Most of the information comes from the Diagnostic and Statistical Manual of Mental Disorders [dsm 87]. This book is considered the bible for psychologists. It contains all the different disorders, how to recognize, features, age of onset, etc.
Anxiety disorders
Anxiety is a diffuse, highly unpleasant, often vague feeling of
apprehension, accompanied by one or more bodily sensations. Anxiety
comes in response to a threat that is unknown, internal, vague, or
conflictual in origin [kaplan 91]. Anxiety disorders are those
disorders that are most commonly found in the general population
[dsm 87]. That is why we
decided to take a closer look at this group of disorders. Anxiety
disorders can be subdivided into five groups:
Essential to panic disorder with or without agoraphobia are recurrent panic attacks. A panic attack is an unexpected period of intense fear or discomfort. For a patient to be diagnosed as suffering from panic disorder, the subject must have had at least four attacks in a month, or an attack followed by a month of fear for another attack. Another diagnostic criteria for panic disorder is when at least four of the symptoms from Table 4.1 can be found and there is no organic factor that initiated the attack.
In a great majority of panic disorders, there is also agoraphobia. The subject will develop some symptoms of agoraphobia as protection against panic disorders. When the subject has agoraphobia, he will not leave the house, stand in a crowd, bus or line unless accompanied. With agoraphobia, the subject is impaired in his social life. When agoraphobia is severe, a person can be completely housebound.
When the subject does not suffer from agoraphobia, there is no or limited impact in his social life or occupational functioning.
Agoraphobia without panic disorder
The essential feature of this disorder is agoraphobia without a
history of panic attacks. Usually the subject is afraid of having a
panic attack with a limited number of the symptoms described in the
previous section. This can be caused by the fact that the subject has
had such an attack before or never had such an attack but is afraid
that it could develop.
Social phobia
Social phobia is the fear of doing something or acting in way that
will be humiliating or embarrassing in front of others. Different
kinds of social phobias are not being able to speak in public, choking
on food when eating in front of others or having hand tremors when
writing in front of others.
Unlike agoraphobia, social phobia has an immediate response when the subject is confronted with the situation. For example, a subject having a fear of eating in front of people, when forced to eat with other people, will have an immediate anxiety response. He will, for instance, choke on his food.
Simple phobia
Essential to this disorder is the fact that there exists a persistent
fear of a circumscribed stimulus other than having fear of a panic
attack or of humiliation or embarrassment. Most common simple phobias
in the general population are, in order of appearance, animals,
storms, heights, illness, injury and death. Simple phobias are common
in the general population
[kaplan 91].
There is invariably an immediate response when the patient is exposed to the simple phobic stimulus. The response can vary from feeling panicky, sweating to difficulty breathing. For example, a person afraid of spiders will immediately react when shown an image of a spider.
Obsessive compulsive disorder
Essential here is the recurrent obsessions or compulsions sufficiently
severe to interfere with the persons normal life. Obsessions are
persistent ideas, impulses or images that are as intrusive as
senseless. Compulsions are repetitive, purposeful and intentional
behaviors that are performed in response to an obsession. Obsessions
can be the repeated impulses of a parent to kill its child or the fear
of becoming infected by shaking hands. Compulsions can be hand washing
or counting.
What phobia to use
People suffering from panic disorder with or without agoraphobia are
those who most often seek professional treatment. Finding people who
suffer from this form of anxiety disorder for an experiment should not
be too difficult. The problem with this disorder is that the panic
attack is unexpected. To test the level of presence, however, we want
an immediate response to the situation.
Agoraphobia without panic disorder has the same problem as panic disorder with or without agoraphobia. With agoraphobia without panic disorder, there is again the suddenness of the anxiety. However, we want the subject to react immediately to the given stimuli.
With social phobia, people react immediately to the stimuli. The disadvantage is that it requires other people to be present. People are hard to model in Virtual Reality since each of them should have its own personality and behavior.
Obsessive compulsive disorder is relatively normal in the general population in its mild form. The problem here is that we want a reaction to the stimuli that is easy to recognize. When it is only a mild form of the disorder, it might make it more difficult to recognize it and thus the level of presence.
Simple phobia has a clear stimuli, and does not require difficult interactions. Since it is the most common of anxiety disorders, it should not be hard to find enough subjects for the experiment. Because of all of these reasons and because there were no clear disadvantages, it was decided to use a simple phobia.
After deciding to treat people with a simple phobia, the question was what phobia to use? Claustrophobia, the fear of enclosed spaces, was eliminated because the experiment would require people to wear an HMD. Fear of flying and fear of storms depended too much on sound. To make these as realistic as possible, we needed good sound capabilities. The sound capabilities of SVE were not yet fully operational when we had to make a decision. This made us drop fear of flying and fear of storms. After some more discussion in the Virtual Environments group and with the psychologists, it was decided to treat people suffering of acrophobia, fear of heights.
Having decided to treat people suffering from acrophobia, a method was needed to treat these people. The following chapter will explain the different treatments and explain why one was chosen to use in VR. After deciding what treatment to use, a method was chosen to build the environments. Finally, a list of requirements will follow that came from the treatment and the development method.
Rob Kooper |
kooper@cc.gatech.edu
|