Abstract
Wood is a sustainable and natural material used in interior design for living environment. Knots are prominent features on wood surfaces, and they affect a user’s building preference and impression. Data on the effects of wood knots on human physiological responses are limited. Hence, further studies should be conducted. This study examined the effects of interior wall images comprising knotty or clear wood on physiological responses. Computer graphics were used to prepare wall images of knotty or clear lumber. A gray image was set as the control. In total, 28 adult Japanese female university students were included in this study. They observed two types of wood interior wall images for 90 s. The control was also set for 90 s. The oxyhemoglobin level in the prefrontal cortex measured by near-infrared time-resolved spectroscopy (TRS) and the activities of parasympathetic and sympathetic nerves assessed using the heart rate variability (HRV) were utilized as physiological indexes. TRS sensors, which emit and receive near-infrared light, were attached to frontal pole (Fp) 1 and Fp2, based on the international 10–20 method. R-R interval was measured using HRV sensors attached based on the three-point guidance method, and frequency data were analyzed to assess high frequency (HF), which reflects parasympathetic nervous system activity, and the ratio of high and low frequencies (LF/HF), which reflects sympathetic nervous system activity. The knotty wood sedated the right prefrontal cortex activity compared with the control and enhanced parasympathetic nerve activity compared with before stimulation. Clear wood sedated the left prefrontal cortex activity compared with the control and suppressed sympathetic nerve activity compared with before stimulation. Subjective evaluations revealed that compared with gray wall images, both knotty and clear wood images significantly promoted comfort, relaxation, and natural feeling and improved overall mood states. In addition, clear wood image had a more positive subjective effect than knotty image. Wall images comprising knotty or clear wood, when used as a visual stimulus, have a physiological relaxation effect among adult women in their 20s.
Highlights
With respect to promoting comfort in an indoor environment, the importance of removing elements with a negative impact on humans has been emphasized
The results showed that the use of Japanese cypress (Chamaecyparis obtusa) as an olfactory stimulus [18,19,20,21] and wood as a tactile stimulus for the palm [22,23,24,25] and soles [26,27] induced a physiological relaxing effect, such as sedated prefrontal cortex activity, enhanced parasympathetic nerve activity, which increases as one relaxes, and suppressed sympathetic nerve activity, which elevates during stress
The oxyhemoglobin level in the left prefrontal cortex while viewing the knotty wood transitioned around the baseline (Figure 4a, black line)
Summary
With respect to promoting comfort in an indoor environment, the importance of removing elements with a negative impact on humans has been emphasized. In the past few years, interest in achieving positive effects, including quality of life (QOL) improvement in the field of indoor environment, has been increasing [4,5,6]. The incorporation of natural elements into the living environment has a positive effect on the health and well-being of occupants [4]. Workspaces that incorporate natural elements, including houseplants, can change the attitudes and behaviors of office workers, thereby improving their productivity and overall well-being [5]. Indoor exposure to nature, such as gardening and gardening work, is effective in improving cognitive, psychological well-being, social outcomes, and life satisfaction among elderly adults requiring care [6]. Research focusing on well-being is conducted [7]
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