Linguistic dual tasking reduces emotionality, vividness and credibility of voice memories in voice-hearing individuals: Results from a controlled trial
Introduction
Traumatic events can result in involuntary re-experiencing of memories, i.e. intrusive memories (Krans et al., 2009). Intrusive memories are multi-modal mental images, including visual, auditory, olfactory, gustatory, and bodily sensations (Ehlers et al., 2002; Kosslyn, 1994; Krans et al., 2009), and form the hallmark symptom of post-traumatic stress disorder (PTSD) (Ehlers et al., 2004; Hackmann et al., 2004).
It has been theorized that a proportion of auditory verbal hallucinations (AVH, ‘hearing voices’) may be conceptualized as intrusive auditory images (Morrison et al., 2002; Morrison, 2001; Steel et al., 2005; Waters et al., 2006). More specifically, several models state that some AVH may be considered to be decontextualized memories that are experienced as sensory perceptions (Hardy, 2017; Steel et al., 2005; Waters et al., 2012, 2006). This is supported by strong associations between experiencing childhood trauma and AVH (Bentall et al., 2012; McCarthy-Jones, 2011), objective observation of similarities in content and theme between traumatic experiences and AVH (Hardy et al., 2005), and the subjective experience of people reporting hallucinations that appear to be replays of actual past events (McCarthy-Jones et al., 2014).
It is established that predominantly emotionality of voices and negative voice-related beliefs (e.g. believing the negative comments that the voices make) are an important cause of voice-related distress (Daalman et al., 2011; Hacker et al., 2008), and decreasing or modifying these beliefs in psychological therapies, such as cognitive therapy (e.g. Birchwood et al., 2014) and imaginary rescripting (Paulik et al., 2018), is proven to be effective in decreasing voice-hearing distress. Dual tasking, i.e. performing a (visual or auditory) task while retrieving a memory, is used routinely in clinical practise to decrease emotionality, vividness, and negative beliefs of visual intrusions. The exact underlying mechanism of dual tasking remains debatable, although there is some evidence that it is based on the working memory (WM) theory of Baddeley (1992). According to the working memory account, dual tasking limits the information processing capacity of the WM (Baddeley and Andrade, 2000). Since memories appear to be susceptible to change during retrieval (James et al., 2015), taxing WM during retrieval reduces the vividness and emotionality of memories more than retrieval only.
However, the focus of the present research is not on investigating potential underlying working mechanisms. Since it has been repeatedly shown that dual tasking decreased the vividness and emotionality of visual images (e.g. Lee and Cuijpers, 2013; Van Schie et al., 2016; Van Veen et al., 2015), we aimed to investigate whether the dual tasking procedure could also decreases emotionality of auditory images; there is some evidence that suggests that way. Several student-based studies, using (autobiographical) memories that were classified as primarily visual or primarily auditory, found that vividness and emotionality of mainly auditory images were reduced after a dual task compared to recall only (Baddeley and Andrade, 2000; Kemps and Tiggemann, 2007; Kristjánsdóttir and Lee, 2011). A study that tested this hypothesis in a clinical sample with PTSD patients, used one primarily visual and one primarily auditory traumatic memory, and these memories were both subjected to three counterbalanced conditions, i.e. visual taxation, auditory taxation, and recall while staring at a dot. Emotionality was rated before and after the experiment. Emotionality of both the visual and auditory autobiographical images decreased, irrespective of the condition (Matthijssen et al., 2017). Although more research is needed, this tentatively suggests that salience of auditory memories can be affected by dual tasking. Besides, it has been observed in clinical practice that dual tasking may also change the credibility of beliefs associated with the memory (De Jongh et al., 2010). Therefore, dual tasking is potentially an interesting treatment for reducing distress of voices by targeting voice-hearing memories.
Recently, mHealth applications based on dual tasking have been deployed as an intervention for (mainly) visual intrusive images. This has produced mixed results, e.g. Tetris was found to be effective, whereas other dual tasks did not decrease vividness and emotionality of intrusions (Asselbergs et al., 2018; Iyadurai et al., 2017; James et al., 2015). In the present study, we used one of the functions in ‘Temstem’ (an application developed for voice-hearers) as the experimental dual task (for details, see Jongeneel et al., 2018). In this function, WM is taxed by a linguistic game, while the user recalls a recent episodic memory of hearing voices.
Two decades ago, research concerning the effectiveness of dual tasking in processing visual intrusive images started by laboratory-setting investigations using a cross-over design (e.g. Andrade et al., 1997; Van Den Hout et al., 2001) and when effectiveness was established, research engaged in studying whether dual tasking decreased future intrusions. Pursuing this two-step approach, the present study is a first proof-of-principle study to test the hypothesis that the mobile dual tasking procedure decreases the emotionality, vividness, and credibility of disturbing episodic memories of AVH compared to recall only in voice-hearing individuals. If results are found to be positive, future studies can investigate whether the decrease of salience and credibility of voice-memories by dual tasking results in a decrease of future intrusions, or voice-hearing.
Section snippets
Participants
This study was part of a larger randomized controlled trial that tested the efficacy of a smartphone application (Temstem) in participants with frequent and disturbing AVH. Participants were recruited from 12 participating specialized mental healthcare institutions in the Netherlands. Further details of this trial are published elsewhere (Jongeneel et al., 2018). Participants of this trial (N = 89) received treatment as usual (TAU) and were after the baseline assessment randomized into one of
Results
Mean scores of emotionality, vividness, and credibility ratings in the recall only condition and dual tasking condition are presented in Table 3. Baseline emotionality and vividness (r = 0.43, p < .01) were significantly positively correlated. Correlations between emotionality and credibility (r = 0.27, p = .109) and vividness and credibility (r = 0.23, p = .151) were not significant.
Mean pre-test to post-test difference scores of the outcomes for both conditions are shown in Fig. 2. The 2
Discussion
The aim of this study was to test the hypothesis that the dual tasking procedure decreases emotionality, vividness and credibility of auditory episodic memories of voice-hearing. The data confirmed this hypothesis, i.e. ratings of all outcomes showed a significantly greater decrease after dual tasking than after recall only. These findings are in line with the theory that WM taxation during retrieval of a memory reduces the emotionality, vividness (Lee and Cuijpers, 2013; Van Schie et al., 2016
Contributors
AJ, SvV, MvdH, and DvdB contributed to the study protocol. AJ collected data, performed the analyses and wrote under supervision of DvdB the first draft of the manuscript.
All authors contributed to and have approved the final manuscript.
Funding
The Temstem trial, whereof this study was part of, was funded by a grant awarded to DvdB and MvdG by the ‘Innovatie Platform Parnassia’ (Monsterseweg 93, 2553 RJ Den Haag, the Netherlands). This study was also supported by funding assigned to DvdB by the Netherlands' EMDR Association (VEN: Postbus 13032, 3507 LA Utrecht, the Netherlands). SvV and MvdH were supported with a TOP grant (40-00812-98-12030) from the Netherlands Organization for Health Research and Development (ZonMw).
Declaration of competing interest
The authors declare that there are no conflicts of interest.
Acknowledgments
The authors thank all participants, therapists, local researchers, research assistants, independent specialists, advisors and participating mental health institutions, without whom this study would not be possible. Special thanks go to Marion Bruns, BSc, for her role in managing data collection and data entry.
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