Texte intégral / Full text (pdf, 20 MiB) - Infoscience - EPFL

6.3. Eye-tracking as Assessment and Diagnosis Tool
6.3 Eye-tracking as Assessment and Diagnosis Tool
As of today, no objective clinical diagnosis test exists when it comes to phobias. It is based
on patients’ accounts of undergone experiences and therefore remains very subjective. Moreover,
the experiment previously described in this chapter raised a number of research directions.
More specifically, while recording eye movements, we have noticed that several traits
in eye contact behavior were recurrent. For example, we noticed rapid eye blinking rates in
some subjects, and very rapid eye movements in others.
For this reason, we propose to use an eye-tracking system, in order to diagnose and
assess, in an objective way, various known features often present in people suffering from
social phobia, and more specifically, in people suffering from fear of public speaking. The
tests we decided to conduct concern the avoidance of salient facial features, the presence of
hyperscanning, and the rates and durations of eye blinks. The avoidance of salient facial
features is a known parameter often present in people suffering from social phobia [Horley
et al., 2003]. Hyperscanning consists of an overly rapid sweeping of the eyes. This factor
equally consists of a feature found to be present in social phobics [Horley et al., 2004]. Eye
blink rates are known to increase with anxiety [Kanfer, 1960] and can therefore be used
as a revealing measure, relative to the anguish caused by the phobia. Finally, we believe
eye blink durations to be another good indicator of the presence of visual contact avoidance
and therefore investigate this feature as well. People suffering from social phobia do not
all present those traits of visual avoidance but many of them do. Our hypothesis was that
phobic subjects would not present all traits but that most of them would at least present one
of them. We conducted our experiment over five social phobic patients and five non phobic
subjects who served as control group. In a first phase, we exposed all ten subjects to two
VR public speaking exercises. The first one was in front of a single virtual actor and the
second in front of an audience. These scenes are depicted in the middle left and bottom left
of Figure 3.1. For these exercises, we used the social phobia setup described at the beginning
of this chapter in order to track the patients’ and control group participants’ eye movements.
The phobic subjects then went through ten weekly sessions of therapy based on the cognitive
behavioral model [Beck and Emery, 1985]. This was a group therapy following the Boston
group protocol [Stern et al., 1999]. Finally, six out of the ten subjects went through a second
eye-tracking session, three from each group. This post-treatment exercise was conducted
under the same conditions as the first one.
6.3.1 Participants
The five social phobic subjects who participated in this study were patients picked by our
psychiatrist collaborator. They completed the MINI [Sheehan et al., 1998] in order for us
to verify the prevalence of social phobia and the absence of comorbidity. All subjects were
aged 25 to 55, with a mean age of 37 for the phobic group and 38 for the control group.
Subjects were not chosen from any specific educational or socio-economical category but
were all of Caucasian type. The phobic subject group was composed of three females and
two males and the control group of three males and two females.
85