One-session computer-based exposure treatment for spider-fearful
individuals e Efficacy of a minimal self-help intervention in a randomised
Birgit H. Müller*, Sandra Kull, Frank H. Wilhelm, Tanja Michael
Department of Clinical Psychology and Psychotherapy, University of Basel, Missionsstrasse 60/62, CH-4055 Basel, Switzerland
a r t i c l e i n f o
Received 11 January 2010
Received in revised form
30 November 2010
Accepted 6 December 2010
Fear of spiders
Behavioural approach test
a b s t r a c t
Computer-based self-help treatments have been proposed to provide greater access to treatment while
requiring minimum input from a therapist. The authors employed a randomised controlled trial to
investigate the efficacy of one-session computer-based exposure (CBE) as a self-help treatment for
spider-fearful individuals. Spider-fearful participants in a CBE group underwent one 27-min session of
standardised exposure to nine fear-eliciting spider pictures. Treatment outcome was compared to spider-
fearful control participants exposed to nine neutral pictures. Fear reduction was quantified on
a subjective level by the Fear of Spiders Questionnaire (FSQ) and complemented with a behavioural
approach test (BAT). Results demonstrate that compared to control participants, CBE participants showed
greater fear reduction from pre- to posttreatment on both the subjective level (FSQ) and the behavioural
level (BAT). Moreover, in contrast to the control group, the obtained subjective fear reduction effect
remained stable in the CBE group at 1-month follow-up. These findings highlight the role of computer-
based self-help as a minimal but effective intervention to reduce fear of spiders.
? 2010 Elsevier Ltd. All rights reserved.
Specific phobias areamong the most common anxiety disorders,
with an estimated lifetime prevalence of 12.5% (Kessler et al., 2005;
Michael, Zetsche, & Margraf, 2007). Among the specific phobias,
fear of animals - a category that includes fear of spiders - is one of
the most common phobic disorders in the population with a life-
time prevalence of 5% (Becker et al., 2000). The treatment of choice
for fear of animals, including spiders, is in vivo exposure to a live
specimen of the animal until the fear reaction is reduced (e.g., Choy,
Fyer, & Lipsitz, 2007). However, in vivo exposure is associated with
high dropout rates and low treatment acceptance. Reasons for
therapy reluctance include fear of confronting the phobic object,
the labour-intensive nature of treatment, duration, cost, and fear of
stigmatisation (e.g., Goldberg & Huxley, 1992; Greist, 1989; Wells,
Robins, Bushnell, Jarosz, & Oakley-Browne, 1994). Other barriers
to treatment include long waiting periods, distance from clinics,
and the fact that the demand for treatment exceeds the supply
of trained therapists (Marks, Kenwright, McDonough, Whittaker, &
Mataix-Cols, 2004; Richards, Lovell, & McEvoy, 2003). Thus, even
though fear of animals appears to be highly common in the general
population only a relatively low percentage of sufferers seek or
To bridge this gap, self-exposure treatments have been found to
be an effective intervention for reducing anxiety and avoidance
behaviour in specific phobia (Ghosh & Marks, 1987; Ghosh, Marks,
& Carr, 1984; Mathews, Teasdale, Munby, Johnston, & Shaw, 1977;
Öst, Stridh, & Wolf, 1998), with drop-out rates comparable to
those of a therapist-directed therapy or any other treatment
(Ghosh, Marks, & Carr, 1988; Proudfoot et al., 2004). An investiga-
tion of potential users of self-help therapies by Graham, Franses,
Kenwright, and Marks (2001) showed that 91% of all those inter-
viewed reported that they would require self-help to be a com-
information and therapeutical advice as well as less fear of stigm-
atisation. Patients of all ages who completed a computer-based
therapy reported total satisfaction (Proudfoot et al., 2003; Wright &
Wright, 1997). However, when it comes to spider phobia it should
be noted that self-help treatment has been found to be significantly
less effective than the therapist-directed one-session treatment
(OST) developed by Öst and colleagues, in which a therapist and
client collaboratively work through the steps of the client’s fear
hierarchy during a single therapy session of up to 3 h (Öst, 1989,
1996). Across four studies on spider phobia Öst et al. (1998)
found clinicallysignificant improvement
* Corresponding author. Tel.: þ41 61 2670867; fax: þ41 61 2672934.
E-mail address: email@example.com (B.H. Müller).
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J. Behav. Ther. & Exp. Psychiat. 42 (2011) 179e184
individually treated clients compared to 31% in a self-help manual-
based treatment at posttreatment.
Computerised self-help exposure treatments that specifically
focus on spider phobia include virtual reality exposure (VRE) and
computer-aided vicarious exposure (CAVE). In VRE, the patient
interacts with a virtual representation of the spider while wearing
headphones and a head-tracking device. Although VRE therapy
has proven to be successful in small samples of adults with spider
phobia (Carlin, Hofmann, & Weghorst, 1997; Garcia-Palacios,
Hoffmann, Carlin, Furness, & Botella, 2002), it is still too expen-
sive and the equipment difficult to set up for it to be a widely used
treatment method for animal phobias.
CAVE uses less advanced technology than VRE. The patient
learns to direct a virtual figure with spider phobia through an
interactive computer setting in order to model self-exposure situ-
ations (such as approaching and remaining in feared situations
normally avoided). Employing three 45-min sessions of interactive
vicarious exposure techniques over a period of 6 weeks, CAVE has
successfully reduced spider phobia in adults (Gilroy, Kirkby,
Daniels, Menzies, & Montgomery, 2000, 2003; Heading et al.,
2001; Smith, Kirkby, Montgomery, & Daniels, 1997) and children
(Dewis et al., 2001). While Gilroy et al. (2000) found superior
treatment effects for the computerand the live-exposure treatment
compared to a relaxation placebo control condition, Smith et al.
(1997) found, contrary to their expectations, no difference bet-
ween two active treatment conditions, one with and one without
feedback in the form of a fear thermometer, and the control
condition. Moreover, a therapist was required to be present the
entire time as an uninvolved observer and the subjective ratings
were not completed with a behavioural outcome measure. Finally,
despite its promising treatment design, CAVE has not been made
available for a wider population with fear of spiders.
The latest generation of computerised cognitive behavioural
therapies (CCBT), such as the program Fear Fighter (Shaw, Marks, &
Toole, 1999), has been developed for patients with agoraphobia,
panic, and other phobias and aims at changing negative automatic
patterns. However, accessibility to the web-based program is pa-
ssword protected and participants who had dropped out reported
that the program was time consuming and required a lot of work
commitment (e.g., Schneider, Mataix-Cols, Marks, & Bachofen,
More recently computerised self-help approaches using the
Internet have been developed to provide greater access to treat-
ment while requiring minimal input from a therapist (for an
overview see Reger & Grahm, 2009). The efficacy of Internet
therapy has been reported for panic disorder (Carlbring et al., 2005;
Carlbring, Westling, Ljungstrand, Ekselius, & Andersson, 2001;
Klein, Richards, & Austin, 2006), social phobia (Andersson et al.,
2006), fear related to a traumatic event (Hirai & Clum, 2005),
posttraumatic stress (Knaevelsrud & Maercker, 2007; Lange, van de
Ven, & Shrieken, 2003), and obsessive compulsive disorder (Lack &
In a benchmark study on spider phobia, Andersson et al. (2009)
compared the results of a guided Internet-delivered self-help
treatment to the 3 h therapist-directed one-session treatment
(OST) as a control condition. The duration of the Internet-delivered
self-help treatment was 4 weeks with an average total work time
of 12 h. It consisted of five weekly text modules presented on
a Web page. A video illustrated the exposure principles and the
participants were instructed to expose themselves with the help
of a friend. Additionally, email contact with a therapist with an
average support per client of 25 min was provided. Mean imp-
rovements on a behavioural approach test (BAT) and the self-report
Spider Phobia Questionnaire (SPQ) suggest that the Internet-
delivered self-help treatment was more effective than the live-
exposure control condition (e.g., Andersson et al., 2009). Effect sizes
from pre- to posttreatment for the SPQ were large for the Internet-
delivered treatment (d ¼ 1.84) and the live-exposure treatment
(d ¼ 2.58). However, the Internet treatment still required therapist
involvement and remained time consuming and labour intense.
Thus more research data about the effectiveness of a minimal-input
computer-based self-help intervention without therapist involve-
ment is desirable.
The aim of the present study was to provide more insight into
the effectiveness of a computer-based one-session treatment in
reducing fear and avoidance behaviour in spider-fearful individ-
uals. In a randomised controlled study, the efficacy of an individual
computer-based exposure (CBE) treatment was tested. Depen-
dent variables were the FSQ on a subjective level and a BAT on an
observable, behavioural level. Fear of spiders is known to be eff-
ectively reduced in a single exposure session (for an overview see
Ziomke & Thompson, 2008). Therefore we assumed we would find
superior outcome results for spider-fearful participants in a CBE
group with exposure to spider pictures compared to spider-fearful
participants in a control group with exposure to neutral pictures.
Two hundred and twenty participants were recruited after
screening in classes at several departments of the University of
Basel using the German-language Spider Anxiety Screening
(SAS, Rinck et al., 2002). The SAS is a four-item questionnaire
designed for efficient screenings of spider-fearful individuals in
largesamples. Each item is rated on a 7-point continuum in relation
to how much the item disturbs the individual from 0 (not at all) to 6
(very much) resulting in a score range of 0e24 and a cut-off score
of >14 for being spider fearful.
After the SAS screening 41 female participants were invited to
complete the German version of the FSQ (Szymanski & O’Donohue,
1995). Only female participants were included in the study to
prevent unexpected variation bias. The FSQ is a valid questionnaire
to discriminate between phobics and nonphobics. It consists of 18
items about fear and avoidance regarding spiders. The FSQ is rated
on a 0e6 scale (0, does not apply to me; 6, very much applies to me).
Excellent internal consistency has been reported with a Cronbach’s
alpha of 0.96 (Rinck et al., 2002).
Finally 36 female participants aged between 18 and 34 years
(M ¼ 23.17 years; SD ¼ 4.21) who fulfilled the inclusion criteria of
being highly spider fearful with SAS scores higher than 14
(e.g., Rinck & Becker, 2007; Rinck, Reinecke, Ellwart, Heuer, &
Becker, 2005) and a minimum cut-off FSQ score of 24 (of
a maximum of 108, e.g., Rinck & Becker, 2007) were available for
randomisation. The criterion of significant impairment of everyday
life for a clinical diagnosis of spider phobia was not required in this
study because the hypothesis tested here refers to fear rather than
impairment. Moreover, according to Rinck et al. (2002) there is
a comparable level of anxiety, physiological arousal, and avoidance
behaviour between spider-fearful individuals and clinically diag-
nosed spider-phobic individuals. Lack of high levels of trait anxiety
and depressive symptoms for all participants was assessed with the
German version of the State-Trait Anxiety Inventory (STAI-trait;
M ¼ 37.27, SD ¼ 6.96; STAI-T; Laux, Glanzmann, Schaffner, &
Spielberger, 1981) and the Beck Depression Inventory (M ¼ 5.08,
SD ¼ 3.42; BDI; Hautzinger, Bailer, Worall, & Keller, 1994). The
follow-up analyses were performed on 17 participants in the CBE
group and 15 control participants with a total of N ¼ 32 participants
B.H. Müller et al. / J. Behav. Ther. & Exp. Psychiat. 42 (2011) 179e184
because of four incomplete FSQ questionnaires at follow-up. See
Fig. 1 for a flow chart of the participants.
1.2. Study design
The study was approved by the German Psychological Society’s
ethics committee for psychological research. Prior to initial
assessment, all participants provided written informed consent.
The experimenter randomly assigned participants meeting the
inclusion criteria to the CBE condition (n ¼ 18) or the control
condition (n ¼ 18).
An online pilot evaluation was set up to identify spider pictures
with a medium fear-arousing level from a set of 24 spider pictures
taken from E. Niewenhuys’s website (Niewenhuys, n.d.) with his
evaluated the 24 pictures on a scale of 1 (very much fear arousing) to
6 (not at all fear arousing). Finally, nine spider pictures were chosen
for the CBE group with a medium fear-arousing level (M ¼ 4.22).
For the spider-fearful control participants, nine neutral pictures
(window, basket, lamp) were selected from the International
Affective Picture System (IAPS; Lang, Bradley, & Cuthbert, 1999).
All pictures were presented on a computer screen with a resolution
of 400 ? 320 pixels.
1.4. Behavioural approach test (BAT)
The BAT involved the following procedure: Standing in front of
a closed room, the participant was asked to open the door and
approach a living house spider (Tegenaria atica) measuring about
5e6 cm across including legs that was in a sealed transparent
plastic container on a windowsill at the far end of the room. Next, if
possible, the participant was to remove the lid, insert a hand, and
try to pick up and hold the spider for at least 20 s. When the
participant had reached and touched the spider, or when she
decided to stop the approach, the remaining distance between
the participant and the spider was noted. The behavioural score
obtained from this measure ranged from 0 to 12. In detail the
BAT comprised 13 steps: 0 ¼ refuses to enter the test room,
1 ¼ stops 5 m from the container, 2 ¼ stops 4 m from the container,
3 ¼ stops 3 m from the container, 4 ¼ stops 2 m from the container,
5 ¼ stops 1 m from the container, 6 ¼ stops close to the windowsill
with the container, 7 ¼ touches the container, 8 ¼ removes the lid,
9 ¼ puts a hand in the container,10 ¼ touches the spider with one
Not meeting inclusion criteria
FSQ scores at pretreatment
lower than 24
Lost to follow-up (n=4)
Incomplete FSQ questionnaires
CBE group n=1
Control group n=3
Assessed for eligibility via SAS
Attended diagnostic assessment
Available for randomisation (n=36)
Allocated to CBE treatment group
Allocated to control group
End of treatment
CBE group n=17
Control group n=15
Fig. 1. Flow chart of participants. CBE, computer-based exposure; FSQ, Fear of Spiders Questionnaire; SAS: Spider Anxiety Screening.
B.H. Müller et al. / J. Behav. Ther. & Exp. Psychiat. 42 (2011) 179e184
forefinger, 11 ¼ holds the spider less than 20 s, and 12 ¼ holds
the spider for at least 20 s.
Participants were tested individually in a sound-attenuated
room. When participants had completed the pretreatment FSQ and
BAT they were seated in front of a computer, 60 cm from the screen,
to perform the CBE. Exposure to the spider pictures for the CBE
group and the neutral pictures for the control participants was
programmed and presented by the E-Studio/E-Prime 1.1 (E-Studio,
1996e2002) on an AMD Athlon (1.2 GHz) computer with a 17-inch
colour monitor and Windows XP system software. The E-Studio/
E-Prime 1.1 allowed accurate presentation of all picture data files.
All instructions were presented on the computer screen. Each
spider picture in the CBE group was presented on the computer
screen for 3 min, with a total standardised exposure time of
27 min. The spider-fearful control participants underwent the
same procedure with presentation of nine neutral pictures and an
equal exposure time of 27 min. A posttreatment FSQ and BAT
concluded the experiment and participants were debriefed.
As follow-up, 1 month later all 36 participants received an
online version of the FSQ by email, which was completed by 32 of
the participants (88.9%). Following Carlbring et al. (2007), we
assumed equivalent psychometric results for the paper-and-pencil
and online versions of the FSQ.
1.6. Statistical design and analyses
The dependent variables were the FSQ scores at the three
measurements, pre- and posttreatment and at 1-month follow-up,
and the number of steps completed in the BAT at pre- and post-
treatment. Because FSQ scores at pretreatment ranged from 25 to
93, t(35) ¼ 19.67, p < 0.001 (mean difference 59.5, SD ¼ 18.15) we
set the factor FSQ score at pretreatment as covariate and tested the
pure treatment outcome effect by covariance analyses. BAT
between-group differences in continuous data did not meet the
assumptions of normal distributions; therefore nonparametric
analysis of variance of ranks was used (ManneWhitney U test).
A positive treatment response is defined as a statistically significant
difference in mean change of FSQ scores and BATsteps between the
CBE group and control participants (e.g., Choy et al., 2007). Partial
the magnitude of change for each treatment group. An alpha level
of 0.05 was used for all statistical tests.
2) was used to calculate effect size and determine
1.7. Clinically significant improvement
Jacobson and Truax (1991) criteria for clinically significant
improvement specify that the participants’ change from pre- to
posttreatment, besides showing a statistically reliable change, must
fall within the range of the normal population or demonstrate
a change towards functionality. To assess the proportion of subjects
who achieved clinically significant improvement the cut-off score
for the FSQ was defined as <24,and for the BAT twosteps of change
in the direction of functionality was required.
2.1. Participant Characteristics at pretreatment
Participants in the CBE and control groups did not differ on
important control variables, such as STAI-trait and BDI question-
naires or pretreatment BAT and FSQ scores (all p > 0.05).
2.2. Pre- to posttreatment effects on FSQ and BAT outcome
All relevant means and standard deviations areshowninTable 1.
2.3. Fear of spiders questionnaire (FSQ)
The mean FSQ scores reported in each group at the three
measurements, pre- and posttreatment and at 1-month follow-up,
are shown in Fig. 2. Covariance analysis with covariate FSQ score
at pretreatment showed that the FSQ score difference between
the CBE group and the control group at posttreatment proved to be
significant, F(1,33) ¼ 4.72, p ¼ 0.037, hp
improvement at posttreatment than the control participants as
seen in a larger reduction in FSQ fear scores. Covariance analysis of
FSQ scores at 1-month follow-up with pretreatment scores as
covariate revealed a significant group effect, F(1,29) ¼ 9.90,
p ¼ 0.004, hp
a superior effect in fear reduction at 1-month follow-up compared
to control participants. Moreover, FSQ scores at follow-up
demonstrate that the achieved fear reduction at posttreatment
remained stable in the CBE group, whereas control participants
showed a slight but not significant increase in their FSQ scores, t
(14) ¼ ?1.67, p > 0.05.
2¼ 12.5%. Participants with
2¼ 25.4%. Participants in the CBE group showed
Means and standard deviations for the outcome measures at pre- and posttreatment and at 1-month follow-up.
CBE group (N ¼ 18)
Pretreatment M (SD)
Control group (N ¼ 18)
Pretreatment M (SD)Posttreatment M (SD) Follow-up (N ¼ 17) M (SD)
Posttreatment M (SD) Follow-up (N ¼ 15) M (SD)
Note: CBE ¼ computer-based exposure, FSQ ¼ Fear of Spiders Questionnaire, BAT ¼ Behavioural Avoidance Test.
Fig. 2. Mean FSQ scores at the three measurements, pre- and posttreatment and at 1-
month follow-up, for the CBE group and the control group.
B.H. Müller et al. / J. Behav. Ther. & Exp. Psychiat. 42 (2011) 179e184
2.4. BAT scores
Mean differences in the BAT (pretreatmenteposttreatment)
served as the data basis for the nonparametric analysis of the
BAT scores. Nonparametric analysis with a ManneWhitney U test
found a significant group effect, U(38) ¼ ?3.48, p ¼ 0.001, from pre-
to posttreatment. As depicted in Fig. 2, the CBE group showed
a greater difference in achieved BAT steps from pre- to posttreat-
ment (mean rank 495.50) than the control group (mean rank
2.5. Clinically significant improvement
Results for the FSQ scores at posttreatment and follow-up
demonstrate that the proportion of participants who achieved
clinically significant improvement (FSQ < 24) was 22.2% in the
CBE group compared to 0% in the control group. BAT results show
a proportion of 27.7% of CBE participants who demonstrated
a two-step change towards functionality compared to 0% of the
control participants. However, even with two steps of improve-
ment participants did not reach at least step 10, which is the
standard criterion in Öst’s studies for clinically significant
The aim of the present study was to investigate the efficacy of
one-session computer-based exposure as a minimal intervention
for fear reduction in spider-fearful individuals. Results from the
self-report FSQ data show larger fear reduction for the CBE group at
posttreatment compared to the control group. Moreover this effect
remained stable at 1-month follow-up. Similarly, the outcome of
the BAT shows less avoidance behaviour at posttreatment in the
CBE group compared to control participants when approaching
a living spider. When we look at the clinically significant imp-
rovement of the FSQ self-report measure, the proportions in the
CBE group of 22% at posttreatment and follow-up (FSQ scores < 24)
are comparable with the 18% improvement on the Spider Ques-
tionnaire reported by Öst, Salkovskis, and Hellstrom (1991). A two-
step improvement in the BAT was found in 27% of the participants
but they did not reach at least step 10, which is the standard
criterion in Öst’s studies for clinically significant improvement. The
lower BAT results in the present study might be due to participants
being instructed to expose themselves without any help from the
experimenter. In contrast to the study by Andersson et al. (2009),
which provided the help of a friend during exposure, and the Öst
studies, which used verbal encouragement from the therapist
to proceed as far as they could (e.g., Öst et al., 1991, 1998), in the
present study the experimenter was explicitly instructed not to
interfere during the BAT procedure after the initial instructions
Overall, the superior treatment effects in the CBE group
compared to a control condition support the development of
computer-based treatments for phobic disorders (Kenwright,
Liness, & Marks, 2001). Nonetheless, it should be noted that
a self-help CBE treatment is somewhat less effective than therapist-
guided live-exposure or guided Internet-exposure treatments.
Computer-based self-help treatment could be offered as a treat-
ment alternative for motivated patients with minimal therapist
contact either in a stepped-care approach in a clinical health care
setting or delivered through the Internet with additional therapist
supervision. In a stepped-care approach, patients are provided
with a self-help intervention in the first steps, with more intensive
interventions reserved for those insufficiently helped by the initial
intervention (van Boeijen et al., 2005; Bower & Gilbody, 2005).
Further development of CBE as an Internet application of one-
session exposure to spider pictures might lead to a long-lasting
reduction of the fear of spiders in awider group of patients. Overall,
current findings support the important role of computer-based
treatments in fear reduction. Given the potential labour and time
reduction, CBE might provide an alternative and ecologically
important treatment approach for spider-fearful individuals.
Despite the successful findings, there are some limitations of our
study. First, the study was conducted with a nonclinical population
of spider-fearful individuals. Although no differences in effect
sizes were reported for self-help studies using either self-report
measures or a diagnostic interview to determine the presence of an
anxiety disorder (e.g., Hirai & Clum, 2006), it would be desirable to
replicate the present findings with a clinically diagnosed phobic
population. Second, research about male responsiveness to CBE
would be of great interest, as this study only used a female sample
of participants. Third, the BAT results were recorded at the moment
when participants refrained from approaching the spider; the
amount of time needed for the participants to approach or to look
at and touch the spider was not measured. We assume even more
distinctive results would be obtained if both distance and time
were taken into account (e.g., Rinck & Becker, 2007).
Fourth, CBE may not be suitable for technophobic individuals.
Moreover, accordingto Marks (1999), patients are more motivated to
start using a computer-administered treatment under brief supervi-
we explicitly omitted any additional information about exposure
Consequently, for future research it would be desirable to investigate
outcome results of CBE in a clinical setting where patients receive
brief supervision including treatment instruction and where the use
of computer-based treatment is suggested by a clinician.
Finally, outcome results of this study were not compared to
a therapist-guided in vivo exposure group, the current clinical
standard. And although the treatment effects were good for the CBE
group, they only reflect average responses and a direct comparison
with real-life exposurewould be desirable to provide an estimate of
the relative effect size of CBE compared to a standard treatment.
In sum, the present findings demonstrate that one single session
of CBE can significantly reduce fear of spiders and avoidance
behaviour in spider-fearful individuals. Although further research,
replication, and evaluation of CBE for spider-fearful individuals is
needed, the present CBE treatment might provide a minimal
intervention for spider-fearful individuals who at present would
The authors would like to thank Corinne Urech and Marcel
Maier for their assistance in data collection and data preparation.
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