Reconceptualizing mind wandering from a switching perspective

In the past two decades, there has been growing interest in understanding the basic psychological processes of mind wandering and its underlying mechanisms (for a review, see Kvavilashvili & Rummel, 2020). Mind wandering refers to a phenomenon in which our attention shifts away from the task at hand toward task-unrelated thoughts (for reviews, see Smallwood et al., 2018; Smallwood & Schooler, 2006, 2015). It has been estimated that up to 50% of our waking time is spent mind wandering (Kane et al., 2007; Killingsworth & Gilbert, 2010). Despite its prevalence, most people view mind wandering from a negative perspective, in which our performance will drop if our mind wanders (for reviews, see Mooneyham & Schooler, 2013; Stan & Christoff, 2018). Indeed, a number of studies have found a negative association between mind wandering and primary task performance, including poorer performance in daily functioning (McVay et al., 2009) and driving (Baldwin et al., 2017; Yanko & Spalek, 2014). However, studies have also shown a positive relationship between mind wandering and both mood and cognition (e.g., Gable et al., 2019; Mazzoni, 2019; Welz et al., 2018). In order to understand how to minimize the costs of mind wandering and maximize its benefits, it is therefore important to determine what factors regulate its occurrence.

Despite mind wandering inherently involving a shift in mental set, no existing study to our knowledge has explicitly examined the role of cognitive flexibility in mind wandering. In the present article, we consider the potential of cognitive flexibility to help explain the nature of mind wandering and its tendencies. In an effort to advance the field, here we first briefly review and discuss the most prominent theories of mind wandering—the executive failure hypothesis (McVay & Kane, 2009, 2010, 2012b), the decoupling hypothesis (Smallwood & Schooler, 2006), the process-occurrence framework (Smallwood, 2013), and the resource-control account of sustained attention (Thomson et al., 2015). Then, we put forward a new perspective centered around cognitive flexibility that was prompted by findings from several mind-wandering studies in older adults (e.g., Gyurkovics et al., 2018; Jordão et al., 2019; Niedzwienska & Kvavilashvili, 2018) and mind-wandering studies involving task-switching paradigms in young adults (e.g., Arnau et al., 2020; Kam & Handy, 2014; Thomson et al., 2014). According to this new switching perspective, the reason why some populations (e.g., healthy older adults) experience distinct patterns of mind wandering stems from differences in cognitive flexibility, as instances of mind wandering are in fact instances of mental set shifting (see Murray & Krasich, 2020, for a similar argument). After presenting the evidence supporting this new perspective, we put forward recommendations for future research aimed at further understanding the importance of cognitive flexibility in mind wandering.

Cognitive flexibility, which can also be referred to as mental set shifting or switching, is one of the three core executive control functions (along with inhibitory control and working memory) that enables us to adjust our thoughts and actions in response to changed priorities or demands (Buttelmann & Karbach, 2017; Diamond, 2013; Miyake et al., 2000). To adapt to changing priorities, for example, we need to inhibit previously relevant thoughts and actions and activate newly relevant thoughts and actions in working memory. In this way, mental set shifting requires involvement of both inhibitory control and working memory (Diamond, 2013). With regard to mind wandering, we propose that it requires cognitive flexibility, as the occurrence of mind wandering entails inhibition of one’s primary task mental set (which enables decoupling to occur) and activation of task-unrelated thoughts in working memory (see Fig. 1).

Considering this switching view alongside existing frameworks and models such as the metacontrol state model (Hommel, 2015), which describes the balance between flexibility and persistence in cognitive processing (Zhang et al., 2020), may provide a way to understand variability in mind-wandering frequency. For instance, given that ADHD has long been found to be associated with dysregulated dopamine neurotransmission (Cook et al., 1995), and dopamine-related interindividual differences have been hypothesized to be associated with interindividual variability in metacontrol defaults (i.e., the control of the current cognitive-control settings; Hommel & Colzato, 2017), it seems possible that the increased mind wandering experienced by individuals with ADHD might be associated with a default metacontrol setting biased towards flexibility (i.e., weak goal shielding and weak mutual inhibition of task-related and task-unrelated mental sets) that may be related to imbalances of neurotransmitters. Moreover, given that older adults tend to report higher levels of positive affect (e.g., Frank et al., 2015) and motivation (e.g., Nicosia & Balota, 2021; Ryan & Campbell, 2021; Seli et al., 2021) than young adults during task performance, and situational factors such as these have been hypothesized to induce a metacontrol setting biased towards persistence (Hommel & Colzato, 2017), it seems possible that older adults’ less frequent reports of mind wandering (e.g., Arnicane et al., 2021; Jordão et al., 2019; Maillet & Schacter, 2016) might be associated with a stronger bias towards persistence (i.e., stronger goal shielding and stronger mutual inhibition of task-related and task-unrelated mental sets).

It may also be possible to account for the effect of mind wandering on creativity (e.g., Gable et al., 2019; Murray et al., 2021; Steindorf et al., 2021; Yamaoka & Yukawa, 2020) by integrating the switching perspective of mind wandering with both the metacontrol state model (Hommel, 2015) and the dynamic framework of thought (Christoff et al., 2016)—a model that provides insight into how thoughts that focus on personally or affectively salient information (i.e., automatic constraints) and thoughts that focus on goal-related information (i.e., deliberate constraints) dynamically influence the nature of thought over time. For example, given that both of these schemas emphasize the importance of flexibility or shifting between mental states in idea generation (for reviews, see Girn et al., 2020; Zhang et al., 2020), it seems possible that the relationship between mind wandering and creative thinking might be mediated by cognitive flexibility. This speculation may be worthy of future research.

In short, we believe that viewing mind wandering from a switching perspective may help explain, at least in part, why some populations experience more mind-wandering episodes while others experience fewer episodes, why participants who indicate higher levels of motivation are less likely to engage in mind wandering during task performance, and why mind wandering is sometimes linked to enhanced creativity.

The strongest evidence to date in support of this new perspective comes from research using the voluntary task-switching paradigm (Arrington & Logan, 2004), for which participants are free to switch tasks or continue with the same task at their preference. Somewhat paradoxically, research has consistently demonstrated that most of the participants decided to switch tasks despite negative consequences (i.e., switch costs; e.g., Irons & Leber, 2016; Kessler et al., 2009; Mittelstädt et al., 2019), although comparatively healthy older adults tended to initiate voluntary task switching less frequently than healthy young adults (Ardiale & Lemaire, 2012; Butler & Weywadt, 2013; Lockenhoff et al., 2020; Terry & Sliwinski, 2012). In light of cognitive aging, this finding may not seem surprising given that repeating the currently active task set requires fewer executive resources than switching to a different task set (Wirth et al., 2018) and switching between task sets or rules increases cognitive load (Arrington & Logan, 2004; Kool et al., 2010). In like manner, we argue that it should not be surprising either that healthy older adults and older adults with Alzheimer’s disease, Parkinson’s disease, and amnestic mild cognitive impairment experience less frequent mind wandering, as a reduced switching ability could contribute, at least in part, to getting “stuck” in a task-focus mode (cf. Walpola et al., 2020).

Additional evidence for the switching perspective of mind wandering comes from the intriguing finding that mind wandering does not always impair young adults’ performance in switching tasks, in contrast to tasks that require sustained attention. Using a probe-caught method, Kam & Handy, (2014) found no significant disruptive effects of mind wandering on task-switching performance. A further study, which investigated the association between mind wandering and task-switching performance over time, observed similar response times and accuracy rates for the trials leading up to “on-task” and “off-task” reports (Thomson et al., 2014), which again suggests that switching performance was unaffected by mind wandering. Similar results were obtained by Arnau et al., (2020), who investigated electrophysiological correlates of mind wandering during a switching task and did not observe slower response times during periods of self-reported mind wandering relative to on-task episodes.

The lack of performance costs, particularly response time costs, for switching tasks is puzzling because mind wandering has consistently been found to disrupt behavioral performance on tasks that tap the other two core executive function measures—inhibition (e.g., Kam & Handy, 2014; Smallwood et al., 2008; Stawarczyk et al., 2011) and working memory (e.g., Kam & Handy, 2014; Krimsky et al., 2017; Unsworth & Robison, 2016). Given this, one might expect that mind wandering should also significantly affect one’s task-switching performance. Although Kam & Handy, (2014) speculated that the null effect of mind wandering on switching-task performance might reflect cognitive flexibility being a less representative executive functioning skill (as it showed the weakest correlations with other executive function measures; for more details, see Miyake et al., 2000), these researchers also noted that switching from the task at hand to task-unrelated thoughts may be a form of switching. In the same manner, we posit that because switching either between task-related mental sets or between task-related and task-unrelated mental sets requires cognitive flexibility, when one mind wanders during performance of a switching task, they continue to engage in a “task-switching mind frame” (i.e., instead of switching between task-related mental sets, the individual switches between task-related and task-unrelated mental sets), and thereby can maintain task-switching performance. This conjecture appears to fit well with previous studies indicating that frequent task/response switches can shift the flexibility-persistence balance (Hommel, 2015) towards higher flexibility (e.g., Fröber & Dreisbach, 2017; Fröber et al., 2018; Zhuo et al., 2021; for a review, see Dreisbach & Fröber, 2019).

Acknowledging that instances of mind wandering are instances of mental set shifting (see Murray & Krasich, 2020, for a similar argument) opens up new avenues for future scientific investigations. First, to directly investigate this new perspective, future research could examine the association between cognitive flexibility and the tendency to mind wander, as despite a number of researchers using a task-switching paradigm as the primary task in their investigation of mind wandering (e.g., Arnau et al., 2020; Kam & Handy, 2014; Thomson et al., 2014), to our knowledge none have explicitly investigated the role of cognitive flexibility in mind wandering. Second, as there are many different types of switching (e.g., rule switching, task set switching, and response set switching), which have been found to activate different brain areas (Ravizza & Carter, 2008), it may be important to investigate how these switching abilities are related and which type is most closely associated with mind wandering. Determining this may help advance the current understanding of the higher incidence of mind wandering in ADHD, and may ultimately shed light on the inconsistent results regarding whether ADHD is associated with deficits in cognitive flexibility (e.g., Halleland et al., 2012; Irwin et al., 2019; Rohlf et al., 2012; Willcutt et al., 2005), which in turn may shed further light on the viability of the switching perspective forwarded here. Third, as an increasing number of studies have revealed distinct effects of intentional and unintentional mind wandering on task performance (e.g., Martínez-Pérez et al., 2021; Moran et al., 2021; Seli et al., 2016a, 2016b; for a review, see Seli, et al., 2016a, 2016b), future research could investigate whether intentional and unintentional mind wandering constitute distinct forms of task-set activation (e.g., counscious or uncounscious activation of task-unrelated mental sets; Arango-Muñoz & Bermúdez, 2021; Lau & Passingham, 2007; Reuss et al., 2011; Weibel et al., 2013) that involve distinct neural mechanisms and might differ with respect to their relationships with cognitive flexibility.

Fourth, considering that in a real-world setting we constantly multitask (e.g., writing an email while listening to music and eating a meal), and studies have found a positive association between self-reported frequency of concurrent use of multiple digital media streams and mind-wandering tendency (e.g., Kane et al., 2017; Ralph et al., 2014; Wiradhany & Koerts, 2021), future research could investigate the association between mind wandering, multitasking, and cognitive flexibility. Fifth, to understand past findings (e.g., McVay & Kane, 2009; Robison & Unsworth, 2018; Unsworth & Robison, 2020) in light of this switching perspective, future studies could investigate whether healthy young adults with higher self-reported mind-wandering tendencies have lower working memory capacity but superior switching abilities. In consideration of previous findings (e.g., McVay & Kane, 2009, 2012b; Miyake et al., 2000; Oberauer et al., 2003; Robison & Unsworth, 2018; Shipstead et al., 2015; Unsworth & Robison, 2020; as discussed in the “Limitations and an alternative viewpoint for the executive failure hypothesis”), the increased mind-wandering frequency seen in healthy young adults with lower working memory capacity could reflect a tendency to initiate more switches between task-related and task-unrelated mental sets in relation to superior switching abilities. Sixth, considering that the executive failure hypothesis (McVay & Kane, 2009, 2010, 2012b) fits with the data in healthy young adults and individuals with ADHD, but does not account for the data in older adult populations discussed in this review, future research should explore the association between cognitive flexibility and the tendency to mind wander in different populations with age in mind, as it could be the case that the executive failure hypothesis applies to young adults whereas the switching account of mind wandering applies to older populations.

The findings reviewed in this article provide initial evidence to suggest that there may be an association between cognitive flexibility and mind wandering, and that distinct patterns of mind wandering may signal and be a product of altered cognitive flexibility. Although more research is needed, the switching perspective of mind wandering put forward here may provide a more comprehensive account of mind wandering that fits better with the experimental findings to date, including why healthy older adults and those with Alzheimer’s disease, Parkinson’s disease, and amnestic mild cognitive impairment experience less mind wandering (e.g., Gyurkovics et al., 2018; Jordão et al., 2019; Maillet & Schacter, 2016; Niedzwienska & Kvavilashvili, 2018; Walpola et al., 2020). This novel line of research may lead to the development of clinical detection tools and therapeutic approaches (e.g., task-switching training) aimed at preserving, or enhancing, the rates of mind wandering in populations with reduced levels of mind wandering (e.g., older adults), as mind wandering does have important functions such as facilitating future planning (e.g., Baird et al., 2011; Mazzoni, 2019; Seli, Maillet, et al., 2017; Seli, Ralph, et al., 2017; Stawarczyk et al., 2011) and the generation of creative ideas (e.g., Gable et al., 2019; Yamaoka & Yukawa, 2020) as well as promoting positive mood (e.g., Welz et al., 2018). Furthermore, recognizing that previous findings on mind wandering can be viewed from a switching perspective may provide an important contribution to our understanding of the basic psychological processes of mind wandering and its determinants, and may help future research to come up with a definition of mind wandering that will gain consensus in the field.