Quantifying stress level reduction induced by urban greenery perception

Urban stress is one of today’s most critical health challenges that urban stakeholders need to urgently address. However, while the positive role of nature for mental health and stress level reduction has been widely reported, the role distinct urban green infrastructure design characteristics play in citizen stress level reduction is yet to be understood. This paper presents a novel methodology where virtual reality, eye-tracking technologies, biometric sensing for heart rate variability, and participant questionnaires have been combined, to evaluate the psychological and physiological stress level reduction capacity of urban green infrastructure. 30 subjects have participated in a virtual reality immersion of 12 urban squares. 360° images were captured for each square, and mapped on a virtual sphere surrounding the participant. For each urban square, the green view index was computed using semantic image classification, and based on the obtained green view index values, the images were organized in two blocks: green >35% and non-green <20%. The eye-tracking data showed significant differences between green and non-green blocks. Fixation counts decreased in the green image block, which is an indicator of stress reduction. The perceived restorativeness scale questionnaire also reported highly significant differences with higher global scores for the green image block.