# Can vibratory bilateral stimulation reduce the emotionality and vividness of negative autobiographical memories?

Cassandre Armand, Fabrice Guillaume, Arnaud Rey

► To cite this version:

Cassandre Armand, Fabrice Guillaume, Arnaud Rey. Can vibratory bilateral stimulation reduce the emotionality and vividness of negative autobiographical memories?. Journal of Behavior Therapy and Experimental Psychiatry, 2026, 91, pp.102090. 10.1016/j.jbtep.2026.102090. hal-05442203v2

HAL Id: hal-05442203

https://hal.science/hal-05442203v2

Submitted on 25 Feb 2026

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons CC BY 4.0 - Attribution - International License
# Can vibratory bilateral stimulation reduce the emotionality and vividness of negative autobiographical memories?

Cassandre Armand<sup>a,b,*</sup>, Fabrice Guillaume<sup>a</sup>, Arnaud Rey<sup>a,b</sup>

## ARTICLE INFO

**Keywords:**

Eye Movement Desensitization and
Reprocessing (EMDR)

Autobiographical memory

Emotional memory

Vibratory bilateral stimulation

## ABSTRACT

Eye Movement Desensitization and Reprocessing (EMDR) is one of the recommended, evidence-based treatments for post-traumatic stress disorder (PTSD). Although the effects of eye movements on the desensitization of traumatic memories have been extensively documented, there are less studies on the effectiveness of vibratory bilateral stimulation (VBS), even though this type of stimulation is often used in clinical practice. In the present study, we tested the effect of VBS on the emotionality and vividness of autobiographical negative memories in healthy participants. After selecting two moderate negative memories, participants had to rate one of these memories on emotionality and vividness scales and to recall it four times without any stimulation or with VBS. In the control condition (without stimulation), emotionality ratings increased after recall, whereas vividness remained unchanged. Most importantly, VBS prevented this emotional rise without affecting vividness. We also found that the more participants were distracted by the VBS, the greater was the reduction in emotionality. These findings therefore provide new encouraging empirical evidence in favour of using VBS to reduce the emotional burden of negative autobiographical memories.

## 1. Introduction

Emotional memories, particularly aversive and intrusive ones, are a key feature of numerous psychological disorders (Brewin et al., 2010; Kip et al., 2023) like depression (Mihailova & Jobson, 2018; Reynolds & Brewin, 1999; Spenceley & Jerrom, 1997), social anxiety disorder, (Seinsche et al., 2023), social phobia (Hackmann et al., 2000), agoraphobia (Day et al., 2004), and obsessive-compulsive disorders (Speckens et al., 2007), among others. These memories are particularly associated with Post-Traumatic Stress Disorder (PTSD) that occurs following exposure to a traumatic event – an event experienced by the subject as a threat to their physical or moral integrity, or that of others. Intrusions of the very emotional memory of this event are a core symptom of PTSD (American Psychiatric Association, 2015), making this memory an important target for PTSD treatment.

Eye Movements Desensitization and Reprocessing (EMDR) is one of the recommended therapies for the treatment of PTSD (World Health Organization, 2013) (see Martin et al., 2021, for a systematic review of PTSD treatment guidelines) and it has now received robust empirical support (e.g., De Jongh et al., 2024). The pivotal procedural element of

the therapy involves the patient recalling a distressing autobiographical memory – along with associated thoughts, emotions, and bodily sensations – while simultaneously engaging in a secondary task. As suggested by the name of the therapy, this secondary task traditionally consisted in performing Eye Movements (EM) from left to right extremities of the visual field. Those EM are induced by following a target, typically the clinician's index finger moving rapidly and horizontally from left to right. Other forms of Alternating Bilateral Stimulation (ABS) appeared later such as bilateral light tactile taps on the patient's hand or binaural sounds played in headphones (Shapiro, 2001).

These variations in ABS were implemented in accordance with one of the earliest hypotheses proposed to account for the effect of ABS in the modulation of emotional autobiographical memories, namely the inter-hemispheric interaction (IHI) hypothesis (Propper & Christman, 2008). Built on the Hemispheric Encoding/Retrieval Asymmetry (HERA) model (Tulving et al., 1994), this hypothesis posits that the effects of ABS rely on two essential features: their bilateral and alternating nature, which are thought to enhance the interaction between right and left cerebral hemispheres. This increased communication is hypothesized to facilitate access to traumatic memories without inducing overwhelming distress,

<footnote><sup>a</sup> Aix Marseille Univ, CNRS, CRPN, Marseille, France</footnote>

<footnote><sup>b</sup> Institute of Language, Communication and the Brain, Aix-Marseille Université, France</footnote>

<footnote>* Corresponding author. Centre for Research in Psychology and Neuroscience (CRPN) – UMR 7077, CNRS, Aix-Marseille Université, 3, place Victor Hugo – Case D, Cedex 3, 13331, Marseille, France.</footnote>

<footnote>E-mail address: cassandre.armand@univ-amu.fr (C. Armand).</footnote>
thereby aiding the reprocessing of these memories and potentially
reducing associated negative emotions.

However, other studies have challenged the IHI hypothesis by
showing that vertical EM exhibited a comparable effect (Gunter &
Bodner, 2008), thereby suggesting that the bilateral and horizontal
characteristics of the ABS may not be the critical therapeutic ingredient
for modulating emotional memories. Therefore, other studies have
gradually proposed to account for the effects of ABS in EMDR using the
Working Memory (WM) Hypothesis (Andrade et al., 1997; Gunter &
Bodner, 2008; Kavanagh et al., 2001; Van Den Hout & Engelhard, 2012).
Based on Baddley and Hitch's model of working memory (Baddeley &
Hitch, 1974), this account proposes that ABS should be considered as a
dual-task (dual as they are performed simultaneously during the recall of
the target memory) and that their effects on the reduction of emotion-
ality and vividness of the target memory are dependent on their degree
of WM taxation. When recalled, the memory enters a labile state,
allowing for its modulation. Performing a dual task induce a competition
in WM. The target memory being recalled is thus degraded, less
emotional and vivid, due to limited cognitive resources. This degraded
trace is then reconsolidated in long-term memory. Following the pro-
posal of the WM account, a considerable body of research has been
conducted investigating the impact of various dual tasks on the reduc-
tion of emotionality and vividness. These dual tasks included mental
arithmetic (Engelhard et al., 2011), copying complex figures/drawing
(Gunter & Bodner, 2008), playing the Tetris game (Engelhard et al.,
2010), holding digits in mind (Isaacs, 2004), or attentional breathing
(Van Den Hout, Engelhard, Rijkeboer, et al., 2011) (see Mertens et al.,
2021, for a recent meta-analysis and Wadji et al., 2022, for a systematic
review).

Most studies that have investigated the effects of dual tasks on
emotional memory have used a similar experimental approach. They are
conducted on non-clinical samples, typically healthy undergraduate
students, who are asked to retrieve an unpleasant memory from their
past. These experimental studies are usually organized in three parts: (1)
participants rate the vividness and emotionality of one negative auto-
biographic memory; (2) they activate this memory whilst engaging in a
dual task; (3) they finally rate again its emotionality and vividness.

Although most of the dual tasks used today in EMDR have been
tested with this type of experimental design, empirical evidence
regarding vibratory bilateral stimulation (VBS) remains scarce. VBS
consist in vibrations applied on the patients' palms via small vibrating
paddles. They deliver short vibrating pulses alternating between the left
and right hand at a controlled and adjustable pace. These devices were
developed for EMDR therapy and are now commonly used in this field.
However, to our knowledge, no laboratory studies have yet investigated
their efficiency in modulating emotional memories.

The aim of this study is to assess whether VBS, applied during the
recall of a negative autobiographical memory, can reduce its emotion-
ality and vividness using a well-established laboratory research para-
digm. A secondary objective is to examine the potential relationship
between the effects of VBS on emotional memories and the level of
distraction induced by this type of stimulation.

According to the WM hypothesis, a passive task like the VBS should
not induce a strong effect on the evolution of emotionality and vividness
compared to the control condition (i.e., recall only). However, the WM
hypothesis predicts that an effect can be observed if the dual task per-
formed during the memory recalls is sufficiently demanding in terms of
attention resources. Consequently, it is reasonable to assume that in-
dividuals who are most distracted by VBS should demonstrate a larger
reduction in emotionality and vividness. That is why, at the end of the
experiment, we asked participants to rate the extent to which VBS
distracted them from the target autobiographical memory recall.

## 2. Methods

### 2.1. Participants

Forty-four participants volunteered for this experiment (Mage =
19.93, SD = 1.421; 41 females, 3 males). An a priori power analysis was
conducted using G*Power 3.1.9.7 for a repeated-measures ANOVA with
a within-subject design focusing on the critical Time × intervention
interaction. Previous studies employing the same paradigm reported
partial η² values ranging from 0.12 to 0.18 (Engelhard et al., 2010; Van
Den Hout, Engelhard, Rijkeboer, et al., 2011; Van Den Hout et al., 2011,
2011). Assuming ηₚ² = .12, α = .05, desired power (1 - β) = 0.95, and a
conservative estimate of the correlation among the repeated measures of
r = 0.50, the required sample size was N = 36. The present study (N =
44) therefore exceeded this requirement, providing adequate power to
detect effects of a magnitude comparable to those observed previously.
All participants were students at Aix-Marseille University and received
credits for their participation. They were fluent in both oral and written
French and had normal or corrected to normal vision. All participants
provided a written informed consent.

### 2.2. Procedure

Two independent variables were tested in this study: (1) Time: a two-level factor (pre-intervention and post-intervention); (2) Intervention: a two-level factor (with or without VBS). All participants recalled two emotional memories — one recalled with VBS, one without — and assessed the emotionality and vividness of their memories before and after the intervention. To control for order effects, the two intervention conditions were counterbalanced across participants (half of the participants starting with the VBS intervention and half without), as well as the order of the memory recall (half of the participants began the experiment with the recall of the first negative memory they retrieved; the other half began with the second). This resulted in four possible counterbalancing orders, each assigned to the same number of participants (i.e., n = 11).

#### 2.2.1. Retrieval of two negative autobiographical memories

Participants were first instructed to retrieve two negative autobiographical memories that “made and still make them feel a negative emotion like fear, anxiety, anger, or sadness”. They were given a few examples, including “being unprepared for an exam” or “witnessing an accident”. Following the retrieval of these two memories, they had to evaluate the level of disturbance induced by the recall of these memories on a Subjective Units of Disturbance scale (SUD, as used in EMDR therapy) ranging from 0: “not disturbing at all”, to 10: “extremely disturbing. Only memories ranging from 3 to 7 were included. If one memory was rated above 7 or below 3 on the SUD scale, the participant was invited to retrieve another negative memory that elicited a sensation of disturbance of a lesser or greater intensity.”

After choosing the two memories that would be used in this experi-
ment, participants were seated in front of a computer screen and a
mouse, at approximately 50 cm from the screen. The experimenter was
seated behind the computer screen, enabling them to monitor the
behaviour of the participant and ensure the proper conduct of the
experiment without viewing the participant's responses on the screen.
All the following instructions were displayed on the screen. Participants
were told they could take as long as they needed to read and fully un-
derstand the instructions, as they would themselves click on 'next' to
continue the experiment.

#### 2.2.2. Pre-intervention assessment of emotionality and vividness

The experiment began with either the first or second retrieved
memory, depending on the pseudo-random counterbalancing order
assigned to each participant. After writing a short paragraph describing
the memory as precisely as possible on lined paper, participants were instructed to retrieve the most disturbing image associated with the memory and to keep this image in mind for the evaluation of its emotionality and vividness. This evaluation was performed by clicking on a scale ranging from 0 to 10 displayed on the computer screen. For emotionality, the scale ranged from 0: "not unpleasant" to 10: "extremely unpleasant." For vividness, the scale ranged from 0: "not clear at all" to 10: "extremely clear."

### 2.2.3. Recalls of memory with or without VBS

The recall phase consisted of four blocks of 30 s, separated by a 10-s break, during which participants were instructed to recall the most disturbing image of their memory while holding a pulsator in each hand. In both conditions, memory recall was performed with eyes open, fixating on a cross displayed at the centre of the screen. In the VBS condition, the stimulation was administered through the pulsators during the four recall blocks. In the recall-only condition, no vibrations were administered.

### 2.2.4. Post-intervention assessment of emotionality and vividness

After the four recall blocks with or without VBS, participants self-evaluated post-intervention emotionality and vividness of the memory in the same manner as during the pre-intervention assessment. Participants then had a 5-min break, during which no specific instructions were given. Once the break was over, the same procedure was applied to the second autobiographical memory: writing a paragraph describing the memory, pre-intervention assessment of emotionality and vividness, recall blocks with or without VBS, and post-intervention assessment of emotionality and vividness.

### 2.2.5. Debriefing on the perception of VBS

Once participants had completed the experiment, the experimenter conducted a debriefing session. During this debriefing, participants were asked to rate, on a scale from 0 to 10, the extent to which the VBS had distracted them from the task of recalling their memories, with 0 indicating no distraction at all and 10 indicating maximal distraction.

## 2.3. Material

The computerised part of the experiment was coded and ran using OpenSesame software (Mathôt et al., 2012) on a Dell Precision 5540 laptop (Dell, Round Rock, TX, USA) with an Intel Core i5-9400H processor (2.50 GHz), 16 GB RAM, and a 64-bit Windows operating system. Instructions and scales were presented on a 24-inch Dell P2419H LED monitor (Dell, Round Rock, TX, USA) with a 1920 × 1080 pixels resolution and 60 Hz refresh rate. The monitor was positioned approximately 50 cm from participants' eyes. We used an EMDR Kit Classic Pulsators & Controller (SE Factory/EMDR Kit, Groningen, The Netherlands) to deliver VBS. In our protocol, we set the pulsators to a standard intensity level and a speed of 2Hz for 30 s per trial. This equated to 60 pulsations per trial, alternating between the participants' left and right hands. Vibrations stopped for 10 s between each recall block, during which the participants could take a short break.

## 2.4. Statistical analysis

Statistical analyses were performed on emotionality and vividness ratings. Bayesian models were fitted using the brms R package (Bürkner, 2017, 2021). Bayesian analyses were chosen over frequentists counterparts because, by incorporating prior expectations, they ground the inference in prior knowledge and plausibility, making them more suitable for regularizing inference in low power situations (Morey & Rouder, 2011; Schad et al., 2020). In addition to better handling small sample sizes, Bayesian methods allow for a direct quantification of the evidence provided by the data in favour of one hypothesis over another. This is implemented through Bayes Factors, which were used in the

present study.

One model was fitted for each hypothesis. For each dependent variable (vividness and emotionality ratings), three models were compared: (a) the *interaction model*, which included the effects of *Time* (two levels: pre- and post-intervention) and *Intervention* (two levels: with or without VBS), as well as their interaction. This model reflects the main hypothesis that applying VBS during the recall of negative memories influences the change in emotionality and vividness from pre-to post-intervention; (b) the *time-only model*, which included only the effect of *Time*, reflecting the hypothesis that repeated recalls alone influence emotionality and vividness ratings, regardless of whether VBS were applied; (c) the *null model*, which included only random effects of participants, with no effect of *Time* or *Intervention*.

Bayes Factors were used to compare these three models, allowing for the quantification of evidence in favour of one model (or hypothesis) over another. Bayes Factors were interpreted according to Jeffreys et al. (1961) benchmarks. In the case of evidence supporting the *interaction model*, the interaction was further examined using Bayesian paired-sample *t*-tests to assess the main effect of time within each intervention condition.

Still in the case of evidence supporting the interaction model, further analyses were conducted to assess whether this effect could be related to the self-evaluated distraction induced by the VBS. Two groups were created based on the distraction ratings provided by participants: individuals who rated the distraction induced by VBS below the median were included in the low-distraction group, and those who rated it at or above the median were included in the high-distraction group. We then assessed whether the reduction in ratings (calculated as pre-intervention minus post-intervention ratings) in the VBS condition differed between the two distraction groups. To this end, a Bayesian independent-sample *t*-test was conducted using the default Jeffreys–Zellner–Siow (JZS) prior (Rouder et al., 2009).

# 3. Results

## 3.1. Effects of time, VBS, and their interaction on emotionality ratings

Emotionality ratings as a function of *Time* (pre-vs. post-intervention) and *Intervention* (with vs. without VBS) are shown in Fig. 1 (left panel). The comparison between the *interaction model* (including the effects of *Time*, *Intervention*, and their interaction) and the *null model* (including only random effects of participants) for emotionality ratings yielded a Bayes Factor of $BF_{10} = 5.6$, indicating moderate evidence in favour of the interaction hypothesis over the null (Jeffreys, 1961). The comparison between the *time-only model* (including only the main effect of *Time* on emotionality ratings) and the *null model* resulted in a Bayes Factor of $BF_{10} = 2.4$, which constitutes weak evidence in favour of the *time-only* model over the *null*. Similarly, the comparison of the *interaction model* with the *time-only* model produced a Bayes Factor of $BF_{10} = 2.3$, also reflecting weak or anecdotal evidence for the presence of a *Time × Intervention* interaction.

The Bayesian paired-sample *t*-tests conducted to further analyse the interaction between *Time* and *Intervention* effects by assessing the main effect of time within each *Intervention* condition are reported in Table 1. A significant effect of *Time* was observed in the control condition, with a Bayes Factor of $BF_{10} = 20.31$, constituting strong evidence for the existence of a main effect of time in this condition. In contrast, the Bayesian paired-sample *t*-test assessing the simple main effect of *Time* in the *VBS* condition provided moderate support for the null hypothesis ($BF_{10} = 0.175$), suggesting an absence of change in emotionality ratings following recalls performed with VBS.

## 3.2. Effects of time, VBS, and their interaction on vividness ratings

For vividness ratings, the Bayes Factor in favour of the *interaction model* including the interaction over the *null model* was $BF_{10} = 0.15$, and
<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Evolution of emotionality (left panel) and vividness (right panel) ratings over time (pre-vs. post-intervention) as a function of intervention condition (with vs. without VBS). Error bars represent 95% confidence intervals.</figcaption></figure>

<caption>**Table 1**</caption>

Bayesian paired t-tests assessing the simple main effect of time (pre vs post) on emotionality ratings in both conditions.

<table><thead><tr><th>Condition</th><th>Comparison</th><th>BF<sub>10</sub></th><th>Error (%)</th><th>Interpretation</th></tr></thead><tbody><tr><td>With VBS</td><td>Pre vs Post</td><td>0.175</td><td>0.057</td><td>Moderate evidence for H<sub>0</sub></td></tr><tr><td>Without VBS</td><td>Pre vs Post</td><td>20.311</td><td>5.50 × 10<sup>-8</sup></td><td>Strong evidence for H<sub>1</sub></td></tr></tbody></table>

Note. BF<sub>10</sub> > 1 indicates evidence for the alternative hypothesis (a difference between pre- and post-intervention ratings), whereas BF<sub>10</sub> < 1 indicates evidence for the null (no difference between pre- and post-intervention ratings).

over the *time-only model* was BF<sub>10</sub> = 0.32, both indicating that the more complex models is not supported by the data. Similarly, the Bayes Factor comparing the *time-only model* to the *null model* was BF<sub>10</sub> = 0.41, providing no substantial evidence in favour of including *Time* as a predictor. Altogether, these results suggest the absence of any effect of time or VBS on vividness ratings.

### 3.3. Effect of distraction induced by VBS on emotionality reduction

The reduction of emotionality and vividness ratings in the VBS condition as a function of the distraction induced by the VBS is shown in Fig. 2. The Bayesian independent-sample *t*-test performed to assess the difference in emotionality reduction between the two distraction groups resulted in a Bayes Factor of BF<sub>10</sub> = 2.97, which constitutes weak to moderate evidence for a significant difference between groups. Interestingly, the distribution of emotionality reduction in the high

distraction group is mostly positive (i.e., an actual reduction of emotionality between pre- and post-intervention ratings), whereas the distribution for the low distraction group is mostly negative (i.e., an increase in emotionality between pre- and post-intervention ratings).

## 4. Discussion

In the present study, a significant interaction between *Time* and *Intervention* on emotionality ratings was observed. The decomposition of this interaction indicated a significant increase in emotionality in the control condition and no difference in the VBS condition. This amplification phenomenon, observed when recalls are performed without any stimulation or dual task, is frequently observed. The literature consistently reports either a trend or a significant increase of emotionality when negative memories are recalled without stimulation (Engelhard et al., 2010; Engelhard et al., 2011; IJdema et al., 2021; Van Den Hout, Engelhard, Rijkeboer, et al., 2011; Van Schie et al., 2016; Van Veen et al., 2020). The addition of VBS during recalls cancelled this amplification phenomenon by maintaining memory emotionality at a stable level. It is therefore important to note that, although the observed effect of VBS on emotional memories appears beneficial by blocking the emotionality amplification, it does not induce a reduction in emotionality, as it would be expected from stimulation used in EMDR.

Interestingly, a significant difference in emotionality changes was observed between the two distraction groups, with a trend towards a decrease in emotionality in the high-distraction group, and a trend towards an increase in emotionality in the low-distraction group. This suggests that the typical EMDR effect of emotionality reduction induced

<figure><img src="image_3.png" /><figcaption>**Fig. 2.** Reduction of Emotionality (left panel) and Vividness (right panel) induced by VBS (calculated as pre-minus post-intervention ratings in the VBS condition) as a function of self-reported distraction induced by VBS (low vs. high).</figcaption></figure>
by dual tasks was observed only in individuals who perceived the VBS as distracting them from their memory recall task. In contrast, individuals who felt less distracted by the VBS exhibited the opposite pattern. These findings are consistent with the predictions of the WM hypothesis, which states that the reduction in the emotionality of negative memories is related to attentional resources that are captured by the dual task.

Surprisingly, the effects observed on emotionality were not repli-
cated for vividness. This result may stem from a methodological issue
during the translation from English to French of the instructions
regarding the evaluation of vividness. The terms used in previous studies
to explain the scale were “extremely clear” and “not clear at all” in English
(Andrade et al., 1997; Gunter & Bodner, 2008) and were literally
translated into French as “extrêmement clair” and “pas clair du tout”. The
terminology appears to have changed since, as more recent studies based
on this laboratory paradigm use the terms “extremely vivid” and “not vivid
at all”, which would be literally translated into French as “extrêmement
vivace” and “pas vivace du tout”. However, one can note that the literal
translation of “vivid” in French is rarely used in everyday speech.
Another possible explanation could be the difference in modality be-
tween the memory being recalled and the VBS. Indeed, in a recent study,
Matthijssen et al. (2019) found a general effect of dual tasking on taxing
WM and a superimposed effect of taxing in matched modality. In the
present study, participants were instructed to recall the most disturbing
image of their memory, suggesting a primarily visual modality, whereas
the modality of the VBS was tactile. This may explain why the vividness
of the memory was not affected by the addition of VBS.

All dependent variables measured in this experiment were subjec-
tive, which could be a limitation of our study. However, the lack of data
assessing the effects of VBS on emotional memories justifies the use of
subjective measures only, as has been done for other types of ABS.
Nonetheless, further research would benefit from including more
objective measures, such as heart rate, skin conductance, pupillometry,
or brain imaging, to assess whether the behavioural effects are observ-
able at the physiological level. Regarding the evaluation of distraction
induced by VBS, future studies could focus on quantifying the degree to
which VBS tax attentional resources using psychometric tools. This
procedure would enable testing variations of the VBS by modulating
what appears to be a key feature of this stimulation in the present study:
its distractibility. One way to achieve this would be to compare this
rather passive task (holding the pulsators) to a more active one by
adding a response instruction, like pressing a button when a vibratory
stimulus occurs. Having this task carried out simultaneously with a re-
action time task would allow the relative change in reaction times to be
used as a measure of WM taxation, rather than subjective ratings
(Matthijssen et al., 2019; Van Den Hout et al., 2011; Van Den Hout &
Engelhard, 2012), and assess if this WM taxation level actually predicts
the reduction of emotional memories.

Although we used a relatively standard methodology compared to
previous studies, it is important to note that some aspects differed from
traditional experiments investigating the effects of dual tasks on
emotional memories. Indeed, a major part of the experiment was com-
puterised. Subjective ratings were provided by clicking on a computer
screen, which the participant knew was not visible to the experimenter.
The repeated memory recalls were also conducted via interaction with
the computer rather than with a human experimenter: instructions were
read by the participants on the screen rather than delivered orally by the
experimenter. Therefore, it is possible that the traditional reductions in
emotionality and vividness induced by ABS observed in previous studies
are actually due to non-specific, common factors (Cuijpers et al., 2019),
such as the patient-therapist relationship or the patient's expectations,
rather than factors specific to ABS themselves. A good way to further
investigate this question would be to reproduce the exact same protocol
as the present study, only replacing VBS with eye movements. Eye
movements should be induced by visual stimulation displayed on a
computer screen rather than a physical target, such as the experimenter's
index finger, as done in some previous studies. If these eye movements

no longer induce reductions in the emotionality and vividness of
memories when the experiment is computerized, this would suggest the
presence of non-specific factors influencing some of the published
studies. Conversely, it would also be interesting to test VBS in a more
“clinical-like” protocol, where the interaction between the experimenter
and the participant is not affected by the automation of the experiment.
If non-specific factors are indeed at play in this field of research, the
beneficial effect of emotional amplification mitigation by VBS observed
in this study may be enhanced to an actual reduction of the memory's
emotionality if used in a more "clinical-like" context, where the
above-cited non-specific factors could add to the actual VBS effect.

However, studies in this field nowadays tend to induce eye move-
ments using visual stimulation displayed on a computer screen rather
than a physical target, such as the experimenter’s index finger. Some of
these recent studies found a very robust effect of eye movements on the
reduction of emotional memories after an intervention comparable to
the one used in our study (Mertens et al., 2020; Van Veen et al., 2020).
Therefore, our results indicate that the evidence supporting the use of
VBS in EMDR therapy is not as robust as that for other forms of
dual-attention tasks (see Mertens et al., 2021, for a recent
meta-analysis).

Nevertheless, it is important to note, as mentioned by Mertens et al. (2021), that it is difficult to generalise results obtained in laboratory models to clinical populations. Effects could be much greater in clinical contexts: first, because pathological emotional memories are typically more intense and vivid than those of healthy subjects, leaving more room for reduction, and second, because clinical sessions are longer and adapted to each individual. That is, the present findings should be interpreted with caution.

CRediT authorship contribution statement

**Cassandre Armand:** Writing – original draft, Software, Methodology, Investigation, Data curation, Conceptualization. **Fabrice Guil-laume:** Writing – review & editing, Supervision, Resources, Conceptualization. **Arnaud Rey:** Writing – review & editing, Supervision, Resources, Project administration, Funding acquisition, Conceptualization.

Ethics approval

Ethics approval was obtained from the Ethics Committee of Aix-
Marseille University (#2023-02-09-016).

Declaration of competing interest

The authors declare no conflict of interest.

Acknowledgements

CA was supported by a doctoral fellowship of the French Ministry of
Higher Education, Research, and Innovation. This research was sup-
ported by the Convergence Institute ILCB (ANR-16-CONV-0002) and the
HEBBIAN ANR project (#ANR-23-CE28-0008).

Data availability

Data will be made available on request.

References

American Psychiatric Association. (2015). *DSM-5 : Manuel diagnostique et statistique des troubles mentaux*.

Andrade, J., Kavanagh, D., & Baddeley, A. (1997). Eye-movements and visual imagery : A working memory approach to the treatment of post-traumatic stress disorder. *British Journal of Clinical Psychology*, *36*(2), 209-223. https://doi.org/10.1111/j.2044-8260.1997.tb01408.x
Baddeley, A., & Hitch, G. (1974). Working memory. *Psychology of Learning and Motivation, 8(2), 47–89.

Brewin, C. R., Gregory, J. D., Lipton, M., & Burgess, N. (2010). Intrusive images in psychological disorders: Characteristics, neural mechanisms, and treatment implications. *Psychological Review, 117*(1), 210–232. https://doi.org/10.1037/a0018113

Bürkner, P.-C. (2017). brms: An R package for bayesian multilevel models using Stan. *Journal of Statistical Software*, 80(1). https://doi.org/10.18637/jss.v080.i01

Bürkner, P.-C. (2021). Bayesian item response modeling in R with *brms* and Stan. *Journal of Statistical Software*, 100(5). https://doi.org/10.18637/jss.v100.i05

Cuijpers, P., Reijnders, M., & Huibers, M. J. H. (2019). The role of common factors in psychotherapy outcomes. *Annual Review of Clinical Psychology*, 15(1), 207–231. https://doi.org/10.1146/annurev-clinpsy-050718-095424

Day, S., Holmes, E., & Hackmann, A. (2004). Occurrence of imagery and its link with early memories in agoraphobia. *Memory*, 12(4), 416–427. https://doi.org/10.1080/09658210444000034

De Jongh, A., De Roos, C., & El-Leithy, S. (2024). State of the science: Eye movement desensitization and reprocessing (EMDR) therapy. *Journal of Traumatic Stress*, 37(2), 205–216. https://doi.org/10.1002/jts.23012

Engelhard, I. M., Van Den Hout, M. A., & Smeets, M. A. M. (2011). Taxing working memory reduces vividness and emotional intensity of images about the Queen's Day tragedy. *Journal of Behavior Therapy and Experimental Psychiatry*, 42(1), 32–37. https://doi.org/10.1016/j.jbtep.2010.09.004

Engelhard, I. M., Van Uijen, S. L., & Van Den Hout, M. A. (2010). The impact of taxing working memory on negative and positive memories. *European Journal of Psychotraumatology*, 1(1), 5623. https://doi.org/10.3402/ejpt.v1i0.5623

Gunter, R. W., & Bodner, G. E. (2008). How eye movements affect unpleasant memories: Support for a working-memory account. *Behaviour Research and Therapy*, 46(8), 913–931. https://doi.org/10.1016/j.brat.2008.04.006

Hackmann, A., Clark, D. M., & McManus, F. (2000). Recurrent images and early memories in social phobia. *Behaviour Research and Therapy*, 38(6), 601–610. https://doi.org/10.1016/s0005-7967(99)00161-8

Iddema, T., Laceulle, O. M., Karreman, A., De Vries, J., & Korrelboom, K. (2021). Does valence contribute to the effects of dual tasking in aversive autobiographical memory? Some unexpected findings. *Journal of Behavior Therapy and Experimental Psychiatry*, 71, Article 101616. https://doi.org/10.1016/j.jbtep.2020.101616

Isaacs, J. S. (2004). Numerical distraction therapy: Initial assessment of a treatment for posttraumatic stress disorder: Traumatology. *Traumatology*, 10(1), 39–54. https://doi.org/10.1177/153476560401000014

Jeffreys, H. (1961). *Theory of probability* (3rd éd.). Oxford University Press.

Kavanagh, D. J., Freese, S., Andrade, J., & May, J. (2001). Effects of visuospatial tasks on desensitization to emotive memories. *British Journal of Clinical Psychology*, 40(3), 267–280. https://doi.org/10.1348/014466501163689

Kip, A., Schoppe, L., Arntz, A., & Morina, N. (2023). Efficacy of imagery rescripting in treating mental disorders associated with aversive memories – An updated meta-analysis. *Journal of Anxiety Disorders*, 99, Article 102772. https://doi.org/10.1016/j.janxdis.2023.102772

Martin, A., Naunton, M., Kosari, S., Peterson, G., Thomas, J., & Christenson, J. K. (2021). Treatment Guidelines for PTSD: A Systematic Review. *Journal of Clinical Medicine*, 10(18), 4175. https://doi.org/10.3390/jcm10184175

Mathöt, S., Schreij, D., & Theeuwes, J. (2012). OpenSesame: An open-source, graphical experiment builder for the social sciences. *Behavior Research Methods*, 44(2), 314–324. https://doi.org/10.3758/s13428-011-0168-7

Mathijssen, S. J. M. A., Van Schie, K., & Van Den Hout, M. A. (2019). The effect of modality specific interference on working memory in recalling aversive auditory and visual memories. *Cognition and Emotion*, 33(6), 1169–1180. https://doi.org/10.1080/02699931.2018.1547271.

Mertens, G., Bouwman, V., Asmervik, J. F., & Engelhard, I. M. (2020). Changing emotional visual and auditory memories: Are modality-matched dual-tasks more effective? *Cognition and Emotion*, 34(4), 656–669. https://doi.org/10.1080/02699931.2019.1666800.

Mertens, G., Lund, M., & Engelhard, I. M. (2021). The effectiveness of dual-task interventions for modulating emotional memories in the laboratory: A meta-analysis. *Acta Psychologica*, 220, Article 103424. https://doi.org/10.1016/j.actψcy.2021.103424

Mihailova, S., & Jobson, L. (2018). Association between intrusive negative autobiographical memories and depression: A meta-analytic investigation. *Clinical Psychology & Psychotherapy*, 25(4), 509–524. https://doi.org/10.1002/cpp.2184

Morey, R. D., & Rouder, J. N. (2011). Bayes factor approaches for testing interval null hypotheses. *Psychological Methods*, 16(4), 406–419. https://doi.org/10.1037/a0024377

Propper, R. E., & Christman, S. D. (2008). Interhemispheric interaction and saccadic horizontal eye Movements Implications for episodic memory, EMDR, and PTSD. *Journal of EMDR Practice and Research*, 2(4), 269–281. https://doi.org/10.1891/1933-3196.2.4.269

Reynolds, M., & Brewin, C. R. (1999). Intrusive memories in depression and posttraumatic stress disorder. *Behaviour Research and Therapy*, 37(3), 201–215. https://doi.org/10.1016/s0005-7967(98)00132-6

Rouder, J. N., Speckman, P. L., Sun, D., Morey, R. D., & Iverson, G. (2009). Bayesian t tests for accepting and rejecting the null hypothesis. *Psychonomic Bulletin & Review*, 16(2), 225–237. https://doi.org/10.3758/PBR.16.2.225

Schad, D. J., Betancourt, M., & Vasishth, S. (2020). *Toward a principled Bayesian workflow in cognitive science* (arXiv:1904.12765). *arXiv*. https://doi.org/10.48550/arXiv:1904.12765

Seinsche, R. J., Fricke, S., Neudert, M. K., Zehtner, R. I., Walter, B., Stark, R., & Hermann, A. (2023). Memory representation of aversive social experiences in social anxiety disorder. *Journal of Anxiety Disorders*, 94, Article 102669. https://doi.org/10.1016/j.janxdis.2023.102669

Shapiro, F. (2001). *Eye movement desensitization and reprocessing (EMDR), second edition: Basic principles, protocols, and procedures*. Guilford Press.

Speckens, A. E. M., Hackmann, A., Ehlers, A., & Cuthbert, B. (2007). Imagery special issue: Intrusive images and memories of earlier adverse events in patients with obsessive compulsive disorder. *Journal of Behavior Therapy and Experimental Psychiatry*, 38(4), 411–422. https://doi.org/10.1016/j.jbtep.2007.09.004

Spenceley, A., & Jerrom, B. (1997). Intrusive traumatic childhood memories in depression: A comparison between depressed, recovered and never depressed women. *Behavioural and Cognitive Psychotherapy*, 25(4), 309–318. https://doi.org/10.1017/s1352465800018713

Tulving, E., Kapur, S., Craik, F. I., Moscovitch, M., & Houle, S. (1994). Hemispheric encoding/retrieval asymmetry in episodic memory: Positron emission tomography findings. *Proceedings of the National Academy of Sciences*, 91(6), 2016–2020. https://doi.org/10.1073/pnas.91.6.2016

Van Den Hout, M. A., & Engelhard, I. M. (2012). How does EMDR work? *Journal of Experimental Psychopathology*, 3(5), 724–738. https://doi.org/10.5127/jep.028212

Van Den Hout, M. A., Engelhard, I. M., Beetsma, D., Slofstra, C., Hornsveld, H., Houtveen, J., & Leer, A. (2011). EMDR and mindfulness. Eye movements and attentional breathing tax working memory and reduce vividness and emotionality of aversive ideation. *Journal of Behavior Therapy and Experimental Psychiatry*, 42(4), 423–431. https://doi.org/10.1016/j.jbtep.2011.03.004

Van Den Hout, M. A., Engelhard, I. M., Rijkeboer, M. M., Koekebakker, J., Hornsveld, H., Leer, A., Toffolo, M. B. J., & Akse, N. (2011). EMDR: Eye movements superior to beeps in taxing working memory and reducing vividness of recollections. *Behaviour Research and Therapy*, 49(2), 92–98. https://doi.org/10.1016/j.brat.2010.11.003

Van Schie, K., Van Veen, S. C., Engelhard, I. M., Klugkist, I., & Van Den Hout, M. A. (2016). Blurring emotional memories using eye movements: Individual differences and speed of eye movements. *European Journal of Psychotraumatology*, 7(1), Article 29476. https://doi.org/10.3402/ejpt.v7.29476

Van Veen, S. C., Van Schie, K., Van De Schoot, R., Van Den Hout, M. A., & Engelhard, I. M. (2020). Making eye movements during imaginal exposure leads to short-lived memory effects compared to imaginal exposure alone. *Journal of Behavior Therapy and Experimental Psychiatry*, 67, Article 101466. https://doi.org/10.1016/j.jbtep.2019.03.001

Wadji, D. L., Martin-Soelch, C., & Camos, V. (2022). Can working memory account for EMDR efficacy in PTSD? *BMC Psychology*, 10(1). https://doi.org/10.1186/s40359-022-00951-0

World Health Organization. (2013). Guidelines for the management of conditions that are specifically related to stress. World Health Organization. https://iris.who.int/handle/10665/85119.