Human-Computer Interaction and Presence in Virtual Reality

Chapter 1
computer interaction and this collaboration between the users to optimize the usability? What
effect does this collaboration have on the sense of presence?
To begin answering these questions, we should start by selecting a single application that
embodies these new developments. This will enable us to ground our understanding in a real
world situation and it can be our test case to test that understanding. The application chosen
for this purpose in this dissertation is Virtual Reality Exposure Therapy (VRET).
1.4 Virtual Reality Exposure Therapy
In psychological therapy, we can use the fact that VR can affect the user at a non-cognitive
level to carefully administer synthetic experiences to the patient necessary to cure his or her
mental illness. Particularly in phobia treatment, VR has already been shown to be effective
with a great number of case studies and several controlled studies 1 . At this moment, phobia
treatment in VR can be said to be outgrowing the experimental stage and is already in use by
a handful of early adopters.
Phobias are characterized by a persistent fear of a
specific object or situation. Phobias are the most
common form of anxiety disorders, which themselves
are the most common psychiatric disorders. In 1998 a
study was done in the Netherlands on the prevalence of
psychiatric disorders in the general population (Bijl et
al., 1998). This study shows that the lifetimeprevalences
of agoraphobia 2 , social phobia and specific
phobias are respectively 3.4, 7.8 and 10.4 %. This
means that 3.4 % of the general population is or has
been suffering from agoraphobia during his or her life.
7.8 % and 10.4 % of the population is or has been
suffering from respectively a social phobia or a specific
phobia during his or her life.
Phobias can be treated by exposing patients to anxietyproducing
stimuli while allowing the anxiety to
attenuate (Bouman et al., 1992). Traditionally, these
stimuli have been generated by presenting the patient
with actual physical situations (In Vivo) or by having
the patient imagine the stimulus (In Vitro). Now, VR
offers a third option: Virtual Reality Exposure Therapy
(VRET). In VRET, the patient is confronted with a
fearful situation by displaying a VE with anxiety
provoking elements such as the VE depicted in figure
1.1 on a display such as a Head-Mounted Display
(HMD) as shown in figure 1.2. During the therapy, the
therapist in collaboration with the patient alters the
synthetic experience of the patient in such a way that
4
Figure 1.1: VE for treatment of
fear of heights (Courtesy of
Virtually Better Inc.)
Figure 1.2: Psychological
treatment in VR, with the patient
wearing a HMD (Courtesy of
David Ready Ph.D.)
1
For a brief overview of the history of phobia treatment in VR, see chapter 3 of this
dissertation.
2
Agoraphobia is the fear of being in places or situations from which escape might be
difficult or embarrassing. (American Psychiatric Association, 1994)