Impacts of Connections to the Outside on Underground Space Occupants’ Psychophysiological Health: A Virtual Reality-Based Experimental Approach

Underground space occupants tend to face more psychophysiological health risks than their aboveground counterparts. Enabling a certain level of connection (e.g., physical, visual, or a mixture thereof) to the outside environments has been recognized as a way to mitigate the risks. However, their impacts on occupants’ psychophysiological health have not been known with any precision. This research, therefore, aims to improve our understanding of the impacts of connection to the outside on occupants’ psychophysiological health. In reality, it would be too expensive to build the physical connections and test their impacts. Virtual reality (VR) can circumvent this problem by bringing a person to immersive environments to carry out experiments. This study firstly developed four VR scenes with different connection designs. Then, it recruited forty-seven participants randomly assigned to the four scenes for the experiments. The participants’ psychophysiological responses, including mental workload, alertness, and mental fatigue, were measured continuously using electroencephalogram (EEG) signals. A series of tests, including Wilcoxon signed-rank and Kruskal-Wallis tests, were performed. The results indicate that i) physical connection to the outside environments has no significant impact on underground space occupants’ psychophysiological states under stress, and ii) while visual connection has no significant impact on occupants’ mental workload and fatigue, it buffers the increase in their alertness levels under stressful situations. Low alertness levels are associated with creativity and novelty. Thus, visual connection to the outside environments is recommended for underground spaces for creative purposes (e.g., art studios and creative media production). This research provides a significant reference for better harnessing underground space by considering their connection to the outside environments.