Reprinted with permission
from the Communications of the ACM 40, 8 (Aug. 1997), 34-39. (c) 1997
Association for Computing Machinery
Overcoming Phobias by Virtual Exposure
Dorothy Strickland, Larry Hodges, Max North, Suzanne
It is not surprising that phobia treatment would
be one of the first successful mental health uses for VR. The sense of
being immersed in another setting is particularly valuable in exposure
therapy, a treatment technique for phobias. Exposure therapy involves
subjecting the patient to anxiety producing stimuli while allowing the
anxiety to attenuate. These stimuli have traditionally been generated
by presenting the patient with actual physical situations (in vivo exposure)
or by having the patient imagine the stimulus.
VR allows a third option of exposure in
a virtual setting which can be safer, less embarrassing, and less costly
then reproducing the real-world situations and more realistic than imagining
the danger. An additional advantage of computer controlled stimuli is
that the patient can more easily regulate the level of the induced anxiety
by modifying the parameters of the world to reduce or increase fear to
match individual tolerance. All phobia treatment studies to date have
used a headset to reproduce the feeling of presence in the anxiety-producing
The first phobia studies conducted during
1993 were for acrophobia---the fear of heights. This phobia is characterized
by a marked anxiety upon exposure to heights, avoidance of heights, and
interference in normal everyday activities as a result of the fear. In
exposure therapy situations the pattern is for patients' anxiety to increase
as they are exposed to more threatening situations, then for anxiety to
decrease as they spend more time in each situation.
Initial research was a collaborative effort
by computer scientist and therapists from three Atlanta universities:
Georgia Tech, Clark Atlanta, and Emory . Of the 478 students initially
screened for acrophobia, 20 entered the study; 17 completed it. Subjects
were randomly assigned to either a treatment group or a wait-list control
group. The treatment group had one pre-treatment VR equipment session
and seven weekly 35- to 45- minute sessions during which they were exposed
to three virtual height situations---a virtual elevator, a series of virtual
bridges and a series of virtual balconies. Anxiety, avoidance, distress,
and negative attitudes towards height decreased significantly for the
treatment group but not for the wait-list group. By all measures, significant
improvement in the phobia response was found among the subjects who completed
the VR treatment. Seven of the 10 treatment completes exposed themselves
to height situations in real life during the treatment period although
they were not specifically instructed to do so.
It is interesting to note that these results
were obtained despite primitive computer worlds and poor headset image
quality. The tests at times involved teleporting the patient from one
location to another. Although patients were aware of the artificial nature
of the scenes, they still felt enough sense of presence to exhibit the
phobic responses while in the headset. Physical symptoms included sweaty
palms, loss of balance, and weakness in the knees. Patients indicated
that a sense of reality in the virtual setting was aided by haptic props.
For example, when riding a glass elevator, a metal bar matching the bar
location in the virtual headset was provided for the subject to hold in
the real world. In the spider phobia discussed later, this same type of
prop matches the "feel" of the virtual to the real world.
Max and Sara North and Joseph Coble
from Clark Atlanta's Virtual Technology Laboratory, have done a follow
up in-depth case study . A subject was asked to rank a list of acrophobic
situations according to the degree of anxiety arousal. The subject was
placed near a virtual bridge that crossed a river in the middle of a simulated
town. The study consisted of one pretest exposure and eight 15- to 28-
minute sessions. The subject started at the least threatening situation
and then progressed, under his own control, to the next level of arousal.
An anxiety measurement was taken every two to five minutes. At one month
post-treatment, the subject was asked to complete an 11-point rating scale
to measure the degree of phobic response change. The patient experienced
significant habituation of anxiety symptoms and exercised less avoidance
of phobic situations after the virtual reality treatment.
Larry Hodges from Georgia Tech's Graphics,
Visualization and Usability Center and Barbara Rothbaum from Emory led
another follow up case study using what they term Virtual Reality Exposure
(VRE) Therapy to treat a 19-year-old undergraduate student with a fear
of heights and in particular a fear of glass elevators. Twice weekly exposure
therapy sessions were conducted for three weeks on a VR glass enclosed
elevator (Figure 2). Time in each exposure was approximately 35 minutes.
Outcome was assessed on measures of anxiety, avoidance, attitude, distress,
and a behavioral avoidance test. VR graded exposure was successful in
reducing fear of heights on all measures.
At about the same time the researchers
in Atlanta were conducting their acrophobia studies, Ralph Lamson, a physician
at Kaiser Permanente, was doing similar work in California in collaboration
with the VR company Division Inc.. Acrophobia patients were recruited
through newspaper ads. Each subject was exposed to one, 50-minute session
where he or she completed a chosen task such as going across the Golden
Gate Bridge or riding in a glass-enclosed elevator. According to Lamson,
all forty of the subjects were able to complete the task of riding up
and down a glass elevator while looking outside after a single VR treatment.
One result of the numerous fear-of-heights
studies was to generate an interest in trying this technology with a variety
of other phobias.
Both Georgia Tech and Clark Atlanta followed
up the acrophobia research with independent fear-of-flying studies. Georgia
Tech conducted a case study using a virtual airplane which duplicated
a passenger seated by the window in a standard commercial jet . The
passenger could look out the window and see the ground and changing sky
scenes (Figure 2). The patient was a 42-year-old female with a debilitating
fear and avoidance of flying. As an outpatient for seven sessions, she
was taught traditional anxiety management techniques. At that point it
was mutually decided between the doctor and the patient that exposure
therapy would be beneficial. VR sessions were held twice weekly with each
session lasting approximately 35 to 45 minutes. A total of six sessions
were conducted. During each virtual exposure, the subject was allowed
to progress at her own pace along a natural progression of scenarios---sitting
on the plane with engines off, sitting on a plane with engines on, taxiing
the runway, smooth take-off, smooth flight, close pass over the airport,
landing, rough takeoff, turbulent flight, and rough landing.
Two days following the last exposure therapy
session the subject completed a planned, cross-country flight with her
family. Although the contribution of the VR treatment to her improvement
is not possible to determine given the prior inclusion of the anxiety
management techniques, the computer-generated simulations were considered
significant for several reasons. First, the patient's reported anxiety
on all measures decreased further following exposure to the virtual plane.
Second, she was able to complete a long flight, one she had avoided for
two years. Third, the usual treatment for fear of flying includes a combination
of anxiety management techniques and exposure. Had VR exposure not been
available, this therapy would have included exposure to actual airplanes,
possibly with the therapist flying with the patient before she flew with
her family. This study raises the issue that VR therapy may be most effective
when combined with traditional treatment techniques.
In an effort to move VR exposure therapy
from the laboratory to everyday clinical use, Georgia Tech and Emory University
are jointly developing a fear-of-flying system based on either a PC or
low-end workstation that will be in a realistic price range for clinical
practice. This system will be field tested in a number of clinics in Atlanta
and other US cities this year.
The Norths did two independent case studies
for fear of flying . These studies are interesting in part because
the subjects were already familiar with VR systems so the novelty effect
of the equipment should not have been a factor. One subject was a 32-year-old
woman and one a 42-year-old man, both clinically diagnosed as having a
fear of flying. The VR scenes simulated an Apache helicopter departing
and then flying over an airport and a city scene. A virtual therapists,
with whom the patient could communicate during the trials, rode in a seat
next to the patient in the computer-generated scenes. Sound and vibration
were included for realism.
The female patient participated in eight
VR exposures which lasted for approximately 30 minutes each over 10 weeks.
The male had five 30-minute sessions over 5 weeks. Both subjects reported
a high level of anxiety at the beginning of each session and gradually
reported lower levels after remaining in the situation for a few minutes.
Each was left in the scene until reporting an anxiety level of zero. Researchers
recorded physical symptoms such as sweaty palms as well as taking subjective
discomfort ratings from the subjects. After the tests ended, the female
patient, with the therapist, was flown in a helicopter to measure any
change in flying anxiety. The flight lasted approximately 10 minutes and
was conducted at low altitude over a beach on the Gulf of Mexico. Similar
to the VR therapy exposures, the subject reported some anxiety at the
beginning; however, the anxiety rapidly declined to a reasonably comfortable
level. Currently the woman claims to be much more comfortable flying for
long distances and experiences much less anxiety. The male subject also
reports a significant reduction in anxiety symptoms after VR therapy sessions
and is now able to fly comfortably.
The recent phobia studies at Clark Atlanta
have been conducted on a PC with a low-cost headset and head tracker,
mouse, joystick, data glove, and VREAM software. The total system cost
was under $10,000, even when bought from an outside company who integrated
the commercial programs and hardware into a package.
Agoraphobia is an unhealthy fear of being
caught in places or situations from which escape may be difficult or embarrassing
(such as being in a crowd, traveling in an automobile, bus, plane, or
being in an elevator). The result is that these individuals are fearful
of leaving their homes to work or even to run simple errands. North chose
60 subjects for an agoraphobia study with VR therapy . Thirty were
placed in the experimental group and 30 in the control group. The experimental
group received eight exposures over eight weeks to a variety of scenes.
Each test lasted approximately 20 minutes. The control group received
no therapy. The Agoraphobia Questionnaire and the Subjective Unit of Discomfort
Scale (SUDS) tests were used to measure on therapy effectiveness. The
students exposed to VR therapy reported significant improvement while
the control group showed no change.
Researchers at the Human Interface Technology
Lab at the University of Washington are investigating the effects on immersive "presence" of physically touching objects in a VE. Hunter Hoffman,
Al Carlin, and Suzanne Weghorst evoked a stronger sense of presence while
in a headset by placing a real object (a plate or a rubber ball) within
the participant's grasp and registering the location of the corresponding
virtual object. They call this technique "tactile augmentation"
and have used it to treat an individual with spider phobia .
In a clinical case study with a patient
who had long term debilitating fear of spiders, the researchers systematically
introduced visually more fearful spider representations and behaviors
into both a virtual kitchen environment and a virtual replica of the laboratory
environment. By simultaneously introducing a large fuzzy plastic spider
precisely registered with a spatially-tracked virtual spider, they demonstrated
the use of tactile augmentation and significantly enhanced the effectiveness
of the VR exposure treatment. After 12 weekly 30-minute sessions using
a Division ProVision 100 system with a Virtual Research VR4 HMD and Polhemus
6D trackers attached to the head, hand,and spider, the patient's ratings
for fear of spiders, as measured by self-report and a survey, decreased
to the point where he was able to resume outdoor camping activities.
Fear of Public Speaking
Frequently identified among the top most
prevalent phobias, fear of public speaking was a subject of another study
at Clark Atlanta University. Comparing control and test groups of undergraduates,
subjects were placed in front of a virtual auditorium that gradually filled
with virtual people. Simulation of room and crowd noise included laughter,
commentary, and applause. The treatment schedule consisted of eight, 10-
to 15- minute weekly sessions. Symptoms experienced by the subjects during
VR therapy mirrored those which most speakers experience during public
presentations. They included increased heart rate, lump in the throat,
dry mouth, sweaty palms, loss of balance, and weakness in the knees. Two
assessment measurements, the Attitude Toward Public Speaking and SUDS
scale, showed significant reduction of anxiety symptoms and the ability
to face the phobic situations after virtual therapy treatment. Subjects
not report the ability to speak comfortably in front of large groups of
Fear of Driving
Several other phobia treatments are in the initial stages. Andrew Berger
of Virtual Psychology Company is conducting a controlled study to determine
how effective a VR driving system for treatment of head injury is in treating
fear of driving. Eighty subjects have been recruited through newspaper
ads for a comparison of four different therapies. Twenty subjects are
using the Pentium-based system with a low-cost headset and customized
Imago VR driving simulation software. The driving scenes progress from
pulling out of a driveway and driving on a side street to more stressful
highway exposure. The schedule is two 30- to 40- minute treatments twice
a week for 12 sessions. The study does not yet have publishable results.
These studies indicate that VR scenes can produce a variety of phobic
symptoms. While vision alone in a headset appears to create phobic anxiety,
most of the researchers mentioned introduced sound into their later research
and found that it heightened the effect. Where applicable, haptic cues
such as a hand bar in an elevator or a furry spider seems to add to the
Although these studies provide encouragement, they raise many questions
the research is just beginning to address:
- How do patients treated with VR therapy compare to control groups using
standard exposure therapies?
- How well do any positive benefits transfer to the real world, and how
long do any of these benefits last once the patient is no longer receiving
therapy? Early research indicates that the sense of fear in the virtual
headset scene is measurably different from the actual experience. In a
study with 40 undergraduates at two universities in Germany, Thomas Schubert
and Frank Friedmann developed a questionnaire to assess feelings and experiences
after headset immersion on a 15-foot diameter platform at a 25-foot height.
After 20 minutes of immersion, the users immediately answered the questionnaire
assessing the fear they experienced. Their preliminary results indicate
that fear of heights is higher if a person perceives his or her own body
as a part of the VE, but that the effect varies depending on other factors.
Several phobia researches have mentioned similar anecdotal results.
- Is the headset critical to the effect, or could the same results be
obtained with less-expensive flat screen VR systems? James Patten at the
University of Virginia has measured how HMD-based VR differs from desktop
3D graphics in introducing psychological responses. Using heart rate variability
to compare arousal in the nervous system when a subject rides a virtual
platform attached to the side of a building in both types of systems,
they found greater sympathetic arousal in the head-tracked condition,
though subjects exhibit this change to differing degrees.
- What are the different effects of the lengths of exposures for the various
tests? Is one, 50-minute exposure as beneficial as eight 15 minute exposures?
For safety reasons, can most patients tolerate 50 continuous minutes in
a virtual scene? At lease one researcher had to redesign his tests to
shorten patient exposure times after several subjects became violently
ill from spending an hour in the headset. Hopefully future phobia research
will benefit from the ongoing safety research (see Viire, Stanney and
Kennedy articles in this same issue).
Despite these and other questions, phobias appear to be the most easily
implemented and convincing example of a beneficial use of VR therapy.
When compared to training spiders and renting airplanes, the computer
is more controllable and inexpensive than the conventional in vivo treatment
technique. A common thread in all the present applications is the ease
with which they can be implemented on present computers. Most researchers
are now using PC's in their labs to create the phobia images. Several
groups are developing customized low-cost systems for sale to clinicians.
With these more affordable VR tools, the best measure of the effectiveness
of exposure therapy may take place in doctor's offices across the country.
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