Abstract:

Objective: To clarify the influence of landscape plant odor types and odor concentrations on human physical and mental health, explore the correlation between physiological responses and subjective perceptions under odor stimulation, provide indicators selection reference for subsequent studies on the effects of landscape plant odor on human health and theoretical basis for smellscape design and optimization. Method: This study utilized ginkgo sarcotesta and osmanthus flowers, common odorous materials in autumn, representing positive and negative odor types, respectively. Through pre-experiments, low and high odor concentration values were set, and COSMOS XP-329IIIR portable odor sensor was used to prepare four groups of odor materials: low-concentration osmanthus, high-concentration osmanthus, low-concentration ginkgo, and high-concentration ginkgo. Fifty-two university students were recruited for the experiment, and their physiological indicators were measured by ErgoLAB and Emotiv Epocx, while their subjective perceptions and emotional indicators were collected using pleasure rating scales, familiarity rating scales, odor intensity rating scales, and odor emotion scales(ScentMove? questionnaire). Compare the differences in the effects of odor types and concentrations on various physical and mental indicators through analysis of variance and non-parametric tests, and then use Spearman rank correlation analysis to test the correlation between physiological and psychological indicators. Result: 1) The pre-measured odor intensity was significantly affected by odor concentration and odor type (P<0.05, P<0.01), while the post-measured odor intensity was only significantly affected by odor type (P<0.05). 2) The six emotional indicators of the ScentMove? questionnaire (desire, peacefulness, happiness, energy, nostalgia, unpleasant feelings)were not significantly affected by odor concentration (P>0.05), but were significantly affected by odor type (P<0.01). Pleasantness was significantly positively correlated with positive emotions such as desire,peacefulness, happiness, energy, nostalgia (P<0.01) and significantly negatively correlated with unpleasant feelings (P<0.01). Familiarity was significantly positively correlated with emotions such as happiness, peacefulness, nostalgia, and energy (P<0.01), and significantly negatively correlated with unpleasant feelings (P<0.05); there was no significant correlation between odor intensity and the six emotional indicators. 3) Skin conductivity level(SCL), average heart rate(AVHR), standard deviation of NN intervals(SDNN), and root mean square of successive differences (RMSSD) were not significantly affected by odor concentration (P>0.05), but were significantly affected by odor type (P<0.01). α brain wave were not significantly affected by odor type or concentration (P>0.05). θ brain wave, low frequency of β (β_L) brain wave, and high frequency of β (β_H) brain wave were significantly affected by odor concentration (P<0.05, P<0.01), but not by odor type (P>0.05). γ brain wave are significantly affected by odor type, and the interaction between odor type and concentration (P<0.05, P<0.01). 4) Among the physiological indicators, low frequency to high frequency energy ratio of heart rate variability(LF/HF), θ brain wave, β_L brain wave, β_H brain wave, and γ brain wave showed the highest correlation with the psychological indicators. Conclusion: Subjectively, the perception threshold of odor intensity varies for different odor types, and the duration of olfactory stimulation can affect people’s ability to perceive odors. Emotional responses are not significantly affected by concentration, but the perception of pleasantness is a major factor influencing emotional experiences. Physiologically, the autonomic nervous system is not sensitive to odor concentration, but shows clear reactions to positive and negative odors; electroencephalogram is more sensitive to odor concentration, with high concentrations of odor causing significant inhibition of brain wave activity. Overall, θ brain wave, low frequency of β brain wave, high frequency of β brain wave, low frequency to high frequency energy ratio of heart rate variability(LF/HF) can serve as effective physiological indicators for studying emotional valence. This study further refines the variables of the impact of plant odors on human health benefits, validates the correlation of commonly used physiological and psychological indicators in olfactory health benefits research, and provides methodological references and theoretical basis for future related research.

Key words: plant smell, olfactory perception, physiological and psychological indicators, odor concentration, odor type