Introduction
Various changes are taking place in South Korean society, including a decrease in the fertility rate, an increase in the use of internet media, and an increase in the types of family structures. Moreover, women’s economic activities have increased, and dual-income families have become a common family structure. These changes have had a substantial impact on the parenting environment and have led to an increase in the use of early childhood education and childcare services. In 2018, the use rate of early childhood education and childcare services in South Korea was estimated at 62.7% for infants aged 0–2 years and 94.5% for young children aged 3–5 years, which was significantly higher than the average for Organization for Economic Co-operation and Development countries (Korea Institute of Child Care and Education, 2021). Due to early drop-off times and late pickup times, young children attending early childhood education institutions may experience sleep difficulties, as they cannot develop lifestyle habits congruent with their biological rhythms (Yu and Kim, 2018).
Sleep accounts for approximately one-third of our daily lives and is closely related to our physical and mental health. When we sleep, our bodies rest physically, physiologically, and mentally, and brain activity decreases (Y.H. Kim, 2015). Sleep plays a vital role in brain development (Peirano and Algarin, 2007) and promotes the production of growth hormones (Tham et al., 2017), which has a positive effect on height (Choi et al., 2012). Sleep also affects young children’s bodies, cognition, emotions, and behavior; it is essential in early childhood development, an important foundational period for lifelong good health (Bonuck et al., 2016).
In 2015, the National Sleep Foundation recommended the following sleep durations: 14–17 hours for 0–3 months of age, 12–15 hours for 4–11 months of age, 11–14 hours for 1–2 years of age, and 10–13 hours for 3–5 years of age (Hirshkowitz et al., 2015). In South Korea, the average sleep time 9 hours and 52 minutes for five-year-olds (Lee et al., 2017) and 9 hours and 56 minutes for four-year-olds (Y.H. Kim, 2015), which are less than the recommended amount of sleep and lower than the averages for other countries. A pediatric research team at Eulji Hospital (2016) compared the sleep times of South Korean infants and toddlers under 36 months of age with infants from other Asian and Western countries. The study found that the average sleep time of South Korean infants and toddlers was 11 hours and 53 minutes, which was 26 minutes less than the average for Asian countries (12 hours and 19 minutes) and 1 hour and 8 minutes less than the average for Western countries (13 hours and 1 minute). We can thus conclude that South Korean children do not get sufficient sleep.
Y.H. Kim (2015) found that young children who got less than 9 hours of nighttime sleep and young children who got between 9 and 10 hours had relatively higher scores for externalizing problems than those who slept 11 hours or more. These results demonstrate that nighttime sleep time is related to externalizing problems in four-year-old children. A study by Jeong (2021) observed that a higher quality of sleep lowered levels of hostile aggression, anxiety, and hyperactivity in three- and four-year-old children, thereby reducing problematic behaviors. Therefore, sufficient sleep in early childhood is an essential aspect of holistic growth and development, as it is closely related to areas of development.
The number of young children with problematic behaviors and sleep problems is increasing. In this context, problematic behaviors refer to behaviors that are not age-appropriate or do not display a normal level of adaptability (Do, 2009). Various problematic behaviors manifest in classrooms, including aggressive behavior in which children hit their peers, trouble paying attention, and exceptional defiance toward teachers and their guidance (Moon, 2008). Problematic behaviors in early childhood can persist through elementary school (Kim, 2015). Young children who are aggressive, confused, and unable to maintain close peer relationships have difficulty adapting socially, even as adults (Hartup, 1992). Clearly, problematic behaviors in early childhood considerably affect adolescence and adulthood, signifying an urgent need to address these behaviors.
In recent years, an increasing number of studies have examined activities conducted in forests instead of classrooms to reduce problematic behaviors in young children related to stress, aggression, emotion regulation skills, and attention (Kim, 2019; Kim et al., 2015; Lee, 2020; Lee and Shin, 2018). The forest becomes a playground for young children and provides a space that stimulates their curiosity, allowing them to exercise their imagination (Lee, 2020). Since playing in the forest offers more space than indoor play (e.g., in classrooms), infants have more fun and can move their bodies more, which contributes to developing their muscles and has a positive effect on the development of sensory organs (Choi, 2013). Forest experience activities also help young children feel emotionally stable by relieving tension and helping them build friendships and suppress or resolve conflict. Consequently, aggression in young children decreases (Lee, 2003).
For infants to become functioning members of society, they need emotional support and the power to control themselves. To do so, they must develop the ability to recognize positive and negative emotions and control and cope with these emotions themselves (Choi, 2012). In the forest, children can organically develop spatial awareness while freely moving about, and infants who have difficulty concentrating can more easily focus on their consciousness and breathing while in the forest’s serene environment (Yoon, 2022). In the forest, infants engage with nature using their five senses, intrigued by various sensory stimuli. They can also push their boundaries and satisfy their innate curiosity (S.K. Kim, 2015); for example, when meditating with infants, incorporating elements that they cannot hold in their hands, such as the “wind,” “sun,” and “light,” can be enriching because these can stimulate creativity and help them discover the beauty and value of nature (Lim, 2008). Forest meditation activities offer infants a multi-sensory perspective of themselves and their surroundings, which can improve their concentration skills and deepen their immersion in activities (Seo, 2017).
An increasing number of studies have focused on using forest activities to improve problematic behaviors in young children; however, few have focused on improving sleep problems in young children. A review of the literature on sleep in young children has shown that most studies have explored either the causes of sleep problems (Jang et al., 2008; Jeong, 2021; M.J. Kim, 2019; Yu, 2019) or sleep measurement scales for young children (Lee and Park, 2016; Seo and Lee, 2020). Therefore, this study aimed to determine how forest activities affect sleep and problematic behaviors in young children by conducting forest meditation activities, forest experience activities, and thematic activities according to the Nuri curriculum. In addition, the study compared changes associated with each type of forest activity to determine the effects of each activity.
Specifically, this study aimed to elucidate the following: 1) the effects of forest activities on changes in the sleep duration of young children; 2) the effects of forest activities on changes in the sleep habits of young children; 3) the effects of forest activities on changes in the problematic behaviors of young children; and 4) the effects that different types (i.e., meditation and experiential) of forest activities have on changes in sleep and problematic behaviors in young children. Thereby, this study aimed to provide data and suggest methods to improve sleep and problematic behaviors in young children and contribute to creating a program that can promote young children’s holistic development.
Research Methods
Study participants
Fifty-nine five-year-olds from two early childhood education institutions in Cheongju City, Chungcheongbuk Province, South Korea, participated in the study. Twenty children were allocated to the forest meditation group, 19 to the forest experience group, and 20 to the control group. The children in the forest meditation and forest experience groups engaged in forest activities, while the 20 children in the control group engaged in thematic activities according to the Nuri curriculum (i.e., the standard curriculum) followed by early childhood education institutions. Before conducting the study, its purpose and content were fully explained to the directors of the early childhood education institutions, the homeroom teachers of each class, and the children’s parents. Afterward, consent forms were obtained from children and parents who expressed their willingness to voluntarily participate in the study. This study was conducted after obtaining approval from the Institutional Review Board of Chungbuk National University (CBNU-202203-HR-0037).
Program site
The program was conducted at the Yongjeong Children’s Forest Experience Center in Cheongju City, approximately 328 meters from the participating early childhood education institutions (six minutes’ walking distance). The Korea Forest Service created the center to allow children to roam freely in a forest and commune with nature through their five senses (Fig. 1).
Program
This study organized and conducted forest meditation, forest experience, and thematic activities according to the Nuri curriculum. The forest (i.e., meditation and experiential) activities were conducted twice a week, for a total of eight sessions over five weeks from May 3 to 31, 2022. Many studies related to early childhood education have reported that the longer the experimental treatment period, the greater the effect. However, if the experimental treatment period is prolonged, the dependent variable may be influenced by external events between the pre- and posttests. Consequently, the experimental period should be determined according to the field conditions by considering previous studies and the relevant empirical background (Kil, 2021). As there are no studies demonstrating an appropriate intervention period for a program aimed at improving sleep problems in infants, a study on the effect of a non-pharmacological intervention for middle-aged and older adults with sleep disorders (Kim, 2016) was referenced. The average length was 5.5 weeks, and the average number of sessions was 7.7. Given that seven or more sessions were shown to be effective in improving sleep, eight sessions were conducted in the present study’s program.
Forest activities were conducted every Tuesday and Friday from 10:20 to 11:20 a.m. (60 minutes). The control group participated in standard curriculum activities in the classroom of the early childhood education institutions without going to the forest, while the forest meditation and forest experiences groups took part in forest activities. The study’s researcher conducted the forest meditation activities, and an early childhood teacher with nature-activity experience conducted the forest experience activities. This researcher graduated from a department of early childhood education, holds a kindergarten teacher certificate, and has worked at an early childhood education institution.
The content of the meditation was structured around activities that could be conducted in a forest and revised and supplemented according to expert opinions from one director of an early childhood education institution, one early childhood teacher, one early childhood teacher with nature-activity experience, and one meditation expert. The forest meditation activities were based on natural objects that could pique young children’s interest and curiosity and that they could easily encounter while walking in the forest (Jang, 2020): Activities were organized under the theme of “Forest, Wind, Sunlight, Insect, Tree, Leaf, Flower, and Fruit.” This theme referred to objects that could be readily encountered in the forest. The forest experience activities were experiential activities that required young children to move; they were planned according to seasonal and spatial circumstances, were based on ecological observations, were experience-oriented, and were structured around forest experiences in real-world settings. The control group engaged in thematic activities according to the Nuri curriculum, the standard curriculum for children aged 3–5. The Nuri curriculum consists of five domains (i.e., physical exercise and health, communication, social relations, art experience, and nature exploration). The content of the sessions in each group’s specific program is shown in Table 1.
Meditation activities included warming up before entering the forest and discussing the safety precautions that must be observed there. The group then moved to a place where they could sit together and practice the breathing meditation. This activity was followed by a walk along a forest path and a meditation in which the children were encouraged to commune with nature to awaken their five senses. The group practiced meditation according to the theme of each session (Forest, Wind, Sunlight, Insect, Tree, Leaf, Flower, and Fruit). The meditation activity concluded with a positive affirmation to help children build their confidence and a positive self-image. The group then paused to evaluate and discuss how they felt while doing the activities. The children then safely returned to the early childhood education institution under the guidance of the homeroom teacher.
Forest experience activities were conducted using the following methods. The group warmed up before entering the forest and discussed the safety precautions that must be observed there. They then walked along a forest path and used their five senses to explore and observe nature according to the theme of each session. They also used natural objects to engage in ecological art and physical activities. After evaluating and discussing their feelings while doing the activities, they returned to the early childhood education institution under the guidance of the homeroom teacher.
Although the activities of the forest meditation and forest experience groups were conducted in the same place, the routes and locations of the activities were separate so that the activities would not interfere with each other. The control group did not go to the forest; instead, they remained in a classroom in the early childhood education institution and engaged in thematic activities according to the Nuri curriculum.
Research tools
Sleep duration and habits
The Korean Children’s Sleep Habits Questionnaire (K-CSHQ) was used to measure changes in the young children’s sleep duration and habits. Lee and Park (2016) adapted the K-CSHQ from the Children’s Sleep Habits Questionnaire (CSHQ) developed by Owens et al. (2000) and verified its reliability and validity for children in South Korea. The scale has been used with infants in various studies, such as those of Cha (2012), Kim (2018), and Kim (2019). Items related to sleep time include “bedtime,” “wake up time,” and “average sleep duration.” Moreover, 33 items are related to sleep habits, including five reverse questions. Sleep habits are divided into sub-items such as bedtime resistance, sleep onset delay, sleep duration, sleep anxiety, night wakings, parasomnia, sleep disordered breathing, and daytime sleepiness. Each item is scored on a three-point Likert scale: 3 points if the sleep habit is observed five or more days a week, 2 points if observed 2–4 days a week, and 1 point if observed 0–1 day a week. Higher scores indicate more severe sleep problems. The Cronbach’s alpha coefficient for the K-CSHQ subscales ranged from 0.37 to 0.68 (Lee, 2016), and that in the study on children with developmental disabilities was 0.70 (Kim, 2019).
Problematic behaviors
The Korean Child Behavior Checklist for Ages 1.5–5 (K-CBCL 1.5–5) was used to measure changes in problematic behaviors in the young children. Kim et al. (2009) standardized the K-CBCL 1.5–5 in South Korea, adapting it from the Child Behavior Checklist (CBCL 1.5–5) developed by Achenbach and Rescorla (2000). The scale evaluates problematic behaviors in young children aged 1.5–5 years and is completed by the primary caregiver. The K-CBCL 1.5–5 consists of 100 items, including subscales of overall problematic behaviors, internalizing problems, and externalizing problems. The internalizing problems subscale comprises the domains of emotional reactivity, anxiety and depression, somatic symptoms, and withdrawal, while the externalizing problems subscale includes the domains of attention problems and aggressive behavior. Each item is scored on a three-point Likert scale (0=Not true; 1=Somewhat or sometimes true, and 2=Very true or often true). Higher scores indicate more severe problematic behaviors. In this study, T-scores were used in the analysis. For the three scales, scores of T≥60 indicated the presence of problematic behaviors. The Cronbach’s alpha coefficient for the K-CBCL subscales ranged from 0.56 to 0.94 (Kim et al., 2009).
Measurement method
To measure the effectiveness of this study’s intervention, tests for sleep (sleep duration and habits) and problematic behaviors were conducted before and after the program was implemented. Sleep duration was investigated three times in total (pretest, after the fourth session, and after the eighth session) to examine changes in sleep duration according to the sessions. After the test questionnaires were distributed to each of the participant’s households, the parents conducted tests on the infants’ sleep and problematic behaviors.
The pretest was conducted from April 25 to 29, 2022. The average sleep duration was investigated again from May 17 to 19, 2022, after the fourth session, to analyze the changes in children’s sleep duration across the sessions. Finally, the posttest was conducted from June 7 to 14, 2022, in the same way as the pretest.
Analysis method
This study conducted pre- and posttests using the K-CSHQ and K-CBCL 1.5–5 to determine the effects of forest activities on sleep and problematic behaviors in young children. The average sleep duration was also investigated after the fourth session’s activities to identify changes in sleep duration across sessions. The data were analyzed using SPSS version 18.0, and the statistical significance level was set to p < .05. One-way analysis of variance (ANOVA) was performed to test the homogeneity of the three groups. A repeated measures ANOVA was performed to determine the differences in the average sleep duration. A Bonferroni analysis was used to determine differences in changes by duration within groups. A repeated measures ANOVA was also conducted to identify the differences between the sleep habits and problematic behaviors of the three groups. In addition, a correlation analysis was conducted to determine the relationship between sleep duration, sleep habits, and problematic behaviors in young children.
Results and Discussion
Participant homogeneity test
The results of the one-way ANOVA, which was conducted to test the homogeneity of the three groups’ sleep duration, sleep habits, and problematic behaviors pretest scores, are shown in Table 2. Average sleep duration was the combined average of daytime naps and nighttime sleep in young children and was converted into minutes for the analysis. The results of the homogeneity test regarding sleep duration and sleep habits showed no statistically significant differences between the children’s average sleep duration and the subdomains of sleep habits, thus confirming that the groups were homogenous. The homogeneity test results regarding the scales of problematic behaviors (total problematic behaviors score, internalizing scale, externalizing scale) showed no statistically significant differences between the total problematic behaviors scores and the internalizing scale, thus confirming the homogeneity of the groups. However, the externalizing scale (F = 5 .404, p = .007) showed a statistically significant difference, which indicated that the level of externalizing problems was not homogeneous between the three groups. Therefore, as it would not be appropriate to verify the effect of the externalizing scale, we excluded it and aimed to solely verify the effect of the total problematic behaviors score and the internalizing scale regarding problematic behaviors.
Effects of forest activities on sleep
Sleep duration
To determine the effects of the forest activities on the participants’ sleep duration, average sleep duration was converted into minutes and analyzed (see Table 3). We tested changes in average sleep duration according to the program type. The changes in the groups over time were not statistically significant. The analysis was conducted again for each group. When we tested the differences in average sleep duration by group, the results showed that the average sleep duration of the forest meditation group increased from 582.00 minutes to 600.50 minutes and then to 606.50 minutes, thereby showing that there was a statistically significant difference (p = .031,
η p 2 = .320
When we compared the average pre- and posttest sleep durations of each group, the forest meditation group’s average sleep duration increased from 9 hours 42 minutes to 10 hours 6 minutes (an increase of 24 minutes), the forest experience group’s average sleep duration decreased from 9 hours 41 minutes to 9 hours 31 minutes (a decrease of 10 minutes), and the control group’s average sleep duration increased from 9 hours 47 minutes to 10 hours 0 minutes (an increase of 13 minutes).
The forest experience group showed a decrease in the average posttest sleep duration compared to the average pretest sleep duration. As the forest meditation and forest experience groups took part in their respective activities simultaneously and at the same children’s forest experience center, the results varied according to the type of forest activity (meditation vs. experiential activities). It is generally known that young children’s sleep duration increases if they are physically active; however, in this study, sleep duration decreased in children who engaged in the forest experience activities. These results align with those of with Williams et al.’s (2019) study, which found that physically active children have a shorter total sleep duration and are more awake at night than less active children. The results also correspond to those of Pesonen et al. (2011), who found that high physical activity levels reduce sleep duration.
Sleep habits
Next, we analyzed the effects of forest activities on young children’s sleep habits and tested the differences in sleep habits according to program type (see Table 4). The changes in the groups over time were not statistically significant. Accordingly, the analysis was conducted again for each group. We tested the differences in sleep habits by each subdomain. We found that the forest meditation group showed a statistically significant difference in the “bedtime resistance” (p = .013,
η p 2 = .283 η p 2 = .200 η p 2 = .313 η p 2 = .318
These results are partly in line with those of Harrison et al. (2004), who showed that meditation activities have a positive effect on improving children’s sleep patterns, reducing anxiety, and improving concentration. In addition, the three statistically significant subdomains of sleep habits (bedtime resistance, sleep onset delay, and sleep anxiety) are common sleep habits that occur in situations before falling asleep. A study on parents’ perceptions of children using meditation mobile applications by Puzia et al. (2002) found that the main reason for their use was to improve sleep problems. Puzia et al. (2002) also reported that younger infants meditate before going to bed to improve their sleep, which is partly in line with the results of the present study.
Effects of forest activities on problematic behaviors
We then examined the effects of forest activities on problematic behaviors in young children, specifically, the differences in total problematic behaviors scores according to program type (see Table 5). Regarding the total problematic behaviors scores, the interaction effect between the groups and time was not statistically significant. A second analysis for each group to test the differences in the total problematic behaviors scores determined that the forest experience group showed a statistically significant difference (p = .004,
η p 2 = .370 η p 2 = .111 η p 2 = .415
These results are consistent with those of other studies that have found that forest experience activities decrease problematic behaviors (Kim et al., 2015; Lee and Shin, 2018). Furthermore, the finding that forest experience activities are more effective than forest meditation activities is in line with Na’s (2011) observation that physical play activities relieve stress and reduce problematic behaviors in young children.
The relationship between sleep duration, sleep habits, and problematic behaviors in young children
A correlation analysis examined the relationship between sleep duration, sleep habits, and problematic behaviors in young children. Table 6 summarizes the results. The correlation analysis revealed a statistically significant positive correlation between sleep habits and problematic behaviors (r = .580, p < .01) in young children.
This result is in line with a study by Do Hyun-joo (2009), who showed that low sleep quality in infants is related to depression and anxiety among inner problematic behaviors. It also aligns with a study by Jeong Yoon-jin (2021), which found that the higher infants’ sleep quality, the lower their problematic behaviors, including hostile aggression, anxiety, and excessive behavioral distraction.
Conclusion
This study aimed to determine the effects of forest activities on sleep and problematic behaviors in young children. Fifty-nine five-year-old children were divided into forest meditation, forest experience, and control groups. The first two groups participated in activities in a forest, while the control group was offered thematic activities in a classroom according to the Nuri curriculum. Before and after the activities, parents completed the K-CSHQ and K-CBCL 1.5–5 to provide data on their children’s sleep duration, sleep habits, and problematic behaviors, which were then analyzed. The following conclusions were drawn based on the study’s results.
First, the forest meditation activities positively affected sleep duration in young children. All three groups’ average pretest sleep duration fell short of the recommended sleep duration for preschool-aged children (10–13 hours). However, the average sleep duration of the forest meditation group after conducting the forest meditation program was found to be the recommended sleep duration. Therefore, the results suggest that conducting static activity-oriented programs, such as forest meditation activities, for young children with insufficient sleep duration can help increase their sleep duration to the recommended amount.
When analyzing the changes in the forest meditation group, we found that their average sleep duration increased statistically significantly between the pre- and posttest following the eighth session. This result suggests that long-term and continuous multi-session programs rather than single-session programs can help increase sleep duration in children to meet the recommended hours of sleep.
Second, the forest meditation activities had a positive effect on the sleeping habits of young children. In the sleep habits domain, the forest meditation group’s scores showed a statistically significant change in the following subdomains: “bedtime resistance,” which refers to the behaviors of young children and their resistance to bedtime before they fall asleep; “sleep onset delay,” which refers to the time it takes to fall asleep; and “sleep anxiety,” which refers to the anxiety young children feel before they fall asleep. The three subdomains of sleep habits that improved in the forest meditation group all occur before falling asleep, not during sleep or after waking up. The children gradually demonstrated their focus on their consciousness and inner self by awakening their senses in the forest and by repeating meditation activities that involved breathing, saying positive affirmations, and communing with nature amid the comfort of the forest. Thus, the findings suggest that the emotional stability in young children resulting from forest meditation activities positively affects their sleep habits before they fall asleep. Therefore, conducting static activities, such as forest meditation activities, for children who have problems falling asleep could help promote emotional stability and foster positive changes in these sleep habits.
Third, the forest experience activities positively affected problematic behaviors in young children. The forest experience group showed a statistically significant decrease in total problematic behaviors score and internalizing problems score, thereby indicating that experiential activities in the forest (where children can move freely) reduce problematic behaviors and latent internalizing in young children, including emotional reactivity, anxiety, depression, somatic symptoms, and withdrawal. This study concludes that the problematic behaviors improved as the children were able to release enough energy after escaping from the confined space of the classroom. In this way, they relieved their tension and stress while freely engaging in activities in the forest (H.C. Kim, 2019). Therefore, to improve problematic behaviors in young children, efforts must be made to develop and structure dynamic activity-oriented programs that allow them to move freely in forest spaces.
Fourth, we found a statistically significant positive correlation between sleep habits and problematic behaviors: Lower sleep habit scores were correlated with lower problematic behaviors scores, and higher sleep habit scores were correlated with higher problematic behaviors scores. This finding indicates that improvements in sleep habits can reduce problematic behaviors in young children. Consequently, sleep habits and problematic behaviors in young children must be managed together. Providing static and dynamic activity-oriented programs together can help improve sleep habits and problematic behaviors.
Finally, we discuss the study’s limitations and provide directions for future research. First, this study examined the effects of forest activities on sleep and problematic behaviors in young children based on a short-term (five-week) experiment. As developmental issues in children require a long-term learning process, a follow-up study is needed to examine ongoing forest activities. Second, as this study was conducted with five-year-old children in Cheongju City, limitations may exist in generalizing its results. Third, the average sleep duration of young children was observed and recorded by parents. Follow-up research could utilize physiological measurement tools to increase accuracy by providing objective values.
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