that vection is the main cause of producing simulator sickness. Arthur describes “vection”
as follows:
“Vection refers to the illusion of self-motion (we perceive ourselves
to be moving when our body is not).”
The work of [KNMS06] shows how eye-movement can control VE-sickness2 . They
found out, that a fixation point decreases the VE-sickness. They expect that the extra movement of the eye causes a conflict of the actual (extra-retinal) eye-movement
and the visual information of eye-movement.
A study with a Virtual Guiding Avatar (VGA) is performed in [LARL04]. The
VGA combines self-motion prediction cues and an independent visual background.
The aim was to decrease simulator sickness. The outcome of the study was that a
VGA improves the sense of presence in the virtual world. The use of such an avatar
reduces the symptoms of simulator sickness significantly.
3.4
A question of histamine?
The Viennese medic Univ. Prof. Dr. Reinhart Jarisch hypothesized that histamine
plays a role in becoming sea sick [JGM+ 04].
Histamine is a biogenic amine which is involved in immune responses. It is produced from the body itself and people absorb it also from food. Normally histamine
do not cause any disorders but in some cases problems arise, because there are not
enough proteins available to break down the histamine.
One of these problems is the effect of sea sickness, and also its related subcategories air sickness, car sickness, and so on, which can occur intensified after
eating dishes with high histamine levels. In his book [JGM+ 04] Prof. Jarisch
describes the role of histamine in different areas of life, but focuses on sea sickness.
He was the first to draw a connection between histamine and sea sickness.
2
VE = Virtual Environment
24
In another study he claims that taking higher dosages of vitamin C helps the
body to compensate the histamine level and then the symptoms decrease [Kem08].
Unfortunately the study was not representative enough because of the low number
of test subjects. Nevertheless this study is a good beginning for further explorations
in this area.
Chapter 4
Evaluation Design
In this section, we give a short overview of the evaluation design of our study. We
start with a short overview over the hard- and software, after that a description of
the configuration of the test environment is following. It is also described how the
software was used and configured. The questionnaire which was made is described
at the end of this chapter.
4.1
Hardware
We perform the cybersickness study in the VR-laboratory at the Interactive Media
Systems Group (IMS), Vienna University of Technology. The study was done on a
3.20 GHz Intel Pentium CPU with 2 GB RAM. The graphics board was a Nvidia
Quadro FX 3400.
A monitor was used with a resolution of 1280x1024 and a frame rate of 85Hz
from IIyama. Synchronously for test persons a video projector was used with a
resolution of 800x600 and a frame rate of 85Hz. It is an Infocus Depth Q, DQ3120.
The hardware is pictured in figure 4.1.
The shutter glasses are from NuVision with the model name 60GX (Figure 4.2).
25
26
CHAPTER 4. EVALUATION DESIGN
Figure 4.1: CRT, tower and video projector
4.1.1
Configuration
The operating system of the PC is Windows XP Professional with Service Pack
3 installed. The graphics card driver is from Nvidia and has the version number
91.31, the stereo driver has the marking 91.31 forceware 3D stereo.
With these drivers it is usually simple to configure the system. The card automatically detects the emitter for the shutter glasses. After that the properties of
the graphic card had to be opened and set the following properties:
• Clone View
• Stereo on
4.2. SOFTWARE
27
Figure 4.2: Shutter glasses
• 1280x1024
• 85Hz
It is important to activate the stereo driver because otherwise the game will not
work in stereo.
Now, all videos were shown in 3D with these configurations on the CRT and on
the video projector.
4.2
Software
For testing cybersickness we used the racing game Trackmania Sunrise. Trackmania
Sunrise from the French game developer studio Nadeo was chosen because some
people have already used it successfully in a 3-D environment and it provides editors
to generate own tracks. It is also possible to store the replays. We created four
different tracks for the training for the reason that the candidates were not bored.
Every person will see each of these tracks on a different day.
28
The tracks are divided into one longer track, two middle length tracks and one
shorter track. You can see the tracks in figure 4.3. Track 1 is the longest with a
time of 9’42”, Track 4 counts 7’19”, Track 3 lasts 5’43” and Track 2 is the shortest
with 03’42”. It was not so easy to find appropriate street courses to trigger motion
sickness symptoms. I created and drove the produced tracks on my own and saved
the replays. These replays were shown to the test persons. A description of how
the tracks were built follows in section 4.4.
(a) Track 1
(b) Track 2
(c) Track 3
(d) Track 4
Figure 4.3: The four test tracks.
4.2.1
The game
Trackmania Sunrise is a racing game in which you can create your own tracks. The
menu is very simple and very easy to understand.
4.2. SOFTWARE
29
When entering the game, the following menu appears (figure 4.4 a)) with four
menu items. The options are: Profile, Solo, Multiplayer and Editors.
In Profile the opportunity to set up own profile with a nickname is given, and
you can choose the car color and your nationality. It is possible to create several
control configurations, for example the keyboard shortcuts for driving issues. There
is also the possibility to have an avatar. There are several avatars pre-installed.
There is also the opportunity to set up several advanced configurations.
The next button is called Solo. In this menu, different campaigns and challenges
can be chosen. There are official and community campaigns and also own campaigns
which can be build in the Editors menu.
The button Multiplayer is clicked on to play a game with human opponents.
The gamers can choose to either play on the same computer with a split screen the screen is divided into two fields - or a game challenge with others in the world.
When clicking on Hot seat a time racing game is started. Here it can also be chosen
if the gamer wants to play over a local network or the internet.
The menu Editors is the thing which is of interest for us. When you click on it,
it brings up another menu which can be seen in figure 4.4 b).
(a) Start menu
(b) Following menu
Figure 4.4: Menu
In this menu you have five options to click on: Track, Ghost, Campaign, Replay
and Skin.
30
The Replays shows your saved driving replays. You can do this, but it is not an
asset. For this study it was very important to do this because this was the function
that was used to show the tracks to the people. Here you have also the possibility
to edit the replays or save them in another format.
In order to to design a track we click on the button Tracks. When this is
done, three challenge types can be chosen (figure 4.5 a)). The difference between
these three challenges are the engine power of the cars. Therefore different cars are
available on the different challenges. After that a menu appears where the daytimes
can be chosen. Between four daytimes can be picked up: Morning, Day, Evening
and Night. This is seen in figure 4.5 b):
(a) challenge
(b) daytime
Figure 4.5: Choose a challenge and daytime
After that the gamer comes straight to the track editor which opens with an
empty field (figure 4.6 a)). On the bottom of the screen the various buttons can
be found to manipulate the terrain, which looks like water. First of all a surface
is created, which is also called an island, on which streets and houses are built on.
When this is done and the island is ready, various street parts can be put on the
surface: Straight lines, lines with preconfigured bends, streets which go up or down,
and some more. A start and goal point also has to be defined. To drive a circuit more than one round - a special start to goal point has to be established. Here start
and goal are on the same place. At the very end there is the possibility to create
an attractive environment.
After working out a track with its streets and houses, it could possibly look like
4.3. BUILDING THE TRACKS
31
the one which can be seen in the figure 4.6 b). In this figure the start (in green) and
the goal (in red) and a few houses are pictured. This is only a test track which did
not find its way into the study; it should only illustrate how a track could look like.
There are also 180 degree turn and 90 degree bend and a few preconfigured ones.
(a) The empty editor
(b) Test track
Figure 4.6: The empty editor and one test track
When the track is perfect it should be saved. After that the track should be
driven by the creator or someone else. This can be done when clicking on the flag in
the left bottom corner. Then a car, which is chosen automatically by the system, is
positioned at the start and a countdown is showing. After having driven the track
successfully, the replay should be stored.
4.3
Building the tracks
In this section the building of the tracks is described. This is important because the
reader should understand which considerations were made to built these different
tracks.
First of all the tracks must have the ability to trigger some symptoms on the test
persons. It is known that most people get sick when they drive fast turnarounds
and this leads to motion sickness. It is the same if someone makes pirouettes. The
person gets dizzy and in the worst case sick. The test tracks should cause these
things.
32
The idea is that in reality winding roads lead to massive illness symptoms. The
fact that Trackmania Sunrise is a good and adequate simulation programme it is
a possibility to reproduce real effects into the 3-dimensional world. The editor
provides good functionality to make personalized tracks in a very easy way. We
ensured that there are some turnarounds, for example 90 degree corners or 180
degree turns. It was also tried to make valleys and mountains in the tracks like on
a mountain road.
The editor also provides the functionality to create a reasonably realistic environment with houses, gardens and industries. This helps the candidates to feel like
driving in a real world. The tracks at the end were very different, one has few hills,
but all tracks have very windy roads. In the pictures in section 4.2 it can be seen
how many bends there are.
4.4
Test Design
The test environment was set-up in the lab of the IMS and the configuration was
the following:
The test was applied for four days. This time period was chosen because it
seemed to be suitable for the participants of the study. If the time period was
longer, it would be harder to find enough test subjects because it was hard to find
enough people for these four days. The test persons sit on a chair in front of the
video projector and wear shutter glasses. They view the Trackmania replay in a
loop for a maximum of 25 minutes. The 25 minutes were chosen because it seemed
that this time is not too long for the persons and not to short to trigger symptoms.
It was a good agreement between the time period in which the test persons feel
comfortable but it can still lead to sickness symptoms. If they become sick, they
can abort sooner. They have to fill in a questionnaire (section 4.5) after the first
and the last session. Additionally they can explain, how they feel a while after the
tests, for example after 15 minutes. To identify if any aftereffects occur, I asked the
test subjects on the next sessions how they were feeling on the day after the session.
The four test tracks, with cars, can be seen in figure 4.7. It can be seen that
4.5. THE QUESTIONNAIRE
33
there are sometimes different cars because the game programme itself chooses the
car. In the figures the difference between the daytimes can be seen, in the test
tracks it was three times midday (Track 1, 2 and 4) and one time evening (Track
3). The tracks are running in an endless loop, until the ESC key on the keyboard
is pressed.
(a) Test drive 1
(b) Test drive 2
(c) Test drive 3
(d) Test drive 4
Figure 4.7: Test drive of all tracks
4.5
The Questionnaire
In this section we present the questionnaire. It is based on the Simulator Sickness
Questionnaire (SSQ) from Kenny at al. [KLBL93]. We translated it to German,
because we think that the test persons will find it easier to understand. The list of
the symptoms in this questionnaire are quite congruent with the symptoms which
are described in section 2.4.
34
The test person had to cross at each category if they suffer
• strongly (1)
• not so strong (2)
• a little bit (3)
• barely (4)
• not at all (5).
They are numbered as following: 5 is no symptom and 1 are severe symptoms.
This is important because the graphs in chapter 5 are labeled with these numbers
from 5 to 1.
At the end of the questionnaire the participants were able to add notes about
experiences which they encountered during the test which were not asked in the
questionnaire. Notes about the test environment or the technical conditions were
possible as well. Not many of them used this field to tell me interesting things, they
rather preferred to share their thoughts and feelings in person.
Fragebogen Cybersickness
Liebe Studienteilnehmerinnen und Studienteilnehmer!
Zum Abschluss des Training bitte wir Sie, uns noch ein paar Fragen zu Ihrem Befinden zu stellen.
Persönlicher Code
Nebenwirkungen
In welchem Ausmaß haben Sie die unten angeführten Beschwerden während des Betrachtens der
Autostrecke empfunden? Bitte markieren Sie die am ehesten zutreffende Kästchen.
sehr
etwas
gar nicht
B01
Müdigkeit, Erschöpfung
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Benommenheit
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Belastung der Augen
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Verschwommene Sicht
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Schwierigkeiten beim Fokussieren
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Konzentrationsschwierigkeiten
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Schwitzen
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Mundtrockenheit
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Platz für sonstige Anmerkungen und Kritikpunkte oder Dinge, die Ihnen beim Training mit den
Shutterglasses, dem Programm, etc aufgefallen sind:
(z.B.: Verbesserungsvorschläge, technische Probleme, andere Nebenwirkungen, …???)
Vielen Dank!
36
Chapter 5
Results
In this chapter, we want to present the results of the study. Although there are
not so many test persons, there exists lots of statistical data, which supports our
hypothesis. The results which we have found in the study are shown here in a
graphical format. It was to prove if adaptation in short time was possible and
therefore we have to analyze all the data which we have acquired from the study.
We want a sickness group and a control group and therefore we have to categorize
the people. All the persons were asked if they are prone to motion sickness or not.
We have built these two groups based on this self-assessment and because of this
we do not have an objective classification. We also take a closer look at the hard
facts, the numbers and diagrams.
5.1
Gender specific differences
First of all we take a look at the test subjects. Table 5.1 shows the classification of
the participants and how they categorize themselves into the two different groups.
A total of 16 people have participated in the study. From these 16 people, 10 do
not suffer from kinetosis, the rest has the tendency to become motion sick. From
the 11 male test persons nine say that they do not get sick, the remaining two
become motion sick. From the five female test persons only one does not suffer
37
38
CHAPTER 5. RESULTS
Not kinetosis
Kinetosis
male female
9
1
10
2
4
6
11
5
16
Table 5.1: Gender division
from kinetosis, the remaining four become sick when they for example drive in a
car. The gender differences will be described further later on.
A little bit more than one third of the test persons suffers from kinetosis, the
rest says that they do not have any problems with it. The statistics is of course a
little bit inprecise because of the small amount of people. However, it corresponds
relatively good with the numbers in the literature. There is talking about numbers
between 20% and 30% ([RP94], [BEN02]). The distribution is pictured in figure 5.1
although this is only a subjective grouping.
Figure 5.1: Division of the two classes
Another important part is the gender difference. As already described above
there were only five female test persons. This is a percentage of 31%. This takes
into account the fact that it is very hard to find test persons, even harder to find
female test persons. It seemed that they are not so interested in taking part in a
study.
Now we go into more detail. The number of females who claimed not to suffer
from motion sickness is marginal. It is only 10% of this class, which is in absolute
numbers only one woman besides nine men. In the literature it is written that
5.1. GENDER SPECIFIC DIFFERENCES
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
39
Minutes day1 Minutes day2 Minutes day3 Minutes day4
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
15:06
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
25:00
08:26
22:56
14:52
23:46
Table 5.2: Time table
women have a wider field of view and this rather leads to motion sickness [JJL00],
and therefore we could also hypothesize that even our female test persons become
rather motion sick than men do. Although we cannot prove it exactly in this study
because we classified the people on the subjective self-assessment. On the other
hand, we have the group of the motion sickness sufferers. Two third of this group
are women, this is four women and two men. This also leads to the assumption that
more women than men suffer from kinetosis but this cannot be proved here.
The fact that women are more prone to kinetosis is visible in the time table.
The time how long the people sit before the projection was written down. This was
made for every session. They had to sit down and watch the Trackmania replays for
up to 25 minutes. Table 5.2 shows all the times of all test persons on the different
days. The first thing which catches the eyes is the fact that nearly all of the test
persons were able to watch the replays for the entire 25 minutes, even the persons
in the kinetosis group. Two subjects did not manage to watch the simulation for
25 minutes each time, one becoming quite ill during the simulation.
40
CHAPTER 5. RESULTS
Figure 5.2 shows the time of the test subjects in a graphical way. It is clearly seen
that all test persons aside from two have reached the 25 minutes. It is visible that
one of the two outliers had only one bad session on the first day, in the other sessions
she reached the goal of 25 minutes. Therefore we can say that she has adapted very
fast to the environment. The second outlier starts with a very bad session on the
first day. She cannot even stay ten minutes in the VR. On the second day it got
much better only to get even worse on the third day. The last day was the best of
her sessions and she only missed the time of 25 minutes by a little. This is hard to
explain but she told me how she was feeling before she entered the environment. On
the first day, she was frightened about what was coming. She suffers very severely
from kinetosis and so a self-fulfilling prophecy catches her mind. And so the logical
reaction of her body was to become sick because she was expecting this reaction.
The second day was a little better because she has seen that it is not so bad in VR.
The third day was worse than the day before because she was out on the previous
day and drank a little too much alcohol. So we can clearly see that the consumption
of alcohol can worsen the symptoms of motion sickness. The last day was very good
again and she was also feeling very good although she did not pass the whole 25
minutes.
5.2
Symptoms
Now we will take a look at the symptoms. To make it more clearly not all persons
are shown. This is because of the fact that almost all the participants in the notkinetosis group have quite similar questionnaire scores. But at first we take a closer
look to the symptoms in the two groups. The symptoms scores of the not-kinetosis
group, called Group 1, are shown in figure 5.3 and the scores of the kinetosis group
- Group 2 - are shown in figure 5.4. These two pictures show the scores from the
first questionnaire.
As described in section 4.5 the scores vary from 1 to 5. 1 means that someone
suffers very strongly on a specific symptom and 5 means that someone has no
symptoms. You can quickly see the fact that the scores which count 5 are very
5.2. SYMPTOMS
41
Figure 5.2: The time axis of all test persons
often represented in the not-sickness group, which means that the persons suffer
very little. There are hardly any outliers in this group. It seemed to be quiet
homogenic. The index numbers are written down in table 5.3.
Average
Variance
Median
Standard deviation
4.06
1.23
4
1.11
Table 5.3: Statistics Q1
avg. score 4.06 (σ = 1.23; µ = 1.11); median = 4
42
CHAPTER 5. RESULTS
Figure 5.3: Sickness symptoms of the not-kinetosis group, Q1
The picture of the sickness group looks different. There exists more diversity and
not so much not-suffering scores. This tells us, that this group has more problems
with kinetosis.
To make things more concrete we want to take out two persons of each group
to show their actual data. In Group 1 that would be test person F and J and in
Group 2 L and P. These four persons were chosen because they are very interesting
ones in their groups. F and J are the ones with the biggest covariance and L and
P are the two who suffer most from kinetosis.
In figure 5.5 you can see the scores of the respective persons. There are little 5
scores and there are much more valleys and mountains. So you can see that there
are also people in Group 1 who claim that they do not suffer from motion sickness
5.2. SYMPTOMS
43
Figure 5.4: Sickness symptoms of the kinetosis group, Q1
but in reality they do suffer from it a little bit. On the other hand the person who
is very prone of kinetosis does indeed have very low scores. And as you can see in
figure 5.2 this person can only last short time in the test environment. That were
the scores of the first questionnaire on day one.
As mentioned before the test persons did not only fill out the questionnaire on
the first day but also on the last day of the study. In figure 5.6 you can see the
scores of the last day. There were certainly a few changes, but they were very
inhomogeneous too. Some symptoms got better, others not. This could have some
reasons. One reason is that the personal mood of the day could vary from hour
to hour and from day to day. This could explain that it looks like that the last
day did not get better but even the contrary. The index numbers of the second
44
CHAPTER 5. RESULTS
Figure 5.5: Symptoms scores of Q1 of 4 test persons
questionnaire are shown in table 5.4.
Average
Variance
Median
Standard deviation
4.29
1.25
5
1.16
Table 5.4: Statistics Q2
avg. score 4.29 (σ = 1.16; µ = 1.25); median = 5
Now we take a closer look at the test persons and their sickness symptoms. To
make the graph not too confusing only three symptoms were recorded. In figure
5.2. SYMPTOMS
45
Figure 5.6: Symptoms scores of Q2 of 4 test persons
5.7 it is seen that the symptoms generally become better. There are a few persons
where one or two symptoms become worse but this is not the norm. In fact most
of the scores stay the same or become better. To make it clearer two extreme cases
were recorded, to take a closer look at their changes. These two people were the
two outliers and do not represent the whole range of test persons but it is much
more interesting to look at them because they have the largest changes of all.
First a person from Group 1 was examined. It is test person F. The graph in 5.8
shows the scores of the first day and the fourth day. The scores of most symptoms
became better. Some of them were the same and only one score got worse. The
test person had more headache than on day one. This could have many reasons, for
example his or her mood of the day. Of course he also could just have had headache
46
CHAPTER 5. RESULTS
Figure 5.7: Three symptoms from all test persons
on that day before the test and so he wrote down, that on this day the headache
was more severe than on the first day. Motion sickness is very hard to understand
because so many things can impact the human organism and the organism of motion
detection. Therefore it is very hard to say which symptoms are caused by the VR
and which are caused by the weather, for example.
We also take a closer look at test person P, who is a member of the second group
(figure 5.9). Here you can also see an improvement of the symptoms in most cases.
But in this case three scores were worse on the last day. For example eye strain
and/or headache. Again, this could be due to many variables. In general, their
condition can be understood to have improved slightly.
To make a relation between Group 1 and Group 2 the two test persons F and P
5.3. ADDITIONAL INFORMATION
47
Figure 5.8: The scores of F on day 1 (=F1) and day4 (=F2)
are taken in relation. You can see this in figure 5.10. It shows a very inhomogeneous
graph. There are valleys and mountains and no clear direction that the symptoms
generally got better. In both groups a very inhomogeneous picture is drawn. There
is no clear path if the symptoms get better or not. The differences are often very
small and therefore it is very hard to read out, if there is an improvement or not.
5.3
Additional information
As mentioned before the test persons had the opportunity to provide additional
information about the test environment. Most of them had a lot of fun doing this
test but it was also sometimes boring for them not to do some active things and
only to sit and watch. Some of them wanted to drive one of the test tracks by
48
CHAPTER 5. RESULTS
Figure 5.9: The scores of P on day 1 (=P1) and day4 (=P2)
themselves and they got the opportunity to do this. They said that it was much
harder to drive with shutter glasses than without. We think that is because they
are not used to it.
Most said that the cars in virtual reality looked very good and in 3-D style but
also complained that it was too light in the room. It was not possible to darken the
room completely. The test person who came in the late afternoon where no sun was
shining, said that the 3-D effect was better and there are less disturbances of the
shutter glasses. Those people who did the test in the morning complained sometimes
that it did not look very 3-D-like and the flickering of the glasses was more obvious,
since they were controlled by infrared rays. These rays are very sensitive to sunlight
which also has infrared parts. Some said that the flickering of the shutter glasses
caused more headache, eye strain and more nausea. The flickering - which was worse
49
Figure 5.10: The scores of P and F in relation
at the border of the projection than in the middle - was a great disturbance for the
people but that could not be removed.
One of the cars in the game was a SUV (Sport utility vehicle). They said when
they saw the track with this car they had more severe symptoms than with the
other cars. This is because the SUV was more wobbly than the sports cars. They
became faster sick, disoriented and dizzy.
One special candidate was the one who has strabismus1 . He only suffers a little
from this illness but it hinders him to get a clear 3-D effect and he needs a few
minutes to focus on a certain point of the projection. He claimed that he had worn
his prism glasses to have a better look and feel of the 3-D environment. One said
1
Strabismus is a condition in which the eyes are not properly aligned with each other.
50
CHAPTER 5. RESULTS
that the 3-D effect is only limited to the car in the middle, but the horizon and the
clouds look very 2-dimensional.
A few said that it was better to sit nearer to the projection area and that it was
better when it was very dark inside the laboratory. One also claimed that looking
with one eye on the projection makes it better. Most of them also said that it was
less exhausting the more often they sit before the screen. One of the candidates
said that he gets tired very fast when he has to look at the screen and that did not
get better even on the fourth day.
But nearly half of the people said that they suffer from aftereffects. These effects
appear a few minutes to hours after the training. They had eye strain, headaches
and nausea. One of the candidates vomited ten minutes after the test and that was
very surprising because none of the other test persons had so hard aftereffects.
One told me that the graphics of this game is not the best in his opinion. He
believed that first-person shooters have better images and look more realistic. The
same person told us that if we drove all tracks with a SUV the whole test would be
more severe for the people and could release more symptoms and aftereffects.
After that training another test was made which was done only by those who
were interested. The test persons had to look at the CRT and not on the projection
and had to say which one was better. Many of the test persons said that on the
CRT the image was much better because it looked much more three dimensional
and their neck hurt less. They found it easier to look on a small screen size but it
seemed that the symptoms were very similar.
One thing recognized was that people who already felt uncomfortable before
doing the tests because they had a headache or a little cold, had slightly more
symptoms than when they were healthy. This fact is also described in the literature
and says that ill people suffer more from kinetosis than others and that the constitution of the day is a big factor in the field of adaptation because the human body
is a very complicated and sensitive system.
It is very hard to provide a good test environment for people in which they also
feel comfortable. There exist disturbances and other inconveniences which influences
51
the sickness scores. Actually the personal feeling of the day makes the scores a little
less reliable. It is quite impossible to ensure that all people feel well and have the
same physiological and emotional state. The only thing which can be concluded is
that persons already claimed to be ill or not feeling well are forbidden to take part
in the test. This was not practicable for us because there were not so many test
persons.
52
CHAPTER 5. RESULTS
Chapter 6
Conclusions
The study lasted nearly a month with a total of 16 test persons. It is however very
hard to find out if the study was successful or not and if the goal was reached.
For my conclusion firstly the hard facts of the questionnaire are taken out. While
it is easy to create some diagrams, it is hard to interpret them correctly. In fact,
the scores of the test persons did change during the study. Most of them got better
whereas a few of them became worse. Generally the study had a positive effect on
the test subjects but it was not so clear whether it was a big success.
When looking at the numbers from the statistics the result looks promising
(table 6.1), even though the differences are very marginal. On average, the test
subjects felt better on the last day than on the first day of the tests. However,
the main problem of this study is that the results are not statistically significant.
Too few people participated in the training, furthermore the difference between the
questionnaire scores were too small. Therefore, we cannot draw a clear conclusion
if adaptation in virtual reality environments is possible although we believe with a
greater amount of test persons the result could be more meaningful.
On the other hand for some persons adaptation in a short time is possible but
it does not work very properly. The main problem is, that in short time there can
appear lots of illness or not well-being situations because of the fact that today’s
physical and emotional state is a very variable factor. If someone suffers from a cold
53
54
CHAPTER 6. CONCLUSIONS
Q1
Average
4.06
Variance
1.23
Median
4
Standard deviation 1.11
Q2
4.29
1.25
5
1.16
Table 6.1: Statistics Q1 and Q2
he or she suffers from this a few days and when the adaptation training takes place
on these days the result is not fully true. However, when performing a long term
training these influences will be reduced. When feeling not so good on several days
during a long term training, there is the opportunity to correct the scores in later
tests. Therefore not well days are averaged and do not count for so much in such a
training.
In this study we have seen that not just alcohol consumption can seriously worsen
the symptoms but also when someone is sick. Two persons have worse sickness scores
than others on these days. This is again a short argument that the human organism
is a complicated and sensitive system. When personal or environmental conditions
change, there could be severe effects on your feeling that day. When something is
not in balance the body could get sick and we feel ill and uncomfortable, therefore
the effects of motion sickness and cybersickness can be worse than when one feels
fit.
We should also not forget the problems with the technical environment. If there
are some disturbances, the training could be massively faulty and there are not
so good results. The flickering of the glasses during daylight was the most severe
distraction for the test persons. They quickly got headaches and complained about
it. On the other hand in the evening the flickering was gone and the test persons
did not mention it. The projection on the wall was slightly big and some of them
found that it was uncomfortable to sit and watch. They have slight pains in the
neck because the distance between the wall and where they were sitting was too
small. But this was just because of the small size of the laboratory. Therefore it
was better to look at the monitor because it was smaller and they did not have to
look up.
6.1. OUTLOOK
55
Overall we can say that the study was successful but not in the way we hoped. In
the short time, there were not so much changes in the sickness scores as we hoped
for. But it leads to the direction that adaptation in a short time is in principal
possible but not in four days. We think that a few more days could improve the
adaptation in quite a good way.
6.1
Outlook
At the very end, we give a short outlook for further studies building upon the results
of this one. The study here itself was successful in my eyes despite I have hoped for
better scores on the last day. It is hard to make a study with subjects to make it
more significant more people would have had to have been recruited.
On the other hand the approach of Univ. Prof. Dr. Reinhart Jarisch is very
interesting. He described in his book [JGM+ 04] that histamine could make sea
sickness heavier. So it is interesting if the same thing could also be important for
simulator sickness or cybersickness. It is interesting if histamine also takes part in
the symptoms of cybersickness or if this amine only has its appearance at the real
motion sicknesses like car, air or sea sickness. This would be an interesting part of
this illness and it should be explored if a histmine free nutrition also leads to better
scores in the field of simulator sickness and cybersickness.
Another research field is how modern computer games are causing motion sickness. There are approaches that computer games cause significant kinetosis because
they become more and more realistic. Due to this more people are confronted with
the problem of kinetosis and most of them have not yet suffered from this illness.
But how severe is this in reality? Does it make sense to increase research in this
field? I say yes because kinetosis in computer games is a very new problem and it
should be explored how many percentage of computer gamers are prone to suffer
from kinetosis. Or does it affect only a small amount of people and therefore it
does not make any difference for the game community as a whole. Furthermore
the flatscreens for computer and also the TV screens grow bigger in time and a big
screen causes more sickness symptoms than a smaller one and therefore they causes
56
more problems in the field of cybersickness.
CHAPTER 6. CONCLUSIONS
List of Figures
2.1
The inner ear and its location in the head (top view, the nose is above)
6
2.2
The inner ear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
2.3
The inner ear (simplified) . . . . . . . . . . . . . . . . . . . . . . .
8
2.4
The equilibrium organ . . . . . . . . . . . . . . . . . . . . . . . . .
10
2.5
A heuristic model of motor control, motion detection, and motion
sickness based on the neural mismatch theory [BEN02]. . . . . . . .
11
2.6
Classification of neural mismatch in provocative environments[BEN02] 13
4.1
CRT, tower and video projector . . . . . . . . . . . . . . . . . . . .
26
4.2
Shutter glasses . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
4.3
The four test tracks. . . . . . . . . . . . . . . . . . . . . . . . . . .
28
4.4
Menu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
4.5
Choose a challenge and daytime . . . . . . . . . . . . . . . . . . . .
30
4.6
The empty editor and one test track . . . . . . . . . . . . . . . . .
31
4.7
Test drive of all tracks . . . . . . . . . . . . . . . . . . . . . . . . .
33
5.1
Division of the two classes . . . . . . . . . . . . . . . . . . . . . . .
38
5.2
The time axis of all test persons . . . . . . . . . . . . . . . . . . . .
41
5.3
Sickness symptoms of the not-kinetosis group, Q1 . . . . . . . . . .
42
5.4
Sickness symptoms of the kinetosis group, Q1 . . . . . . . . . . . .
43
5.5
Symptoms scores of Q1 of 4 test persons . . . . . . . . . . . . . . .
44
5.6
Symptoms scores of Q2 of 4 test persons . . . . . . . . . . . . . . .
45
5.7
Three symptoms from all test persons . . . . . . . . . . . . . . . . .
46
5.8
The scores of F on day 1 (=F1) and day4 (=F2) . . . . . . . . . . .
47
5.9
The scores of P on day 1 (=P1) and day4 (=P2) . . . . . . . . . . .
48
57
58
LIST OF FIGURES
5.10 The scores of P and F in relation . . . . . . . . . . . . . . . . . . .
49
List of Tables
5.1
5.2
5.3
5.4
Gender division
Time table . . .
Statistics Q1 . .
Statistics Q2 . .
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6.1
Statistics Q1 and Q2 . . . . . . . . . . . . . . . . . . . . . . . . . .
54
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60
LIST OF TABLES
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Kinetosis / Motion Sickness A new Approach for Adaptation in Virtual

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