The purpose of this study was to investigate the effects of forest play activities on children ''s emotional vocabulary and physiological changes of stress. The study design was divided into three stages. The first stage is to analyze the research papers related to forest play and present research direction and basic data. In the second stage, we examined the effects of forest play activities on children''s emotional vocabulary. In the third stage, the effectiveness of the forest play activities were compared with the control group, and at the same time, the salivary cortisol level was analyzed to investigate the physiological change of the stress.
A total of 174 papers were set as research subjects among forest play papers for children from 2009 to 2018. Looking at the number of papers published by year, the total number of papers related to children are 1 in 2009, 3 in 2010, 8 in 2011, 7 in 2012, 29 in 2013, 22 in 2014, 26 in 2015, 26 in 2016, 22 in 2017, 24 in 2018. The thesis for only children were published 1 in 2009, 1 in 2010, 4 in 2011, 13 in 2012, 19 in 2013, 13 in 2014, 19 in 2015, 18 in 2016, 13 in 2017, 19 in 2018.
Looking at the research method of forest play papers for children, the total number of experimental papers was 55.17% for 96 papers, 9.77% for observation papers, 17.82% for research papers, 5.75% for case studies, 6.32% for literature reviews and 5.17% for other papers.
Looking at trends by target age, in the case of the papers which studied on the single age, the number of papers researching on age 2 was 4 articles (3.51%), 3 articles (2.63%) for the 3 years old, 11 articles (9.65%) for the 4 years old and 41 articles (35.96%) for the 5 years old. A total of 46 articles (40.36%) consisted of children aged between 2 and 5 years. A total of 9 articles (7.89%) were published for infants and children with infancy.
The following is a review of the research trends of 114 papers which classified children development into six stages of physical development, cognitive development, language development, emotional development, social development, and self concept development.
The number of theses that studied emotional development accounted for 35 articles (30.7%), social development was 29 articles (25.44%), cognitive development was 19 articles (16.67%), self concept development was 16 articles (14.04%), physical development was 7 articles (6.14%), language development was 4 articles (3.51%) and other development was 4 articles (3.51%). As a result of the above analysis, it was necessary to study the language development and the forest play.
The purpose of second stage study was to investigate the effect of forest play activities on children ''s emotional vocabulary change. Forest play activities were conducted for 498 children aged 4 to 5 years old who visited the environmental training in G city for forest play activity for 1 hour.
The design of the forest play activity program was implemented by recon figuring one, two, three (Environmental Protection Agency Certification No. 2014-119), an environmental program approved by the Ministry of Environment. The first step forest observation, the second step forest sounding, the third step water ecology observation, the fourth step natural observation, the fifth step wooden piece puzzle making and the sixth step were put a pine cone at the target.
As a result, positive vocabulary was significantly improved from 0.95 pre forest play to 1.15 post forest play (p=.003) and negative vocabulary was significantly decreased from 1.27 to 0.41 (p=.000). The results of emotional vocabulary change according to sex, positive vocabulary of male children increased significantly from 0.96 to 1.36 (p=.000), in the case of negative vocabulary, it decreased significantly from 1.42 to 0.55 (p=.000). In the case of female children, negative vocabulary was significantly decreased from 1.12 to 0.26 (p=.000), but the positive vocabulary increase was not significant (p=.851). As a result of age, for a 4-year-old children, positive vocabulary did not show significant difference between before and after forest play (p=.471), and negative vocabulary was significantly increased from 1.04 pre forest play to 0.41 post forest play (p=.000). For a 5-year-old children, positive vocabulary was increased significantly from 0.96 to 1.23 (p=.001) and negative vocabulary was decreased significantly from 1.41 to 0.41 (p=.000). As a result of this study, it was found that play activities using various natural objects in the forest were directly related to nature, resulting in positive vocabulary increase and negative vocabulary decrease.
The purpose of third stage study was to investigate the effects of forest play activities on the physiological changes of the stress and emotional vocabulary of children. A total of 36 children participated in the kindergarten aged 4～5 years old, 17 in the control group and 19 in the experimental group. Forest play activities consisted of 6 stages in accordance with the level of kindergarten students, and the program was carried out at G City Environmental Training Center.
Before and after the experiment, the emotional vocabulary evaluation site was self - measured and the salivary cortisol was analyzed to evaluate changes in the body ''s stress hormones. As a result, in the control group, the positive vocabulary was significantly increased from 0.14 to 1.53 (p=.003), but the negative vocabulary decrease was not significant (p=.059). In the experimental group, the positive vocals were significantly increased from 0.47 pre forest play to 2.84 post forest play (p=.000). Negative vocabulary was significantly decreased from 1.94 to 0.00 before forest play (p=.000). In the analysis of salivary cortisol, the change in salivary cortisol concentration was not significant (p=.667) in the control group, from 0.179 μg·d-1 to 0.161 μg·dl?1. However, the experimental group showed a significant decrease from 0.202 μg·d-1 pre forest play to 0.161 μg·d-1 post forest play (p=.049).
These results suggest that forest play activities may be helpful in improving the vocabulary ability and stress reduction of children because of the positive vocabulary increase, negative vocabulary decrease and saliva cortisol concentration decrease.