The effectiveness and equivalence of different versions of a brief online Best Possible Self (BPS) manipulation to temporary increase optimism and affect

Abstract

Background and objectives:
The Best Possible Self (BPS) has been found to be an effective manipulation to temporarily improve optimism and affect. The BPS has been used in different formats. In some versions, participants just write about their best possible future, while in others this is combined with imagery. An imagery only version has not been tested yet. The aim of the current study was to examine the effectiveness of three different versions of the BPS and their equivalence in improving optimism and affect.

Methods:
In an online study format, participants (N = 141) were randomly assigned to one of four conditions: (1) writing and imagery BPS; (2) writing BPS; (3) imagery BPS; and (4) a typical day (TD) control condition.

Results:
Results showed that each BPS condition significantly improved optimism (i.e. increased positive future expectancies and decreased negative future expectancies) and affect (i.e. increased positive affect and decreased negative affect). Equivalence testing showed that all online BPS conditions were equivalent in increasing optimism and affect, thereby confirming that both the writing and imagery elements of the BPS can independently from each other increase optimism and positive affect in a healthy population.

Limitations:
Only the immediate effects of the BPS formats on increasing optimism and affect were measured.

Conclusions:
The BPS manipulation can be employed in different ways for potential future exploration, depending on the research question, design and context and/or E-mental health applications for the treatment of individuals suffering from psychological complaints.

Full text

Journal of Behavior Therapy and Experimental Psychiatry 79 (2023) 101837
Available online 23 January 2023
0005-7916/© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
The effectiveness and equivalence of different versions of a brief online Best
Possible Self (BPS) manipulation to temporary increase optimism and affect
Jantine J.L.M. Boselie
a
,
*
, Linda M.G. Vancleef
b
, Susan van Hooren
a
, Madelon L. Peters
b
a
Clinical Psychology, Open University, 6401 DL, Heerlen, the Netherlands
b
Clinical Psychological Science, Maastricht University, 6200 MD, Maastricht, the Netherlands
ARTICLE INFO
Keywords:
Optimism
Positive affect
Best possible self
Writing
Imagery
Online intervention
ABSTRACT
Background and objectives: The Best Possible Self (BPS) has been found to be an effective manipulation to
temporarily improve optimism and affect. The BPS has been used in different formats. In some versions, par-
ticipants just write about their best possible future, while in others this is combined with imagery. An imagery
only version has not been tested yet. The aim of the current study was to examine the effectiveness of three
different versions of the BPS and their equivalence in improving optimism and affect.
Methods: In an online study format, participants (N =141) were randomly assigned to one of four conditions: (1)
writing and imagery BPS; (2) writing BPS; (3) imagery BPS; and (4) a typical day (TD) control condition.
Results: Results showed that each BPS condition signicantly improved optimism (i.e. increased positive future
expectancies and decreased negative future expectancies) and affect (i.e. increased positive affect and decreased
negative affect). Equivalence testing showed that all online BPS conditions were equivalent in increasing opti-
mism and affect, thereby conrming that both the writing and imagery elements of the BPS can independently
from each other increase optimism and positive affect in a healthy population.
Limitations: Only the immediate effects of the BPS formats on increasing optimism and affect were measured.
Conclusions: The BPS manipulation can be employed in different ways for potential future exploration, depending
on the research question, design and context and/or E-mental health applications for the treatment of individuals
suffering from psychological complaints.
1. Introduction
Optimism is the tendency to expect that good things will happen in
the future (Carver, Scheier, & Segerstrom, 2010). This tendency to hold
global positive future expectancies has been associated with benecial
coping strategies (Rasmussen, Wrosch, Scheier, & Carver, 2006),
applying different coping strategies more exibly (Rasmussen et al.,
2006; Solberg Nes, Segerstrom, & Sephton, 2005), increased subjective
well-being and longevity and decreased illness (King, 2001; Lee et al.,
2019; Rozanski, Bavishi, Kubzansky, & Cohen, 2019). Importantly,
research has shown that optimism is modiable with a manipulation
called the Best Possible Self (BPS; Peters, Flink, Boersma, & Linton,
2010), making it possible to investigate the causal inuence of opti-
mism. The BPS is a positive future thinking technique based on work by
King (2001) in which participants are typically asked to write about and
imagine a life in the future where everything turned out for the best. In
the control condition, participants write about and imagine a typical day
(TD). A recent meta-analysis demonstrated that the BPS manipulation is
effective in increasing optimism and positive affect (Carrillo et al.,
2019).
The BPS has been applied successfully with different delivery modes
(i.e. online or face-to-face; individually or in a group) and with different
components, such as a writing component only or combining writing
and imagery components (Carrillo et al., 2019; Loveday, Lovell, &
Jones, 2018). Both writing and imagery have been shown to have
benecial effects. In the case of writing, results of a meta-analysis
demonstrated that disclosing information, thoughts, and feelings about
personal and meaningful topics through writing (also known as exper-
imental emotional disclosure) has psychological and health benets
(Frattaroli, 2006). Similar to the positive effects of writing, a brief
guided mental imagery exercise has been shown to have benecial ef-
fects on mental health (Bigham, McDannel, Luciano, & Salgado-Lopez,
* Corresponding author. Clinical Psychology, Open University, P.O. Box 2960, 6401 DL, Heerlen, the Netherlands.
E-mail addresses: jantine.boselie@ou.nl (J.J.L.M. Boselie), l.vancleef@maastrichtuniversity.nl (L.M.G. Vancleef), Susan.vanHooren@ou.nl (S. van Hooren),
madelon.peters@maastrichtuniversity.nl (M.L. Peters).
Contents lists available at ScienceDirect
Journal of Behavior Therapy and Experimental Psychiatry
journal homepage: www.elsevier.com/locate/jbtep
https://doi.org/10.1016/j.jbtep.2023.101837
Received 17 January 2022; Received in revised form 23 December 2022; Accepted 21 January 2023

Journal of Behavior Therapy and Experimental Psychiatry 79 (2023) 101837
2
2014). In an attempt to maximise the effectiveness of the BPS exercise as
a single session manipulation, Peters et al. (2010) added a 5 min mental
imagery component to the original writing exercise. However, moder-
ator analysis of a recent meta-analysis showed that the BPS manipula-
tion with or without the imagery component yielded similar outcomes
(Carrillo et al., 2019). Nevertheless, the effectiveness of the BPS with
and without the imagery component have not been directly compared in
one study, neither whether imagery alone can be an effective
manipulation.
Since both writing and imagery exercises in general have been shown
to be effective (Bigham et al., 2014; Frattaroli, 2006) but the BPS
manipulation with or without the imagery component yield similar
outcomes (Carrillo et al., 2019), we hypothesised that all three BPS
formats (writing and imagery BPS; writing BPS; imagery BPS) compared
to the control TD condition 1) are effective in improving optimism (i.e.
increasing positive future expectancies and decreasing negative future
expectancies) and affect (i.e. increasing positive affect and decreasing
negative affect), and (2) all three BPS formats are equivalent in effec-
tiveness. Insight into the independent effects of both BPS elements (i.e.
writing and imagery) in improving optimism and affect increases the
ability to apply the BPS more exibly, tailored to study goals and/or
E-mental health applications for the treatment of individuals suffering
from psychological complaints.
2. Method
2.1. Participants
A total of 141 (22 male; mean age =22.1 (SD =7.8) years, age range
18–79 years) healthy participants were included in this online study.
Participants were recruited via posters shown at diverse locations at
Maastricht University and advertisements on social media platforms.
Furthermore, psychology students could sign up for the study via a
research participation platform for course credits. Participants were
randomly assigned within the online program (Qualtrics) to one of four
conditions: BPS writing and imagery condition (n =34; 5 male; mean
age =21.3 (SD =6.1) years); BPS writing condition (n =37; 6 male;
mean age =20.6 (SD =2.4) years); BPS imagery condition (n =37; 5
male; mean age =24.5 (SD =12.4) years) and the TD control condition
(n =32; 6 male; mean age =21.7 (SD =6.3) years). One participant did
not disclose her age (BPS imagery condition). Participants could choose
to either execute the study in Dutch (n =48) or in English (n =93),
depending on their native language/preference.
2.2. Optimism manipulation
Participants in the BPS condition were required to either 1) write and
imagine, 2) write or 3) imagine about a life in the future where every-
thing turned out for the best. Participants in the control condition had to
write about a typical day. The BPS instructions were as follows (Peters
et al., 2010; Sheldon & Lyubomirsky, 2006): Think about your best
possible self means that you imagine yourself in the future, after everything
has gone as well as it possibly could. You have worked hard and succeeded at
accomplishing all the goals of your life. Think of this as the realisation of your
dreams, and that you have reached your full potential. The TD instructions
were as follows: Think about your typical day’ means that you take notice of
ordinary details of your day that you usually don’t think about. These might
include particular classes or meetings you attend to, people you meet, things
you do, typical thoughts you have during the day. Think of this as moving
through your typical day, hour after hour. All participants were requested
to think for 1 min about what to write and/or imagine. Participants were
than instructed to write uninterrupted for 15 min, or imagine for 5 min
or write and imagine their BPS for 20 min (i.e. 15 min writing and 5 min
imagery). Participants in the TD condition were requested to think for 1
min about what to write and imagine, then to write for 15 min, followed
by 5 min of imaging the story they had just nished writing.
2.3. Questionnaires
2.3.1. Optimism
The Life Orientation Test-Revised (LOT-R) (Scheier, Carver, &
Bridges, 1994) measures dispositional optimism and was used in the
current study to examine baseline differences in optimism between the
conditions. It consists of 10 items: three positively phrased items (e.g.
‘I’m always optimistic about my future’), three negatively phrased items
(e.g. ‘I rarely count on good things happening to me’) and four ller
items (e.g. ‘It’s important for me to keep busy’). The items are rated on a
ve-point Likert scale, ranging from 1 (strongly disagree) to 5 (strongly
agree). The total LOT-R score is obtained by summation of the scores on
the positively phrased items and the reversed scores on the negatively
phrased items. The total score ranges from 10 to 30. Higher scores reect
higher levels of dispositional optimism. The LOT-R has been demon-
strated to be a reliable and valid measurement instrument (Scheier et al.,
1994). A Dutch and English version of the LOT-R was used. The internal
consistency in this study was satisfactory with a Cronbach’s alpha’s of
0.76 (Dutch version) and 0.84 (English version).
2.3.2. Affect
Affect was measured with the Positive and Negative Affect Schedule
(PANAS) (Watson, Clark, & Tellegen, 1988). The PANAS consists of 20
items, with 10 items that measure positive affect (PA; e.g., ‘excited’ and
‘inspired’) and 10 items that measure negative affect (NA; e.g. ‘nervous’
and ‘afraid’). Participants indicate the degree to which a certain feeling
is present at that moment on a ve-point Likert scale ranging from 1 (not
at all) to 5 (extremely). Subscale scores can range from 10 to 50, with
higher scores on NA items reecting higher levels of emotional distress.
In contrast, high PA scores correspond to experiencing more feelings
that are pleasurable. The PANAS subscales have been demonstrated to
be valid and reliable (Crawford & Henry, 2004). Cronbach’s alphas in
the present study for the baseline measurement on the positive subscale
were 0.84 (Dutch version) and 0.84 (English version). Cronbach’s alphas
for the baseline measurement on the negative subscale were 0.90 (Dutch
version) and 0.83 (English version).
2.3.3. Future expectancies
The Future Expectancies (FEX) scale (Hanssen, Peters, Vlaeyen,
Meevissen, & Vancleef, 2013) is an adaptation of the Subjective Prob-
ability Task (SPT; MacLeod, Byrne, & Valentine, 1996) and measures
positive and negative future expectancies. It consists of 20 items that
make statements about positive (n =10; e.g. ‘people will admire you’)
and negative (n =10; e.g. ‘things will not turn out as you had hoped’)
future events. The statements cover ve different domains (work,
health, personal, social and general). The items are rated on a
seven-point Likert scale, ranging from 1 (not at all likely to occur) to 7
(extremely likely to occur). Higher scores reect a higher estimated
likelihood of positive (FEX-Pos) or negative (FEX-Neg) future events.
Total scores range from 10 to 70. The internal consistency of the FEX
subscales have been demonstrated to be satisfactory (Hanssen et al.,
2013). Cronbach’s alphas in the present study for the baseline mea-
surement on the positive subscale were 0.91 (Dutch version) and 0.85
(English version). Cronbach’s alphas for the baseline measurement on
the negative subscale were 0.87 (Dutch version) and 0.83 (English
version).
2.4. Procedure
Participants were informed about the online study procedure. After
they had given consent for their participation, they completed questions
on demographic information, the LOT-R, the FEX and the PANAS. Next,
participants completed one of the four manipulations: writing and im-
agery BPS; writing BPS; and imagery BPS, writing and imagery TD. Af-
terwards, the participants were asked to ll out the FEX and the PANAS
again, to measure the changes in optimism and affect, respectively. The
J.J.L.M. Boselie et al.

Journal of Behavior Therapy and Experimental Psychiatry 79 (2023) 101837
3
data were collected online using the Qualtrics program. Participants
could indicate whether they wanted to receive 0.5 research points
(available for psychology students of … University) or enter a lottery,
where ve participants were randomly selected to receive a
€
5-euro
voucher. Participants were debriefed via e-mail after data collection for
the study was completed. This research was approved by the … …
University.
2.5. Data analyses
In total, 243 participants were included in the study. Participants
who provided incomplete data were removed from the dataset (n =96).
Data from six participants were removed (remaining N =141) as the
total duration of the study completion exceeded more than 2 h, while the
expected study duration was estimated to take at most around 26 min
(BPS condition: 1 min contemplating about the story to write, 15 min
writing, 5 min imagery and 5 min to complete the questionnaires).
Durations above 2 h are not considered to represent a conscientious
attempt. Data were checked for normal distribution and reliability an-
alyses were performed on the LOT-R questionnaire, positive and nega-
tive PANAS questionnaires, and the positive and negative FEX
questionnaires. Analysis of variance analyses (ANOVA’s) were used to
check for baseline differences between the conditions for optimism
(LOT-R) and age. Sensitivity analysis (Lakens, 2022; Perugini, Gallucci,
& Costantini, 2018) with G*Power (Faul, Erdfelder, Lang, & Buchner,
2007) was performed to determine which effect sizes this study is sen-
sitive to detect, as a priori sample size calculation was not performed.
The effectiveness of the optimism manipulation on increasing positive
and negative future expectancies and positive and negative affect was
tested with repeated measures ANOVAs with condition as a between
subjects’ factor, and time (pre-and post-measurements of the FEX and
PANAS) as a repeated factor. A signicant condition ×time interaction
effect was followed up with an ANOVA with difference scores and
posthoc pairwise comparisons to test the differences between the four
conditions. To examine the changes in the FEX and PANAS scores within
each condition, follow-up analyses were performed using
paired-samples t-tests. Cohen’s d was calculated (based on the formula d
=t (n1 +n2)/√ n1n2 √ df) derived from Nakagawa and Cuthill (2007).
In case of non-signicant differences between the three BPS formats,
equivalence tests were conducted. Additional equivalence testing was
necessary, as failing to nd a signicant difference between groups is not
equal to showing that the groups were comparable in their effect (i.e.
equivalently effective; Lakens, 2017; Lakens, Scheel, & Isager, 2018). To
test whether the BPS groups were equivalent in their effects on
improving optimism and affect, equivalence testing was conducted with
a two one-sided test (TOST) procedure using a predesigned spreadsheet
(Lakens, 2017). In the TOST procedure, an upper and lower equivalence
bound is specied based on the smallest effect size of interest (SESOI).
Given our sample size,
α
(0.05) and desired power (0.9), our SESOI was
determined as Cohen’s d =0.8, with the resulting equivalence bounds
being d =- 0.8 and d =0.8.
3. Results
3.1. Baseline descriptives
Results of the ANOVA’s revealed no signicant differences between
the three BPS formats (BPS writing and imagery (optimism: m =13.9;
SD =4.50; age: m =21.3; SD =6.13), BPS writing (optimism: m =13.9;
SD =4.50; age: m =20.3; SD =6.13), BPS imagery (optimism: m =14.0;
SD =4.42; age: m =24.5; SD =12.42) and TD condition (optimism: m =
15.3; SD =3.75; age: m =21.7; SD =6.29) in optimism level (i.e., Lot-R
questionnaire; F (3, 137) =0.85, p =.47) and age (F (3, 137) =1.77, p =
.16) at baseline. Sensitivity analysis (Lakens, 2022; Perugini et al., 2018)
with G*Power (Faul et al., 2007) indicated that repeated measures
ANOVA (4 groups; 4 measurements) with N =141 would be sensitive to
detect small effects (i.e.,
η
2 =0.014; Cohens d =0.24) with 80% power
(alpha =.05).
3.2. Manipulation effects
The repeated measures ANOVAs revealed a signicant interaction
effect for FEX positive future expectancies (F (3, 137) =5.18, p =.01,
η
p
2
=0.10), FEX negative future expectancies (F (3, 137) =3.69, p =
.01,
η
p
2
=0.08), PANAS PA (F (3, 137) =3.74, p =.01,
η
p
2
=0.08) and
PANAS NA (F (3, 137 =2.80, p =.04,
η
p
2
=0.06). See Table 1 for the
mean (SD) of future expectancies and affect pre- and post-manipulation,
displayed per condition. Follow-up pairwise comparisons showed that
all BPS conditions (writing and imagery; writing; imagery) signicantly
differed from the TD condition on the difference scores for FEX positive
future expectancies (p =.03, p <.001, p =.02,respectively), PANAS PA
(p =.03, p =.05, p =.04, respectively) and FEX negative future ex-
pectancies (p =.03, p =.02, respectively), with the exception of the BPS
writing and imagery format compared to the TD condition on FEX
negative future expectancies (p =.28). None of the BPS format condi-
tions differed signicantly from the TD condition on decreasing PANAS
NA (p =.11, p =.06, p =.23, respectively). Follow-up paired t-test
analyses (Table 2) showed that participants in the BPS writing and im-
agery condition, BPS writing and BPS imagery all scored signicantly
higher on positive future expectancies and PA, and lower on negative
future expectancies and NA after the manipulation. Participants in the
TD condition did not score signicantly different on any of the variables
following the TD instruction. To test whether the BPS groups were
equivalent in their effectiveness in increasing FEX future expectancies
and PANAS affect scores, equivalence testing was conducted. Results of
the TOST procedure showed that the BPS conditions were equivalent in
their effectiveness, with the observed effect sizes falling signicantly
within the equivalent bounds of d =- 0.8 and d =0.8. See Table 3 for the
results of the TOST procedure.
4. Discussion
The current study’s results show that both elements of the BPS
manipulation, namely writing and imagery, are independently effective
in improving optimism (i.e. increasing positive future expectancies and
decreasing negative future expectancies) and affect (i.e. increasing
positive affect and decreasing negative affect), as every online Best
Possible Self (BPS) manipulation format (i.e., writing and imagery BPS;
writing BPS; imagery BPS) was found to be equivalently effective in
improving optimism and affect. This nding is in line with previous
studies, which have shown that either writing or imagery have bene-
cial effects on emotional and cognitive variables (Bigham et al., 2014;
Conroy & Hagger, 2018; Frattaroli, 2006; King, 2001). In the current
study, we showed that an imagery exercise as short as 5 min may already
have positive effects on well-being, albeit possibly only immediate ef-
fects. Notably, recent meta-analyses showed that there was no evidence
that adding an imagery task increased the benecial effects of a writing
task (Carrillo et al., 2019; Heekerens & Eid, 2021). Similarly, the current
study’s effect sizes and equivalence testing do not support the idea that
combining both elements leads to a greater manipulation effect. One
could argue that this nding may not be surprising, as evidence of a
meta-analysis suggests that the efcacy of all psychological bona de
treatments are roughly equivalent (i.e. Dodo bird verdict; Wampold
et al., 1997). However, later meta-analyses and comparison studies have
identied differences between different treatments or found only sup-
port for this premise when looking at secondary outcome variables
(Marcus, O’Connell, Norris, & Sawaqdeh, 2014; Tolin, 2010). Further-
more, previous research showed that mental imagery had stronger ef-
fects on emotions and cognitions than verbal processing of the same
material (Holmes, Lang, & Shah, 2009). Hence, current study results add
to previous ndings and shed light on the efcacy of the different BPS
formats.
J.J.L.M. Boselie et al.

Journal of Behavior Therapy and Experimental Psychiatry 79 (2023) 101837
4
Next to the benets of being able to investigate the causal inuence
of optimism and affect and being able to conduct research online, the
current study’s results specically show that the BPS manipulation can
be employed in different and exible ways for potential future explo-
ration, depending on the research question, design and context. The
benet of writing compared to imagery is for example the enhanced
controllability for research leader and/or therapist. A possible benet of
mental imagery is that it can be integrated, employed more easily and is
exible in daily life. Moreover, as both writing and imagery are inde-
pendently effective in improving optimism and affect, one could
consider taking into account the personal preference of the participant.
People differ for example in their ability to imagine (i.e. vividness;
Cumming & Eaves, 2018) or writing ability because of for example
dyslexia and functional illiteracy, making them more inclined to prefer
one method over the other. It should be noted that the current study’s
results only refer to the immediate effects after conducting the BPS once.
Future research should examine whether a combined writing and im-
agery BPS intervention, which is applied multiple times and for a longer
duration may have a more benecial effect on the long term. It is
conceivable for example, that for longer durations one may want to
guide participants in their future orientation with a writing component,
but give them the exibility to use the imagery exercise in daily life or
with the purpose of having a booster effect.
Although participants reported signicantly less negative affect
within all the BPS format conditions and not in the TD condition, this
effect failed to reach signicance when the BPS conditions were directly
compared with the TD condition. This is in line with results from a meta-
analysis examining the effects of the BPS manipulation (Carrillo et al.,
2019). The obtained effect size for negative affect was considerably
small (d =0.192), which was even reduced to nil (d =- 0.047) when the
only study with a non-active control group (i.e. waiting list) was
excluded from the analysis. In contrast, the meta-analysis showed a
moderate effect size (d =.511) of the BPS manipulation on positive
affect. The authors suggested that these results imply that the BPS
manipulation might be more effective in increasing positive affect than
in decreasing negative affect, which is in line with the aim of positive
psychology exercises to promote positive emotions (protective factors)
rather than purely focussing on decreasing negative emotions (Layous &
Lyubomirsky, 2014). Surprisingly, all the BPS formats signicantly
decreased negative future expectancies compared to the TD condition,
with the exception of the BPS writing and imagery format. Thus,
although participants in the BPS writing and imagery format reported
signicantly less negative future expectancies, this effect was not
signicantly different from participants in the TD condition. It is unclear
why this effect was found solely for the BPS writing and imagery format.
Previous studies have repeatedly found that participants in the writing
Table 1
Mean (SD) of future expectancies and affect pre- and post-manipulation, displayed per condition.
BPS writing and imagery (n =34) BPS writing (n =37) BPS imagery (n =38) Typical Day (TD) (n =32)
Pre-
measurement
Post-
measurement
Pre-
measurement
Post-
measurement
Pre-
measurement
Post-
measurement
Pre-
measurement
Post-
measurement
m (SD) m (SD) m (SD) m (SD) m (SD) m (SD) m (SD) m (SD)
Positive future
expectancies
51.32 (9.15) 55.68 (6.64) 49.08 (8.89) 54.49 (7.26) 51.13 (7.84) 55.55 (7.54) 53.22 (6.52) 53.59 (8.56)
Negative future
expectancies
35.09 (11.28) 31.00 (10.07) 36.19 (8.23) 30.78 (8.23) 34.82 (9.16) 29.32 (8.98) 32.75 (8.18) 31.91 (10.09)
Positive affect 32.79 (7.28) 35.26 (6.71) 30.65 (6.84) 32.81 (7.88) 33.76 (5.92) 36.05 (5.67) 34.03 (6.86) 33.28 (7.13)
Negative affect 20.06 (7.88) 16.79 (6.39) 20.49 (6.64) 17.03 (5.81) 19.63 (8.02) 16.76 (7.99) 19.72 (6.92) 19.13 (8.22)
BPS =Best Possible Self; TD =Typical Day (control condition).
Table 2
Results of the paired-samples t-test follow-up analyses on future expectancies and affect, displayed per condition.
BPS writing and imagery BPS writing BPS imagery TD
m (SD) t Cohen’s
d (CI)
m (SD) t Cohen’s
d (CI)
m (SD) t Cohen’s
d (CI)
m (SD) t Cohen’s
d (CI)
Positive future
expectancies
4.35
(5.66)
4.49** 1.56
(1.01–2.11)
5.41
(5.75)
5.72** 1.91
(1.35–2.46)
4.42
(5.42)
5.03** 1.68
(1.14–2.21)
.38
(5.77)
.37 0.13
(−.37–.63)
Negative future
expectancies
−4.09
(7.99)
2.98* 1.04
(.52–1.55)
−5.41
(5.62)
5.85** 1.95
(1.39–2.51)
−5.50
(5.24)
6.47** 2.16
(1.58–2.74)
−.84
(7.28)
.66 0.24
(−.26–.74)
Positive affect 2.47
(5.41)
2.67* 0.93
(.42–1.44)
2.16
(4.89)
2.69* 0.90
(.41–1.38)
2.29
(4.21)
3.35** 1.12
(.62–1.61)
−.75
(3.39)
1.25 0.45
(−.06–.95)
Negative affect −3.27
(5.11)
3.72** 1.30
(.76–1.83)
−3.46
(4.99)
4.22** 1.41 (.89-
1,92)
−2.87
(3.86)
4.58** 1.53
(1.00–2.05)
−.59
(4.10)
.82 0.29
(−.21–.80)
BPS =Best Possible Self; TD =Typical Day (control condition). CI =95% condence interval of Cohen’s d. * =p <.05; ** =p <.001.
Table 3
Results of the equivalence testing.
Positive future expectancies Negative future expectancies Positive affect Negative affect
d t df p d t df p d t df p d t df p
BPS writing and imagery &
BPS writing
−0.19 2.59 68,66 0.006 0.19 2.54 58,70 0.007 0.06 −3.11 66,69 0.001 0.04 −3.21 68,18 0.001
BPS writing and imagery &
BPS imagery
0.01 3.33 68,34 0.001 0.21 2.48 55,90 0.008 0.04 3.21 62,17 0.001 0.09 2.99 61,09 0.002
BPS writing & BPS imagery 0.18 −2.63 68 0.005 0.02 −3.31 67,75 0.001 0.03 3,25 65,57 0.001 0.13 2.81 61,96 0.003
BPS =Best Possible Self, d =observed Cohen’s d. Note: the BPS conditions are equivalent in their effects on all the variables, as the scores fall within the equivalence
bounds d =- 0.8 and d =0.8. Based on the output of a TOST spreadsheet (Lakens, 2017).
J.J.L.M. Boselie et al.

Journal of Behavior Therapy and Experimental Psychiatry 79 (2023) 101837
5
and imagery BPS compared to participants in the TD condition report
less negative future expectancies after the BPS exercise (e.g. Boselie,
Vancleef, & Peters, 2016, 2017; Boselie, Vancleef, Smeets, & Peters,
2014; Hanssen et al., 2013).
Having both BPS elements being independently effective increases
the ability to apply the BPS manipulation more exibly, tailored to a
study design, but also increases the exibility for the integration of the
BPS in online interventions or E-mental health applications for the
treatment of individuals suffering from psychological complaints. Pre-
vious research has shown that positive psychology exercises in general
can be applied in the clinical setting as a stand-alone intervention. The
BPS manipulation has been successfully incorporated in larger positive
psychology interventions (D’raven, Moliver, & Thompson, 2015; Peters
et al., 2017; Pietrowsky & Mikutta, 2012) in patients with depression or
combating chronic pain conditions and has been implemented as an
adjuvant to contemporary psychological treatment approaches such as
cognitive behavioural therapy (Bannink, 2018; Geschwind, Arntz,
Bannink, & Peeters, 2019). The Best Possible Self (social relationships: i.
e. imagine and write about your best possible future interpersonal re-
lationships) exercise signicantly reduced hopelessness and increased
optimism in a population of suicidal patients that were admitted to an
inpatient psychiatric unit (Huffman et al., 2014). Having the option to
exibly adjust the BPS exercise to the patient and/or therapist prefer-
ence increases the possible clinical application possibilities. It should be
noted that the BPS exercise is often adjusted in clinical populations in
order to account for the potentially harmful impact of eliciting aware-
ness between a self-perceived greater discrepancy (Self Discrepancy
Theory; Higgins, 1989) between the actual self (i.e. who you are now)
and the ideal self (i.e. who you want to be). For instance, the BPS in-
structions for chronic pain patients were more directive and concrete
and they were asked to formulate what their best possible future will
look like, despite pain (Peters et al., 2017). Future research is necessary to
examine the BPS as a stand-alone intervention, and whether modied
instructions are necessary in a clinical setting and what the long-term
clinical effects are.
The ndings of this study have to be seen in the light of some limi-
tations. First, the generalisability of present ndings are limited, as the
sample consisted of predominantly younger adults with the same cul-
tural background (Western Europe). Second, a priori sample size
calculation was not performed. Sensitivity analysis indicated that this
study would not be able to reliably detect effects smaller than
η
2 =
0.014/Cohens d =0.24. A third limitation concerns the lack of follow-up
measurements. The current study assessed only the immediate effects of
the BPS intervention. Additionally, it is unclear whether there is a dose-
response relationship between the number of times the BPS exercise is
repeated and the effectiveness of the BPS exercise or whether there are
additional benets of combining writing and imagery components when
applying the BPS multiple times. Adding short and long-term measure-
ments provides the opportunity to exclude that the benecial effects of
the BPS are merely due to a priming effect and/or mood induction
(Heekerens & Eid, 2021). Additionally, several pairwise comparisons
were made, creating a risk of alpha ination for individual comparisons.
A common solution is to adjust the signicance threshold (alpha level)
during the null hypothesis, although some have argued this is only
necessary when conducting exploratory research (Cramer et al., 2016)
or if researchers make a decision about a joint null hypothesis after
rejecting at least one (and not all) constituent null hypotheses (i.e.
disjunction testing; Rubin, 2021). Finally, online assessment enables less
control over the task and procedure. However, the current study results
demonstrated that the BPS manipulation can be successfully deployed in
an online setting, which is in line with previous research (Carrillo et al.,
2019; Loveday et al., 2018). In a meta-analysis of experimental disclo-
sure, psychological health effect sizes actually tended to be larger when
studies had participants disclose at home compared to a controlled
setting (Frattaroli, 2006). The author suggested that participants feel
more comfortable at home, which as a result, may increase engagement
in the disclosure process.
In conclusion, both BPS elements (i.e. writing and imagery) were
successful both in combination and independently from each other in
increasing optimism and positive affect in a healthy population, making
it possible to apply the BPS exibly, considering the research question
and design. Future research is necessary to examine the effects of
employing an online BPS to treat psychological complaints and identify
the possible underlying working mechanisms of the BPS manipulation.
Declaration of interest, and role of funding organizations
This research was funded by grant 022.003.038 from NWO, The
Netherlands Organisation for Scientic Research, awarded to the Dutch-
Flemish Research School of Experimental Psychopathology. There are
no nancial or other relationships that might lead to a conict of
interest.
CRediT authorship contribution statement
Jantine J.L.M. Boselie: Conceptualization, Methodology, Formal
analysis, Investigation, Resources, Data curation, Writing – original
draft. Linda M.G. Vancleef: Conceptualization, Methodology, Writing –
review & editing. Susan van Hooren: Writing – review & editing.
Madelon L. Peters: Conceptualization, Methodology, Writing – review
& editing, Supervision, Funding acquisition.
Declaration of competing interest
There are no nancial or other relationships that might lead to a
conict of interest in submitting this manuscript. All authors have
contributed read and approved the paper. No other manuscripts from
the same dataset have been submitted or published elsewhere.
Data availability
Data will be made available on request.
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