With the omnipresence of technology and the high prevalence of urban or suburban life, nature exposure has significantly decreased over the last few decades. For instance, attendance to the main United States national parks has declined nearly 7% between 1993 and 2010 (Stevens et al., 2014). The COVID-19 pandemic also contributed to exacerbate this issue. In a recent survey conducted by Moore et al. (2020), it was reported that, during virus outbreak, time spent outside by Canadian children and youth reduced, whereas screen and social media time increased. Literature has, however, shown that nature exerts many positive impacts, including benefits for health (Bowler et al., 2010; Twohig-Bennett and Jones, 2018), affects (McMahan and Estes, 2015), stress (Hunter et al., 2019; Yin et al., 2020) and even cognition (Ohly et al., 2016; Stevenson et al., 2018). Considering the high demands known to incur from technology usage, multitasking and other daily life challenges, nature’s positive effect on cognition can be particularly useful to reduce fatigue or depletion. Such effects have been observed through lab and outdoor experiments, often relying on pre-post interventions to assess the potential recovery effects of nature on executive attention. Benefits have been observed on many cognitive activities including but not limited to creative problem solving (Atchley et al., 2012), working memory (Shin et al., 2011; Berman et al., 2012), inhibitory control of competing stimuli (Berman et al., 2008; Chung et al., 2018) and sustained attention (Berto, 2005; Pasanen et al., 2018).

According to Attention Restoration Theory (hereafter ART; Kaplan, 1995), nature’s benefits on attention originates from the characteristics nature inherently possesses. More precisely, ART posits that attention can be restored when the person-environment interaction has four factors. A person must first garner a sense of being physically or conceptually away from any distraction, worry or demanding situation from their daily life (being away). One must also be exposed to a context that is compatible with their purpose and inclinations (compatibility). Restorative environments must also capture visual attention with their fascinating properties (fascination) as well as be sufficiently rich and coherent such that attention is not only captured but also sustained (extent). Nature can help recover attention in response to these four properties; yet, fascination may play a particularly important role. Fascination is deemed effortless and automatic (James, 1892; Baumeister et al., 2000), typically involves attractive patterns difficult not to attend (Berto et al., 2010) and links to the tendency to process information under uncertainty (Kaplan and Kaplan, 1989; see also Mueller et al., 1972). At moderate levels—referred to as soft fascination—it is similar to James’ (1892) concept of involuntary attention (i.e., attention that requires no effort, triggered by a stimulus’ “direct exciting quality”), promoting a reduction in demands on executive-based attention (Kaplan, 1995, 2001; see also Pearson and Craig, 2014) and thus allowing directed attention to rest and recover as supported by improved performance on cognitive tasks observed at post-intervention assessments (e.g., Berman et al., 2008; Atchley et al., 2012; Sahlin et al., 2016). Fascination is driven by bottom-up processing and it differs from directed (or voluntary) attention, which rather refers to top-down effortful processes driven by inner intentions (Eimer et al., 1996). Both forms of attention have been associated with different origins and mechanisms of action in the brain (e.g., Näätänen et al., 1980; Mayer et al., 2004; Landau et al., 2007; Prinzmetal et al., 2009; but see Peelen et al., 2004). In ART, Kaplan proposed that nature can help recover the limited voluntary attention resources depleted by cognitively-demanding daily tasks because of its capacity to effortlessly capture involuntary attention (Herzog et al., 1997; Kaplan and Berman, 2010).

Consistent with ART, recent empirical work supports the notion that fascinating stimuli of nature can softly capture involuntary attention. For instance, Berto et al. (2010) fatigued participants before asking them to perform a Sustained Attention to Response Task (SART) where they needed to monitor sequences of built and nature environments of low and high fascination and respond on infrequent targets that appeared either on a cued position (valid trial) or at random (invalid trial). Their results showed that the cost/benefit difference in reaction time between valid and invalid trials was improved in the high fascination trials, but not in low fascination trials, for both images of nature and built environments. They interpreted this result as evidence that high fascinating stimuli reduced the need to suppress and inhibit distraction, hence facilitating the involuntary attention orienting toward the target. Hopman et al. (2020) relied on resting-state posterior alpha power changes to examine whether a multiday trip to nature could induce differences in introspection and internally-focused attention as compared with pre- and post-trip control testing. According to the authors, the lower resting state posterior alpha power changes they observed during the nature trip was consistent with ART’s view that nature exogenously captures involuntary attention, hence reducing possibilities for internal reflection (see also Ulrich et al., 1991; Chung et al., 2018; Olszewska-Guizzo et al., 2018; Scott et al., 2020).

A few studies have also directly investigated the role of attention through eye-tracking measures, including fixation, eye blinks and pupillary measures. Such metrics have been shown to provide a window to the deployment and engagement of visual attention and cognitive activity (e.g., Kahneman, 1973; Beatty, 1982; Culham et al., 1998; Van Orden et al., 2001; Irwin and Thomas, 2010; Chen et al., 2011; Shultz et al., 2011; Unsworth and Robison, 2017; Marois and Vachon, 2018). For instance, Berto et al. (2008) assessed the amount of engagement toward images of high-fascinating nature and low-fascinating built environments using fixations and saccadic movements measured by an eye-tracking system. Their results showed that low-fascination built (non-restorative) environments triggered more fixations than nature high-fascination images, suggesting inferior volition of attention during exposure to high-fascination nature. Valtchanov and Ellard (2015) also observed consistent results by showing a lower number of fixations, fixations of longer durations and a reduced amount of eye blinks when viewing nature scenes compared with urban scenes (see also Franěk et al., 2018). Moreover, Martínez-Soto et al. (2019) replicated the reduced number of fixations and their longer duration for nature restorative images compared with urban non-restorative images, but also showed higher pupil dilation for restorative nature images, which they ascribed to the superior affective preference for restorative nature environments. Overall, these results support ART’s interpretation that restorative environments elicit lower engagement of voluntary attention, particularly when comparing urban and nature scenes.

Yet, it has also been shown that attention restoration by nature may benefit from higher attentional engagement toward the restorative stimuli which contradicts the idea that attention would rest rather than being engaged toward restorative nature. For example, Duvall (2011) asked participants to take part in an outdoor-based intervention that consisted of taking at least three 30-min walks per week for 2 weeks. Participants were either assigned to a condition in which they had to develop a walking schedule with the researcher before the intervention (standard care group) or had to use awareness strategies regarding the environment while they were walking (engagement group). Results showed that subjects in the engagement group significantly improved their attentional functioning on a modified version of the Attentional Functioning Index (e.g., Cimprich, 1992). Pasanen et al. (2018) reached similar conclusions with people taking a single walk in an outdoor natural environment while being actively engaged toward the setting (e.g., looking around, finding one’s favorite place or searching for a place related to one’s situation in life). Indeed, participants who were asked to actively engage during their walk showed reduced commissions errors on the SART at post-test. These results strongly suggest that superior engagement and deployment of voluntary attention toward the restorative setting might be better for attention restoration (see also Lin et al., 2014; Browning et al., 2020). In fact, a recent eye-tracking study conducted by Stevenson et al. (2019) supported this conclusion. Specifically, the authors asked participants to either walk through a natural environment or urban environment while wearing a mobile eye tracker and performing the attention network task before and after the walk. Their results showed a faster and more stable pattern of results on the attention network task for participants that walked in nature, supportive of restoration of attention. Moreover, a higher fixation rate was observed for participants who walked in nature compared with those walking through a city. This finding supports the notion that voluntary attention might be active when one is being exposed to nature, which is in direct opposition with ART and with the other eye-tracking studies discussed above (cf. Berto et al., 2008; Valtchanov and Ellard, 2015; Franěk et al., 2018; Martínez-Soto et al., 2019).

One way to better understand the mechanisms underlying attention restoration by nature is to investigate the impacts of several nature settings characterized by different levels of restoration-promoting properties. This allows one to control for any potential specific nature-urban differences that might be difficult to disentangle in studies employing nature vs. urban comparisons (Scott et al., 2020). According to Szolosi et al. (2014), all nature is not equal, and more importantly, nature that specifically contains patterns of mystery may be particularly useful at opening opportunities for rest and mental state recovery given the known relationship between mystery and fascination (Herzog and Kropscott, 2004; Stamps, 2004). Here, mystery is defined as the characteristics of a setting that promote exploration, engaging and sustaining a person’s interest or fascination because of the sense that it can provide more than the information immediately available (see Kaplan and Kaplan, 1982, 1989; Stamps, 2004; Szolosi et al., 2014). It refers to settings that contain certain portions of the landscape that are obstructed or concealed (curvier patterns, richer in texture and poorer in color and luminance) such as a bend in a trail, a view hidden by foliage, or a stream that meanders out of sight (Hammitt, 1980; Gimblett et al., 1985). Given its ability to encourage one to venture, engage and discover more than there is—thus its close relation with fascination—mystery could offer benefits for attention restoration, especially given the aforementioned relation between engagement and restorative benefits (cf. Duvall, 2011; Lin et al., 2014; Pasanen et al., 2018; Browning et al., 2020). Therefore, manipulating mystery levels of nature images offer the possibility to control for restoration potential by relying only on nature images, putting aside any undesirable variability that would arise from urban settings.

Using a recognition memory task, Szolosi et al. (2014) showed that, with longer presentation duration at encoding (presumably permitting greater opportunity for deployment of voluntary attention), nature images perceived and rated high in mystery were significantly better recognized than those perceived low in mystery. Moreover, results on a self-reported perceived restoration scale supported that high-mystery images were considered more fascinating and restorative than low-mystery images. While investigating the impact of mystery and showing that it could lead to increased restorative benefits, Szolosi et al. (2014) also outlined an important aspect related to the role played by both voluntary and involuntary forms of attention during restoration. Given that involuntary processes are typically automatic and rapid while voluntary ones are controlled and contingent on greater time spent on task, manipulating image exposure time allowed them to simulate demand on attention and assess whether, at different durations, benefits could be observed. By observing that longer presentation durations entailed larger benefits, they showed memory performance was in fact related to the extent of directed/voluntary “effort” deployed with increased viewing time. Besides, the authors ran a mediation analysis and showed that the differences in benefits on recognition memory performance between both mystery sets were attributable to ratings in perceived fascination, but only for longer exposure durations (for 5 and 10 s, but not for 1 s). This outcome suggests that the positive effect of mystery, which in fact could be explained by differences in fascination levels, emerged only for longer periods wherein voluntary forms of attention could be deployed. Hence, from their perspective, nature endowed with higher restorative potential might be related to superior cognitive engagement and, therefore, higher recruitment of voluntary attention. To our knowledge, Szolosi et al. (2014)’s study represents the only investigation of the role of attention during restoration relying on two sets of nature images characterized by different restoration potential. However, Szolosi et al. (2014)’s evidence on the active role of attention remains indirect, meaning that the alleged superior engagement of attention during exposure to more restorative, high-mystery nature images was assessed through the differential impact of several exposure durations on recognition memory performance.

The goal of the current study was to follow-up on Szolosi et al. (2014) study by exploring how voluntary attention could be deployed while being exposed to nature images of different mystery levels, with presumably different potential for restoration. To reach this goal, participants were asked to actively look at 80 images (40 low- and 40-high mystery images which previously elicited restoration effects; see Szolosi et al., 2014) for 5,000 ms each and rate them on their fascinating and aesthetic properties. The objective of this task was to promote engagement of voluntary attention. While participants were deploying their attention toward the nature images, an eye tracker system collected measures of pupil size and eye fixations. Spontaneous eye blinks (see Espinosa et al., 2020) were also measured given their known relationship with cognitive functioning (e.g., Jongkees and Colzato, 2016; Eckstein et al., 2017). These measures were used to assess the extent to which participants were actively engaged toward each image of nature, thereby determining the impact of mystery on attention deployment given its positive relation with the number of fixations and pupil size, and its negative association with blink rate, blink duration and fixation duration (e.g., Kahneman, 1973; Beatty, 1982; Culham et al., 1998; Van Orden et al., 2001; Irwin and Thomas, 2010; Chen et al., 2011; Shultz et al., 2011; Unsworth and Robison, 2017; Marois and Vachon, 2018). Such a manipulation permitted attentional engagement with nature on a much shorter time scale than many ART intervention studies, skewing toward involuntary forms of attention in comparison with previous ART literature, but still with durations long enough to presumably engage voluntary attention controlled processes similar to Szolosi et al. (2014). Considering that participants were asked to actively (and voluntarily) look at the images and to rate them, if differences in attention engagement metrics should emerge, this would be attributable to a different level of voluntary attention engagement facilitated by the characteristics of each (high- or low-mystery) image.

In line with Szolosi et al. (2014), high mystery nature was expected to be perceived as more fascinating and rated with higher levels of likeability. We also anticipated increased attentional engagement as measured by the eye-tracking measures (i.e., increased pupillary dilations and fixation number, and reduced blinks and fixation duration) for high-mystery images compared with low-mystery images given Szolosi et al. (2014)’s demonstration that memory performance benefited from longer exposure durations, especially for high mystery images. Per ART’s perspective, the alternative hypothesis was that eye-tracking measures could rather support lower engagement (i.e., inferior pupillary dilations and fixation number, and increased blinks and fixation duration) for high-mystery images compared with low-mystery images given the notion that voluntary attention is expected to rest while one is exposed to restorative nature.

The current study provides one of the first direct explorations of the deployment of attention while viewing nature images of different mystery levels, i.e., with allegedly different potential for restoration (cf. Szolosi et al., 2014). To reach this goal, we collected eye-tracking measures (i.e., pupil size, fixations, and blinks) to investigate whether participants’ attention would be more engaged and active while viewing high-mystery images compared with low-mystery images using the same set of pictures as Szolosi et al. (2014). Participants were also asked to provide ratings of likeability and fascination on a subscale of the Shortened Perceived Restorativeness Scale. Results first replicated the higher ratings of fascination observed by Szolosi et al. (2014) for high-mystery images, as well as extended these findings to demonstrate high-mystery images were also more liked. More importantly, eye-tracking measures showed that attention was more active and engaged when participants were looking at images with more mysterious features, providing evidence toward a greater deployment of voluntary attention for these settings as participants were asked to actively look at the images for 5 s before rating them on their fascination and aesthetic properties. Indeed, for high-mystery trials, pupil size—even when controlling statistically for luminance variability—was larger, fixations were more frequent and of shorter duration, and eye blinks were less frequent. Given the relationship previously demonstrated between attention involvement, pupil size, fixations, and blinks (Kahneman, 1973; Beatty, 1982; Culham et al., 1998; Van Orden et al., 2001; Irwin and Thomas, 2010; Chen et al., 2011; Shultz et al., 2011; Unsworth and Robison, 2017; Marois and Vachon, 2018), these results support the view that raising the mystery level in nature increases one’s attentional engagement which in turn potentially augments the restorative potential of nature (cf. Duvall, 2011; Lin et al., 2014; Pasanen et al., 2018; Browning et al., 2020).

The fact the Szolosi et al. (2014) observed better memory for the more mysterious nature images is consistent with our demonstration of higher engagement for those same images. In fact, literature has shown that improved memory performance at recall was related to higher engagement and more optimal deployment of attention at encoding as supported by larger pupil sizes, increased visual exploration and less eye blinks (Shultz et al., 2011; Irwin, 2014; Kucewicz et al., 2018; Damiano and Walther, 2019; Meghanathan et al., 2019; Miller et al., 2019). These results also provide evidence in favor of the potentially active role of voluntary attention during restoration reported by Szolosi et al. (2014). In their study, longer viewing durations incurred higher demands on voluntary attention processes that are controlled and sustained as opposed to involuntary attention mechanisms known to be transient, rapid and automatic. This increased exposure duration led to superior benefits for memory performance (Posner et al., 1980, 1982; Wright and Richard, 2000). Here, we show that the same set of high-mystery images indeed leads to a higher attention engagement that can potentially be ascribed to voluntary mechanisms.

While no actual measure of restoration was collected, our findings are also consistent with studies in which a superior restoration experience was related to higher engagement toward nature (e.g., Duvall, 2011; Lin et al., 2014; Szolosi et al., 2014; Pasanen et al., 2018; Browning et al., 2020). In these studies, the positive impact of nature exposure on cognitive performance was amplified when participants performed tasks that promoted their engagement toward the nature setting (e.g., actual vs. virtual exposure, enhanced awareness toward the nature setting or stimuli, or longer viewing time). The fact that these studies showed optimized restoration with higher engagement contradicts ART’s view that voluntary attention is resting when one is exposed to nature, and thus puts our results into context. As shown by Szolosi et al. (2014) and supported by other literature showing a positive relationship between fascination and mystery (cf. Kaplan and Kaplan, 1982, 1989; Herzog and Kropscott, 2004; Stamps, 2004), higher levels of mystery can engage one’s attention toward nature scenes and in turn improve the restorative experience. Because we observed higher measures of attentional engagement, this suggests that settings characterized by greater restoration potential tend to engage one’s voluntary attention.

The observation of higher voluntary attentional involvement for the settings containing more restoration potential (i.e., higher levels of mystery and higher fascination ratings) seem at first glance to contradict most of the eye-tracking studies focused on the deployment of visual attention during interaction with nature (Berto et al., 2008; Valtchanov and Ellard, 2015; Franěk et al., 2018; Martínez-Soto et al., 2019). In these studies, participants were typically exposed to nature and urban settings either in real or virtual form (i.e., using images), and oculometric measures were collected to infer their attention deployment toward the settings. Supported by these metrics, the authors observed that urban environments were generally related to higher involvement of voluntary attention (e.g., more fixations and larger pupil dilation) when compared to nature environments. Consistent with ART, they interpreted this pattern of results as evidence that voluntary attention is resting during its restoration because nature—which led to inferior attention involvement—did contribute to attention restoration, as opposed with urban environments.

Yet, to fully explore the mechanisms of attention restoration, one must also compare nature environments of different restoration potential. Our investigation thus focused on comparing two sets of nature images of different restoration potential and contradicted these studies. An explanation for such an opposite view can originate from the type of fascination that is triggered by nature and urban images. According to Kaplan and Berman (2010), urban environments tend to trigger hard rather than soft fascination, which contains bottom-up stimulation that automatically captures attention and requires directed attention to resist. This explains why urban environments may be less restorative than nature settings (Berman et al., 2008). Nature settings can trigger soft fascination and the attraction they typically elicit does not incur resistance nor inhibition that might require executive-based attention (Kaplan, 1995, 2001; Pearson and Craig, 2014). Exposure to (softly fascinating) nature setting thus entails lower engagement than urban environments because no effort is required to inhibit the “competing” attraction driven by nature. Yet, one could also be exposed to nature settings that are considered less fascinating, with stimuli that might be less preferred and cause reduced attention deployment. Such would be the case for low mystery nature settings, as opposed to high mystery nature settings stronger in the fascination they elicit. Considering both our results and those raised by the other eye-tracking studies, a pattern can emerge.

Here, we propose that the relationship between attentional engagement of the environment and restoration potential may be characterized by a quadratic trend, in the form of an inverted-U shaped relationship. At the lower level of the engagement continuum, suboptimal attention restoration may be possible with nature settings that are less captivating (e.g., low mystery settings) where one would be less involved toward the setting, in a state that might approach inattentiveness. At moderate levels of engagement, optimal attention restoration might be related to soft fascination with nature settings sufficiently captivating (e.g., high mystery images) to attract one’s attention without consuming it and drawing from executive attention. On the highest end of the continuum, urban settings characterized by hard fascinating stimuli may engage one’s attention even more than high-mystery nature images while also consuming it, thereby reducing their potential for restoration. Such a situation could be described as a state of distractibility, where one’s mental resources would be too involved toward the urban stimuli to allow voluntary attention to restore. Figure 4 depicts such a curvilinear relationship between attention engagement and restoration potential according to the type of exposure. Although this hypothesis admittedly goes slightly beyond our results, it does reconcile the observation of higher engagement toward (non-restorative) urban settings reported by previous eye-tracking studies with our observation of higher engagement toward (more restorative) high-mystery nature images, compared with (less restorative) low-mystery nature images. However, further investigation is needed to better understand the differences in attention involvement toward these three types of settings and to fully explore the relationship between engagement and restoration. Different types of urban scenes should also be compared, manipulating the level of fascination and engagement they elicit to investigate this potential moderating effect on attention restoration as well (see, e.g., the urban control environments of Hopman et al., 2020; Scott et al., 2020, which somewhat counterintuitively elicited lower levels of engagement than nature environments such as a sandy riverbank in the desert, perhaps because participants in the urban condition were sitting outside on a familiar college campus looking at a concrete wall).

Per our results, voluntary attention would be engaged in the attention restoration process. Yet, an alternative hypothesis remains. Although the superior cognitive engagement observed for high-mystery images for the 500–5,000 ms time-window could be specifically ascribed to mechanisms of voluntary attention typically observed on longer and sustained periods (e.g., Wright and Richard, 2000), one could still argue that it rather represents mechanisms of involuntary attention in a sense similar to what is proposed by ART. Recall that, per ART’s viewpoint, involuntary attention would be captured by the fascinating stimuli of nature, then reducing further voluntary attention demands on the system, allowing at the same time restoration of executive attention. Although the effects observed occurred on a longer period and hardly represent involuntary mechanisms (which are normally automatic and fast-acting; see Posner et al., 1980, 1982), disentangling the voluntary and involuntary mechanisms of attention deployed while participants looked at the nature images may be difficult. In light of our results, it seems, however, more likely that voluntary attention processes were engaged, although this does not exclude any previous/automatic involvement of involuntary attention, especially given the previous demonstration of superior involuntary attention engagement when interacting with restorative nature scenes (cf. Berto et al., 2010; Olszewska-Guizzo et al., 2018; Hopman et al., 2020).

However, one may wonder how increased attention engagement toward the nature setting might contribute to the restoration of cognitive (and allegedly voluntary attention) resources (Kaplan, 1995; Berman et al., 2008; Kaplan and Berman, 2010). As suggested by Szolosi et al. (2014), those attentional benefits might originate from a balance between involuntary and voluntary attentional networks. Specifically, more mysterious nature and their physical properties likely seem to evoke a sense of soft fascination, and this type of fascination can engage a person’s attention fairly automatically. In turn, instead of using cognitive resources to strictly inhibit (automatically and involuntarily) responding to stimuli that may demand high involvement of executive attention (i.e., for urban scenery, similar to the word dimension in a Stroop color naming task; Stroop, 1935, where individuals must overcome oppositional logic to correctly name ink colors rather than to incorrectly read words), we propose the mystery and soft fascination inherent in nature may facilitate the engagement of a person’s voluntary attention, hence reducing cognitive demands and providing an explanation to the cognitive benefits typically ascribed to restoration by nature. This would be in line with the bulk of the visual-spatial literature showing that exogenous (involuntary) cueing can in turn facilitate sustained (voluntary) processing of visual information (e.g., Fernandez-Duque and Posner, 1997; MacLean et al., 2009; Dugué et al., 2020; Nguyen et al., 2020). Critically, this view would also reconcile both evidence that involuntary attention is automatically and effortlessly captured (e.g., Berto et al., 2010; Olszewska-Guizzo et al., 2018; Hopman et al., 2020) with that related to the benefits of superior attention engagement toward the nature setting (Duvall, 2011; Lin et al., 2014; Szolosi et al., 2014; Pasanen et al., 2018; Stevenson et al., 2018). Even so, future work should specifically investigate this switch in the form of attention that is engaged (from automatic involuntary to controlled voluntary) to better understand how both forms of attention may be involved during exposure to restorative nature.

Within classical literature, authors have lauded nature for its ability to provide a venue that can facilitate cognitive clarity (Emerson, 1836; Thoreau, 1854). That is, nature seems to offer many people a place that can engage their attention effortlessly, while at the same time allowing them to maintain some attentional volition. Findings from our study align well with this notion. Interactions with certain natural settings appear to engage a form of attention that resonates with both bottom-up (involuntary) and top-down (voluntary) cognitive processes. Hence, interacting with nature may not permit directed attention to rest, but rather engages it in a way that resonates with bottom-up visual properties of the environment. Such resonance may serve to recalibrate flexible attention’s relationship with the environment, moving away from top-down inhibition to sources of interference that may be cognitively depleting and effortful toward the capture of attention by fascinating stimuli, thereby facilitating its restoration. The culmination of this work could eventually lead to the development of cognition-supportive systems or interventions that might be used by workers, students, or simply people who seek attention recovery following—or preceding—any period of cognitive fatigue. The stress and the cognitive challenges (e.g., interruptions, distractions, rapid and complex problem solving, dual tasking, information retention, and long periods of vigilance) that students (e.g., Misra and McKean, 2000; Robotham and Julian, 2006; Versaevel, 2014; Guerra-Carrillo et al., 2017) and workers from an office (e.g., Young and Berry, 1979; Jett and George, 2003; Crompton, 2011; Mak and Lui, 2012) or high-risk domains (e.g., Dehais et al., 2014; Grier, 2015; Hodgetts et al., 2017; Marois et al., 2019) confront might be mitigated by using these interventions.

In conclusion, future work should consider the extent to which interacting actively with high-mystery nature scenes translates into secondary benefits on cognitive tests but especially measures of executive attention. Further investigation of the proposed attentional resonance between top-down and bottom-up forms of processing is also needed to assess how perception, deployment of attention, memory, and even internal thoughts (mind wandering) can be impacted by mystery, fascination or other image properties. For example, these studies could provide converging evidence on whether cognitive engagement with high-mystery, and thus more fascinating, nature settings may impact mind wandering thoughts compared to low-mystery settings. This could provide additional evidence of the active engagement of directed attention during restoration by nature.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Colorado Multiple Institutional Review Board, University of Colorado Denver. The patients/participants provided their written informed consent to participate in this study.

AM and JW developed the study concept and experimental design. AM and BC contributed to the acquisition and analysis of the data under the supervision of JW. All authors took part in the interpretation of the data. AM, JW, and BC drafted the manuscript and key revisions were provided by AS. All authors approved the final version of the manuscript for submission.

AM was employed by the company Thales Research and Technology Canada. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.