Field of daydreams? Integrating mind wandering in the study of sluggish cognitive tempo and ADHD

Abstract In this editorial perspective, we consider the potential conceptual and empirical overlap between the research on mind wandering, particularly in its pathological extreme, and that on sluggish cognitive tempo (SCT) as it has diverged from research on attention‐deficit/hyperactivity disorder. The more advanced state of research findings on the nature and correlates of mind wandering relative to that of SCT is used to suggest a variety of avenues of investigation into SCT, such as its phenomenology, positive and negative correlates, research methods, theory building, and potential to inform interventions. These and other avenues drawn from the field of mind wandering are likely to prove fruitful in further revealing the nature of SCT and its relationship to mind wandering.

research findings on the nature and correlates of mind wandering relative to that of SCT is used to suggest a variety of avenues of investigation into SCT, such as its phenomenology, positive and negative correlates, research methods, theory building, and potential to inform interventions. These and other avenues drawn from the field of mind wandering are likely to prove fruitful in further revealing the nature of SCT and its relationship to mind wandering.
One of Tim's dominant characteristics is that he is extremely spacey most of the time… He tends to be hypoactive, passive, and unengaged and if not actively engaged by someone will fade out and daydream… When we read the "checklist" that has been created for SCT it was as though Tim was being described for the first time on paper.
E-mail from a concerned mother In recent decades, two literatures have advanced in parallel that seem enticingly overlapping. In cognitive psychology and neuroscience, there has been substantial advancement in understanding the nature of mind wandering, largely driven by interest in understanding the brain's default mode network (Christoff et al., 2016). In clinical psychology and psychiatry, there has been growing interest in sluggish cognitive tempo (SCT), another apparent attention deficit, given its relevance for and contrast with attention-deficit/hyperactivity disorder (ADHD) and other mental disorders (Becker et al., 2016).
Although they arose independently, the fields share conceptual and empirical overlap. First noted a decade ago (see Becker & Barkley, 2018), this overlap was implied in recent empirical findings on SCT. Here, we describe how mind wandering and SCT are conceptually related and offer a research agenda to integrate these two fields to advance theory and practice.

CONCEPTUAL AND EMPIRICAL OVERLAP IN SCT AND MIND WANDERING
Mind wandering is defined as a type of spontaneous thought lacking strong constraints on the thought contents that is distinct from but similar to daydreaming (Christoff et al., 2016), with a daydreaming frequency scale often used to measure mind wandering and some scholars referring to them as synonymous. Likewise, although SCT includes mental confusion, slowed behavior, and sleepiness, "daydreams" is used most frequently as a cardinal item of SCT (Becker et al., 2016). 1 Both conditions appear to involve a decoupling of attention from the external environment and its redirection to This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.  (Smallwood & Schooler, 2015). Although it would be overly simplistic to suggest that SCT and ADHD can be cleanly carved into internal versus external distractions, this heuristic may prove to be a useful starting point to advance discovery on the distinction and covariation of SCT and ADHD.
Until recently, there were no data directly linking mind wandering and SCT. There are now two studies demonstrating SCT to be associated with greater mind wandering . These studies found the association between ADHD inattentive symptoms and mind wandering to be largely eliminated when SCT symptoms were included in the model.
Notably, both studies used a cross-sectional design and assessed mind wandering using a self-report measure of daydreaming frequency often used in studies of mind wandering. Nevertheless, these initial findings call into question whether the link between mind wandering and ADHD is as robust as previously believed (Bozhilova et al., 2018).

Parallel findings linking SCT and mind wandering with functional outcomes
Beyond conceptual links, SCT and mind wandering are also associated with similar domains of functioning and maladjustment. Perhaps most consistently, they are both associated with increased negative mood symptoms, including depression (Becker & Barkley, 2018;Smallwood & Schooler, 2015). Although unstudied in the SCT field, the content and temporal nature (e.g., thinking about the past or future) of mind wandering experiences appear to be highly relevant in establishing whether mind wandering predicts negative mood and depressive symptoms (Smallwood & Schooler, 2015).
Mind wandering also negatively impacts reading comprehension, likely because the latter requires ongoing monitoring and encoding of inputs (Smallwood & Schooler, 2015) and actively holding what is read and understood in mind (working memory).
Mind wandering may cause a decoupling of attention from such external monitoring of text as well as competing for working memory capacity. A recent study found SCT symptoms to prospectively predict poorer reading (including reading comprehension) whereas ADHD inattention uniquely predicted poorer math achievement .
SCT is reliably associated with social difficulties, and social withdrawal and isolation in particular (Becker & Barkley, 2018 (Smallwood & Schooler, 2015). We are not aware of any studies that have tested SCT in relation to these positive attributes, though parents of children with elevated SCT often comment on the potentially positive attributes of daydreaming. As noted previously, "In considering SCT, although daydreaming itself is not pathological and is beneficial for play, imagination, and creativity, the duration, intensity, and content of daydreams may be especially important for clinical assessment and discrimination" (Burns et al., 2020, p. 467). Grounded in a developmental psychopathology framework, there is a need for empirical research examining in tandem the costs and benefits of SCT.
3. Bridging methods. To expand beyond the use of subjective rating scales and to promote multi-method investigations, the study of SCT would greatly benefit from incorporating methods that have become standard in the mind wandering field. Mind wandering is most frequently studied using experience sampling methods, often using the sustained attention to response task (SART).
While completing the SART, a participant may be asked to indicate when they notice that their thoughts have wandered from the task (self-caught method) or be periodically asked as to their  (Christoff et al., 2016). These findings provide fertile ground for examining the potential brain basis and behavioral correlates of SCT, both independently and in relation to ADHD. Integrating multiple units of analysis, including brain circuitry, physiology, and behavioral tasks, alongside existing self/informant-report measures of SCT, will be important for situating findings within broader literatures and, perhaps most importantly, essential for building comprehensive theories of SCT.

Informing intervention. Meditation involves practice to train
one's ability to maintain focus or attention on a particular object or thought, and therefore is a natural starting place for interventions aiming to reduce mind wandering (Smallwood & Schooler, 2015). Mindfulness-based approaches, within a larger cognitive-behavioral framework, may also be a fruitful avenue for intervention for youth and adults with SCT (Becker & Barkley, 2018). It will be especially important for intervention trials to not only evaluate whether mindfulness-based interventions reduce SCT symptoms, but also improve both behavioral task performance (e.g., SART performance) and reduce functional impairments (e.g., social or academic impairment). As for pharmacological intervention, clinical reports suggest that serotonergic reuptake inhibitors having some use in managing ruminative thoughts and obsessive-compulsive disorder (fluvoxamine) may be helpful for managing pathological mind wandering; one of several potential drug treatments yet to be explored in the field of SCT.

CONCLUSION
This paper outlines some of the numerous ways that the study of SCT and, by default, ADHD will be advanced by a careful consideration of mind wandering, its nature, correlates, research methods, and interventions, as they may be applicable to our understanding of SCT.
We propose that it is well past time for mind wandering and SCT to cease operating in parallel research silos, and instead, to integrate these fields in an effort to better understand the nature, impacts, and intervention strategies for individuals who experience excessive daydreaming.