Last changed 22 Nov 2020 ............... Length about 4,000 words (39,000 bytes).
(Document started on 20 Sep 2015.) This is a WWW document maintained by Steve Draper, installed at You may copy it. How to refer to it.

Web site logical path: [] [~steve] [myNewWave] [this page]

Green space effects

By Steve Draper,   Department of Psychology,   University of Glasgow.

This page is to summarise and hold pointers about the "Green space" phenomenon. I feel we can call it a phenomenon because there are too many reports of carefully observed effects to leave much doubt that there is something substantial here; but no agreement on theory, nor on the scope of the field or area. I list a few student research projects here in this field. I then mention some published papers, selected to illustrate some of the various aspects of the area.

Some projects here on green space

Maxine Swingler,   Niamh Stack   Steve Draper, have all supervised undergraduate research projects in this area. There have been at least two student projects showing that primary school pupils are significantly better at concentrating on school work after a visit to a green space, than after a break of some other kind. Such work elsewhere has also been published e.g. Wallner18.

Some lit. refs on green space

Here are (only) a few published papers on the green space phenonmenon, arranged to illustrate a series of distinct ideas, and so to give some idea of the variety of work in the area.

1. Some of the early papers report medical effects. [The first idea about the effects of green space.]
Note that in this first example, it is a view through a window, not being outside in the green space, that is beneficial.

The introduction in the next article, which is from a medical journal, cites reports of numerous types of medical benefit from green space: longevity, cardiovascular diseases, people's self-reported general health, mental health, sleep patterns, recovery from illness, social health aspects and birth outcomes. But it emphasises that little is known of the mechanisms underlying them.

2. The most often cited "theory" is Attention Restoration Theory (ART). This focusses attention on the idea that the ability to control one's attention is a finite resource that diminishes (fatigues) as it is used, and how green space exposure can replenish attention, and more generally a variety of cognitive abilities. [This is an idea about the cause of green space effects (depletion of a finite mental resource); and also of specific effects (lower cognitive performance of various kinds, until restoration occurs).]

3. On the other hand, an interview in New Scientist with neuroscientist Daniel Levitin has him asserting that what stresses (fatigues) humans is not concentrating attention but switching contexts; and the remedy is day-dreaming not necessarily green space. (I however think that the restorative properties of green spaces often are to do with being able to let your mind drift while walking with nothing too taxing in the way of carrying out the walk. So that this perspective may be important.) [A different idea about the cause of green space effects.]

But perhaps we could also connect this to the concept of flow. Different kinds of attention. Novelty yet irresponsibility: thus avoiding both boredom and stress.

4. Plant chemicals, and other ecological factors. [Yet wider ideas about the causes of green space effects.]

5. Physical exercise. [An alternative wider idea about the causes of green space effects.]
Opezzo et al (2014) [Opezzo14]] is a notable paper in this area. Firstly, it asks the question of whether the physical exercise usually involved in being in a green space is in fact the main cause of the benefit. Given the enormous amount of evidence for the benefit of exercise to not only physical health, but also mental health, it is important to research this. The study showed that both green space and exercise have a significant benefit, and that although exercise has a greater effect, green space has an additional, independent, one. That is: exercise is important, but not the sole explanation for the effect. From now on, we should scrutinise every study to see whether exercise has been ruled out as an explanation of the results.

The study used "divergent thinking" as its measure, which is a common test of creativity. [This paper thus also offers evidence of a second effect of green space, other than improved attention.]

Furthermore, the study measured the duration of the effect: the improvement in divergent thinking lasted only about two minutes. Most studies fail to measure how long their effect lasts, tacitly assuming that it is durable. It may be that this explains a puzzle in some of the studies of green space effects on school pupils' attention, where teachers were positive that the green space condition results in marked improvements in attention, yet the study failed to show any improvement in tests of learning. It could be that the effect lasts for less than a whole school period (plus time for a test as well).

6. A general effect on well-being as well as on health and on cognitive performance. [This paper thus offers evidence of another, wider effect of green space.]

7. Wider effects on children's upbringing. [This paper thus offers evidence of yet another, wider effect of green space.]

There are increasing claims about the benefits of lots of outdoors time for children over long periods (years).

Web documents, mostly with literature references

Carol Craig's centre (materials written roughly 2018).   Entry by a Jigsaw diagram index   a more textual index

Particularly these articles:   1   2   Young People


What is it about "green space" that determines its effectiveness?

Being in nature vs. videos vs. still pictures

Studies of whether window glass makes a difference

Hahn08 paper raises the question


Trait measures of nature-relatedness

There are several measures of "nature-relatedness" (and a wikipedia entry lists more with references):

From an experimental psychology perspective, however, they are disappointing.

It would not be hard to address such weaknesses should someone wish to do so, and discover whether there is a property something like nature-relatedness with stable meaning. It would be a kind of attitude.

However these "criticisms" may be beside the point. These scales appear to come from a different viewpoint and are used for a different purpose. Often they are used on visitors to green-related facilities, where the degree of public support is important: both political support for policies, but even more for funding support for such things as public gardens, or tree planting. Most such things do not need to appeal to a majority, they only need a particular subgroup to desire them. Getting an instrument for these purposes would be a different issue. As one report put it, this is about developing a "Monitor of engagement with the natural environment", and not about whether greenspace is a general effect on most people. Such instruments do not require majority usage.

Affect and Wellbeing

Bergomi13 reviews self-report measures of mindfulness.

McMahan18 discusses several measures of affect.
In particular the frequently used PANAS (Positive and Negative Affective Schedule) which is a 20 item scale, with separate subscales for positive and negative: see Watson88 for details.

The short Warwick-Edinburgh Mental Well-Being Scale (SWEMWBS): StewartBrown09. The SWEMWBS is a 7-item version of the original 14-item Warwick-Edinburgh Mental Wellbeing Scale and measures a combination of eudaimonic and hedonic wellbeing. Each item is a statement about an individual's experiences over the past two weeks, responded to on a five point Likert scale. It contains only positively worded items, and a greater average score indicates greater mental wellbeing. It is brief, widely used, and has strong psychometric properties.

Subjective measure of restorativeness

There is questionnaire based on self-report of feelings of restorativeness: the Perceived Restorativeness Scale (PRS). Hartig97 discusses it; Han18 reviews it.


Physiological measures

Snell19 gives some details of these; as does Alvarasson10.

Attention control i.e. ability to direct attention

These include Snell19 gives some details of these; as does CDix20; and many other papers e.g. Berman08.
Manley99 discusses SART; Kaplan10 deals with SART briefly.


Opezzo14 used, describes, and gives references for three different measures, which capture different aspects of creativity.

One test is for "Divergent thinking", using GAU (Guilford's Alternate Uses test).

"Convergent thinking" is a test of another aspect of creativity. The compound remote-association test (CRA) measures this.

"Barron's symbolic equivalence" task (BSE; Barron, 1963). The BSE depends on the generation of analogies.

Time scale / duration

Cross-sectional studies

A cross-sectional study does a single one-time questionnaire of a sample, and then looks for correlations (in this field) between (1) how often the participant (P) looks out of the window and what type of view they see, with (2) their wellbeing, stress etc. Mathew19 and Kernan10 are of this kind.

It might be quite good in these times, since people were caught in lockdown and not able to choose their view of greenspace, and so this type of study would avoid the full force of self-selection which tends to confound cross-sectional research.

Active intervention on two occasions: e.g. over a week

While these are possible and have been done by students, it is more effort, and usually you lose a part of your participants who don't return for the second session. Some of my most impressive student projects have nevertheless been done this way (though not as a level 3 quant. project); and one of them was in fact done online for reasons other than lockdown.

One occasion: immediate effect within 30 - 60 mins

This would be practicable in a one-occasion online study, where you take a participant for an hour or less, and apply both pre/post measures and one or more interventions. CDix20 is an example.

Some time durations of interventions: for the length of green space exposure in various studies

There is no standard length of how long someone needs to be exposed to green space for there to be a reliable effect. (In many studies, this is the length of the intervention, which is preceded by a baseline pre-test; and followed by a post-test.) Examples include:

Duration of beneficial effect

A lot of papers seem to assume the effect is lasting, but in fact this is a key issue, handled poorly in many experimental designs. Simply expecting it is a "restorative" actually implies that it will wear off soon, as a rest in the middle of a walk does.

Opezzo14, who measured boosts to "creativity", report that their effect lasted only 2 mins. beyond the end of the intervention. Ulrich84 looked at the benefit of having a window that looks on to greenspace for 4-5 days, but says nothing about whether the effect stopped as soon as they went home; or whether further effects are to be had depending on the room outside the hosptial they move to after they leave.

Research questions I would like to be answered if money, time and effort were not a problem ...

Abbreviated bibliography

The important papers on this page I have given a full reference for, in the subsection where they are discussed. (They are also in this section in abbreviated form.) To save myself typing and fiddling about, here is an abbreviated list of more references. Each paper is referred to by tags like "Kernan10", which means that the first author's name is Kernan and date of publication is 2010; and the DOI is given, so you can get at the paper with a single click, at least usually enough to see the title and authors and perhaps abstract. However to get at a full copy you still have work to do in navigating the library's access to the paper.

Time of day effects on school tests that tries to use attention restoration as an explanation

  • Sievertsen,H.H., Gino,F. and Piovesan,M. (2016) "Cognitive fatigue influences students' performance on standardized tests" doi: 10.1073/pnas.1516947113

    This discusses a) "cognitive fatigue" in children cf. "attention restoration"; b) A time of day effect on test scores; c) A 20-30 min. rest immediately prior to test also shows an effect.
    We identify one potential source of bias that influences children's performance on standardized tests and that is predictable based on psychological theory: the time at which students take the test. Using test data for all children attending Danish public schools between school years 2009/10 and 2012/13, we find that, for every hour later in the day, test scores decrease by 0.9% of an SD. In addition, a 20- to 30-minute break improves average test scores. Time of day affects students' test performance because, over the course of a regular day, student's mental resources get taxed. Thus, as the day wears on, students become increasingly fatigued and consequently more likely to underperform on a standardized test.

    Note however, that this study has a VERY tiny effect size (but reached significance due to the huge sample size): so not only is this not about a "green" intervention, but it seems too small to bother about.

    Zhao project happiness at UBC

    The survey questions

    Project Happiness
    How are you feeling?
    Welcome! This survey is about your immediate experiences and takes about 5
    minutes to complete. You can participate anytime, anywhere on UBC Vancouver or
    Okanagan campus, and as many times as you want!

    Scales are mostly   0...10   or   -10...0...+10,   with 2 anchor points.

    1. How happy are you feeling at this moment?
    2. How stressed are you feeling at this moment?
    3. How energetic are you feeling at this moment?
    4. How anxious are you feeling at this moment?
    5. How relaxed are you feeling at this moment?
    6. How upset are you feeling at this moment?
    7. How tired are you feeling at this moment?
    8. How confident are you feeling at this moment?
    9. How busy are you at this moment?
    10. How beautiful is your current environment?
    11. How clean is your current environment?
    12. How quiet is your current environment?
    13. How spacious is your current environment?
    14. How hot is your current environment?
    15. How safe is your current environment?
    16. How comfortable is your current environment?
    17. How healthy are you feeling these days?
    18. How long have you been at UBC? (Please specify how many years and months)
    19. How satisfied are you with your life these days?
    20. How much financial stress do you feel on a day-by-day basis?
    21. Are you currently with any friends right now? If so, how many?
    22. What were you doing just before taking the survey?
    23. What is your gender?
    24. Which year were you born?
    25. Please indicate your exact location on the map: ...

    Web site logical path: [] [~steve] [myNewWave] [this page]
    [Top of this page]