Heightening fear response to horror video scenes byapplying vibratory stimuli to upper bodies ofviewers
Ibuki Tara, Shogo Okamoto, Yasuhiro Akiyama, and Yoji Yamada
Abstract—We investigated the possibility of heightening thefear response to horror video scenes by applying vibratory
stimuli to the upper bodies of the viewers. In earlier studies,such vibratory stimuli were demonstrated to increase basic
emotions, including arousal and valence; however, their effects
on the viewers’ response to scary experiences have yet to bestudied. The participants of our study watched two types ofhorror video scenes with and without 1-s vibratory stimuli.
The combinations of movies and vibratory conditions wererandomized. After accounting for the effects of the videos, weobserved that the subjective level of fear and skin conductancesignificantly increased when the participants experienced upperbody vibration when viewing horror scenes. The findings of thestudy can be exploited in developing emotionally appealing audiovisual contents.

Fig. 1. Vibratory device adapted from [3].

scene where a monster appeared suddenly.

I. I NTRODUCTION
Vibratory stimuli are applied to the upper bodies of viewers
to heighten their emotional response to audio-visual content
such as movies and games [1]–[3]. Prior researchers haveinvestigated the effects of vibratory stimuli on the emotional
response of viewers to various genres of audio-visual content. In these studies, physiological indices and subjective
ratings were used to investigate the emotion levels inducedby vibratory stimuli. Two types of questionnaire items are
typically used in these studies. In one method, the qualityof experience, such as realism and immersion, was the focus.
In the other method, arousal and valence were rated as theelements of emotions based on the circumplex model ofaffect [4]. However, the effect of applying vibratory stimuli
on the upper body on the fear response to videos has not beeninvestigated.
In this study, this effect on the level of fear response tohorror videos was examined. Skin conductance response on thehand was measured as the physiological index, and subjective
fear was rated using a Likert scale. We investigated the effectof vibratory stimuli on the skin conductance response andsubjective score of fear.
II. E XPERIMENT
A. Audio-visual contents
Two horror videos were used as the audio-visual content.
Each video was approximately 2–3 min long and included aThis study was approved by the Institutional Review Board, Hino Campus,
Tokyo Metropolitan University (426).
All authors are with the Department of Mechanical Systems Engineering,
Nagoya University, Japan. Shogo Okamoto is also with the Department ofComputer Sciences, Tokyo Metropolitan University, Japan.

978-1-6654-1903-1/22/$31.00 2022 IEEE

B. Vibratory stimulus
Voice coil motors (Vp408, Acouve Laboratory, Inc., Japan)
were used to present the vibratory stimuli. As shown in Fig. 1,
they were attached to the left and right sides of the shoulders,
chest, abdomen, and waist of the participants using a strap
vest. The vibration started with the monster’s appearance andlasted for a second. The vibration amplitude was constant, andthe frequency decreased linearly from 110 Hz to 20 Hz over asecond. All the voice coil motors were actuated with the same
vibration pattern simultaneously.
C. Measurement of the fear response
We recorded the skin conductance response on the participants’ hands and their subjective rating of the fear elicitedin them by appearance of the monster. The skin conductanceincreases with an increase in skin moisture, owing to sweating,which indicates intense emotions. The skin conductance generally starts rising within 1–2 s after the onset of the stimulus,peaks within 1–2 s, and then, tapers [5]. We analyzed theamount of increase from the commencement of the rise tothe peak, which is generally called the amplitude. We used ameasurement unit (AP-U030m II, Nihon Santeku Ltd., Japan)
and an amplifier (MaP1720CA, Nihon Santeku Ltd., Japan)
to record the skin conductance. After watching each video,
the participants rated the level of fear elicited in them by
the scenes of the monster’s appearance using a nine-grade
questionnaire. Fear emotion is not elicited when only thevibratory stimulus is presented. Therefore, in the experiment,
we did not measure the skin conductance and subjective
evaluation in response to the vibratory stimulus alone.

254

D. Participants(a) Effect of vibration

E. Experiment tasks
The participants watched two horror videos. The vibratory
stimulus was applied for one of these two videos. The change
in skin conductance in response to the scene of the monster’s
appearance was recorded, and the participants rated the levelof fear they experienced in reaction to the scene after eachtrial. Before each trial, the participants stayed in a resting state
for several minutes until their skin conductance became steady.
The order of the videos and the combinations of the video andvibration conditions for each participant were randomized.

y = avib xvib + avideo xvideo + constant(1)where the first and second terms represent the effects of thevibration and video, respectively. xvib was one, when thevibration was present; otherwise, it was zero. xvideo was one
when the participant watched Video 1 and zero when theparticipant watched Video 2. Thus, avib was the increase in theskin conductance amplitude or questionnaire rating owing to
the vibratory stimulus. avideo was the increase when watching
Video 1, compared with Video 2. The model parameters were
calculated using the least-squares method, with the objective
variable being either the skin conductance amplitude or subjective score. We determined the effects of the vibration andvideo by testing whether avib and avideo were significantly
different from zero in the t-test.
III. R ESULTS
There was a moderate correlation between the skin conductance amplitude and subjective score (r = 0.627, p = 0.001).
Fig. 2 shows the values of avib and avideo in (1). For boththe skin conductance amplitude and subjective score, avib wasgreater than zero (skin conductance amplitude: p = 0.007
and subjective score: p = 0.006). The vibratory stimulus
increased the skin conductance response and subjective fear
elicited by the horror scenes. avideo was greater than zeroin the skin conductance model (p = 0.003), unlike in the1

ΎΎ

0.5

ܽ୴୧ୠ

0.5

ΎΎ
ܽ୴୧ୠ

00

10.5

0.5

ΎΎ
ܽ୴୧ୢୣ୭

0

Coefficient for
subjective score

Coefficient for skinconductance amplitude(b) Effect of video

F. Analysis
We analyzed the skin conductance amplitude and subjectivescore in the questionnaire, which were normalized using
arithmetic means between the two trials for each participant.
Three participants were excluded from the skin conductanceanalysis because their conductance did not respond to audiovisual and vibratory stimuli. In the experiment, the participants
watched two different videos, one of which was presented
with vibrations. Therefore, it was necessary to eliminate theeffect of the videos from the skin conductance amplitudes andquestionnaire ratings to investigate the effect of the vibratory
stimulus. We modeled the skin conductance amplitude andsubjective score for each trial as the linear summation of theeffect of vibration and that of the video as follows.

1

Coefficient for
subjective score

Coefficient for skinconductance amplitude

The participants were 15 university students, who were unaware of the study objectives. They provided written informed
consent.

0ܽ୴୧ୢୣ୭
െ0.5-0.5

Fig. 2. Value and standard error of avib and avideo in the model of skinconductance amplitude and subjective score (**: p < 0.01).

subjective score model (p = 0.605). In other words, the skinconductance response to Video 1 was stronger compared toVideo 2. However, the subjective score was the same for bothvideos.
IV. D ISCUSSION
The vibratory stimuli increased both the skin conductance
amplitude and subjective score, indicating that the fear response to the horror videos was heightened. The study engendered an interesting question. Why was the skin conductance
response to Video 1 stronger, although both videos were rated
as equally scary? The answer may be found in the introspective
reports provided by the participants, which indicated that mostparticipants were more startled by the monster’s appearance inVideo 1. The skin conductance response to the startling monster appearance scene in Video 1 might have been stronger.
In other words, although Video 1 might not have been scarierthan Video 2, it was more startling.
V. C ONCLUSION
We investigated the possibility of heightening the fear
response to horror videos by applying vibratory stimuli to theupper bodies of viewers. The vibratory stimuli increased theskin conductance amplitude and subjective score, indicatingheightened fear. This effect can be utilized to enhance emotional reaction to horror movies, video games, and other audiovisual content. In the future, more horror videos should be
examined in experiments to obtain more general conclusions.
R EFERENCES[1] P. Lemmens, F. Crompvoets, D. Brokken, J. van den Eerenbeemd, and G.J. de Vries, “A body-conforming tactile jacket to enrich movie viewing,”
in IEEE World Haptics 2009-Third Joint EuroHaptics Conference andSymposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems, 2009, pp. 7–12.

255

[2] G. Karafotias, A. Teranishi, G. Korres, F. Eyssel, S. Copti, and M. Eid,
“Intensifying emotional reactions via tactile gestures in immersive films,”
ACM Transactions on Multimedia Computing, Communications, andApplications, vol. 13, no. 3, pp. 1–17, 2017.
[3] I. Tara, S. Okamoto, Y. Akiyama, and Y. Yamada, “How important is thetiming of vibrotactile stimuli for the excitation of an emotional response
for audio-visual content?” in IEEE Global Conference on Consumer
Electronics, 2021, pp. 157–159.
[4] J. A. Russell, “A circumplex model of affect.” Journal of Personality andSocial Psychology, vol. 39, no. 6, p. 1161, 1980.
[5] I. Tara, S. Okamoto, Y. Akiyama, and Y. Yamada, “Temporal characteristics of skin conductance and subjective intensity in response to unpleasantaudio-visual and vibrotactile stimuli,” in IEEE International Conferenceon Intelligence and Safety for Robotics, 2021, pp. 24–27.

256