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Behaviour Research and Therapy 46 (2008) 122–129
www.elsevier.com/locate/brat
Shorter communication
Acceptance versus distraction: Brief instructions, metaphors and
exercises in increasing tolerance for self-delivered electric shocks
Jenny McMullena, Dermot Barnes-Holmesa, Yvonne Barnes-Holmesa, Ian Stewartb,
Carmen Lucianoc, Andy Cochranea,
a
Department of Psychology, National University of Ireland, John Hume Building, Maynooth, Ireland
b
Department of Psychology, National University of Ireland, Galway, Ireland
c
University of Almeria, Almeria, Spain
Received 18 April 2007; received in revised form 31 August 2007; accepted 10 September 2007
Abstract
The current study compared the effects of an acceptance versus distraction rationale on coping with experimentally
induced pain. Eighty participants were randomly assigned to one of five conditions: Full-Acceptance, Full-Distraction,
Instruction-only-Acceptance, Instruction-only-Distraction and No-Instructions. Participants completed a simple
matching task and were intermittently given the choice either to receive an electric shock and continue, or to avoid the
shock and terminate the task. Only the Full-Acceptance strategy (that included experiential exercises and a metaphor)
had a significant effect on task tolerance as measured by an increase in the number of shocks delivered post-intervention
relative to baseline. In addition, the participants in both of the acceptance conditions showed lower levels of believability in that they were more likely to continue with the task even when reporting more pain. The results support
the prediction that acceptance-based interventions work by undermining the behavioural-control functions of
pain-related thoughts and feelings, and call for a systematic analysis of how metaphors and exercises work in analogue
research.
r 2007 Elsevier Ltd. All rights reserved.
Keywords: Experimental pain; Acceptance; Distraction; Instruction following; Electric shocks
Introduction
There are now a number of published analogue studies that have demonstrated that acceptance-based
approaches lead to greater tolerance for experimentally induced physical stressors relative to strategies that
focus on controlling the associated distress (McCracken, Vowles, & Eccleston, 2004). An early study examined
the behavioural (task persistence) and subjective (self-report) effects of a control- versus an acceptance-based
protocol, using a cold-pressor task (Hayes et al., 1999). The findings demonstrated that the acceptance
rationale led to greater task persistence relative to the control protocol. Additionally, the participants in the
Corresponding author. Tel.: +353 1 708 4765; fax: +353 1 708 4767.
E-mail address: cochrane.andy@gmail.com (A. Cochrane).
0005-7967/$ - see front matter r 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.brat.2007.09.002
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acceptance condition reported reduced believability of thoughts and feelings as reasons for discontinuing the
task.1
Subsequent analogue studies have also demonstrated that acceptance appears to increase tolerance to
aversive stimulation relative to cognitive control strategies (Gutiérrez, Luciano, Rodriguez, & Fink, 2004;
Masedo & Esteve, 2007; Páez-Blarrina et al., in press). In one analogue study, however, neither acceptance nor
control-based coping produced an increase in cold-pressor tolerance (Keogh, Bond, Hanmer, & Tilston, 2005).
Unlike the other studies, however, the Keogh et al.’s analogue ‘‘interventions’’ involved relatively brief
instructions with no experiential exercises or metaphors. To date, no attempt has been made to examine the
effects of the method by which an acceptance- versus control-based intervention is delivered, that is, by
instructions alone or in combination with the use of metaphor and exercises.
The current study examined two methods of delivery: (1) a brief and simple instruction for accepting or
distracting and (2) an instruction for accepting or distracting combined with a relevant experiential exercise
and metaphor. The study compared the effects of each protocol on tolerance and self-reported pain produced
by electric shock stimulation, using procedures derived from Gutiérrez et al. (2004). The interventions were
presented as digitised video-clips, as part of a participant-controlled computer program, which aimed to
reduce any inadvertent experimenter cuing. We predicted that only the acceptance condition with an exercise
and metaphor would increase tolerance for self-delivered shocks. We also predicted that if acceptance
increased tolerance this would occur primarily through a reduction in the believability of pain-related
thoughts and feelings as a basis for discontinuing the aversive task.
Method
Participants
A total of 97 individuals agreed to participate, with a total of 80 individuals completing the study. The 17
participants who did not complete failed to meet various criteria for inclusion. All participants were recruited
through word of mouth from students and ex-students of the National University of Ireland, Maynooth and
University College, Dublin (46 female and 34 male) with a mean age of 28.5 (SE ¼ 7.03). Participants with a
history of chronic pain, epilepsy or a medical condition that could be adversely affected by participation
(e.g. metal joint replacement) were excluded. Participants were randomly assigned to each of the five
conditions, after controlling for age, gender and number of shocks delivered during the first shock task
(described below), until each condition contained 16 individuals. The participants did not receive any
remuneration for their participation, and the study was conducted in accordance with the ethical guidelines of
the Department of Psychology at the National University of Ireland, Maynooth.
Materials and apparatus
A portable personal computer was used to deliver the experimental phases including calibration of aversive
stimulation, the two shock tasks, and the therapeutic interventions. A Lafayette 824151S isolated square wave
stimulator (ISWS) was used to provide electrical stimulation via electrodes attached to the palmar surface of
the forearm. Experimental sessions were conducted in a quiet room free from distraction.
Believability measure
Consistent with Gutiérrez et al. (2004), the believability of increasing levels of self-reported pain as a reason
to stop the task was assessed by examining the relationship between this rating and shock tolerance.
Specifically, this was measured by calculating the number of participants who reported increased pain levels
post-intervention, relative to the first task, but still increased the number of self-delivered shocks received. The
term believability is thus used here simply to denote a response-discordance between the rating of pain and
shock tolerance.
1
The term ‘‘acceptance’’ embraces multiple interpretations, but for the purpose of the current study we defined acceptance as a technique
that reduces the behavioural control functions of targeted thoughts and feelings by disconnecting them from overt behaviour.
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Procedure
Participants were assigned to one of five conditions. The Full-Acceptance (F-ACC) and Full-Distraction
(F-DIS) conditions contained instructions to accept or distract combined with a relevant experiential exercise
and metaphor. The Instruction-based-Acceptance (I-ACC) and Instruction-based-Distraction (I-DIS)
conditions contained brief instructions only (full scripts available from the second author on request).
Finally, a no instruction group (No-I) was also included in which no strategy was provided. All participants
received the same general instructions, and were told that the study involved the presentation of brief
electric shocks that would be unpleasant but innocuous. They were also informed that they were free to
discontinue the experiment at any stage. Participants were seated in front of the computer to start the
calibration phase.
Calibration of aversive stimulation
The purpose of this phase was to determine a starting voltage for the subsequent two shock tasks. Two
10 mm diameter sensor electrodes were attached 2 cm apart on the palmar surface of a participant’s nondominant forearm. Participants wore headphones to amplify appropriate auditory stimuli and eliminate any
distractions. The ISWS was located behind the participants so that they could not observe any manipulation.
The experimenter sat behind the participant during this phase and subsequent shock tasks so that she could
observe responses and deliver the shocks on schedule. On-screen instructions informed the participants that
electric shocks of increasing intensity would be delivered to determine the voltage of shocks that would be used
during subsequent stages of the experiment. The instructions reiterated that the shocks would be unpleasant
but harmless and the participants were reminded that they could choose to terminate the experiment at any
time.
Participants used the mouse to click on an on-screen button to indicate their readiness to start, and then
they were exposed to a series of shocks that gradually increased in voltage. Before each shock two buttons
appeared on the screen, giving the participants the choice to either ‘‘Click here to end the experiment’’ or
‘‘Click here to receive a shock and continue.’’ If the participants chose to continue, a brief shock was delivered
and they were asked to rate the painfulness of the shock on a Visual Analogue Scale (VAS) from 0 (no pain) to
100 (pain as bad as it could be). Once the participant had rated a shock at 50 or above, the calibration phase
ended, and the voltage of the last shock received was set as the voltage level used for the MTS shock task,
which followed immediately.
First MTS shock task
This phase was identical for all five conditions of the experiment. The participants were asked to follow the
on-screen instructions and undertake a simple matching task. On each trial of the MTS, a single digit number
appeared in a box at the top of the screen as a sample stimulus, and three single-digit numbers in similar boxes
were presented along the bottom of the screen as comparisons. The participants selected the matching
comparison by clicking on it with the mouse. A correct response was given feedback in the form of the word
‘correct’ appearing in the centre of the screen accompanied by an audible beep. An incorrect response
produced the word ‘wrong’ without any sound. Correct responses were reinforced with the delivery of points
on a VR 9 schedule. These points appeared in the top right corner of the screen.
After approximately every 11th trial, the screen cleared and a red cross was presented along with two onscreen buttons. This configuration indicated that the participants now had the option to receive a shock and
continue or avoid the shock and thereby end the task. The button in the left corner read ‘Click here to end’
while that on the right read ‘Click here to receive a shock and continue with the task’. If the participants chose to
end the task they proceeded to the next stage of the experiment. If they chose to continue, the screen cleared
for 1 s and they then received a shock. The participants were prompted to rate the painfulness of the shock
using the VAS and then to click on a button at the bottom of the screen to continue with the task.
The experimenter, according to a standardised schedule, gradually increased the frequency and duration of
the shocks (protocol available from the authors); the voltage remained at the level set during the calibration
stage. Unbeknown to the participants there was a preset maximum of 15 shocks during this phase.
Participants who received all 15 were excluded from the remainder of the study and were thanked and
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debriefed. Participants who opted to end the shock task before receiving this maximum proceeded to the
intervention phase.
Full acceptance and distraction interventions and second MTS shock task
The participants were given a brief break of no more than 5-min before beginning the next stage of the
experiment. Upon starting, they were asked to follow the on-screen instructions, and the experimenter left the
room and remained outside until this phase was completed. Participants in both conditions were instructed to
watch a series of video clips in a particular order; they were told that they could replay any clip by re-clicking
on the on-screen button corresponding to that clip. At the end of each clip, participants were asked
to write down a brief summary of what they had just been told and what they did. The video clips for
the two full interventions differed in terms of content (i.e., acceptance versus distraction) but were closely
matched in terms of duration, word-count and non-intervention-specific instructions (e.g., all participants
were informed at regular intervals that the strategy they had been given would help them continue with the
shock task).
The first clip was identical for both the F-ACC and F-DIS conditions. Participants were first asked to write
down three thoughts that they had when they decided to end the previous shock task. The second clip involved
an experiential exercise, which differed across the two conditions. All of the participants were asked to open an
envelope, which had been left beside the computer. The F-ACC group then removed a piece of paper on which
was written ‘I cannot walk’. The participants were asked to repeat this phrase aloud while walking once
around the room. The aim of the exercise was to teach the participants to disconnect what they say to
themselves from what they actually do. In the F-DIS condition the participants found a blank piece of paper
inside the envelope and were asked to imagine a pleasant scene on it. They were then asked to pick up one of
the pieces of paper on which one of their own thoughts was written, and to repeat this thought aloud while
walking once around the room. They were asked to distract themselves from the thought by imagining the
pleasant scene. The aim of this version of the exercise was to teach the participants to distract themselves from
shock-related thoughts and feelings. The third clip, identical across conditions, asked participants to
summarise the exercise they had been given in Clip 2.
In the fourth clip, the F-ACC group were asked to consider that during the next task they could notice
shock-related thoughts and feelings, but continue with the task, regardless of the content of those thoughts.
The ‘walk round the room’ exercise was used as an example of a possible disconnection between thoughts and
behaviour. The F-DIS group were asked to consider that during the next task, they could distract themselves
from the shock-related thoughts and feelings, and continue with the task, by imagining their pleasant scene, as
they had during the ‘walk round the room’ exercise. In effect, both groups were encouraged to continue with
the shock task, but the F-ACC group were asked to do so regardless of their thoughts about the shocks
whereas the F-DIS group were asked to employ a distraction strategy to cope with the shock-related thoughts
in order to continue.
The fifth clip introduced a metaphor relevant to the particular intervention. Both groups were asked to
imagine that continuing with the shock task was comparable to crossing a muddy swamp. The F-ACC group
were told that the best way to cross the swamp was just to notice any unpleasant thoughts and feelings and
carry them with them as they continued to the other side of the swamp, because they could have those
thoughts and act differently to what they thought or felt. The F-DIS group were told that the best way to get
across the swamp was to think of more pleasant images while continuing to cross the swamp, because
removing the unpleasant thoughts and replacing them with more pleasant and positive things would help them
to continue with the shock task.
The sixth and seventh clips provided the participants with a rationale for the study. Both groups were told
that the aim of the study was to help people suffering from chronic disabling pain and therefore it was
important that they continue with the next shock task for as long as possible. The experimental task was
compared to a real life situation in which they suffered from chronic pain. In this imaginary scenario, the
matching task was a boring job that they had to do in order to earn money to support their family; the electric
shocks were like bouts of chronic pain that had to be endured in order to do the job.
The eighth video clip informed participants that if they did not wish to replay any video clip they should
report to the experimenter.
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The second MTS shock task was identical to the first for the F-ACC and F-DIS groups, except
for the inclusion of video-based reminders of the relevant intervention. The reminder video-clips differed in
content (i.e. either acceptance- or distraction-based), but were matched for word count and duration
(approximately 52 s). The video-clips appeared in the top left corner of the screen at the same time as the red
cross. The participants could replay the clip if they wished and then continue the task as before by choosing
whether or not to receive the next shock.
Instruction-based acceptance and distraction interventions and second MTS pain task
Participants assigned to these conditions were asked to remain in the room after the first shock task for a
short break. They were provided with magazines to read, while the experimenter remained outside. After
30 min had elapsed (i.e., duration matched with the ‘‘Full’’ intervention groups) the experimenter re-entered
the room and gave the participants written instructions explaining the next stage of the experiment.
Participants were informed that during the next shock task a video clip would appear on screen at the same
time as the red cross. The instructions on the video clip would advise them of the best way to cope with the
shocks and they were asked to use this information as best as they could.
The second shock task was identical to the first task except for the inclusion of the video-based
interventions. The video clips were presented in the top left corner of the screen alongside the red cross. The
clips for the two interventions were again matched for word count, duration (approximately 30 s) and nonintervention-specific information. The message conveyed in the I-ACC condition informed the participants
that the best way to deal with the task was to accept that the shock was going to hurt and to simply notice the
pain and continue with the task as best as possible. The I-DIS participants were informed that the best way to
deal with the task was to distract from the pain and continue with the task as best as possible. After the video
clip had been played the task continued as described for the first shock task, with the participants choosing
whether to receive the next shock or discontinue the experiment.
No-instructions condition and second MTS pain task
Participants in this condition remained in the room for 30 min after the first task. They were provided with
some magazines to read. After 30 min had elapsed the participants started the second shock task that was
procedurally identical to the first shock task.
Final measures
When the participants chose to discontinue the second shock task (or reached the maximum of 15 shocks),
the headphones and electrodes were removed. All participants (except No-I group) were asked to rate on an
11-point scale how useful (0 ¼ not useful 10 ¼ very useful) the assigned strategy was, and how difficult
(0 ¼ very easy 10 ¼ very difficult) it was to use during the shock task. They were also asked to summarise the
strategy in their own words.
Results
The data met the assumptions of normal distribution (Kolmogorov–Smirnov test) and thus parametric tests
were employed in subsequent analyses.
Pre-Intervention group differences
The means (+SE) are presented in Table 1. Three one-way ANOVAs confirmed that the five groups did
not differ significantly in terms of age, number of shocks received and pain ratings during the first MTS task
(all p’s4.09).
Shock tolerance
The means (+SE) for the number of shocks delivered in both tasks are presented in Table 1. The F-ACC
group showed the largest and the No-I group the smallest increase in number of shocks received from task 1 to
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Table 1
Mean (+SE) number of shocks delivered and subjective pain ratings
Age
First task
Shocks
Pain rating
Second task
Shocks
Pain rating
F-ACC
F-DIS
I-ACC
I-DIS
No-I
29.69 (2.13)
27.13 (.61)
29.06 (2.13)
27.69 (1.84)
28.81 (1.78)
5.44 (.99)
48.67 (6.369)
3.56 (.94)
53.18 (7.618)
3.44 (.758)
41.86 (7.294)
4.75 (.86)
52.37 (.8.263)
2.31 (.72)
46.34 (8.425)
8.38 (1.13)
42.60 (6.19)
4.69 (1.14)
51.64 (7.96)
3.75 (.77)
43.64 (6.05)
2.56 (.73)
55.09 (8.02)
2.50 (.88)
41.00 (8.85)
Note: Pain rating: 0 ¼ no pain, 100 ¼ pain as bad as it could be.
Table 2
Means (+SE) for ratings of usefulness and difficulty of assigned strategy
F-ACC
F-DIS
I-ACC
I-DIS
Usefulness
Difficulty
4.40
3.75
3.38
3.81
5.87
5.38
4.75
5.75
(.74)
(.65)
(.43)
(.51)
(.78)
(.79)
(.67)
(.57)
Note: Useful: 0 ¼ not useful, 10 ¼ very useful; Difficulty: 0 ¼ very easy, 10 ¼ very difficult.
task 2, with only the I-DIS group showing a decrease. A 2 5 mixed repeated measures ANOVA was
conducted with the time of testing (first versus second shock task) as the within-participant variable and the
five conditions as the between-participant variable. The ANOVA yielded a significant main effect for
condition (F (4, 75) ¼ 4.089, p ¼ .0047, Z2p ¼ .18), and an interaction between condition and time of testing
(F (4, 75) ¼ 7.165, po.0001, Z2p ¼ .27). Given the significant interaction, separate repeated measures ANOVAs
were conducted for each of the five conditions. The ANOVAs indicated that tolerance increased significantly
for F-ACC (F (1, 15) ¼ 14.48, p ¼ .0017, Z2p ¼ .49), and decreased significantly for I-DIS (F(1, 15) ¼ 5.618,
p ¼ .032, Z2p ¼ .026). None of the other conditions yielded a significant change in tolerance (all p’s4.1).
The F-ACC effect remained significant (i.e., po.01) after a Bonferroni correction, but I-DIS did not.
VAS pain and believability
The mean VAS pain ratings associated with the shocks during the first and second tasks are
presented in Table 2. The mean ratings given by the F-ACC, F-DIS and No-I groups were lower overall
(i.e. less pain) for the second relative to the first shock task, whereas the ratings given by the two instruction
only conditions increased. A 2 5 mixed repeated measures ANOVA yielded no significant effects
(all p’s4.4).
The relationship between the self-reported pain ratings and shock tolerance was used as a behavioural
measure of the believability of pain. Insofar as the acceptance intervention served to disconnect thoughts and
feelings from action, it was predicted that participants would increase the number of self-delivered shocks even
if they reported increased pain levels relative to the first task. Across the five conditions, the ratios of
participants who self-delivered more shocks even though they reported more pain were as follows: F-ACC, 6/6
participants; F-DIS, 2/4; I-ACC, 7/9; I-DIS, 2/7; No-I, 0/5.
To analyse the differential effects of the interventions, the two acceptance groups were combined, as were
the two distraction groups. The relation between self-reported pain ratings and shock tolerance was
statistically significant (w2 (1, 26), 7.095, p ¼ .008). In other words, a greater percentage of participants in the
two acceptance conditions who reported an increase in level of pain from pre- to post-intervention, also
increased the number of self-delivered shocks.
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Adherence measures
The participants in the four intervention groups provided a written summary of the assigned strategy at the
end of the experiment. Two independent raters were asked to categorise these summaries as being consistent
with either acceptance- or distraction-based strategies. All the participants in the two acceptance groups were
categorised as reporting an acceptance strategy, and all participants in the two distraction groups were
categorised as reporting a distraction strategy.
Finally, the participants in the four intervention groups were asked to rate their assigned strategy in terms of
usefulness and difficulty. No obvious differences emerged (Table 2). Two one-way ANOVAs indicated that
participants’ reports of usefulness and difficulty did not differ significantly across the four interventions:
Usefulness (F (3, 59) ¼ .505, p ¼ .7); Difficulty (F (3, 59) ¼ .507, p ¼ .7).
Discussion
The main findings of the current study are consistent with earlier research (e.g., Gutiérrez et al., 2004; Hayes
et al., 1999) in that only the F-ACC participants showed a significant increase in the number of self-delivered
shocks during the second task. Furthermore, the data indicate that participants from both of the acceptance
conditions showed lower levels of believability relative to the other groups. The F-DIS condition also
improved pain tolerance (but not significantly), whereas I-DIS reduced tolerance (but again non-significantly
when correcting for multiple tests). Interestingly, the No-I condition produced no effect in terms of tolerance,
which therefore suggests that the I-DIS intervention may have had a negative effect. Strictly speaking, of
course, neither distraction condition produced a significant effect, unlike the F-ACC condition, which is
consistent with previous research and current experimental predictions.
The five groups in the current study did not differ in terms of self-reported pain levels. In contrast, Gutiérrez
et al. (2004) reported a significant reduction in self-reported pain for the Distraction group. It is unclear why
this disparity emerged, but it may be related to procedural differences. For example, a possibly important
difference is that the protocols were implemented using video-clips in the current study, whereas Gutiérrez
et al. involved direct social interaction with a researcher–therapist. Interestingly, earlier research employing
the same video-based interventions as the current study also failed to find any changes in pain reports across
the groups (Johnson et al., 2004).
The present study is the first to show that experiential exercises and metaphors play a critical role in the
effectiveness of experimental analogues of acceptance-based interventions. Of course, the current findings
are restricted to a relatively artificial pain-induction task and a relatively small, non-clinical sample, but the
results do call for a careful and systematic analysis of how exercises and metaphors work in future analogue
research.
Acknowledgements
The preparation of this paper was supported by the Irish Research Council for the Humanities and Social
Sciences through a Government of Ireland Scholarship to the last author.
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