POWERED BY NATURE – The psychological benefits of natural views and daylight
For centuries nature has been our habitat. Many aspects of this natural habitat still have pronounced influence on our health and wellbeing. In this dissertation, two important aspects of nature have been studied; views to nature and exposure to daylight. The main focus has been on positive effects of these two phenomena as well as on the underlying psychological pathways of these beneficial effects.
The first chapter of this dissertation presented a review of the evidence for beneficial health effects of nature and daylight. The main conclusion of this chapter was that natural views and daylight exposure rendered very similar beneficial effects on a variety of health outcomes, but both phenomena have been studied in two separate research fields. Not only did this separation oftentimes result in ignorance with respect to contributions of one phenomenon while studying the other, but there were also substantial differences in the experimental paradigms used, the outcome variables, and the proposed underlying mechanism. Therefore, it was as of yet unclear whether natural elements and daylight exhibit similar beneficial effects and whether they share psychological underlying pathways. For these reasons, the aim of this dissertation was twofold. First, we wanted to test whether daylight and natural environments share underlying psychological mechanisms. Second, beneficial effects of nature and daylight were studied separately, but within uniform research paradigms to establish whether their health-benefits overlap.
A first series of experiments investigated possible underlying psychological pathways. The focus was on preference and associative pathways. Preference ratings are important in view of the adaptive function of preferences, guiding humans toward healthy -and away from unhealthy- environments. Chapter One reported a consistent preference for environments that are natural, bright, and sunny as opposed to urban, dark, and overcast environments. These findings were found for explicit preference, but not for implicit preferences. Two studies also investigating implicit preference for environments differing in naturalness, brightness, and weather type did not yield any evidence for implicit preferences. Importantly, we were also not able to replicate earlier findings concerning implicit preferences for natural environments. Preference for daylight over artificial light was further reported in Chapters Four and Six and higher preference ratings for natural as opposed to urban environments were reported in Chapters Three and Five. These higher preference ratings provided a first indication for possible restorative effects of daylight through psychological pathways.
Psychological mechanisms were further investigated in Chapters Three (for nature) and Four (for daylight). This time, the focus was on associative patterns, which are closely related to preference formation and have been previously theoretically linked to restorative potential. The series of experiments performed in these two Chapters aimed at testing whether and how associations differ between nature or daylight and their artificial counterparts. Results indicated that both daylight and natural environments generally evoked more positive associations than respectively electric light and urban environments. The valence of the associations generated with natural as opposed to urban environments mediated the preference ratings for these environments. The causal directionality of this relation was further investigated for natural environments by guiding the valence of associations. To this end, participants were instructed to generate either only positive or only negative associations and to suppress all oppositely valenced associations. The outcomes of these conditions rendered mixed results. Preference ratings for natural environments remained unaffected by the association instructions, whereas preference ratings for urban environments declined when generating only negative associations as compared to only positive associations.
Whereas natural environments and daylight both evoked more positive associations, the influence of these associations on preference formations differed between them. For natural environments, the valence of associations significantly mediated the effect of environment type on preference. However, for daylight the valence of associations did not mediate preference outcomes. Therefore, we did not guide the valence of associations with daylight versus electric light.
Not only did we investigate the relation between valence of associations and preference, we also studied the role of associations in restorative outcomes. For both natural environments (Chapter Three) and daylight (Chapter Four), little evidence for restorative effects of the manipulation was found. We hypothesized that the association generation task possibly interfered with the restoration process. On the other hand, in Chapter Three, we found that generating positive associations resulted in an improved restoration of positive affect. We postulated that natural environments generate more positive thoughts and that positive thoughts, in turn, can be restorative.
From the studies investigating psychological pathways for the effects of nature and daylight, we learned that they both generated more positive associations and higher preference ratings than electric light and urban environments. However, the relation between associations and preference ratings appeared to differ between the two phenomena, indicating that they could work through different psychological pathways.
These differences between daylight and nature proceeded when comparing the beneficial effects of nature and daylight on self-regulation, mood, and physiology. A uniform research paradigm was chosen to test these effects; ego-depletion. Chapter Five focused on the effects of nature, while controlling for daylight influences and Chapter Six investigated beneficial effects of daylight as compared to electric light while view content was kept constant.
In both chapters, the ego-depletion inductions were not always successful. Irrespective of this, Chapter Five reported consistent beneficial effects of natural environments on Heart Rate Variability and hedonic tone. By testing effects of nature after a depleting as well as a control task, we were further able to challenge the notion of restorative versus instorative effects. Contrary to the beneficial effects found for natural environments, no such effects were found for daylight. No difference in restoration outcomes were reported for daylight as compared to electric light in Chapter Six.
To conclude, we found that both daylight and nature generated higher preference ratings as well as more positive associations than their artificial counterparts. In a uniform research paradigm we established beneficial effects of nature, but not of daylight. In Chapter Seven, we postulated that the lack of evidence for beneficial effects of daylight could be due to the separation of daylight from view content. The psychological benefits of daylight may depend on exactly the factor we tried to single out; view content.
Femke Beute PhD Thesis is available at http://repository.tue.nl/780722