From oppressiveness to stress: A development of Stress Reduction Theory in the context of contemporary high-density city

Due to intense urbanization in the last decade, high-density city has become a major type of human habitat globally. In those cities, oppressiveness has been recognized as a dominating environmental perception. Stress Reduction Theory is a leading theory that explains the relationship between environmental exposure and mental stress. However, the theory missed that perceived oppressiveness may substantially explain impacts of environmental exposure on mental stress in the context of high-density city. This study aimed to address that significant theoretical deficiency. A new pathways model was proposed to investigate whether and to what extent environmental exposure impacts mental stress through perceived oppressiveness. To test this pathways model, we conducted an online photo-based experiment with Hong Kong city residents. Firstly, we used a grid method to randomly choose 90 street spots in the city area. We created one GIF image by integrating nine Google Street photos to cover the full 360° viewshed for each spot. The percentage of all streetscape elements for each GIF image was measured. Then, 1396 participants were randomly assigned to view three of 90 GIF images. After viewing each image, participants reported perceived oppressiveness, perceived environmental quality, and acute mental stress responses. Lastly, participants reported their socioeconomic, demographic, and other background information. We identified three pathways linking streetscapes to mental stress response. After controlling for covariates, perceived oppressiveness was the major mediator to link streetscapes and mental stress, explaining 50.2% of relationship. Tree canopy and sky had the greatest association with lower level of stress through perceived oppressiveness, while vehicles and billboards had the greatest association with higher level of stress through perceived oppressiveness. This new pathways model confirms the major role of perceived oppressiveness in interpreting the impact of urban streetscapes on mental stress in the high-density cities. The results suggest an update of Stress Reduction Theory is feasible and necessary.