Journal of Anxiety Disorders 23 (2009) 806–812

Contents lists available at ScienceDirect

Journal of Anxiety Disorders

Dosed versus prolonged exposure in the treatment of fear: An experimental
evaluation and review of behavioral mechanisms
Sophie Rubin *, C. Richard Spates, Douglas A. Johnson, Leigh Jouppi
Western Michigan University, Kalamazoo, MI, United States

A R T I C L E I N F O

A B S T R A C T

Article history:
Received 17 September 2008
Received in revised form 11 March 2009
Accepted 13 March 2009

Exposure-based treatments have proven effective in treating a range of fears and phobias and can be
accounted for by mechanisms described in behavioral theory. Enhanced dosed and dosed-only exposure
are promising new behavioral approaches for treating fears and phobias. Thirty-nine participants withspeech anxiety were randomly assigned to a prolonged exposure (PE) condition, a positively enhanced
dosed exposure (PDE) condition, a dosed-only exposure (DE) condition, or a negatively-supplemented
dosed exposure (NDE) condition. Results indicated that both the PDE and DE conditions produced lessmeasured aversive arousal and signiﬁcantly more rapid arousal reduction than the tested alternatives.
These techniques may represent an important advancement, in that the treatment gains of traditional
exposure therapies might be achieved without the degree of aversive arousal (and possibly high drop out
rates) typically seen in exposure therapies. Additionally, these data contradict prevailing opinion
concerning the necessity for sustained aversive arousal during exposure-based treatment.
ß 2009 Elsevier Ltd. All rights reserved.

Keywords:
Exposure therapy
Dosed exposure
Behavior theory
Prolonged exposure
Speech anxiety
Social anxiety disorder

Exposure-based therapies are effective in treating a variety offear-based problems, including agorophobia, panic, posttraumaticstress disorder (PTSD), social, and speciﬁc phobia (Chambless &Ollendick, 2001; Choy, Fyer, & Lipsitz, 2007; Hirai, Vernon, &Cochran, 2007; Parsons & Rizzo, 2008). According to behavioral
theory, fears are principally acquired through a combination of
respondent and operant conditioning (Barlow, 2002; Forsyth,
Barrios, & Acheson, 2007; McAllister & McAllister, 1995; Todd &Pietrowski, 2007). Through respondent pairing, neutral stimuli
acquire the evocative properties of conditioned stimuli. As such,
fearful settings and physiological stimuli (CSs) may come to elicit
fearful reactions (CR). Through stimulus generalization, othersimilar settings and physiological stimuli may also elicit the fearful
reaction. One can also come to acquire fear in the presence ofsimilar stimuli and contexts through the observation of fear
responding in others.
From an operant conditioning perspective, the phobic/fearfulsituations may have stimulus functions beyond that of aconditioned stimulus (Spates & Rubin, 2007). The phobic/fearfulsituation may also serve as a conditioned establishing operation(CEO). More speciﬁcally, the phobic/fearful situation functions as areﬂexive CEO which is correlated with a worsening in conditions
and whose offset will function as reinforcement (Michael, 2004).

* Corresponding author at: P.O. Box 20415, Kalamazoo, MI 49019, United States.
Tel.: +1 269 352 6922.
E-mail address: sophierubin@gmail.com (S. Rubin).
0887-6185/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.janxdis.2009.03.005

Reﬂexive CEOs will evoke escape and avoidance behaviors that arethen reinforced by the relatively immediate reduction or removalof that CEO. Thus, any behavior that reduces or removes thephobic/fearful situation or some aspect of this situation will be
automatically reinforced.
Prolonged exposure is one evidence-based treatment for fear
(Barlow, 2002; Boudewyns & Shipley, 1983; Richard, Lauterbach, &Gloster, 2007). An axiomatic feature of this treatment is theextended duration of ‘exposure’ or ‘confrontation’ with the real or
imagined fear context while sustaining modest to high levels ofaversive arousal. During therapy this is accomplished within a safe
context and guided by a treatment rationale that has been
explained to the client. The behavioral principle that mostparsimoniously accounts for the success of this procedure is
respondent extinction. Before treatment, the conditioned stimulus
elicited a conditioned fearful emotional response (such as muscle
contractions, sweating, increased heart rate, adrenal secretion,
galvanic skin response, etc.). Since this conditioned stimulus iscontinuously presented without an unconditioned fear eliciting
stimulus the conditioned stimulus loses its fear-evocative properties and becomes a neutral stimulus (McAllister & McAllister,1995). During this process, others have argued that a signiﬁcantalteration in information processing also occurs (Foa & Kozak,
1986).
Another treatment based on respondent extinction is graded
exposure (Barlow, 2002; Richard et al., 2007). We distinguishgraded exposure from prolonged exposure merely for conceptual
reasons, recognizing that graded prolonged exposure often occurs

S. Rubin et al. / Journal of Anxiety Disorders 23 (2009) 806–812

during in vivo exposure interventions (Seim & Spates, 2008).
Flooding, on the other hand, would look like prolonged exposure
without grading. Although both procedures involve the repeatedpresentation of a fear eliciting conditioned stimulus, they differ inthat graded exposure involves a progression from the least
evocative conditioned stimulus to the most evocative conditioned
stimulus. A hierarchy of stimuli is constructed based on theirevocative properties and progression through the hierarchy occurs
when at least partial extinction takes place on the earlier steps. For
example, therapists only progress through later steps in thehierarchy if clients demonstrate a reduction in emotional
responding at earlier steps.
Dosed exposure is yet another possible treatment for phobias(Pittman et al., 1996; Seim & Spates, 2008; Spates & Koch, 2003;
Spates & Rubin, 2007; Waller, 2004). Unlike graded exposure, there
is no progression through a hierarchy of feared stimuli. Like
prolonged exposure, the fearful stimulus, either imagined or real, ispresented at moderate to maximal strength. Unlike prolonged
exposure however, the fearful stimulus is not presented for an
extended continuous duration. Instead, clients are repeatedly
exposed to the fearful stimulus for very short durations of time.
There is a brief time period between exposures referred to here as
the inter-trial interval, after which the feared stimulus is presented
again. This cycle continues until extinction is complete. Thus, theextinction-relevant unpairing of the CS/US is more gradual and lessdense with this procedure (i.e., it takes place over repeated trials
rather than over a single continuous trial of exposure). It ishypothesized that such dosed exposure may be more acceptable toclients who are sometimes unwilling to go through a prolonged
exposure treatment, and more acceptable to clinicians who areoften unwilling to administer a strongly aversive procedure toclients (Zayfert & Black, 2000). Note that in all of the respondent
extinction procedures, operant unpairing of the conditioned
establishing operation is also likely occurring simultaneously.
That is, the fear-arousing context is being presented in the absenceof both a worsening of conditions (operant unpairing of thereﬂexive CEO) and the conditioned stimulus with which it was
originally paired (respondent extinction) and presumably whichgave rise to aversive properties. All involve repeatedly presenting astimulus with acquired evocative properties (CEO, CS, CS2) without
the original or any other stimulus that has negative emotional
evocative properties (UEO, US, CS1, respectively).
Eye movement desensitization and reprocessing (EMDR) is
another treatment for fears and phobias (Shapiro, 1989). EMDR
involves induction of saccadic eye movements on the part of theclient while they are asked to recall the feared situation or trauma(Spates, Koch, Cusack, Pagoto, & Waller, 2008; also see Shapiro,
1995 for a detailed description of EMDR). While the EMDRintervention package is an effective treatment (Chambless &Ollendick, 2001; Spates et al., 2008; Waller, Mulick, & Spates, 2000)
the mechanism by which it achieves its effects has been debated(Foley & Spates, 1995; Lohr, Tolin, & Lilienfeld, 2000; Pittman et al.,
1996; Renfrey & Spates, 1994; Spates & Koch, 2003; Spates, Waller,& Koch, 2000). As Spates and Koch note ‘‘many features of eye
movement desensitization and reprocessing treatment play no
essential role in the outcome, and that what is left after
dismantling the components of treatment are core elements of
exposure therapy, administered in a dosed fashion, rather thancontinuously, as is more typically done with exposure therapy.’’(pp. 72–73). Therefore, EMDR can be conceptualized as a dosed
exposure procedure as described earlier.
Exposure-based treatments are listed as ‘‘Evidence Based’’ or‘‘Efﬁcacious’’ by the APA Task Force on the Identiﬁcation and
Dissemination of Efﬁcacious Treatments (Chambless & Ollendick,2001) and more recently by the Institute of Medicine in relation to
the treatment of PTSD (IOM, 2008). These treatments have been807

relatively brief, with some instances consuming only a few
treatment sessions. However, there are reported attrition rates
as high as 40–50% with prolonged exposure treatments (Zayfert &Black, 2000). Although prolonged exposure has been endorsed as‘‘empirically supported,’’ such a high dropout rate is unacceptableon practical grounds. Hembree et al. (2003) have argued that thedrop out rate for prolonged exposure is no different than for othertreatments, and that much of the drop out associated withprolonged exposure occurs before the client has experienced asingle therapeutic exposure. Implied therefore is that somepatients drop out during either the rationale or extensive
psycho-education phases of prolonged exposure. Arguably thismakes the case even stronger concerning the potential aversive
arousal generated by such procedures, even during the early
description of what the patient ‘will’ experience. Although
admittedly, client drop out can occur for many reasons unknown
to the therapist or investigator. While much attention has been
focused on prolonged exposure due to its well achieved stature, if
other procedures addressing fear generate equal and high attrition,a similar conclusion can be reached regarding the need forcontinuing research to establish procedures that reduce such
attrition while retaining effectiveness.
In addition to the high levels of attrition that are often seen
during exposure-based therapies, there is another challenge that is
potentially problematic. During exposure-based treatments, clients may engage in escape or safety behaviors such as leaving or
avoiding the situation. Exposure to the situation operates as areﬂexive CEO that evokes these behaviors, which in turn are
negatively reinforced by the removal of the exposure (if they aresuccessful), thus suggesting the importance of operant conditioning in the maintenance of phobias (Barlow, 2002; McAllister &McAllister, 1995). While therapists can often prevent the overt
instances of such behavior (through response prevention), thecovert instances are more problematic. For instance, the client may
resort to distracting thoughts and images to avoid contact with thefeared stimuli, especially when confrontation with the feared
stimuli is prolonged and extensive. Such efforts may undermine
the therapeutic process by preventing respondent extinction andoperant unpairing from taking place. Research suggests strongly
that such safety behaviors interfere with treatment success (EunJung, 2005; Morgan & Rafﬂe, 1999).
1. Focus of the present investigation
Public speaking anxiety is a form of social anxiety disorder thathas been the topic of numerous research investigations (Ayres,
1988a,b; Foley & Spates, 1995; Hu, Bostow, Lipman, Bell, & Klein,
1992; Hu & Romans-Kroll, 1995). Hu et al. and Hu and RomansKroll demonstrated that individuals who have negative thoughts
just prior to giving a public speech experience a higher level ofanxiety both during and after the real or imagined speech thanthose individuals who have positive thoughts just prior to a speech.
The implication is that during a course of exposure-based
treatment, a more rapid diminution of anxiety might occur if
episodes of contact with the feared speech context are interspersedwith brief periods of positive imagery or positive self-statements,
rather than prolonged contact with the fear-arousing speech
imagery.
A variation of dosed exposure, called enhanced dosed exposure,addresses these implications (Vianna, Cammarota, Coitinho,
Medina, & Izquierdo, 2003). The enhanced version differs in that
supplemental stimuli are added during the inter-trial interval. For
example, clients are asked to imagine a positive scenario such as
winning the lottery or playing with their favorite pet. Thus, theenhanced version may involve a counter-conditioning component,
depending on the nature of the supplemental stimuli.

808

S. Rubin et al. / Journal of Anxiety Disorders 23 (2009) 806–812

Hu et al. (1992) and Hu and Romans-Kroll (1995) investigatedthis hypothesis. In one study (1995), participants were assigned to
one of two conditions. Participants were asked to imagine either
the contents of a paragraph that contained positive attitudes
toward giving a speech or neutral attitudes toward giving a speechprior to actually giving a speech. Participants’ heart rate andsubjective reports of anxiety were measured while giving a speech.
Results indicated that a speech-relevant positive attitude prior to
speech delivery resulted in reduced subjective reports of anxiety
and cardiovascular reactivity when compared to a speech-relevant
neutral attitude condition.
In another study (Hu et al., 1992) individuals were exposed topositive thinking just before imagining giving a speech, while
participants’ subjective reports of speech anxiety and heart rate
were evaluated. Thirty participants were recruited who reported afear of public speaking based on a fear survey from a prescreening
session. Participants were randomly assigned to one of three
conditions. The three conditions consisted of being presented with
30 s of speech-relevant positive, negative, or neutral thinking justprior to the presentation of the target imagery (for 15 s duration),
which involved imagining giving a speech to an audience (i.e., adosed exposure arrangement).
Experimental sessions consisted of presenting a sentence in theparticipants’ own voice played through a tape recorder. Participants were instructed to spend 30 s thinking about the sentence.
When the 30 s ended, participants were instructed to imagine thepublic speaking scene for 15 s. After the 15 s had elapsed,participants were asked to rate the target fear image in terms of
how much fear they felt. This process continued for 10 iterations.
Results indicated that instructions for speech-relevant positive
thinking prior to imagining a public speaking scene were related toa statistically signiﬁcant reduction in both subjective ratings of fear
and heart rate. Instructions for speech-relevant negative thinking
prior to imagining a public speaking scene were related toincreases in subjective reports of fear and heart rate.
The present investigation was designed as an extension of the
Hu et al. study (1992). Although having many similar features, it
was not conceptualized as a treatment study, given thatparticipants were not treated for the full range of behaviors thattypically constitute speech anxiety. This study focused instead on
the respondent behaviors only along with subjective ratings of
distress, and on a narrower range of the stimuli that elicit such
responses in order to better isolate and examine variables for use in
future treatment packages. In doing so, it attempted to address therelative beneﬁts of dosed exposure and enhanced dosed exposure
on process variables that we believe impact treatment success (i.e.,
moment-to-moment aversive arousal and subjective distress). The
goal was to evaluate whether these approaches may be superior tothe conventional prolonged exposure. Since the design entailed
repeated observation and measurement, the question of whether
any of these approaches result in a more rapid reduction of
measured distress was answerable. Finally, we believe that theﬁndings identify some of the underlying behavioral processes that
may account for the success of treatment packages that include
these components (i.e., EMDR).
The current study improved upon Hu et al. (1992) by recruiting
individuals who were screened for public speaking anxiety using a
structured questionnaire. It substituted more reliable dependentmeasures of autonomic arousal than were used in Hu et al. (1992).
Further, the target fear imagery was held constant, as well as the
temporal parameters of exposure. Instructions for the ‘‘positive’’and ‘‘negative’’ imagery that were interspersed between episodesof imagining the target image were altered to achieve hypothesized stronger effects. Further, the putative ‘‘positive’’ and‘‘negative’’ effects were speciﬁcally assessed as measured preexperimentally by autonomic arousal in the presence of thereferenced instructional and imagined stimuli. While the current
study retained positive and negative experimental conditions, theydiffered from those used in Hu et al. (1992). Hu et al. utilized
speech-relevant positive or negative inserts between target scene
imagining. The current investigation used generalized positive andnegative scenes (not speech-relevant) and also added two
additional comparison groups: prolonged exposure and dosed
only (indicating that the inter-trial interval is left free of any
imagery). The present investigation was designed to test the
impact of dosed versus prolonged exposure on subjective andphysiological measures as well as to examine two varieties of
dosed exposure (positive and negative).
2. Method
2.1. ParticipantsCollege students (n = 39) were recruited from classes and public
postings. Participants were primarily white (n = 28), female(n = 22), who suffered from speech anxiety. The mean age of theparticipants was 21.92. They were screened using the Personal
Report of Communication Apprehension (PRCA-24) (McCroskey,1982). Participants were eliminated from the study if they scoredbelow 18 on the public-speaking component of the PRCA-24. In
addition, participants who were taking medications (excluding
birth control), had heart problems, or any other diagnosed physicalor psychiatric conditions were screened from the study in order toensure that such conditions would not interfere with thedependent measures.
2.2. Setting
The experiment was conducted in a university laboratory in thepsychology department with only the participant present and two
experimenters. Two experimenters were present for 100% of
sessions for the purpose of inter-observer agreement andindependent variable integrity. The room contained only essential
equipment (physiological monitoring equipment, printer, multilevel rack, two tables, two computers, and three chairs). In all
experimental conditions the delivery of the auditory instructions
and auditory stimuli were presented via computer. This helped toensure that the independent variables were presented in aconsistent manner. Experimenters only needed to start theappropriate computer program for each condition. The female
voice used was kept constant across all conditions. The computer
also presented a tone that prompted the participant to give a
Subjective Units of Discomfort (SUDs) rating.
2.3. Apparatus/dependent measures
Facial electromyography (f-EMG) is a valence-speciﬁc measureof affect that assesses the electrical activity of the spontaneous orreﬂexive movements of speciﬁc facial muscles (Rotteveel, de Groot,
Geutskens, & Phaf, 2001). It has been reported that this measure isable to detect minimal differences in speciﬁc muscle activity evenin absence of an overtly visible expression. Facial EMG measures ofthe musculus zygomaticus for smiling and the musculus corrugator supercilii for frowning have been useful in the measurementof valenced states (Rotteveel et al., 2001). For this experiment,
GS27 pre-gelled disposable sEMG electrodes and the Procomp 2
with BioGraph Inﬁniti software from Bio-Medical Instruments
were used.
Facial EMG for negative emotions was recorded via small
electrode pads placed near participants’ inner left eyebrow. Facial
EMG for positive emotions was recorded via small electrodes
placed between participants’ lower right cheek and mouth area.

S. Rubin et al. / Journal of Anxiety Disorders 23 (2009) 806–812

Facial EMG was used in this investigation to permit a more
discriminating measure of ‘‘positive’’ and ‘‘negative’’ emotion bothpre-experimentally as an operational criterion of whether thenontarget imagery achieved its intended effects, and as a dependentmeasure of arousal. This measure replaced the heart ratephysiological measure used in several previously referenced studies.
Subjective Units of Discomfort (SUDs) is a widely used measureof current arousal. It was used at the end of each period of target
image confrontation. This consisted of 10 opportunities to provide
ratings through the course of the experiment. SUDs scores ranged
from 1 (least amount of anxiety) to 10 (most amount of anxiety).
2.4. Independent variables
Participants were randomly assigned to one of four experimental
conditions: positively enhanced dosed exposure (PDE), negativelysupplemented dosed exposure (NDE), prolonged exposure (PE), anddosed exposure (DE). Total exposure time to the target imagery was
2.5 min across all conditions. Ten participants were assigned to all
conditions except for the DE condition in which there were 9participants. The speciﬁc conditions are outlined below.
The target public speaking scene participants were asked toimagine for 15 s was the same as that used in Hu et al. (1992) and is
described as follows:‘‘Imagine that you are about to present an important speech to alarge audience in an auditorium. As you stand at the podium on
the stage just before you begin speaking, you look out and see
all of the faces in the audience looking at you, waiting for you tobegin. As you stand there, you feel your legs are wobbly andyour mouth and throat are dry.’’This target public speaking scene was kept constant across allconditions and was presented in a human female voice via a
computer recording. The same voice was also used in all conditions.
After 15 s elapsed, participants were asked to rate their level ofanxiety on the SUDs. This process continued for a total of 10
iterations. Between episodes of imaging the target scene, participants were exposed to one of the following conditions while
continuous physiological measures were taken (f-EMG as described).
2.5. Negative condition (NDE)
Participants assigned to this condition were exposed to aselection process that involved identifying the sentence producing
the most valence-speciﬁc arousal from among 10 sentences
containing negative connotations (i.e., ‘‘Imagine that you justcame home to ﬁnd your window open and your pet missing,’’‘‘Imagine that you received a failing grade in a class that you reallyenjoy.’’, etc.). For each sentence the participant was asked toimagine the situation described. Based on the f-EMG data, thesentence most aversive (as determined by corrugator activity) for
each participant was selected for use in subsequent exposures.
Participants then began the active intervention component of thecondition. They were exposed to the selected negative sentencewith 30 s of imagined exposure, which was then followed by thetarget public speaking scenario with 15 s of imagined exposure.
Following this, a SUDs rating was collected again. This negative
sentence/target public speaking/SUDs rating cycle continued for an
additional 10 iterations.
2.6. Positive condition (PDE)
Participants assigned to this condition were exposed to aselection process that involved identifying the sentence producing809

the most valence-speciﬁc arousal from among 10 sentences
containing positive connotations (i.e., ‘‘Imagine that you just
won $1000 in lottery tickets and you are now at your favorite store
spending the money,’’ ‘‘Imagine that someone you are attracted tocomments on how beautiful/handsome you are.’’, etc.). For eachsentence the participant was asked to imagine the situation
described. Based on the f-EMG data, the sentence most pleasant (asdetermined by elevated zygomaticus activity) for each participant
was selected for use in subsequent exposures. Participants thenbegan the active intervention component of the condition. They
were exposed to the selected positive sentence with 30 s ofimagined exposure, which was then followed by the target public
speaking scenario with 15 s of imagined exposure. Following this, a
SUDs rating was collected again. This positive sentence/target
public speaking/SUDs rating cycle continued for an additional 10
iterations.
2.7. Dosed-only condition (DE)In this condition, participants were asked to imagine the target
public speaking scene for 15 s. After the 15 s has elapsed,participants were asked to rate their level of anxiety on the SUDs
rating scale. After the 30 s has elapsed (without instructions toimagine any scenes), participants were then asked to imagine thetarget scene again for 15 s. This cycle continued for a total of 10
iterations.
2.8. Prolonged exposure (PE) condition
In this condition, participants were exposed to the target public
speaking scene for 15 s followed by a SUDs rating. This cycle oftarget public speaking scene/SUDs rating continued for 10
iterations, all occurring consecutively within a 2.5-min period.
This period of time is also the total amount of time thatparticipants in the three other conditions were asked to imagine
the target speech scene. Participants were then asked to rate theirlevel of anxiety on the SUDs rating scale.
2.9. Inter-observer agreement
Two experimenters were present for all sessions. One
experimenter was seated unobtrusively in the corner of the room
whose assigned role was to monitor participants’ faces for unusual
movements such as coughing, sneezing, yawning, and scratching.
Any such movements were recorded for the purpose of editing out
unintended changes in the f-EMG readings. The other experimenter was seated in front of a computer that displayed the f-EMG
data and whose assigned role was to monitor the equipment incase of equipment malfunction.
IOA was collected for 100% of sessions. IOA was calculatedusing point-by-point agreement ([agreements/agreements +disagreements]  100). Two separate observers reviewed the
f-EMG data and recorded the speciﬁc segments that should be
calculated and reported as well as edited out due to unusual
responses due to coughing, sneezing, etc. IOA was 92% and 93%,
respectively. All disagreements were reviewed until an agreement
was met.
2.10. Independent variable integrity
IVI was collected for 100% of sessions. Experimenters unobtrusively observed the experimental equipment to ensure that thecomputer was playing the auditory stimuli in the prescribedfashion. Any observations of equipment failure would have been
immediately recorded and corrected. However, no such instances
occurred.

S. Rubin et al. / Journal of Anxiety Disorders 23 (2009) 806–812

810
Table 1
Summary table of dependent measures averages.
TrialGroupa

1

2

3

4

5

6

7

8

9

10

SUDs rating

PDE
NDE
PE
DE

5.0
6.9
6.4
5.3

5.1
6.8
6.3
5.1

4.2
6.3
6.1
4.7

4.6
6.0
5.6
3.9

3.9
6.7
5.5
4.3

3.7
6.4
5.4
3.8

3.4
6.2
5.2
3.3

3.5
5.6
5.3
3.6

3.2
4.9
5.0
3.4

3.0
5.0
5.1
3.1

Corrugator activity

PDE
NDE
PE
DE

6.58
7.22
7.22
7.31

7.19
9.17
7.93
7.11

6.96
7.18
7.73
7.96

7.52
7.06
8.10
7.73

7.74
7.30
9.35
7.64

6.44
6.80
8.68
7.66

6.84
7.48
8.64
7.29

6.71
9.20
8.76
7.93

6.42
7.77
8.84
6.75

7.18
7.77
8.70
7.33

a
PDE = positively enhanced dosed exposure.
NDE = negatively-supplemented dosed exposure.
PE = prolonged exposure.
DE = dosed-only exposure.

3. Results

Table 2
Summary of effect sizes.

Analyses of covariance through linear regression (which takes
into account both time and group membership) were conducted onprincipal dependent measures to assess for group differences inboth slope and level, using the trial number as the covariate. Tukey
post hoc analyses were conducted to determine the source ofvariation. Table 1 displays averages of the dependent measures for
all trials across groups and conditions. Fig. 1 displays the mean
SUDs ratings during phobic scene trials. Table 2 describes the effectsize comparisons for all permutations of experimental conditions.
An analysis of covariance through linear regression on SUDs
ratings indicated a signiﬁcant main effect for the treatment groups(p < .001). Tukey post hoc comparisons evaluated the source ofvariance (adjusted p value of .05). The PDE condition produced
signiﬁcantly lower SUDs ratings than both the NDE conditions andthe PE conditions. The NDE condition produced signiﬁcantly higher
SUDs ratings than both the PE and DE conditions. The PE condition
produced signiﬁcantly higher SUDs ratings than the DE condition.
There were no other signiﬁcant differences between groups on thismeasure.
An analysis of covariance through linear regression on
corrugator activity indicated a signiﬁcant main effect for thetreatment groups (p < .001). Fig. 2 displays the mean corrugator
activity during phobic scene trials. As with SUDs ratings, Tukey
post hoc comparisons were run to evaluate the source of variance(adjusted p value of .05). The PDE condition produced signiﬁcantly
lower corrugator activity than the NDE and PE conditions. The PE
condition resulted in signiﬁcantly higher corrugator activity thanComparison

SUDs

NDE vs. DE
NDE vs. PDE
PE vs. DE
PE vs. PDE

0.94
0.86
0.64
0.61

0.11
0.39
0.41
0.67

DE > NDE, p < .05a, nsb
PDE > NDE, p < .05
DE > PE, p < .05
PDE > PE, p < .05

NDE vs. PE

0.19

0.30

PE > NDEa, p < .05a
NDE > PEb, nsb

DE vs. PDE

0.04

0.29

PDE > DE, p < .05a, nsb

Corrugator

Results

Note: NDE = negatively-supplemented dosed exposure, DE = dosed exposure,
PDE = positively enhanced dosed exposure, PE = prolonged exposure. Results: (>)
equals ﬁrst condition has lower mean score than second condition and (<) indicatesthe opposite. ns = nonsigniﬁcant.
a
SUDs scores only.
b
Corrugator scores only.

Fig. 2. Mean corrugator activity during phobic scene trials.

the DE condition. There were no other signiﬁcant differences
between groups on this measure.
While zygomaticus activity was measured in this study, thedata were considerably less consistent and interpretable than thecorrugator activity, and thus is not reported here. Previous
methodological reports on f-EMG have indicated that this site isalso a less reliable measure of valenced arousal than the corrugator(Larsen, Norris, & Cacioppo, 2003). For this reason, only the data forthe corrugator measures are reported here.
4. Discussion

Fig. 1. Mean SUDs ratings during phobic scene trials.

SUDs ratings indicate that PDE and DE conditions were the mosteffective in reducing reports of distress. As Fig. 1 demonstrates, all

S. Rubin et al. / Journal of Anxiety Disorders 23 (2009) 806–812

conditions show reductions in reported distress over time;
however, the DE and PDE conditions were consistently lower at
every trial including the ﬁnal trial. This interpretation is conﬁrmedby the ANCOVA through linear regression and Tukey post hoc
analyses.
On the corrugator measure, both PDE and DE conditions wereless aversive than the PE condition. The corrugator measure, basedon previous work, is quite sensitive to negative valenced arousal inregards to fear (Hu & Wan, 2003). The ﬁndings on the corrugator
activity correspond to the ﬁndings on the SUDs measure acrossconditions.
Overall, both PDE and DE conditions appear to be promisingdevelopments for the treatment of fear inasmuch as both produced
greater and more rapid reductions in aversive arousal—the corefeature of fear. This study also contributes to the literature in that
there have been few controlled studies on imaginal exposure (Choyet al., 2007). The current study suggests a treatment innovationthat could potentially be much more acceptable to clients and may
avoid the typical attrition rates associated with prolonged
exposure.
However, this study also contained limitations that should becorrected in future studies. Namely, participants in both the PDE
and NDE conditions were exposed to all ten emotion-valenced
sentences prior the initial SUDs rating, whereas participants in the
prolonged and dosed-only conditions (PE and DE) received no such
advanced exposure. This was due to the study design that gave
greater weight to preliminary functional assessments and accurately selecting emotionally valenced sentences to be used during
the inter-trial interval for these groups. Nonetheless, an ANOVA on
the means for the initial trial revealed no signiﬁcant differences
between groups on SUDs ratings and corrugator activity (p = .194
and .901, respectively), thus ruling out any undue inﬂuence of thisprior exposure to independent variable scenes. Another limitationof this study, that primarily impacts external validity, is the lack offollow-up data. Future studies should include follow-up measures
to assess the generalization and durability of the results.
While use of the PRCA in this study was an improvement over
Hu et al. (1992), inclusionary criteria could be even more speciﬁc toensure that participants are indeed diagnosable as socially anxious.
Additional measures such as the Anxiety Disorders Interview
Schedule (ADIS) (Brown, Di Nardo, & Barlow, 1994) could be
included to increase the odds of selecting phobic individuals.
Another important difference between the current study andthe studies conducted by Hu et al. concerns the nature of the
supplemental stimuli. The basic paradigm in the studies conductedby Hu et al. involved participants imagining a positive/negative
statement concerning speech giving prior to imagining or actuallygiving a speech. The paradigm used in the current study involved
participants imagining a general positive/negative statement prior
to imagining giving a speech. Whether or not this change inprocedures made the intervention more or less effective isunknown.
Given that stimuli related to giving a speech are likely to be
aversive to speech anxious individuals, it is possible that evenpositive thoughts about speech giving may be slightly aversive.
Therefore, it is possible that general positive statements would beless aversive than positive statements concerning speech giving,
potentially resulting in Hu’s procedures being less effective thanthe procedures used in the current study. On the other hand, since
positive statements about giving a speech are more relevant to thetarget imagery, it is also possible that positive statements such as
Hu’s would be more effective than general positive statements.
Ultimately, it is unknown how these categories of positive
statements would compare in terms of effectiveness. Futurestudies should examine direct comparisons of these positive
statement categories.

811

Although there appears to be little outcome differences
between PDE and DE conditions, we are lacking data on theacceptability of such procedures. Therefore, it is important for
future studies to measure acceptability by participants of therespective procedures, and still further, to evaluate participant
preference for the procedure(s). Of course, such evaluations should
retain measures that evidence changes in subjective reports andphysiological states. As others have noted, exposure-based
treatments are an effective therapeutic tool, however, acceptanceand retention are important considerations (Choy et al., 2007;
Zayfert & Black, 2000).
Finally, because this is the ﬁrst study that utilized the complete
experimental procedures described and it differs from Hu et al.
(1992) in potentially important ways, it is conceivable that theobserved ﬁndings might be attributable to unknown and therefore
unspeciﬁed method effects. All effort was made however toimplement safeguards against such unintended systematic effects.
Ultimately, replication of this study in ours and other laboratories
should clarify this likelihood.
Positively enhanced dosed exposure and dosed exposure
represent exposure-based therapies that, on the basis of thisinvestigation, produce less aversive arousal and may be more
acceptable to clients than traditional exposure-based treatments.
Furthermore, the lessened aversive arousal may reduce thelikelihood that clients will engage in safety behaviors (i.e., whenclients feel less threatened, there is a reduced motivation toescape). Finally, if treatment gains of traditional exposure
therapies can be achieved without the traditional drop out rates,
this would represent a signiﬁcant advancement in the treatment offears and phobias.
References
Ayres, J. (1988a). Antecedents of communication apprehension: a reafﬁrmation. Communication Research Report, 5, 76–83.
Ayres, J. (1988b). Coping with speech anxiety: the power of positive thinking. Communication Education, 37, 289–296.
Barlow, D. H. (2002). Anxiety and its disorders: the nature and treatment of anxiety andpanic (2nd ed.). New York: The Guilford Press.
Boudewyns, P. A., & Shipley, R. H. (1983). Flooding and implosive therapy: direct
therapeutic exposure in clinical practice. Plenum Press: New York.
Brown, T. A., Di Nardo, P. A., & Barlow, D. H. (1994). Anxiety Disorders Interview Schedulefor DSM-IV (ADIS-IV). San Antonio, TX: Psychological Corporation/Graywind Publications Incorporated.
Chambless, D. L., & Ollendick, T. H. (2001). Empirically supported psychologicalinterventions: controversies and evidence. Annual Review of Psychology, 62,
685–716.
Choy, Y., Fyer, A. J., & Lipsitz, J. D. (2007). Treatment of speciﬁc phobia in adults. ClinicalPsychology Review, 27, 266–286.
Eun-Jung, K. (2005). The effect of the decreased safety behaviors on anxiety andnegative thoughts in social phobics. Journal of Anxiety Disorders, 19, 69–86.
Foa, E. B., & Kozak, M. J. (1986). Emotional processing of fear: exposure to corrective
information. Psychological Bulletin, 99(1), 20–35.
Foley, T., & Spates, C. R. (1995). Eye movement desensitization of public-speaking
anxiety: a partial dismantling. Journal of Behavior Therapy & Experimental Psychiatry, 26, 321–329.
Forsyth, J. P., Barrios, V., & Acheson, D. T. (2007). Exposure therapy and cognitive
interventions for the anxiety disorders: overview and newer third-generation
perspectives. In: D. C. S. Richard & D. Lauterbach (Eds.), Handbook of exposure
therapies (pp. 61–108). Burlington, MA: Elsevier Inc.
Hembree, E. A., Foa, E. B., Dorlan, N. M., Street, G. P., Kowalski, J., & Tu, X. (2003). Do
patients drop out prematurely from exposure therapy for PTSD? Journal of Traumatic Stress, 16, 555–562.
Hirai, M., Vernon, L. L., & Cochran, H. (2007). Exposure therapy for phobias. In: D. C. S.
Richard & D. Lauterbach (Eds.), Handbook of exposure therapies (pp. 247–270).
Burlington, MA: Elsevier Inc.
Hu, S., Bostow, T. R., Lipman, D. A., Bell, S. K., & Klein, S. (1992). Positive thinking reduces
heart rate and fear responses to speech-phobic imagery. Perceptual & Motor Skills,
75, 1067–1073.
Hu, S., & Romans-Kroll, J.-M. (1995). Effects of positive attitude toward giving a speechon cardiovascular and subjective fear responses during speech in anxious subjects.
Perceptual & Motor Skills, 81, 609–610.
Hu, S., & Wan, H. (2003). Imagined events with speciﬁc emotional valence produce
speciﬁc patterns of facial EMG activity. Perceptual & Motor Skills, 97, 1091–1099.
Institute of Medicine of the National Academies, Committee on Treatment of Posttraumatic Stress Disorder, & Board on Population Health and Public Health

812

S. Rubin et al. / Journal of Anxiety Disorders 23 (2009) 806–812

Practice, (2008). Treatment of posttraumatic stress disorder: an assessment of theevidence. National Academies Press.
Larsen, J. T., Norris, C. J., & Cacioppo, J. T. (2003). Effects of positive and negative affecton electromyographic activity over zygomaticus major and corrugator supercilii.
Psychophysiology, 40, 776–785.
Lohr, J. M., Tolin, D. F., & Lilienfeld, S. O. (2000). Final comments on Lipke’s critique ofLohr, Tolin, and Lilienfeld (1998). The Behavior Therapist, 23, 145–147.
McAllister, W. R., & McAllister, D. E. (1995). Two-factor theory: implications forunderstanding anxiety-based clinical phenomena. In: W. T. O’Donohue & L. Krasner (Eds.), Theories of behavior therapy: exploring behavior change (pp. 145–171).
Washington, DC: American Psychological Association.
McCroskey, J. C. (1982). An introduction to rhetorical communication (4th ed.). Englewood Cliffs, NJ: Prentice Hall.
Michael, J. L. (2004). Concepts and principles of behavior analysis (Revised edition).
Kalamazoo, MI: Association for Behavior Analysis.
Morgan, H., & Rafﬂe, C. (1999). Does reducing safety behaviors improve treatment
response in patients with social phobia? Australian and New Zealand Journal of
Psychiatry, 33, 503–510.
Parsons, T. D., & Rizzo, A. A. (2008). Affective outcomes of virtual reality exposure
therapy for anxiety and speciﬁc phobias: a meta-analysis. Journal of Behavior
Therapy & Experimental Psychiatry, 39, 250–261.
Pittman, R. K., Orr, S. P., Altman, B., Longpre, R. E., Poire, R. E., & Macklin, M. L. (1996).
Emotional processing during eye movement desensitization and reprocessing
therapy of Vietnam veterans with chronic posttraumatic stress disorder. Comprehensive Psychiatry, 37, 419–429.
Renfrey, G., & Spates, C. R. (1994). Eye movement desensitization: a partial
dismantling study. Journal of Behavior Therapy & Experimental Psychiatry, 25,
231–239.
Richard, D. C. S., Lauterbach, D., & Gloster, A. T. (2007). Description, mechanisms ofaction, and assessment. In: D. C. S. Richard & D. Lauterbach (Eds.), Handbook of
exposure therapies (pp. 1–28). Burlington, MA: Elsevier Inc.
Rotteveel, M., de Groot, P., Geutskens, A., & Phaf, R. H. (2001). Stronger suboptimal than
optimal affective priming? Emotion, 1, 348–364.

Seim, R., & Spates, C. R. (2008, May). The efﬁcacy of brief exposure durations in thetreatment of animal phobias. Poster session presented at the annual meeting of the
Association for Psychological Science, Chicago, IL.
Shapiro, F. (1989). Efﬁcacy of the eye movement desensitization procedure in thetreatment of traumatic memories. Journal of Traumatic Stress, 2, 199–223.
Shapiro, F. (1995). Eye movement desensitization and reprocessing: basic principles,
protocols, and procedures. New York: Guilford Press.
Spates, C. R., & Koch, E. (2003). From eye movement and desensitization and reprocessing to exposure therapy: a review of the evidence for shared mechanisms.
Japanese Journal of Behavior Analysis, 18(2), 62–75.
Spates, C. R., Koch, E., Cusack, K., Pagoto, S., & Waller, S. (2008). Eye movement
desensitization and reprocessing. In: E. Foa, T. Keane, M. Friedman, & J. Cohen(Eds.), Effective treatments for PTSD. Guilford Press.
Spates, C. R., & Rubin, S. (2007). Dosed versus prolonged exposure in treating fear:
emerging evidence of a less aversive treatment alternative. Australian and New
Zealand Journal of Psychiatry, 41(Supplement 2), A352.
Spates, C. R., Waller, S., & Koch, E. I. (2000). A critique of Lohr et al.’s (1998) review of
EMD/R and Lipke’s commentary: of messages and messengers. Behavior Therapist,
23, 148–154.
Todd, J., & Pietrowski, J. (2007). Animal Models of exposure therapy: a selective review.
In: D. C. S. Richard & D. Lauterbach (Eds.), Handbook of exposure therapies (pp. 29–
60). Burlington, MA: Elsevier Inc.
Vianna, M. R. M., Cammarota, M. P., Coitinho, A. S., Medina, J. H., & Izquierdo, I. (2003).
Pharmacological studies of the molecular basis of memory extinction. Current
Neuropharmacology, 1, 89–98.
Waller, S. A. (2004). Continuous and interrupted exposure therapy in the treatment ofpublic speaking anxiety (Doctoral dissertation, Western Michigan University,2004). Dissertation Abstracts International-B, 65, 2117.
Waller, S. A., Mulick, P. S., & Spates, C. R. (2000, March). Interventions for PTSD: a metaanalysis and quantitative review. In Proceedings of the third world congress of theInternational Society for Traumatic Stress Studies.
Zayfert, C., & Black, C. (2000). Implementation of empirically supported treatment for
PTSD: obstacles and innovations. The Behavior Therapist, 23, 161–168.