社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

Original paper

Interpretation of visually evoked posture responses:
Representative of presence or visually induced motion sickness?
視覚誘導性姿勢変化の解釈：臨場感または映像酔いを代表するのか？
Akihiro Sugiura*1) 2), Shino Ota2), Miho Shimura3), Yui Itou2), Hiroki Takada3), Kunihiko Tanaka2)
杉浦明弘 *1) 2)，太田紫乃 2)，志村美保 2)，伊藤唯 2)，髙田宗樹 3)，田中邦彦 2)
1) Graduate School of Information Science, Nagoya University
2) Faculty of Health Science, Gifu University of Medical Science3) Graduate School of Engineering, University of Fukui
1) 名古屋大学大学院情報科学研究科
2) 岐阜医療科学大学保健科学部
3) 福井大学大学院工学研究科

Abstract
We examined whether visually evoked posture responses (VEPRs) were associated with feelings of presence or visuallyinduced motion sickness (VIMS) during the viewing of a movie showing roundtrip sinusoidal motion. Eleven students (5 males,
6 females; age: 21–22 years) participated in this study. The movie, which showed several balls in various positions and a green
cross at the center, was projected onto a white wall. The VEPRs in the participants were evaluated using objective index for bodysway. Feelings of presence and VIMS as subjective assessments were determined with sensations of self-motion (vection) anda simulator sickness questionnaire (SSQ), respectively. The participants watched a nonmoving movie for 60 s as a pretest. Eachtrial consisted of the participants watching a motion movie for 180 s and then an initial static movie for 60 s. Six trials involving
three viewing distances(150,200,300cm) and side- and depth-motion movie viewings were performed in a random sequence.
For presence, the body sway indexes and subjective assessments of presence were significantly and positively correlated. In
particular, in the frequency analysis, the amplitude at the same wavelength of the cyclic motion in the movie was the best index
of presence because it was adaptable to various conditions. On the other hand, no significant positive/negative correlations
were found between the body sway indexes and the SSQ scores. Using VEPRs for detecting VIMS requires caution because thesubjective symptoms that were induced by VIMS were occasionally developed without the VEPRs.

抄

録

我々は，正弦往復運動映像観視時の視覚誘導性姿勢変化 (VEPRs) が，臨場感覚もしくは映像酔いのどちらと深く関連しているか検証を行った．11 名の学生 ( 男性 5 名，女性 6 名，年齢 21-22 歳 ) が実験に参加した．実験ではいろ
いろな位置にある多数の球と中央の緑色の十字を基本とする映像を白い壁に写しだした．VEPRs は客観的重心動揺指標によって評価された．そして主観的評価としての臨場感覚と映像酔いは，それぞれ自己運動感覚 (vection) とシ
ミュレータ酔いアンケート (SSQ) によって測定された．実験参加者は，はじめに，事前実験として球が止まっている映像 ( 静止映像 ) を 60 秒間観視させた．次に，球が正弦往復運動している映像 ( 運動映像 ) を 180 秒間観視させ，その後，最初の映像 ( 静止映像 ) を同様に 60 秒間観視させた．実験参加者は，観視距離 3 種類 (150,200,300cm)，映像運動方向 2 種類 ( 奥行き，左右 ) を組み合わせた 6 条件をランダムに実施した．臨場感に関して，重心動揺指標と主観的な臨場感の評価は有意な相関関係を示した．特に，周波数解析より計算された映像中の往復運動と同じ周期成分の強度は，多様な条件に適応可能であったため，最良の客観的臨場感評価法であった．一方，重心動揺指標と－ 35 －

社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

映像酔いスコア間に有意な正負の相関は認められなかった．また，VEPRs を用いた映像酔い検出には注意が必要である．これは，映像酔いに起因した主観的症状は VEPRs を伴わずに発現することが稀にあるためである．
Key words: v isually evoked posture response (VEPR), visually induced motion sickness (VIMS), presence, self-motion
sensation, body sway
キーワード：視覚誘導性姿勢変化，映像酔い，臨場感，自己運動感覚，重心動揺

1. Introduction

objective assessments.

Recent advances in audiovisual and virtual environment

VEPRs that are attributed to both video and visual(VE) technologies have been utilized to create high-accuracy

environments occur when human beings are participating

virtual scenes. The aim of VE technology is to provide

in VEs, which mainly consist of videos [17-19]. Ohmi et al.

presence, which is defined as a feeling of being in the scene[20] and Freeman [21] proposed that objective evaluations[1]. VE technology is indispensable in amusement facilities

of presence can involve VEPRs measurements. In addition,that provide such presence. In addition, VE technology isthey reported that subjective and objective VEPRs

also utilized in many non-amusement fields, such as training

assessments exhibit the same tendencies in various viewing

and education [2-4]. In particular, medical rehabilitation orconditions.
Viewing movies in VEs favorably affects presence, but ittreatment that utilizes VEs shows better outcomes [5-7].
VE technology is mainly based on the control of

can also cause complex symptoms that are similar to motion

information input to a sensory organ. The control ofsickness as a collateral effect and that are generally calledvisual input is used most often in VE technology because

visually induced motion sickness (VIMS) or cyber sickness

the majority of information that is obtained in daily life[22]. Stanney has shown that 88% of VE participants

is obtained visually [8], and visual information affects

developed VIMS when viewing virtual reality movies for anhuman activity the most. Edwards has reported that visualhour [23]. VIMS is generally explained by sensory conflict

information has the most significant effects on humantheory that suggests the presence of conflicts among theposture control and constitutes more than 50% of all

visual system, labyrinthus vestibularis, and the participant’

inputs [9]. Postural responses that are induced by visuals experience [24, 25]. However, the detailed mechanisms

information, such as motions or gradients, are called visually

underlying the development of VIMS are unclear. Many

evoked posture responses (VEPRs) [10].

previous VIMS studies have mainly focused on the factors

Assessments of VEs generally apply subjective methods,that provoke VIMS or the participant’s internal tendencies

such as after-action questionnaires, and oral interviews thatfor VIMS [26, 27]. Similar to the assessments of presence,

overtly mention presence or being there and various types ofboth subjective and objective evaluations of VIMS have been

expression that categorize each element of presence [11-14].

proposed. The representative subjective assessments include

Freeman et al. suggested that subjective evaluations thata nausea profile [28], a simulator sickness questionnaire

use the overt expression of the term presence are unable to(SSQ) [29], and a fast motion sickness scale [30]. For thesufficiently assess the situations around the participant inobjective assessments of VIMS, changes in autonomic

the VE because presence is a relatively unfamiliar constructnerve activity are detected by measuring physiological(word) to most nonexperts [15]. Moreover, they noted

factors, such as sudation, blood pressure, and respiration.

that the subjective assessments of presence could include

On the other hand, Smart et al. [31] and Villard et al. [32]instability because the participants evaluate presence

reported that measurements of body sway while participants

by referring to their prior experience [16]. To improve

are viewing a movie detect VIMS. These findings raise thethe reliability of the assessments of presence, subjective

question: “What do changes in participant’s body swayassessments that were based on common experience andwhile they are viewing a movie represent?” In other words,

that had easy to understand questions about presence were

“Do changes in body sway better represent presence orutilized. Moreover, the establishment of an assessment

VIMS?” Answering this question is useful for developmentof the presence involves the interpretation of the genesisof the safe and effective VE (high presence and low VIMS).

phenomenon and the indication of coincident subjective andIn addition, answer to this question may provide beneficial－ 36 －

社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

findings to industry and medical fields. In order to answer(average) ± 6.06 (S.D.), total score: 15.02 (average) ± 10.5

this question, which has been seldom addressed in previous(S.D.)) who did not have vision or equilibrium problems

studies, we investigated if VEPRs better represent presence

participated in this study. Through the MSSQ-short that theor VIMS by simultaneously evaluating body sway as an

participant performed before examination, we confirmed

objective assessment of presence and VIMS.

that the distribution of participants did not have sensitivity
bias attributed to sensory conflict. In order to control for

2. Materials and Methods

participant conditions, we instructed the participants to

2.1 Stimulus and apparatus

get enough sleep and to prevent the overuse of their eyes

The visual stimulus consisted of a movie that was createda day before examination. The study was approved by thewith 3ds Max 2015 computer graphics software (Autodesk,

Research Ethics Committee at Gifu University of Medical

Inc., San Rafael, CA, USA). A screenshot of the movie

Science. Written consent was obtained from the participantsthat was used in this study is shown in Figure 1. The basic

after the purpose and significance of the study and theconstruction of the movie consisted of a large number ofnature and risk of the measurements were explained, bothballs that were shown at random positions and a green crossorally and in writing. In addition, the study was conductedthat was shown at the center position as the point of regard.

in line with the 1964 Declaration of Helsinki and its later

The direction of motion in the movie followed two

amendments or comparable ethical standards.

patterns: depth direction (Z-direction) and side direction

The experimental setup that was utilized in this study(X-direction). The motion in the movies was sinusoidal at

is shown in Figure 2. We performed the measurements in

0.25 Hz in each direction and was generated by moving

a controlled environment (illuminance: 13 lx) in order tocamera-simulated ocular globes (the balls themselves did

avoid any variations that were caused by visual stimuli.

not move). The amplitude of the sinusoidal motion in all

The protocol followed is as shown in Figure 3. First, a

directions was set to 150 as a software setting.

participant watched a static (nonmoving) movie for 60 s as

For presentation of the movie, the movie was projected

pretest. Next, the participant watched a sinusoidally moving

onto a white wall that was 150, 200, or 300 cm in front

movie for 180 s. Finally, the initial static movie was shownof the participant with a domestic three-dimensional (3D)

again for 60 s. By treating this 240-s task as one trial, six

projector (EH-TW5100, Seiko Epson Corporation, Suwa,

trials (direction setting: Z-direction and X-direction; viewing

Japan) in order to determine the effects of viewing distancedistance settings: 150, 200, or 300 cm) were performed in a(angle). The projected movie size was 157.5 cm × 280 cm,

random sequence in order to avoid an order effect. During

the pixel size was 1,920 × 1,080, and the viewing distancethe duration of the trials, body sway was continuously

was set to 150, 200, or 300 cm. Thus, the view angles wererecorded. The trial interval was set to more than 5 min. Each55° × 86° (at 150 cm), 43° × 70° (at 200 cm), or 29° × 50

participant watched all examination movies in a day.

° (at 300 cm). The participants watched the experimental

For the subjective measurements, presence and VIMS

movies as 3D movies, and 3D glasses (ELPGS03, Seikosymptoms were measured. The assessment of presence in

Epson Corporation, Suwa, Japan) were used as a parallax

this study used words that precisely represented presence

barrier. To enable the objective evaluation of body sway,

because presence is a relatively unfamiliar construct tothe participant stood on a Wii Balance Board (Nintendo

most nonexperts [15]. It was expected that the viewing ofCo., Ltd., Kyoto, Japan) in Romberg’s posture. In order tothe global motion movie would provide the viewer with

continuously measure the position of the center of pressure

the illusion of self-motion (vection). Considering that

(COP), FitTri ver. 1.1c self-build stabilometry software [33]presence is also a sensation that is caused by the motion

and WiimoteLib [34] for the Wii Balance Board that wascharacteristics of the movie, the degree of the sensation

created by Yoshimura were used.

of vection can serve as an assessment of presence that is

2.2 Procedure and design

limited to the viewing of the motion movie. Thus, in thisEleven volunteer students (5 males and 6 females,

study, the participants orally reported their feelings ofage range: 21–22 years, motion sickness susceptibility

body sway (sensation of vection) every 30 s by using aquestionnaires-short (MSSQ-short [35]) adult score: 7.19

visual analog scale (VAS) that ranged from 0 to 100 after－ 37 －

社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

the sensory scale was explained (0: quiet stance to 100:

amplitude component at 0.25 Hz that were obtained fromrollover).

the frequency analysis also exhibited similar results. First,

Next, for the VIMS assessment, the participants

increases in the motion movie viewing time increased all ofcompleted the SSQ, which was been used in a number

the body sway indexes, including the amplitude componentof previous studies, before and after each motion movie

that was obtained at 0.25 Hz from the frequency analysis.

viewing.

Second, all of the index values decreased with increasing

2.3 Analysis

viewing distance. Third, when the motion movie viewing

The COP measurements were sampled at 100 Hz by thewas stopped, all of the index values decreased. Forth, thesebasic setting of the Wii balance board. In addition, a clinicaltendencies increased when the movies were viewed in thetest of body sway was performed with a stabilometer at 20

Z-direction compared with the movies that were viewed in

Hz. The COP data were downsampled at 20 Hz, and low-

the X-direction.

pass filtered at 10 Hz in order to adapt the clinical standard.

Tables 1a-c and Tables 2a-c show correlation coefficients

The continuous COP data were separated by intervals

between body sway indexes and the VAS value. Moreover,of 60 s of viewing time in order to analyze each time

Figures 5a and 5b show the correlation coefficients of thesegment. We reported that the position of the COP moves in

VAS value and each body sway index. Each body sway

synchronization with the phase in the motion movie whenindex was highly correlated (0.75 > r > 0.99, P < 0.01). In

the participants watch movies with low-frequency global

addition, different correlations were not found for viewing

motion [36]. Thus, in order to evaluate the synchronization

distance or movie direction. However, the relationshipaccuracy of the movie viewing, each separate data unit

between the VAS value and the body sway indexes differedunderwent a frequency analysis with a fast Fourier transformfrom the relationships between each body sway index. The

with a Hamming window. Moreover, the total locus length

relationships between the VAS value and the body sway

(TLL), area, and standard deviation of the COP data for theindexes were significantly and positively correlated. For

motion direction of the movie, which are generally indexes

the X-direction motion movie viewing, the correlationof body sway, were calculated in each separate data unit.

coefficients tended to decrease with increases in viewing

Then, in order to examine the relationships of each of the

distance. However, for the Z-direction motion movie

body sway indexes and the VAS value of presence, Pearson

viewing, the correlation coefficient for the 150-cm viewing

product-moment correlation coefficients were calculated for

distance was relatively high, but the correlation coefficient

all time segment results.

did not tend to decrease with increases in viewing distanceFor the SSQ, the total score and 3 subscores (oculomotorin the 200-cm and 300-cm cases. In addition, different

discomfort, disorientation, nausea) were calculated in eachcorrelations relative to the kind of body sway index were notcondition (See [29] for the SSQ calculation methods).

also found in the results for viewing the movies in the bothThen, a Scheffe’s multiple comparison (significance level:

directions.

0.05) with 2 time levels (pre- and post-test) and 3 viewing

For the SSQ results (total score and 3 subscores), a

distance levels (150, 200, or 300 cm) was performed using

Scheffe’s multiple comparison with 2 time levels (pre- andORIGIN Pro 8.5 (OriginLab, Corporation, Northampton,

post-test) and 3 viewing distance levels (150, 200, or 300

MA, USA).

cm) resulted in significant differences, as shown in Tables 3aand 3b. Table 3a shows the results for viewing the movies

3. Resultsin the X-direction, and Table 3b shows the results for

The temporal changes in the indexes of body sway andviewing the movies in the Z-direction. For all of the viewing

the VAS value of the feeling of presence while viewing theconditions, all of the average SSQ scores after viewing

various movies were analyzed (Figure 4a and 4b). Figure

the movie were higher than those before viewing movie.

4a shows the results for the X-direction motion movies, andIn addition, significant increases were found, as shown in

Figure 4b shows that the results for the Z-direction motion

Tables 3a and 3b. In contrast, for X-direction movie viewing

movies. Both the VAS value and all of the body sway

with a 300-cm viewing distance, the SSQ scores were low

indexes showed similar results, and the VAS value and thecompared to the scores in the other conditions. Consistent－ 38 －

社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

increase/decrease tendencies in the SSQ scores according toabove, previous studies have described a number of

the kind of movies or viewing distance were not found.

considerations in evaluations of presence. We considered it

In order to examine the relationships between eachhighly possible that the variability in the direct subjective

body sway index and the subjective VIMS assessments,

assessments and the assessments that were based on

Pearson product-moment correlation coefficients were

multiple definitions caused further turmoil in participants

calculated with the differences in the SSQ scores between

and the enhancement of instability in the assessments ofthe postscores and prescores and the differences in the bodypresence. Therefore, in this study, the vection that occurred

sway index values between those in the 120-s to 180-s

as a result of viewing the global motion movie was used astime segments and those in the pretest (Tables 4a and 4b).

a substitute measure for the assessment of presence. Kuno

These results did not show any effects of the kind of movie,

et al. reported that the sensation of vection and the VEPRs

viewing distance, body sway index, or SSQ score.

are highly correlated [37]. In addition, Ijsselsteijn et al.
evaluated a virtual reality system by measuring vection,

4. Discussion

presence, and VEPRs. They indicated increases in both the

For the body sway index during the motion movie

subjective evaluation of presence and the instability of bodyviewing, area, TLL, standard deviation of the movie motion

sway with increased viewing angles [38]. The results for the

direction (indexes of instability), and amplitude component

evaluation of presence (vection) in this study, as shown inat 0.25 Hz (calculated with a frequency analysis as an index

Figures 4a and 4b, agreed with the results of these previous

of synchronization acuity to the phase of the motion of thestudies (substitution of presence with the VEPRs and themovie) were calculated. The results of this study agreed

relationship between viewing angle and presence). However,with those of our previous study [36], in which the subjects

the relationship between exposure time with repeated stimuli

watched sinusoidal reciprocating motion movies at 0.3

and the degree of presence have not been reported before.

Hz. Both studies reported the same tendencies: instability

The relationships of the VAS value of presence and the(increased index values) increased with increases in viewing

body sway indexes indicated different tendencies dependingtime and stability (decreased index value) increased whenon the motion direction in the movie. When X-direction

the motion in the movie stopped.

motion movies were viewed, this relationship was

The body sway indexes were highly correlated (Tables 1asignificantly correlated (P < 0.05). However, the correlationand 1b). This was thought to be because these indexes were

coefficient decreased with increases in viewing distancecommonly designed to detect instability. In addition, the(Figure 4a and Table 1). On the other hand, when Z-direction

correlations between the results of the frequency analysis

motion movie were viewed at a 150-cm viewing distance,and each body sway index were also highly correlated.

the correlation coefficients between each body sway index

These results indicated that an increase in instability

and the VAS value of presence were higher than those for(increased amount of body sway per unit time) was assumed

the other viewing distances. In contrast, at both the 200- andto occur with an increase in synchronization acuity.

300-cm viewing distances, the tendency for the correlation

For the feeling of presence while viewing the movie,

coefficients to decrease with increases in viewing distancethe participants evaluated their feelings of presence with

was not found (Figure 4b and Table 2). The body sway

subjective direct answers (self-motion), and body sway

index and the amplitude component at 0.25 Hz to the motion

was measured as the objective evaluation. As mentioned indirection of the movie changed depending on the viewing

the introduction, Lessiter et al. reviewed previous studies

distance and motion direction of the movie, as shown inthat defined presence in various ways [14]. Freeman et al.

Figures 4a and 4b. Specifically, the maximum change in the

pointed out that assessments of presence should avoid using

body sway index and the amplitude component at 0.25 Hz

the actual word presence because the term is unfamiliar to

was found in the 150-cm viewing distance and Z-direction

nonexperts [15]. In addition, these authors noted that the

motion condition. The minimum change was found in thesubjective assessments of presence can potentially include

300-cm viewing distance and X-direction motion condition.

instability because the human beings evaluate presence by

Ideally, it is preferable that all of the correlation coefficientsreferring to their prior experiences [16]. As summarized

are the same in all of the settings, including the medium－ 39 －

社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

settings. However, the results of this study showed that

resulted in discomfort, such as eye strain or disorientation,

the correlations between the subjective and objectivein these participants.

evaluations were reduced in conditions of low instability

For the correlations between the subjective evaluation

for body sway and low synchronization accuracy. Previc etof VIMS (difference between the SSQ score from after

al. reported that VEPRs synchronized motion in the movie

viewing movie to before) and the objective evaluation

is likely to be observed without vection [39, 40]. A similar(difference between the body sway index value that was

result was obtained in our previous study [41]. This situation

calculated in the 120-s to 180-s time segment and that inoccurred especially in response to the low effects of motion

the pretest), significant correlations were not found in eachin the movie because the participants could find their own

viewing condition (Tables 4a and 4b). These results in thisbody sway if he/she experienced a large effect. We suggest

study suggested that the relationships between each SSQ

that viewing a X-direction motion movie at a 300-cm

score and the body sway index were small. Therefore,

distance fell under this situation.

the relationship between the degree of symptoms that are

The index for body sway that was the most stable was

induced by VIMS and the body sway indexes were small.

the TLL (r = 0.75 in the X-movie and r = 0.7 in the Z-movie

In other words, the degree of symptoms that were inducedwith 150-cm viewing distance). In contrast, as previously

by VIMS was not accompanied by characteristics changes

described, the correlation coefficients between the VAS

in the VEPRs, which does not always occur with vection

value of presence and each body sway index were relatively[39,40]. We have reported that this phenomenon was a

low for X-direction motion movie viewing at a 300-cm

response to correct conflict conditions between the visualviewing distance compared to the other viewing conditions

and equilibrium senses [41]. Moreover, we also reported that(r max = 0.35, r min = 0.25). In this viewing condition, thehumans who are prone to motion sickness based on sensory

amplitude component at 0.25 Hz indicated that the highest

conflict theory tend to be prone to body sway [41]. Thus,

correlation coefficient (r = 0.35, P < 0.01). Hence, thethese findings suggested that we can treat the occurrence

frequency analysis was the best index for the objectiveof the VEPRs as an indicator of the occurrence of VIMS.

assessment of presence because it was adaptable to various

However, in essence, the VEPRs do not directly represent

conditions (however, this index is limited to the viewing of

the degree of subjective symptoms because the VEPRs area roundtrip motion movie).

just a conflict correction response. Furthermore, using the

For the symptoms that were attributed to VIMS during

VEPRs for detecting VIMS requires caution because thethe viewing of the movie, the participants evaluated VIMS

subjective symptoms that were induced by VIMS were alsowith the SSQ, and body sway was measured as an objective

occasionally developed without the VEPRs.

assessment. SSQ is currently considered the gold standard

Recently, VE technology is frequently utilized forfor the subjective evaluation of VIMS. For instance,business purposes. As previously discussed, VE technology

Solimini [42] and Naqvi et al. [43] investigated the effects

favorably affects presence, but it can also cause the VIMS.

of stereoscopic viewing on VIMS with the SSQ. Moreover,In terms of business, movie creators may create a production

the SSQ has been frequency used in many previous studies

anticipating an increase in revenue. Thus, the movies

evaluating VIMS. Thus, we considered the SSQ to be acreated by profit seekers have the potential to cause huge,

well-supported questionnaire for evaluating VIMS.

unanticipated health hazards of VIMS, which may pose a

For the SSQ results for the evaluations that weregrave societal threat. In contrast, excessive self-regulation

performed before/after viewing the movie, a tendency

assists diffusion of unattractive movies, a decline of thefor both the SSQ total and SSQ subscores to increaseindustry, and inhibition of advancement of VE technology.

significantly after viewing the movie in most of the viewing

In this way, VE technology attaches particular importanceconditions was recognized (Tables 3a and 3b). However, theon balance between safety and benefit. This study discusses

relationships between each different SSQ score after/before

the role of VEPRs in movie evaluations. The results ofviewing the movie and the viewing conditions were notthis study are expected to contribute toward system andconsistent. Thus, these results, including the changes in theinfrastructural improvement for the creation of movies with

SSQ subscores, suggested that the movie used in this study

balance between safety and benefit.

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社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

5. Conclusion

the body sway indexes and the SSQ scores were found.

In this study, we investigated whether the VEPRs indicate

Therefore, performing objective assessments of the degree

presence or VIMS. The subjective assessment of presenceof subjective symptoms induced by VIMS by measuring

was the sensation of self-motion (vection) and that of VIMS

body sway was difficult. On the other hand, measuring

was the SSQ. Measuring body sway was performed as an

the VEPRs might be useful for detecting VIMS because

objective assessment for both presence and VIMS. The

the VEPRs are likely an indication of the occurrence offollowing results were demonstrated:

VIMS (defensive response). However, using the VEPRs forI) Significantly positive correlations between thedetecting VIMS requires caution because the occurrence

body sway indexes and the VAS value of presence wereof subjective symptoms that were induced by VIMS wererecognized. In particular, the amplitude component at theoccasionally detected without the VEPRs.

same wavelength of cyclic motion in the movie, which was
calculated by frequency analysis, was the best index for the

Acknowledgments

objective assessment of presence because of its adaptability

I would like to express the deepest appreciation to myin various conditions (motion direction of movie andadvisor Dr. Masaru Miyao, Professor at Nagoya University

viewing distance). However, when the subject experienced

for his support and guidance. I would also like to thank thelittle effects of the motion movie, the correlations between

eleven participants who participated in this experimental

the subjective and objective evaluation decreased.

study. This work was supported by a JSPS KAKENHI

II) No significantly positive/negative correlations between

Grant-in-Aid for Scientific Research (C), 15K00702.

Table 1

Table 2The Pearson product-moment correlation coefficients of the

The Pearson product-moment correlation coefficients of therelationship between each body sway indexes and the VAS value of

relationship between the body sway indexes and the VAS value ofpresence for the X-direction motion movies. (a): viewing distance,

presence for the Z-direction motion movies. (a): viewing distance,

150 cm; (b): viewing distance, 200 cm; and (c): viewing distance,

150 cm; (b): viewing distance, 200 cm; and (c): viewing distance,

300 cm.

300 cm.

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社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

Table 3aTable 3bMultiple comparison analysis results of the Simulator Sickness Questionnaire (SSQ). (a) the X-direction motion movies, and(b) the Z-direction motion movies.

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社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

Table 4aDistance

150 cm200 cm300 cm

SSQ category

Item ((180 s - 120 s) time segment - Pre test)
Amp. at 0.25Hz

Area

TLL

S.D.x

Total (Main)

0.41

0.09

0.13

0.38

OD (Sub)

-0.19

-0.24

-0.31

-0.17

N (Sub)

0.43

0.2

0.2

0.43

D (Sub)

0.63*

0.28

0.4

0.58

Total (Main)

0.4

0.12

0.12

0.38

OD (Sub)

0.21

0.04

-0.02

0.17

N (Sub)

0.47

0.21

0.19

0.45

D (Sub)

0.44

0.1

0.21

0.46

Total (Main)

0.1

-0.12

-0.19

-0.12

OD (Sub)

-0.09

-0.15

-0.19

-0.25

N (Sub)

-0.31

-0.41

-0.42

-0.42

D (Sub)

0.53

0.26

0.19

0.43

*: P < 0.05 n = 11
OD: Oculomotor Discomfort (Sub score), N: Nausea (Sub score), D: Disorientation (Sub score)
Amp. at 0.25 Hz: Amplitude at 0.25 Hz, TLL: Total locus length,
S.D.x: Standard deviation at X-direction

Table 4bDistance

150 cm200 cm300 cm

SSQ category

Item ((180 s - 120 s) time segment - Pre test)
Amp. at 0.25Hz

Area

TLL

S.D.z

Total (Main)

-0.28

-0.31

-0.29

-0.2

OD (Sub)

-0.27

-0.3

-0.29

-0.19

N (Sub)

-0.04

-0.06

0.03

0.04

D (Sub)

-0.26

-0.28

-0.29

-0.25

Total (Main)

-0.08

-0.16

-0.16

-0.11

OD (Sub)

-0.23

-0.26

-0.29

-0.22

N (Sub)

-0.33

-0.4

-0.37

-0.35

D (Sub)

0.32

0.2

0.26

0.23

Total (Main)

-0.05

-0.05

-0.1

-0.01

OD (Sub)

-0.18

-0.21

-0.21

-0.1

N (Sub)

-0.18

-0.19

-0.23

-0.12

D (Sub)

0.22

0.27

0.19

0.17

*: P < 0.05 n = 11
OD: Oculomotor Discomfort (Sub score), N: Nausea (Sub score), D: Disorientation (Sub score)
Amp. at 0.25 Hz: Amplitude at 0.25 Hz, TLL: Total locus length,
S.D.z: Standard deviation at Z-direction

Pearson product-moment correlation coefficients of the relationships between the difference in the postscore and prescore SSQ
scores and the difference in the body sway index values between the 120-s to 180-s time-segment and that in the pretest. (a) the
X-direction motion movies, and (b) the Z-direction motion movies.

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社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

Figure 2
The setup utilized in the study. The participant stood on a Wii
Figure 1

Balance Board in Romberg’s posture, and body sway was

Screenshot of the movie used in this study. A large number

measured with a 150-, 200-, and 300-cm viewing distance to theof balls were located at random positions and a green crossscreen.

was located at the center position as a point of regard in themovie space. The direction of motion in the movie followed
two patterns: depth direction (Z-direction) or side direction(X-direction), and the movies were 3-dimensional withbinocular stereopsis.

Figure 3
Study protocol. A subject watched a static (nonmoving) movie for 60 s as a pretest. Next, the participant watched a sinusoidal
moving movie for 180 s and then a static (nonmoving) movie for 60 s. By treating this 240-s task as one trial, eight trials (direction
setting: Z-direction or X-direction, viewing distance settings: 150, 200, or 300 cm) were performed in a random sequence.

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社会医学研究．第 33 巻 1 号．Bulletin of Social Medicine, Vol.33(1)2016

Figure 4a

Figure 4b

The temporal changes in the body sway indexes and the subjective measurements that were made with a visual analog scale ofpresence. (a) Results for the X-direction motion movies. (b) Results for the Z-direction motion movies. The solid line in eachgraph represents average value, and the error bars represent standard error.

Figure 5a

Figure 5b

Correlation coefficients of the VAS value and each body sway index. (a) Results for the X-direction motion movies. (b) Results
for the Z-direction motion movies.

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