Human-Computer Interaction and Presence in Virtual Reality

Chapter 3
announcements in the national media offering
psychological treatment for acrophobia. To be included
in the study, patients had to fulfill the DSM-IV
(American Psychiatric Association, 1994) criteria of
acrophobia, acrophobia had to be the main problem,
and patients had to be unable to complete a Behavioral
Avoidance Test. In all, 68 subjects completed the VR
treatment.
VR system
The user interfaces for patient and therapist were
similar to the current state-of-the-art. The patient wore
the HMD with six DoF tracking. Besides visual
stimulation, auditory stimuli were provided in the form
of wind and people talking. The patients could only
move their viewpoints as far as the limited range of the
tracker and the limited range of physical movement in
reality allowed.
Further movement of the patient’s viewpoint could be
performed by the therapist by use of a joystick or by
using an autopilot; Pressing a number on the keyboard
resulted in the system automatically moving the patient
from the current location to the location corresponding
to the number pressed. The video signal for the HMD
was also displayed on a monitor, allowing the therapist
to see what the patient could see.
The three virtual environments were based on real
situations. The first environment was Magnaplaza, a
mall in the center of Amsterdam, which features
several floors and escalators, as shown in figure 3.10.
The second environment included a firestair besides a
three-story building, as shown in figure 3.11. The last
environment was the rooftop terrace of a seven-story
building of the University of Amsterdam, overlooking
the Magnaplaza mall across the street, as depicted in
figure 3.12. None of these environments contained
elements which could be changed by the therapist.
3.5.4 Interpreting observations
20 treatment sessions of the case described in the
previous paragraphs were recorded on video, allowing
the observations to be made in an unobtrusive way.
Subjects were asked for permission to make the
recordings before the therapy.
The observations were classified using the Language /
Action Perspective. As such, pressing a button can be
similar to uttering a sentence, allowing us to include
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Figure 3.9: The physical setup as
used for the therapy.
Figure 3.10: VE of Magnaplaza
mall.
Figure 3.11:VE of firestairs.
Figure 3.12: VE of rooftop terrace.