Introduction
Police officials, compared to the past, are experiencing an increase in work intensity due to growing safety needs from the public, increasing demand for social services, and expanding scope of their duties (Park and Jeong, 2017). The social atmosphere that undervalues public authority and the law has led to frequent incidents where police officials are subjected to not only curses and verbal abuse but also physical assaults and brutality while handling civil complaints. Police officials are required to suppress their emotions and prioritize the emotions of the public even under these circumstances, and this emotional labor causes job stress (Kim, 2015; Park, 2020; Kim and Chang, 2022; Kim and Noh, 2022). Police officials are one of the occupations suffering intense job tension compared to other occupations, and are reported as a high-risk group that is highly likely to become vulnerable to diseases due to stress from such a demanding job (Selye, 1983; Kop and Euwema, 2001). Such severe or prolonged stress can cause emotional instability or conflicts as well as sustained tension in the autonomic nervous system, including both the sympathetic and parasympathetic systems, which can result in mental and physical disorders or illnesses (McKenzie-Mohr et al., 1995). Thus, there is a need for stress management policies to reduce the damages from stress exposure on police officials.
The natural environment or plant landscapes have been found to not only alleviate people’s stress through the sense of stability from greenness (Kaplan and Kaplan, 1989; Ulrich et al., 1991; Parsons et al., 1998) but also highly effective in improving the quality of life (Son et al., 2003). Prior studies have reported that the level of plant cultivation activity and positive emotions among visitors to gardens, which are a natural environment, showed a positive correlation with positive affect and a negative correlation with negative affect (Jang et al., 2020). High positive affect indicates states of high energy, complete focus, and joyful occasions, while low negative affect indicates states of calmness and tranquility (Watson et al., 1988). While the natural environment in the past merely provided humans with living foundations and products (Yoo, 2013), it is now considered an essential element for the physical and psychological health of people today (Lopez-Mosquera and Sanchez, 2013).
Recently, brainwaves and heart rate variability are measured to obtain quantitative data on the effects of plant landscapes such as roadside flowerbeds or gardens on the psychological changes in humans, but there is still insufficient research. Electroencephalogram (EEG) measures electrical activity in the cerebral cortex by recording or observing brain activity (Berger, 1929; Schaul, 1998), and it is used as an indicator for human mental physiology.
Therefore, this study seeks to develop a roadside flowerscape model that reflects seasonal changes in a flowerscape such as spring, summer, and fall, and obtain positive effects by improving the mental health and quality of life for police officials suffering from trauma due to the nature of their occupation. Accordingly, we provided an opportunity for police officials to actually create a roadside flowerscape near their workplaces and observe and manage the plants. This is aimed at providing foundational data by investigating the positive effects that can reduce negative affect or stress and increase brain activity and positive affect in police officials.
Research Methods
Participant selection
To examine EEG, electrocardiogram (ECG), and psychological changes of police officials in the high-risk job group before and after creating a seasonal roadside flowerscape, we measured EEG and conducted surveys on 18 participants (8 males and 10 females, average age 37.1 ± 9.0 years) from Sunchang County in April (before the experiment) and June 2023 (after the experiment). Participants were selected in compliance with the selection criteria used in general brain research (Son et al., 1999; Lee, 2009), and only those who voluntarily agreed to the study by signing a consent form were included. Prior to the test, the intent and methods of the experiment were sufficiently explained to ensure understanding and cooperation before proceeding with the measurements.
Experimental method
EEG and ECG measurements and the surveys were conducted at the Sunchang Police Station from 10 a.m. to 4 p.m. (Fig. 1). The experimental space measured 5.5 m in length, 3.5m in width, and 2.6m in height, with the temperature set at 24 ± 0.5°C and humidity at 60 ± 10%. To examine psychological and physiological changes in police officials before and after creating a roadside flowerscape, a seasonal roadside flowerscape was created in May 2023 (Fig. 1) and maintained by constantly replacing plants with seasonally appropriate species until November. When creating the landscape, police officials removed the existing withered plants, mixed compost and commercial soil into regular soil using shovels, and planted and watered springblooming flowers such as Cytisus scoparius, Achillea millefolium, Melampodium paludosum, and Lilium Asiatic Hybrids. For the summer landscape, male police officials planted larger plants such as Canna spp., while female officials created the flowerscape using more portable plants like Pennisetum alopecuroides. In the fall, they created and managed the flowerscape with seasonally appropriate plants in the similar method. Typical plants included Cytisus scoparius in spring, Canna spp. in summer, and Juniperus scopulorum 'Blue Arrow', Anemone hupehensi, and Hylotelephium spectabile in fall and winter.
EEG measurement and analysis method
The computerized EEG (brain mapping) of the participants was measured using the BIOS-STX system (BioBrain Inc., Daejeon, Korea). During the EEG and ECG measurements, the flowerscape created at the police officials’ workplace was positioned by the roadside, allowing participants to view the flowerscape 5–6m away through glass windows from indoor space. Participants were to sit on a chair in the most comfortable position during the EEG measurement (Kim, 1998; Jang et al., 2014). The EEG and ECG devices were placed 90cm behind the participants. As participants entered the laboratory, we provided an overall explanation of the experiment and received a signed consent form, and helped them acclimatize to the external environment as they put on the measuring device. EEG measurements were taken following the internationally recognized 10–20 electrode placement system (Jasper, 1958), attaching a wireless EEG device consisting of 8 channels (Fp1, Fp2, T3, T4, O1, O2, Fz, Pz), a ground electrode, and a reference electrode to the participant’s head. ECG measurements were taken for 120 seconds after attaching disposable electrodes to both sides of the chest (Fig. 2). Here, participants put on disposable earplugs to control external noise. Physiological signal data were analyzed using BioScan software (BioBrain Inc., Daejeon, Korea). EEG and ECG data were processed through Fast Fourier Transformation (FFT) to obtain the power spectrum for each frequency band, and compared using relative power to reduce individual differences. Moreover, the average EEG power spectrum values for each electrode were obtained, after which brain maps were generated. The brain maps visualized the fluctuations in electrical energy by indicating lower potentials in blue and higher potentials in red according to the cerebral cortex regions.
Analysis of psychological characteristics
Korean Version of the Positive Affect and Negative Affect Schedule (PANAS)
The Korean version of the Positive Affect and Negative Affect Schedule (PANAS) measures human affect itself that indicates mental health (Diener, 1984), and it is widely used in self-report studies on affect that is divided into two factors: positive affect and negative affect. To measure positive and negative affect, we used the PANAS developed by Watson et al. (1988) and validated by Park and Lee (2016). The PANAS consists of adjectives in 20 items, 10 for positive affect and 10 for negative affect, and each item is rated on a 5-point Likert scale (0: Strongly disagree 4: Strongly agree). The internal consistency (Cronbach’s α) in this study was .941 for positive affect, and .867 for negative affect.
Preference and loyalty toward seasonal roadside flowerscape
The preference for the roadside flowerscape was assessed by having participants rate their responses on a 5-point Likert scale as they looked at the flowerbed before and after creating the flowerscape. The internal consistency (Cronbach’s α) for the preference in this study was .716.
Loyalty was defined as the tendency to lead to the intention to recommend or repurchase, and it can be classified into emotional, cognitive, and behavioral loyalty (Oliver, 1999). Emotional and cognitive loyalty can be seen as the experiential image gained through satisfaction with roadside flowerscapes or plants, which refers to the cognitive stimulation or emotional enjoyment that can be obtained from repeated use such as repurchase or revisit (Keller, 1993; Zeithaml et al., 1996). The loyalty scale used in this study was adapted from the customer loyalty scale developed by Gremler (1995) and tailored to fit the context of roadside flowerscapes. The scale consisted of 3 items, each rated on a 5-point Likert scale (1: Strongly disagree - 5: Strongly agree). The internal consistency (Cronbach’s α) for the loyalty scale in this study was .938.
Statistical analysis
Statistical analysis in this study was conducted using IBM SPSS ver. 25.0. The reliability of the measurement tools was analyzed by calculating Cronbach’s α. EEG and ECG data, the Korean version of the PANAS, and preferences for the flowerscape were analyzed using the Wilcoxon paired signed-rank test, a nonparametric test for paired samples. EEG differences by gender were analyzed using the Mann-Whitney U test, a nonparametric independent samples test. The correlation between key variables such as loyalty of police officials was analyzed using Pearson’s correlation analysis. Demographic variables and the distribution of loyalty according to the general background were analyzed using frequency analysis.
Results and Discussion
Demographic characteristics of survey respondents
The average age of all survey respondents was 37.1 years ( ± 9.0), and 44.4% (n = 8) were male and 55.6% (n = 10) were female. The age distribution was as follows: 38.9% (n = 7) were in their 30s, 27.8% (n = 5) in their 40s, 22.2% (n = 4) in their 20s, and 11.1% (n = 2) in their 50s. In terms of education, 77.7% (n = 14) were university graduates, 16.7% (n = 2) were high school graduates, and 5.6% (n = 1) had a graduate degree. The average monthly household income levels were as follows: 38.8% (n = 7) earned between 2–3 million KRW, 27.8% (n = 5) earned between 3–4 million KRW, 27.8% (n = 5) earned between 4–5 million KRW, and 5.6% (n = 1) earned below 2 million KRW. Regarding the number of household members, 66.6% (n = 12) lived with 3–4 people, 16.7% (n = 3) lived alone, 11.1% (n = 2) lived with two people, and 5.6% (n = 1) lived with 5 or more people. In terms of rank, 44.4% (n = 8) were police officers, 33.3% (n = 6) were inspectors, 16.7% (n = 3) were assistant inspectors, and 5.6% (n = 1) was a senior police officer. As for work experience, 38.9% (n = 7) had been in service for 10 years or more, 22.2% (n = 4) had less than 1 year of experience, 22.2% (n = 4) had between 1–5 years of experience, and 16.7% (n = 3) had between 5–10 years of experience.
Analysis of physiological characteristics
Changes in EEG and ECG before and after creating the seasonal roadside flowerscape
As a result of examining EEG and ECG changes in police officials before and after creating the seasonal roadside flowerscape (Tables 1, 2; Fig. 3), it was found that the indicator of relaxation and immersion such as RST (Ratio of SMR to theta), the indicator of comfort such as ASEF (Spectral Edge Frequency 50% of alpha spectrum band), and the indicator of stability and relaxation such as RSMT (Ratio of (SMR~mid beta) to theta) tended to increase after the landscape creation in all brain areas, although it was not statistically significant, including the prefrontal lobes (Fp1, Fp2) and temporal lobes (T3, T4). RMT (Ratio of mid beta to theta), the attention indicator, increased after creating the flowerscape in the left hemisphere prefrontal lobe (Fp1), and RMB (Relative mid beta power spectrum) increased in the prefrontal lobes (Fp1, Fp2) in charge of cognition, thinking, and creativity (Sokolov, 1963; Kim, 2010) (p < .05). Moreover, SEF 50% (Spectral edge frequency 50%), an indicator for brain activity in relaxed and stable state, increased with statistical significance after creating the roadside flowerscape in the right hemisphere occipital lobe (O1) that is in charge of emotional functions, visual/spatial recognition, and artistic activities (Kimura, 1973; Kim and Chang, 2001). These results suggest that the roadside flowerscape not only promotes relaxation and attention but also increases brain activity. The usefulness of garden activities by creating a roadside flowerscape is supported by Kaplan’s (2001) report that horticultural activities or plants reduce stress and promote tranquility, as well as the findings of Ulrich (1981) and Kwak (2004) that cultivating plants or using natural objects bring not only environmental effects but also emotional effects such as psychological stability. Moreover, the report by Song (2004) that simply viewing plants in daily life provides mental and physical stability and activates brain function supports the findings of this study, where creating and managing a seasonally appropriate roadside flowerscape improved brain activity and attention in relaxed and stable states.
As a result of examining changes in the autonomic nervous system of police officials in the high-risk job group after creating the roadside flowerscape (Table 3), it was found that the parasympathetic nervous system nHF (normalized High frequency) that is an indicator for stability and relaxation increased during the autonomic nervous activity, while nLF (normalized Low Frequency), which is an active indicator of the sympathetic nervous system that increases when our body is tense, decreased after creating the roadside flowerscape. Moreover, the TP (total power), which reflects autonomic nervous activity and the ability to adequately cope with internal and external stressors, tended to increase after creating the roadside flowerscape, but there was no statistical significance. The heart rate, which is an indicator for autonomic nervous activity that decreases in a relaxed state, remained within the normal range before and after creating the roadside flowerscape in both groups, although there was no statistical significance. These findings are supported by Joung et al. (2015), Eom (2016), and Song et al. (2017), claiming that landscape sensitivity in a forest is more effective in activating the parasympathetic nervous system and suppressing the sympathetic nervous system compared to the urban landscape, thereby maintaining the balance of the autonomic nervous activity.
Changes in EEG by gender before and after creating the seasonal roadside flowerscape
As a result of examining EEG changes in police officials by gender before and after creating the seasonal roadside flowerscape (Tables 4, 5; Fig. 4), it was found that the stability and relaxation indicator RSA (Relative slow alpha power spectrum) increased in the right hemisphere pre-frontal lobe (Fp2) more in male participants than female after creating the flowerscape, showing statistical significance. In addition, RAHB (Ratio of alpha to high beta), the stability and relaxation indicator, and RFA (Relative fast alpha power spectrum), the indicator for immersion and creativity in a relaxed state, also increased in the male group after creating the flowerscape in the prefrontal lobes (Fp1, Fp2) that is associated with cognition, thinking, and creativity (Kim, 2010; Sokolov, 1963), showing statistical significance. The findings that RSA, RFA, and RAHB increased more in male participants than female suggest that viewing the flowerscape reduced arousal and tension levels while enhancing creativity and stability. Furthermore, the attention indicator RLB (Relative low beta power spectrum) increased in the prefrontal lobes (Fp1, Fp2), and the focus indicator RMB (Relative mid beta power spectrum) increased in the left hemisphere prefrontal lobe (Fp1) in males more than in females after creating the flowerscape (p < .05). However, the stress and tension indicator RHB (Relative high beta power spectrum) increased in the left hemisphere prefrontal lobe (Fp1) among females more than males after creating the flowerscape, showing statistical significance. These results suggest that males experienced an increase in stability, relaxation, attention, and focus after creating the flowerscape, and a decrease in tension and stress compared to females. Michim and Wimberly (2012) and Joung (2018) reported that gardens or green spaces increase contact with nature and promote physical activity such as exercising, and physical activity in such green spaces promotes physical and mental health by reducing stress and mental fatigue. These reports align with the result that males, who engaged in more physical activity such as shoveling or planting large plants when creating the roadside flowerscape, showed greater positive effects such as stability and relaxation than females. However, the results of this study were different from the study by Jang et al. (2016a), who analyzed EEG for exposure to landscape by flower color without actually creating the landscape and discovered that females showed higher SEF 50% and RMB in alpha waves, indicating improved attention in a comfortable state among females. The findings were also different from Park et al. (2023), who analyzed EEG of adults with developmental disabilities by gender after agricultural activities and revealed that females showed greater effect of care farming than males in terms of brain quotients. This suggests that further research is needed to determine whether the differences are due to the creation of and exposure to the flowerscape, or the characteristics of the occupation.
Analysis of psychological characteristics
Korean version of the PANAS
As a result of examining the differences in positive and negative affect of police officials in the high-risk job group before and after creating the roadside flowerscape (Table 6), it was found that the total score for positive affect increased from 19.83 ± 7.09 to 25.17 ± 9.55 after creating the flowerscape, showing statistical significance. However, the total score for negative affect decreased from 14.11 ± 5.58 to 13.17 ± 4.50, although there was no statistical significance, indicating a positive effect of the roadside flowerscape. These findings align with the report by Jang et al. (2016b), which showed that spaces with indoor gardens resulted in lower levels of negative emotions such as fatigue, tension, and depression and higher levels of positive emotions such as vitality compared to lounges or office spaces without gardens. This suggests that flowerscapes featuring natural elements affected positive emotions of viewers. Moreover, this study’s findings that positive affect increased after creating the roadside flowerscape are supported by Ulrich et al. (1991), who took physiological measurements such as heart rate and electromyogram (EMG) and revealed that natural landscapes reduced negative affect such as anger and sadness as well as stress in highly stressed students. Furthermore, the results of this study are also supported by Joung (2018), who reported from the assessment of the effectiveness of citizen-participatory forest care that positive affect increased after participating in the activity while negative affect decreased with statistical significance, and also by Hartig et al. (2003) and Wells and Evans (2003), who reported that natural environments evoke positive emotions and reduce stress levels.
Preference and loyalty toward the seasonal roadside flowerscape
As a result of examining the differences in landscape preference scores in police officials before and after creating the roadside flowerscape, it was found that the preference for the roadside flowerscape increased after creating the flowerscape, showing statistical significance (Table 7). As a result of examining the loyalty of police officials toward the roadside flowerscape (Table 8), it was found that approximately 50% of police officials responded positively (“Agree” or “Strongly agree”) to only Loyalty 3 (“I would actively recommend creating a roadside flowerscape to my friends or acquaintances”). The positive response rates (“Agree” or “Strongly agree”) for Loyalty 1 (“I can speak positively about creating a roadside flowerscape to others”) and Loyalty 2 (“I think I would want to see the roadside flowerscape again”) were somewhat low at 30–40%. These results align with Jang et al. (2021), who reported a similar positive response rates (“Agree” or “Strongly agree”) of approximately 50% across all Loyalty 3 items in a plant experience program at a care farm targeting firefighters in a high-risk job group. However, this study’s 40–50% positive response rates showed much difference from Jang et al. (2020), who reported about 76–85% response rates (“Agree” or “Strongly agree”) for all Loyalty 3 items in the garden visitor loyalty survey for the general public. This suggests the need for continuous support using natural landscapes to improve the psychological and physiological health and quality of life for those in high-risk occupations.
Correlation between key variables and loyalty to the seasonal roadside flowerscape
The correlation between loyalty of police officials and key variables ranged from .26 to .79, indicating there is a relationship between variables. Loyalty, positive affect, and flowerscape preference of police officials showed positive correlations, while negative affect showed negative correlations with statistical significance (Table 9). This indicates that higher values for key variables such as positive affect and flowerscape preference and lower values for negative affect lead to higher loyalty. In particular, there was a relatively high positive correlation above .8 between loyalty and positive affect, between loyalty and flowerscape preference, and between positive affect and flowerscape preference of public officials. Therefore, creating a seasonal roadside flowerscape could enhance accessibility to plants, intention to purchase plants, and positive affect among police officials in the high-risk job group. The report by Lee (2007) claiming that higher exposure to plants, which is a captivating element of natural landscapes, can have a positive influence on affect supports this study’s findings that higher positive affect due to the roadside flowerscape leads to higher loyalty and landscape preference.
Conclusion
This study conducted EEG and ECG measurements and surveys twice (before and after the experiment) on total 18 male and female participants with an average age of 37.1 ± 9.0 to examine the psychological and physiological effects of creating a seasonal roadside flowerscape for police officials in the high-risk job group. The results of EEG and ECG changes in police officials showed that their stability and relaxation (RSMT: Ratio of (SMR~mid beta) to theta), attention (RMT: Ratio of mid beta to theta, RMB: Relative mid beta power spectrum), and brain activity (SEF 50%: Spectral edge frequency 50%) increased after creating the roadside flowerscape (p < .05). Moreover, creating the roadside flowerscape increased stability, relaxation, attention, and focus and decreased tension and stress (RHB: Relative high beta power spectrum) more in males than females, showing statistical significance. The differences in positive and negative affect in police officials before and after creating the roadside flowerscape showed that positive affect increased after creating the flowerscape (p < .05), while negative affect decreased, indicating the positive effect of creating the roadside flowerscape. The preference for the roadside flowerscape among police officials increased after creating the flowerscape (p < .05). Their loyalty to the roadside flowerscape was relatively lower than the general public, showing 40–50% positive response rates for “Agree” and “Strongly agree”. As for the correlations between key variables and loyalty to the seasonal roadside flowerscape, loyalty, positive affect, and flowerscape preference of police officials showed positive correlations, while negative correlations were found with negative affect, showing statistical significance. The results of this study indicate that creating a seasonal roadside flowerscape inside and outside the workplace of police officials increases stability, relaxation, and attention of police officials while decreasing tension and stress. Therefore, the positive effects of creating natural landscapes using plants for police officials suffering from severe occupational trauma can improve their quality of life and alleviate stress. However, it is necessary to come up with a plan to increase loyalty and reduce stress by providing continuous support using natural landscapes in order to improve the psychological and physiological health and quality of life for police officials in the high-risk job group. In particular, further research should examine in detail the differences in physical and mental effects depending on the intensity of gardening activities between male and female participants. While we measured EEG and conducted the surveys face-to-face, the sample and time were limited due to the occupational nature of police officials, which presents limitations in making definitive conclusions based solely on the results of this study. Thus, additional research is needed to revalidate these findings.
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