Elucidation of Individual Differences in the Psychological Effects of a Forest Environment (107-123)
Authors: Chorong Song, Harumi Ikei, Takahide Kagawa, and Yoshifumi Miyazaki
Abstract: There is a significant positive relationship between exposure to forest environment and physical and mental health, although individual differences exist within these responses; this phenomenon has raised questions in various fields. Here we show that the psychological effect of a forest environment can differ depending on a subject’s initial values. Experiments were conducted in 46 forested areas in Japan. Twelve male Japanese university students participated in each experiment (N = 552 subjects; 12 subjects × 46 areas); of these, data obtained from 536 subjects (mean age, 21.6 ± 1.6 years) were used for analysis. Subjects walked around their assigned areas for 15 min and subsequently sat on chairs while viewing the landscape of their assigned areas for 15 min. The Profile of Mood State (POMS) questionnaire was used to investigate psychological responses and was applied for both conditions—before and after walking and viewing the forest areas. Changes in POMS, both after walking and viewing forest environment, were largely associated with individual differences. We analyzed the correlation between the “initial values (before walking or viewing forest area)” and “changes observed in them following the forest walking and viewing (after walking or viewing a forest area − before walking or viewing a forest area)” based on the “law of initial value (LIV).” Significant negative correlations between the “initial value” and “changes observed in them following forest walking and viewing” were shown in all subscales of “tension–anxiety,” “depression–dejection,” “anger-hostility,” “fatigue,” “confusion,” and “vigor” on the POMS score. Subjects with high initial values showed a decrease in these values after walking in and viewing a forested area, whereas those with low initial values showed an increase in these values. In conclusion, the present study identified a factor of individual differences in the psychological effects of a forest environment using the subject’s initial values.