1. Introduction
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The purpose of this study was to investigate the physiological recovery effects of olfactory, visual and olfactory–visual stimuli associated with garden plants. In a randomized controlled study design, ninety-five Chinese university students were randomly selected to be exposed to stimulus materials, namely the odor of Osmanthus fragrans and a corresponding panoramic image of a landscape featuring the plant. Physiological indexes were measured by the VISHEEW multiparameter biofeedback instrument and a NeuroSky EEG tester in a virtual simulation laboratory. The results showed the following: (1) In the olfactory stimulation group, from before to during exposure to the stimuli, the subjects’ diastolic blood pressure (DBP) (ΔDBP = 4.37 ± 1.69 mmHg, Today, due to the rapid development of urbanization and diversified and complex social pressures, people’s various health risks are aggravated [Researchers have found that plant scents stimulate nerves in the brain through the olfactory sulci, inducing the central nervous system and endocrine system to secrete hormones, thereby affecting various physiological reactions [In addition, many studies have shown that viewing landscapes of green spaces can reduce stress and promote mental health [Previous studies have shown that the stimulation of plant smells or plant landscapes can affect the health of humans. Three kinds of indicators are used to measure human physiological health, namely autonomic nervous system (ANS) indicators, central nervous system (CNS) indicators and biological indicators reflecting the stress response. The autonomic nervous system is also known as the visceral or involuntary nervous system, and its function is not under conscious, voluntary control. The ANS is related to vital functions such as respiration, heart rate and blood pressure and plays an important role in dynamically controlling the body’s response to internal and external stimuli and in subtly regulating biological homeostasis [The central nervous system, composed of the spinal cord and the brain, plays an important role in the pattern of human behavior. People’s hearing, tasting, smelling, feeling and seeing are all controlled by the central nervous system [‘It penetrates people’s hearts and spleens’ is a Chinese idiom used to describe the fragrance of plants as comforting [In addition, most previous studies on the restorative function of garden plants only focused on the olfactory or visual level, in other words, on a single dimension. As we know, people’s activities in urban green space involve comprehensive experiences of vision, smell and other senses [Therefore, the aim of this study was to move past the single sensory dimension approach by adopting ‘multidimensional perception’ as its research core. We used the smell of a common Chinese garden plant (Osmanthus fragrans) and a panoramic image of the corresponding landscape (a garden landscape photograph with Osmanthus trees as the main content taken by a panoramic camera) as the stimulus materials and used a group of college students with normal olfactory and visual abilities to compare and analyze the effects of olfactory, visual and olfactory–visual stimuli on various physiological indexes. Our aim was to expound the relationship between garden plant smellscapes and human health in order to provide a theoretical basis for the objective evaluation of the effect of the smell landscapes of garden plants on human health and to guide the scientific construction of garden plant smell studies. The following specific questions were put forward: (1) Are people’s autonomic nervous systems or central nervous systems affected by their smelling an Osmanthus, viewing a landscape of an Osmanthus or smelling the plant’s fragrance while viewing the landscape? (2) If so, are there any differences among the above three cases? (3) If there are differences, are they manifested in the autonomic or central nervous system? What are the differences between the two nervous systems?