Urban Forestry & Urban Greening 55 (2020) 126855
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Urban Forestry & Urban Greening
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Short communication
Individual differences in the psychological effects of forest sounds based on
type A and type B behavior patterns
Hyunju Jo a,1, Harumi Ikei a,1, Chorong Song a,b, Yoshifumi Miyazaki a,*
a Center for Environment, Health and Field Sciences, Chiba University, 6-2-1 Kashiwa-no-ha, Kashiwa, Chiba 277-0882, Japan
b Department of Forest Resources, Kongju National University, 54 Daehak-ro, Yesan-eup, Yesan-gun, Chungcheongnam-do 32439, South Korea
ARTICLE INFO
Handling Editor: Matilda van den Bosch
Keywords:
Nature therapy
Natural sound
High-Resolution sound
Psychological relaxation
Individual difference
Type A personality
Semantic differential method
Profile of mood states
Kwansei gakuin (KG) daily life questionnaire
ABSTRACT
Studies on the psychological effects of nature have been increasing, but few studies have focused on individual
differences in these effects. The purpose of this study was to examine the individual differences in the psycho
logical effects of forest sounds based on Type A and Type B behavior patterns. The Kwansei Gakuin (KG) daily life
questionnaire was used as an indicator for Type A and Type B behavior patterns. This study included 29 female
university students (mean age, 22.3 ± 2.1 years) who were exposed to high-resolution forest and city sounds for
60 s, and they provided subjective evaluations on a modified Semantic Differential method and the Profile of
Mood States questionnaire. After exposure to the forest sounds, the Type A group (n = 12) reported higher levels
of feeling comfortable, relaxed, and natural, as well as lower levels of anger–hostility, than the Type B group
(n = 17). The findings demonstrated that the Type A and Type B groups experienced different psychological
effects from forest-derived auditory stimulation.
1. Introduction
Human have evolved in nature over the past 6–7 million years
(Brunet et al., 2002). Researchers mentioned that the physiological
functions of the human body have adapted to natural environment
(Miyazaki et al., 2011; Song et al., 2016). However, since the industrial
revolution started in the 18th century, the dwelling environments of the
number of people have been changed from natural environments to
urban environments (United Nations, Department of Economic and So
cial Affairs, Population Division., 2014). Artificial environments such as
those in urban areas induce stress in modern people (Lederbogen et al.,
2011), whose bodies have adapted to exist in natural environments
(Miyazaki et al., 2011; Song et al., 2016).
Recent research has focused on the relaxing effects of nature as a
solution for stress (Miyazaki, 2018; Song et al., 2016; Doimo et al.,
2020). In the progressive field of forest therapy research, several studies
have reported the psychological effects of forest therapy. One study
analyzed the responses of 60 female participants using a modified Se
mantic Differential (SD) method and reported that they felt more
comfortable, relaxed, and natural after walking in forests compared with
walking in cities (Song et al., 2019a, 2019b). Song et al. (2019a, 2019b)
recruited 65 female participants and used the SD method to show that
viewing forests also induced comfortable, relaxed, and natural feelings
compared with viewing in cities. In total, 585 male participants who
responded to a Profile of Mood States (POMS) questionnaire had lower
scores for the subscales of tension–anxiety, anger–hostility, depres
sion–dejection, fatigue, and confusion after walking in forests than
walking in cities. Moreover, their vigor subscale scores were higher in
forest environments than in city environments (Song et al., 2018). A
recent study on 650 male participants who completed the POMS ques
tionnaire showed that compared with viewing cities, viewing forests
increased the participants’ positive mood state of vigor, decreased
negative mood states (Song et al., 2020). Another research used the
POMS questionnaire revealed that during winter season, forest recrea
tional activities increased psychological relaxation in female partici
pants (Bielinis et al., 2019).
Individual differences in responses to forest therapy have also been
studied (Song et al., 2013; Ikei et al., 2013). Song et al. (2013) reported
the physiological effects of forest therapy comparing the pulse rates and
blood pressures of 485 participants who were evaluated based on Type A
and Type B behavior patterns (Friedman and Rosenman, 1974; Jenkins
et al., 1974). The Type B group had significantly lower pulse rates and
* Corresponding author.
E-mail addresses: hyunju.jo@chiba-u.jp (H. Jo), hikei@chiba-u.jp (H. Ikei), crsong@kongju.ac.kr (C. Song), ymiyazaki@faculty.chiba-u.jp (Y. Miyazaki).
1 These authors contributed equally to this work.
https://doi.org/10.1016/j.ufug.2020.126855
Received 11 March 2020; Received in revised form 31 August 2020; Accepted 6 September 2020
Available online 10 September 2020
1618-8667/© 2020 The Author(s).
Published by Elsevier GmbH. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/).
H. Jo et al.
diastolic blood pressures in the forest environment than in the city
environment, whereas the Type A group experienced no differences in
pulse rates and diastolic blood pressures between the two environments.
Ikei et al. (2013) analyzed POMS data for 420 participants and reported
that the Type A group had significantly higher anger–hostility subscale
scores than the Type B group in both environments.
Notwithstanding the research into forest therapy, little is known
about the individual differences in the effects of nature-derived auditory
stimulation. The present study examined individual differences in terms
of Type A and Type B behavior patterns using the nature-derived audi
tory stimulation data from Jo et al.’s study (2019), which explored the
psychological effects of exposure to 60 s of high-resolution forest and
city sounds on 29 female university students using the modified SD
method and POMS.
The present study aimed to clarify individual differences regarding
Type A and Type B behavior patterns using data from the modified SD
method and POMS, acquired in the auditory stimulation experiment of
Jo et al., 2019.
2. Materials and methods
2.1. Participants and statements
Urban Forestry & Urban Greening 55 (2020) 126855
2.4. Psychological measurements
The modified SD method and POMS subscale scores were used to
evaluate the psychological effects of forest and city auditory stimuli. The
modified SD method (Osgood et al., 1957) consisted of three opposing
adjective pairs: “comfortable to uncomfortable,” “relaxed to aroused,”
and “natural to artificial,” and each adjective pair was evaluated on 13
levels (e.g., very uncomfortable: − 6, moderately uncomfortable: − 4;
slightly uncomfortable: − 2, indifferent: 0, slightly comfortable: 2,
moderately comfortable: 4, very comfortable: 6). The POMS, which
measures mood states, includes six subscales: tension–anxiety, depres
sion–dejection, anger–hostility, vigor, fatigue, and confusion (McNair
et al., 1964). We used a short form of the POMS with 30 questions
adapted from the Japanese version to reduce participant burden
(Yokoyama, 2005). As an indicator of Type A and Type B behavior
patterns, the KG daily life questionnaire was used to classify the Type A
and Type B groups (Yamazaki et al., 1992). The questionnaire comprises
55 items for which participants choose one of three options (yes,? or no)
for each question, and scores of 2, 1, or 0 are given for the replies. A total
score of ≤43 points classified a participant in the Type B group, whereas
a score of ≥44 points classified a participant in the Type A group
(Yamazaki et al., 1992).
The information on participants has been briefly described based on
that by Jo et al. (2019). In that study, 29 healthy female university
students (mean age ± standard deviation, 22.3 ± 2.1 years) partici
pated. All participants signed an individual written informed consent.
The study was conducted in accordance with the Declaration of Helsinki,
and the experiment was approved by the Ethics Committee of the Center
for Environment, Health, and Field Sciences at Chiba University, Japan
(project ID number 36). The experimental information was also regis
tered in the University Hospital Medical Information Network (UMIN) of
Japan (ID UMIN000034821).
2.2. Auditory stimulation
The auditory stimulation protocol was based on that described by Jo
et al. (2019). High-resolution sounds, with a sample rate of 96.0 kHz and
24-bit quantization, were used to heighten the realism of the auditory
stimuli. Forest sounds included a murmuring brook sound recorded in
the Togakushi forest in the Nagano Prefecture. The city sounds included
traffic sounds recorded at the Shibuya intersection in Tokyo. The audi
tory stimuli were presented to participants via headphones at levels of
48.6 dB (forest sound) and 51.5 dB (city sound). The sensory intensity of
both auditory stimuli was evaluated as easy-to-hear sounds.
2.3. Experimental design
The experimental design was based on that described by Jo et al.
(2019). To maintain the same physical and soundproof conditions, the
experiment was conducted in a chamber with an artificial climate
(temperature: 25 ◦C; relative humidity: 50 %; illumination: 200 lx) at
the Center for Environment, Health and Field Sciences at Chiba Uni
versity, Japan. Participants received an explanation regarding the
measurement protocol. We performed a within participants experiment.
Each participant was instructed to rest for 1 min with eyes closed. Then,
one auditory stimulus (forest or city sound) was played for 1 min.
Physiological activities (heart rate variability and near-infrared spec
troscopy) were continuously measured. Thereafter, the participants
completed the subjective tests (modified SD method and POMS) for
about 2 min. The effect of the other auditory stimulus (city or forest
sound) was assessed after a short resting period (5–7 min). The order of
the auditory stimuli was counterbalanced. The Kwansei Gakuin (KG)
daily life questionnaire to identify Type A and Type B behavior patterns
was applied after the measurement protocol in a waiting room.
2.5. Statistical analysis
Wilcoxon rank sum test was used to compare the psychological ef
fects between Type A and Type B groups. Statistical analysis was con
ducted using SPSS (version 21.0, IBM, Armonk, NY, USA). Statistical
significance was considered with p-values of <0.05.
3. Results and discussion
According to the KG daily life questionnaire scores, the Type A group
included 12 participants (from 44 to 66 points) and the Type B group
included 17 participants (from 27 to 43 points).
Fig. 1 shows the comparisons between the Type A and the Type B
groups of the subjective feeling scales of comfortable–uncomfortable,
relaxed–aroused, and natural–artificial after exposure to the forest (a) or
city (b) sounds, as measured using the modified SD method.
The Type A group felt significantly higher comfortable feelings from
the forest sounds, evaluating it as “moderately-to-very comfortable,”
than the Type B group who evaluated it as “slightly-to-moderately
comfortable” (p < 0.05; Fig. 1a). The Type A group, who indicated that
the forest sound evoked “moderately-to-very relaxed” feelings, experi
enced significantly more relaxed feelings than the Type B group for
whom it evoked only “slightly-to-moderately relaxed” feelings (p <
0.01). The Type A group reported a “moderately-to-very natural”
feeling, in response to the forest sounds, and experienced significantly
more natural feelings than the Type B group who reported only “slightly-
to-moderately natural” feelings (p < 0.05).
There was no significant difference between the Type A and the Type
B groups on the three scales of comfortable–uncomfortable, relax
ed–aroused, and natural–artificial with respect to city sounds (Fig. 1b).
For the comfortable–uncomfortable scale, both groups reported the
sound as “indifferent-to-slightly uncomfortable,” indicating no signifi
cant difference. For the relaxed–aroused scale, no significant difference
was observed as both groups reported “indifferent-to-slightly aroused”
feelings. Similarly, for the scale of natural–artificial, both groups eval
uated the sound as “slightly-to-moderately artificial,” showing no sig
nificant difference.
Fig. 2 shows the scores for the tension–anxiety subscale for the forest
sound (a) and the scores for the anger–hostility subscale for the city
sound (b). The mean score for the tension–anxiety subscale for the forest
sound was significantly lower in the Type A group (0.4 ± 0.2) than in
the Type B group (1.9 ± 0.6; p < 0.05).
The mean score for the anger–hostility subscale for the city sound
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H. Jo et al.
Fig. 1. Comparison between Type A and Type B groups’ subjective feelings as
measured by a modified Semantic Differential method after auditory exposure
to forest (a) and city sounds (b); data are expressed as mean ± standard error,
Type A group: n = 12, Type B group: n = 17, ** p < 0.01, * p < 0.05, as
determined by the Wilcoxon rank sum test.
was also significantly lower for the Type A group (0.5 ± 0.3) than for the
Type B group (2.2 ± 1.0; p < 0.05).
These findings indicate that the Type A group felt significantly more
“comfortable,” “relaxed,” and “natural,” and significantly lesser ten
sion–anxiety after listening to forest sounds than the Type B group. Also,
the Type A group experienced lesser anger–hostility when listening to
city sounds than the Type B group.
In a previous study examining the effects of forest therapy on Type A
and Type B behavior patterns (Song et al., 2013), after viewing forest
and city environments for 15 min, the Type B group showed signifi
cantly lower pulse rates and blood pressures (i.e., a higher physiological
Urban Forestry & Urban Greening 55 (2020) 126855
relaxation) in the forest environment than in the city environment,
whereas environments did not have any effect on the Type A group.
However, in the present study, the Type A group experienced higher
psychological relaxation effects from the forest auditory stimulation
than from the city sounds, which is not in line with the previous study’s
report.
Although the exact reason for the discrepancy in results is unknown,
it is important to recognize that the two studies differed in their ap
proaches. Song et al. (2013) examined the physiological effects in a field
experiment, whereas the present study examined the psychological ef
fects in an indoor auditory stimulation environment.
Our results do nonetheless indicate significant differences in the ef
fects of auditory simulation for both Type A and Type B groups. In future
studies, it will be necessary to consider Type A and Type B behavior
patterns, in addition to sex, age, and so on, when selecting participants
for natural therapy research. In the current study, the participants were
only exposed to the auditory stimuli for 60 s. Thus, to facilitate more
extensive investigations, future studies will also use longer exposures to
forest sounds.
4. Conclusion
The purpose of this study was to investigate individual differences in
the psychological effects of auditory forest stimuli as an indicator of
Type A and Type B behavior patterns. Exposure to forest auditory
stimulation showed that the Type A group felt significantly more
“comfortable,” “relaxed,” and “natural” and experienced significantly
lower tension and anxiety than the Type B group. Therefore, a difference
exists in the psychological effects of forest auditory stimulation between
the Type A and Type B groups.
Role of the funding source
This research was funded by the Vehicle Racing Commemorative
Foundation.
CRediT authorship contribution statement
Hyunju Jo: Data curation, Investigation, Resources, Visualization,
Writing - original draft, Writing - review & editing. Harumi Ikei:
Investigation, Methodology, Project administration, Resources, Visual
ization, Writing - review & editing. Chorong Song: Data curation,
Investigation, Resources. Yoshifumi Miyazaki: Conceptualization,
Funding acquisition, Investigation, Methodology, Project
Fig. 2. Comparison between Type A and Type B groups’ subjective feelings of tension–anxiety and anger–hostility as measured by the Profile of Mood States
questionnaire, after auditory stimulation with forest (a) and city sounds (b); data are expressed as mean ± standard error, Type A group: n = 12, Type B group:
n = 17, * p < 0.05, as determined by the Wilcoxon rank sum test.
3
H. Jo et al.
administration, Resources, Supervision, Writing - review & editing.
Declaration of Competing Interest
The authors declare no conflict of interest.
Acknowledgments
We appreciate Seiya Enomoto of JVCKENWOOD Victor Entertain
ment Corporation for providing the high-resolution sound sources.
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