Measuring green space effects on attention and stress in children and youth: A scoping review
Attention and stress outcomes in children as they relate to responses to green space settings should be carefully reviewed and interpreted
To date, no structured literature reviews focus on the measurement approaches used to measure green space, attention and stress in studies of nature’s impact on children. This measurement-focused scoping review asked 1) What are the different ways that attention and stress are measured in green space research with children?, and 2) What are the different ways that green space is measured in this research? This review intends to clarify for researchers which attention, stress and green space measures are commonly used, clarify ambiguities concerning labels and definitions, and offer direction for future research.
There are two theories that frame the effects of green space on attention and stress, Attention Restoration Theory (ART) and Stress Reduction Theory (SRT). Measurement of children’s attention and stress in response to green space uses subjective and objective measures. Subjective measures include Likert-based rating forms (perceived attention or stress), and objective measures include physiological (e.g. heart rate or cortisol), behavioral measures (counts of behaviors), or perceptual/cognitive tasks (i.e. attention tasks administered in real time).
Findings from the 42 studies included in this review were organized by the type of measure: (1) Attention-Relevant Measures and (2) Stress-Relevant Measures, including a mix of subjective and objective measures for both attention and stress. Green space was categorized into (1) place-based metrics, (2) satellite-based technology metrics, (3) researcher-designed instruments measuring green space, and (4) validated scales supported by previously published research.
Studies that investigated green space and attention most often used a subjective Kaplan ART restoration measure, a subjective attention deficit hyperactivity disorder (ADHD) measure, or an objective measure (e.g., working memory). The few studies that look at two or more of these simultaneously suggest that these metrics may not be equally sensitive to green space and that the relationship between these metrics, and their relationship to the major explanatory theory of ART, are poorly understood. Attention is a complex construct involving multi-faceted brain-based neurophysiological processes and current measurement approaches may not be sensitive or nuanced enough to capture effects of green spaces. Studies that explored green space and stress found more comparable objective measures such as heart rate decreases when in green spaces compared to non-green spaces. However, more research is needed on subjective measurements of stress because the no stress studies have been replicated using the same subjective measurements. Lastly, studies on green space measures in child-focused studies have evolved in the last two decades to use more place-based and satellite-based metrics instead of relying on rating instruments to quantify the amount of green space surrounding school and residential areas.
The findings of this review highlight the need for more research on the relationship between subjective and objective measures when investigating green space effects on children, and greater care in interpreting the findings. Further research focusing on the degree to which ADHD and objective attention correlate with restoration is needed. Although stress research uses a robust set of objective measures, researchers have not yet identified a stable set of subjective stress measures replicated across studies. Finally, additional research on the relationship between stress and attention as outcomes of green space exposure is warranted.