How Do Communication Cues Change Impressionsof Human-Robot Touch Interaction?
Takahiro Hirano1,2 · Masahiro Shiomi1 · Takamasa Iio1,3 · Mitsuhiko Kimoto1,2 · Ivan
Tanev2 · Katsunori Shimohara2 · Norihiro Hagita1

Received: date / Accepted: date

Abstract Communication cues, e.g., gaze behaviors
and touch styles, are essential factors in the closeinteraction of people with social robots. Even though thecommunication cues are broadly investigated in humanrobot interaction, it remain unknown how they change
human impressions of social robots in haptic interaction
situations. For better understanding of communication
cues in human-robot touch interaction, we conducted anexperiment with 28 participants who interacted with arobot with gaze behaviors and touch styles. We prepared
two gaze behaviors and three touch styles based on past
research works. Our experimental results showed thatparticipants preferred a gaze behavior more that only
looks at their faces during a touch than a gaze behavior
that looks at their faces, hands and returns to their face.
They also preferred a touch style in which they touched
the robot more than touch styles where a robot touches
them.
Keywords Human-Robot Interaction, Haptic Interaction,
Touch, Communication Cue

This paper is an extended version of a previous work of
Hirano et al. [1] and contains additional experimentresults and more detailed discussions.
1Intelligent Robotics and Communication Labs., ATR,
2-2-2 Hikaridai Keihanna-Sci. City, Kyoto, Japan
2 Doshisha University, 1-3 Tatara Miyakodani
Kyotanabe-shi, Kyoto, Japan
3 Osaka University, 1-3 Machikaneyama Toyonaka
Osaka, Japan
E-mail: m-shiomi@atr.jp

1 Introduction

A physical existence enables robots to communicate withpeople through haptic interaction like humans do (Fig. 1).
Haptic interaction is one promising research topic for thehuman-robot interaction research field, similar to thehuman-human interaction research field. In humanscience literature, the positive effects of haptic interaction
have already been broadly investigated and both mental
and physical benefits have been unveiled [2-7]. Haptic
interactions are well known to change the behaviors ofothers and facilitate various efforts in human science
literatures [8-14]. Past research reported that the physicalpresence of robots influences interactions with people
differently or more strongly than computer graphic-based
agents [15-18]. Following these results, researchersinvestigated the following positive effects of a robot's
haptic interaction: mental therapy [19], increasing
motivation [20], and attitude changes by touch [21-23].

Fig. 1 Robot touches a person

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For more natural touch interaction, such communication
cues as gaze behaviors during touch are essential. Except
for touch interactions, the following communication cues
have been thoroughly investigated: gaze behavior in suchcontexts as approaching [24], encounters [25, 26], objecttransfers [27, 28], and conversations [29-32]. These
research works suggested that the design of gazebehaviors should be different, based on each context toimprove the perceived naturalness or comfort. For
example, Gharb et al. investigated that representing of
own intention by looking at an object is essential torealize natural interaction for both humans and robots in
hand-over situations [27]. But, gaze behavior effects havenot been thoroughly investigated yet in haptic interaction.
Touch style should also be considered for natural touch
interaction. Touch styles in past research works [20, 22,23] can be categorized into three kinds: touching a robot,
being touched by a robot, and mutual touch, i.e., a person
touches a robot, which then touches the person’s hand.
These works investigated the influences of touch style on
the impressions of a robot, but they did not compare all
three touch styles together. Since they only partiallycompared their effects, it remains unknown which touchstyle is better for natural touch interaction.
Therefore, we must learn much about communication cue
effects, i.e., the combination of a gaze behavior and atouch style toward perceived impressions of a robot. If
we can identify the effects of these three factors, suchknowledge would increase the understanding of thecommunication cues in human-robot touch interaction
and help construct friendlier relationships between people
and robots through touch interaction, like humans [5, 7].
For this purpose, we employed two gaze behaviors andthree touch styles in our experiment design where a robot
simply chats with a person through a touch interaction.
We experimentally investigated communication cue
effects in human-robot touch interaction to identify
which combinations are appropriate to increase a robot’s
perceived friendliness. We note that the purpose of thisstudy is to investigate basis effects of the touch style andgaze behaviors, therefore we focused on a simple
situation to investigate their effects.
2 Related Work
2.1 Gaze cue in human-robot interaction

Gaze behaviors play an important role in conveying robot
intentions to partners in human-robot interaction. In
particular, robotics researchers have focused onconversation situations, e.g., Mutlu et al. designed a set ofgaze behaviors for a robot to signal different participant
roles in multi-party conversations [31]. Kuno et al.
developed gaze behaviors for a museum guide robot to do
an information-providing task more naturally [30].
Komatsubara et al. developed gaze behaviors in group

Hirano et al.

conversations for an educational robot that interacts withchildren at an elementary school [33].
The investigation of gaze behaviors is also expanding toother situations in human-robot interaction. Satake et al.
developed an approaching algorithm that included a gazebehavior design for a mobile social robot to notify a target
person of its presence [24]. Hayashi et al. proposed apatrolling behavior for mobile social robots to show theiravailability through locomotion path and gaze behaviors[25]. Gharb et al. investigated the effects of gazebehaviors in hand-over situations and reported that gazebehaviors in which the givers first look at the object andthen at the receivers are preferred patterns for suchsituations [27].
Similar to these situations, understanding the gazebehavior effects on a robot’s perceived friendliness inhuman-robot touch interaction is critical for social robots.
However, even though researchers are broadly
investigating the effectiveness and appropriate design ofgaze behaviors depending on each situation, manyquestions remain unanswered concerning how gazebehaviors during touch interactions change theimpressions of the interaction partners. Therefore, in thispaper we consider touch styles and investigate the gazebehavior effects during human-touch interaction on the
feelings of the people with whom the robot is interacting.
2.2 Touch styles in human-robot interaction

Among three touch styles in human-robot interactions, themost commonly investigated style is “touching a robot.”For example, Shibata et al. developed a seal robot named
Paro for mental therapy with senior citizens throughhaptic interaction, including touching it [19]. Yamazaki etal. investigated how huggable devices reduced anxiety
through conversations [34]. Another perspective of thetouching a robot style is the recognition of touch
interaction from people [35-37]. For example, Cooneyused inertia sensors to recognize full-body gestures by
haptic interactions with a humanoid robot [37].
Compared to the touching a robot style, two other modes
have received much less attention. A few research works
investigated the effects of being “touched by a robot.”
Cramer et al. reported that being touched by a robot
decreased machine-likeness but negatively affected
dependability [21, 22]. Chen et al. investigated the effects
of a robot’s touch with verbal communication cues [23],and Shiomi et al. investigated the effects of “mutual
touch” in the context of increasing the motivation ofinteraction partners [20]. Fukuda et al. investigated theseeffects by analyzing Medial Frontal Negativity by EEG to
determine whether mutual touch changes people’s
perceived unfairness in the ultimatum game [38].
These research works illuminated the effects of touchstyles in human-robot touch interaction, but they did notHow Do Communication Cues Change Impressions of Human-Robot Touch Interaction?

3compare all of the combinations of touch styles or focus
on the effects of other communication cues, even thoughgaze cues play important roles in interactions with people.
Therefore, in this paper we investigate both effects
between gaze behaviors and touch styles on theimpressions of interactions with humans.
3 Robot for Experiment

We experimentally prepared a humanoid robot with two
gaze behaviors and three touch styles and conducted ourexperiment with a Wizard-of-Oz technique.
3.1 Robot

(a)

(b)

(c)

Fig. 2 Pepper’s gaze behavior: looking at participant’s face(a), participant’s hand (b) and participant’s face again (c)We employed a personal humanoid robot, Pepper,
developed by Softbank Robotics (Fig.1) that has 20
DOFs: two in its head, shoulders, elbows and waist, one
for its wrists, hands, and knee, and three for its wheel. The
robot is 121 cm tall and is equipped with microphones,
cameras, a depth sensor, touch sensors etc. It has fivefingers on its hands.
3.2 Design of gaze behaviors

To design gaze behaviors for touch interactions, we
focused on related works [24, 25, 31] and found thatthese research works mainly reported the importance of
keeping eye-contact with interaction partners. Thus, we
decided to investigate a face-only gaze behavior thatmaintains eye-contact during a touch.

(a)

(b)

Fig. 3 Round plastic yellow sphere on stand (left) and Pepper
touching a hand (right)

Also, we focused on related work that investigated theeffects of gaze behaviors in hand-over situations where arobot hands something to a person because in suchsituations the hands of the givers and the receivers
literally become closer like in actual touch interactions
from a physical perspective. Gharb et al. investigated theinfluences of six kinds of gaze behaviors [27] and argued
that gaze behaviors, including when the giver looks at theobject and then at the receiver, are preferred byparticipants more than gaze behaviors where only thereceiver is looked at: i.e., face-only gaze behavior.
Therefore, we also employed this face-hand-face gazebehavior that looks at the face, the hand, and then the faceagain and maintains eye-contact during the touch.

3.3 Design of touch styles

Face-only

Touched-by-robot

The robot constantly looks at the interacting person’s faceduring the touch (Fig. 2-a). Before the experiment, we
adjusted its face direction so that it directly looks at eachparticipant’s face.

In this touch style, the robot touches a person who does
not actively touch the robot. We placed a stand near the
robot on which the interacting person’s hand is put. The
stand’s height is identical to Pepper’s left hand in thetouch-robot condition, and the same round plastic yellow
sphere is placed on the stand (Fig. 3-a). The robot asked
the interaction partners to “please put your hand on thestand.” After they did so, the robot touched their handswith its right hand (Fig. 3-b).

Face-hand-face

The robot looks at the interacting person’s face first (Fig.
2-a), then at the person’s hand (Fig. 2-b), and finally at theperson’s face again (Fig. 2-c). The durations and timingsof the gaze behaviors were based on Gharb’s work [27].

To design touch styles for interactions, we also focused onrelated works [20-22] (described in Section 2) and foundthat mainly three touch styles are used: touching a robot,
being touched by a robot, and mutual touch.
Touch-to-robot
In this touch style, a person touches the robot, but the
robot does not actively touch the person (Fig. 2). First,
the robot asks the interaction partner to “please touch myleft hand” and then extends it. We put a round plastic
yellow sphere in its left hand to create uniform touchfeelings among the other conditions.

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Hirano et al.

We assume that face-only gaze behaviors will have
similar positive effects on touch interactions with people
based on past related works [24, 25, 31]. However, one
research work showed that face-hand-face gaze behavior
caused more positive impressions than face-only gazebehavior [27]. Since phenomena related to gaze behaviors
during touch are highly unexplored, we made twocontradictory hypotheses about their effects based on
different theories and considerations.
Hypothesis about positive effects of communicating
intention of touch by gaze
(a)

(b)

(c)

(d)

Fig. 4 Scene of mutual-touch style

To design the robot’s touching behavior, we employed theknowledge of human science literature that investigates
the effects of touching speed on impressions [39]. Since
this previous paper reported that touching at a speed of 5
cm/s was evaluated more positively than 0.5 or 50 cm/s,
we set the speed of the robot’s hand during the robot’s
touching to about 5 cm/s. Pepper’s touching behavior was
pre-programmed, and its hand followed a fixed trajectory,
based on the size of a human hand.
Mutual-touch
In this touch style, a person touches the robot, and therobot actively returns the touch. Therefore, this condition
mixes both the touch-to-robot and touched-by-robot
conditions. First, the robot asked the interacting person totouch its left hand (Fig. 4, a) and then extended it (Fig. 4,b), as in the touch-to-robot condition. After the interacting
person touched the robot’s hand (Fig. 4, c), the robot
touched the human hand with its own right hand (Fig. 4,d), as in the touched-by-robot condition. Thus, both therobot and the interacting person touch each other. For thiscondition, we also used the robot’s identical touching
behavior of the touched-by-robot condition.
4 Experiment
4.1 Hypotheses and predictions
4.1.1 Hypothesis about gaze behavior

A past research work, which focused on gaze behaviors ina handing situation, showed that only keeping eye-contact
caused negative impressions since the robot failed tocommunicate its intention by a gaze. Gharb et al. reported
that gaze behaviors, including when the giver looks at theobject and then at the receiver, i.e., communicating
intention by gaze, are preferred over gaze behaviors that
only look at the receiver, i.e., only keeping eye-contact[27]. Therefore, we believe that face-hand-face gazebehavior will contribute to more comfortable touch
behavior and be perceived as friendlier feelings of therobot. Based on these considerations, we made thefollowing hypothesis:
Prediction 1-1-a: A touch interaction with a face-handface behavior will be perceived as more comfortable thana touch interaction with a face-only behavior.
Prediction 1-2-a: A touch interaction with a face-handface behavior will be perceived as friendlier than a touch
interaction with a face-only behavior.
Hypothesis about negative effects of communicating
intention of touch by gaze
Past research concluded that maintaining eye-contact isessential to realize more natural feelings of interaction
with robots. Even if these research works focused on
different situations from touch interactions, concentrating
on eye-contact enabled robot behaviors to be perceived as
more natural and contributed to friendlier impressions [24,25, 28]. Turning the robot's eyes away from interaction
partners during touch might be perceived negatively.
Therefore, we believe that face-only gaze behavior willcontribute to more comfortable touch behaviors and be
perceived as friendlier feelings of the robot. Based onthese considerations, we made the following hypothesis:
Prediction 1-1-b: A touch interaction with a face-only
behavior will be perceived as more comfortable than atouch interaction with a face-hand-face behavior.
Prediction 1-2-b: A touch interaction with a face-only
behavior will be perceived as friendlier than a touch
interaction with a face-hand-face behavior.

How Do Communication Cues Change Impressions of Human-Robot Touch Interaction?

5

4.1.2 Hypothesis about touch styles

4.2 Conditions

We assume that the mutual touch style will have similar
positive effects on touch interactions with people based on
the past related works about human-robot touch
interaction. However, several research works showed thattouch styles cause negative impressions, including being
touched by a robot. Similar to our hypothesis about gazebehaviors, since the phenomena related to touch styles are
greatly unexplored, we made two contradictory
hypotheses about their effects based on different theories
and considerations.

Our experiment had a within participant design. Eachparticipant joined six sessions, combinations of two gazebehaviors (face and face-hand-face) and three touchstyles (touch-to-robot, touched-by-robot, and mutual
touch).

Hypothesis about positive effects of robot’s touch

4.4 Procedure

Several past research works on human-robot touch
interaction showed that the mutual-touch style is preferredmore than the touch-to-robot style [20, 38]. Even thoughthese research works did not investigate the effects of thetouched-by-robot style, since the mutual-touch styleincludes the same touch behavior of the touched-by-robot
style, it will probably not be negatively evaluated morethan the touched-by-robot style. Therefore, we believethat the mutual-touch style will contribute to more
comfortable touch behavior and be perceived as eliciting
friendlier feelings than other touch styles. Based on these
considerations, we made the following hypothesis:
Prediction 2-1-a: A touch interaction with a mutualtouch will be perceived as more comfortable than touch
interactions with touch-to-robot and touched-by-robot
styles.
Prediction 2-2-a: A touch interaction with a mutualtouch will be perceived as friendlier than touch
interactions with touch-to-robot and touched-by-robot
styles.
Hypothesis about negative effects of robot’s touch
Past research works about human-robot touch interaction
showed that touched-by-robot may cause negative
impressions [21-23]. On the other hand, several researchworks about touch interaction with robots showed thattouch-to-robot caused positive impressions [19, 34].
Therefore, we believe that the touch-to-robot style willcontribute to more comfortable touch behavior and be
perceived as friendlier than the other touch styles. Basedon these considerations, we made the following
hypothesis:
Prediction 2-1-b: A touch interaction with a touch-torobot will be perceived as more comfortable than touch
interactions with touched-by-robot and mutual-touchstyles.
Prediction 2-2-b: A touch interaction with a touch-torobot will be perceived as friendlier than touch
interactions with touched-by-robot and mutual-touchstyles.

4.3 Pariticpants

Twenty-eight people (14 women and 14 men whose
average ages were 36.4, S.D 9.39) participated.

Before the first session, the participants were given abrief description of our experiment’s purpose andprocedure. This research was approved by our
institution’s ethics committee for studies involving
human participants. Written, informed consent was
obtained from all of our participants.
We placed in front of the robot a chair on which theparticipants sat during the experiment. In all theconditions, after requesting a touch from the robot, it hada short chat with them, such as “I’m 121 cm tall andweigh about 28 kg. I’m lighter than you thought, right?”
We prepared six chat contents to avoid repeating themamong the conditions. During the chat in the touched-byrobot and mutual-touch styles, the robot patted the handof the participants three times. The order of theconditions and the chat contents were counterbalanced.
The participants filled out a questionnaire after eachsession.
4.5 Measurements

To investigate the effects of gaze and touch on the
feelings of the participants, we measured two subjective
items by the questionnaires: the feeling of comfort of thetouch interaction, and the robot’s perceived friendliness.
The items were evaluated on a 1-to-7 point scale.
5 Results

In our analysis, we considered gender effects in addition
to the gaze behavior and touch styles because past
research in the human-human interaction research fieldreported that touching causes different effects based on
gender differences [5, 40].
5.1 Verification of predictions 1-1 and 2-1: feelings ofcomfort of touch interactions
Figures 5 and 6 show the questionnaire results about the
feelings of comfort of the touch interactions. We
conducted a three-factor mixed ANOVA for each scale
on gaze, touch, and gender and identified significant
main effects in the gaze factor (F(1,26)= 5.253, p=.030,
partial η2=.168), the touch factor (F(2, 52)=5.706,
p=.006, partial η2=.180), and the simple interaction

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Hirano et al.

effect between touch and gender (F(2, 52)=4.114, p=.022,
partial η2=.137). No significance was found in thegender factor (F(1,26)= 2.476, p=.128, partial η2=.087),
the simple interaction effect between gaze and gender(F(1,26)= 2.574, p=.121, partial η2=.090), the simple
interaction effect between gaze and touch (F(2,52)=0.928, p=.402, partial η2=.034), or the two-way
interaction effect (F(2, 52)=0.194, p=.824, partialη2=.007).
Multiple comparisons with the Bonferroni method of thesimple main effects of touch in males were significant intouch-to-robot > touched-by-robot (p=.001) and touchto-robot > mutual-touch (p =.006). There was no
significance between touched-by-robot and mutual-touch(p=1.000) as well as none of the touches in females
between touch-to-robot and touched-by-robot (p=1.000),
touch-to-robot and mutual-touch (p=1.000), and touchedby-robot and mutual-touch (p=1.000).
Multiple comparisons with the Bonferroni method
revealed significant differences in the simple main effectof touch in touched-by-robot (female>male, (p =.021)),and there was no significance between touch-to-robot (p=.946) and mutual-touch (p=0.080).
Next we summarize the effects of each factor based on
the above descriptions. For gaze behavior, theparticipants felt significantly higher comfort in the faceonly gaze behavior than in the face-hand-face gazebehavior (p<.05). Concerning touch style and gendereffect, the male participants felt significantly higher
comfort in the touch-to-robot style than in the other touchstyles (p<.05), but female participants did not show any
significant differences. These results support prediction
1-1-b but not prediction 1-1-a. Prediction 2-1-b ispartially supported, and prediction 2-1-a is not supported.

Feeling of comforts (females)
7
6
5
4
3
2
1
Touch-to-robot

Touched-by-robot

Face-only

Mutual-touch

Face-hand-faceFig. 6 Feelings of comfort of robot’s touch (females). Female’s
touched-by-robot is significantly higher than male’s touched-byrobot.

Perceived friendliness (males)
7

6
5
4

3
2
1

Touch-to-robot

Touched-by-robot

Face-only

Mutual-touch

Face-hand-faceFig. 7 Perceived friendliness (males). Touch-to-robot is higher
than touched-by-robot in male participants.

Feeling of comforts (males)

Perceived friendliness (females)

7

7

6

6

5

5

4

4

3

3

2

2
1

1
Touch-to-robot

Touched-by-robot

Face-only

Mutual-touch

Face-hand-faceFig. 5 Feelings of comfort of robot’s touch (males). Face-onlygaze behavior is higher than face-hand-face gaze behavior
regardless of gender. Touch-to-robot is higher than touched-byrobot and mutual-touch in male participants.

Touch-to-robot

Touched-by-robot

Face-only

Mutual-touch

Face-hand-faceFig. 8 Perceived friendliness (females). Female’s face-hand-facegaze behavior is higher than male’s face-hand-face gazebehavior. Female’s touched-by-robot is higher than male’s
touched-by-robot. Also, female’s mutual-touch is higher thanmale’s mutual-touch.

How Do Communication Cues Change Impressions of Human-Robot Touch Interaction?

5.2 Verification of predictions 1-2 and 2-2: perceived

friendliness of robot.
Figures 7 and 8 show the questionnaire results ofperceived friendliness. We conducted a three-factor
mixed ANOVA for each scale on gaze, touch, and genderand identified significant main effects in the touch factor(F(2, 52)=3.599, p=.034, partial η2=.122), the genderfactor (F(1,26)= 5.484, p=.027, partial η2=.174), thesimple interaction effect between gaze and gender(F(1,26)= 4.457, p=.045, partial η2=.146), and thesimple interaction effect between touch and gender (F(2,52)=3.534, p=.036, partial η2=.120). We found no
significance in the gaze factor (F(1,26)= 0.309, p=.583,
partial η2=.012), the simple interaction effect between
gaze and touch (F(2, 52)=0.311, p=.734, partial η2=.012),
or the two-way interaction effect (F(2, 52)=0.224, p=.800,
partial η2=.009).
Multiple comparisons with the Bonferroni method
revealed significant differences in the simple main effects
of gender in face-hand-face (female > male (p=.013))
and no significance in face-only (p=.067). We found no
significant differences in the simple main effects of gazein male (p=0.281) and female (p=0.071).
Multiple comparisons with the Bonferroni method
revealed significant differences in the simple main effects
of touch in males (touch-to-robot > touched-by-robot(p=.003) and no significant differences in other touch inmales (touch-to-robot and mutual-touch (p=0.198),
touched-by-robot and mutual-touch (p=0.193)) and all
touch in females (touch-to-robot and touched-by-robot(p=1.000), touch-to-robot and mutual-touch (p=1.000),
and touched-by-robot and mutual-touch (p=1.000)).
Multiple comparisons with the Bonferroni method
revealed significant differences in the simple main effects
of gender in touched-by-robot (female > male (p=.007))and mutual-touch (female > male (p=0.034)). There wasno significant difference in touch-to-robot (p=0.167).
We next summarize the effects of each factor from theabove descriptions. None of the gaze behaviors
significantly changed the friendliness perceived by theparticipants; note that the female participants felt
significantly higher friendliness in the face-hand-facegaze behavior than the male participants (p<.05). For the
touch style and the gender effect, the male participants
felt significantly higher friendliness in the touch-to-robot
style than in touched-by-robot style (p<.05), but female
participants did not show any significant differences. The
female participants felt significantly higher friendliness inthe touched-by-robot and mutual-touch styles than themale participants (p<.05).
These results showed that neither predictions 1-2-a and 12-b were supported. Prediction 2-2-b is partially
supported, and prediction 2-1-a is not supported.

7

6 DISCUSSION
6.1 Design implications of gaze behavior

Our study clarifies how gaze behaviors in human-robot
touch interaction changed people’s feelings toward therobot. The results show that keeping eye-contact during
touch interaction improves the feelings of comfort of arobot’s touch. The results also show that preferred gazebehavior during touch interaction would be different
based on gender. On the other hand, gaze behavior did not
improve the friendliness perceived by the people.
Moreover, the results are contrary to past research workthat focused on a handing interaction situation [27]. In
handing interactions, the looked-at-object is critical tocommunicate the giver’s intention; but in touch
interactions, such gaze behavior that communicatesintention was negatively evaluated, suggesting that therequired gaze behaviors are different between handing
and touch interactions. This result is an importantconsideration for interaction designs of social robots thatphysically interact with people.
One possible explanation for the negative effects of facehand-face gaze behavior is that the robot looked awayfrom its interaction partners before touching them.
Physical contact is a main difference between handing andtouch interactions. As reported in human-humaninteraction literatures [2-7], physical contacts strongly
influence the feelings of the interacting people; in suchsituations, a robot that looks away might be negatively
perceived by its interaction partners. Keeping eye-contact
through face-only gaze behavior would probably beembraced by them.
6.2 Design implications of touch style

Our experimental results showed a more complex
phenomenon than past research. The touched-by-robot
style showed more negative impressions than the touchto-robot style, similar to past research works [21, 22]. On
the other hand, the results showed opposite results from apast research work [20] that concluded that touch-to-robot
is preferred over mutual-touch with male participants.
These results suggest that touched-by-robot provides
more negative feelings than touch-to-robot, but it remains
unknown in which direction the factor will change theimpressions of mutual-touch: positive or negative.
One possible explanation of the negative effects ofmutual-touch is the sense of the robot’s hand. A past
research work [20, 38] which reported the advantages ofmutual-touch used sponge-based soft hands for its robot,
unlike our research work. Moreover, the material of therobot’s hand would probably change the perceived
warmth during the touch compared to Pepper’s plasticbased hand. Since past research reported that soft andwarm feelings are important for positive impressions

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through touch interaction [41, 42], these factors might be
one reason for the negative effects of mutual-touch in our
experiment.
One possible future work of this research is to consider
different measurements, e.g., not only questionnaires but
also facial expressions and/or interviews. Deeper analysis
would be useful to find the reasons why our experimental
results showed different trends from past study.
6.3 Multi-modal effects between gaze behaviors andtouch styles toward feelings of touch and gaze
As described in Section 6.1, the experimental results
showed that gaze behaviors influence the feeling of
comfort of the robot’s touch, i.e., people felt more
comfortable with the robot’s touch in the face-only gazebehavior than the face-hand-face gaze behavior. To
scrutinize such multi-modal effects, i.e., whether the
touch style influence impressions about gaze, we
additionally measured the feeling of comfort of the robot’s
gaze. The touch styles showed no significant difference,but it was a non-ignorable value (p=.056); participantspreferred touch-to-robot to touched-by-robot in thecontext of the feeling of comfort of the robot’s gaze.
These results suggest that since gaze behavior and touchstyle are mutually influential, identifying detailed
relationships between other kinds of communications cues
is important for more natural and acceptable touch
interactions with a robot.
6.4 Limitations

Since our experiment was only conducted with anexisting robot (named Pepper) robot generality is limited.
The effect shown in the experiment would probably bemoderated if our participants interacted with a robot witha different appearance, size, and so on. For example,
Pepper’s eye design is different from human eyes. Since
this design simplifies making eye-contact with interaction
partners, it also influences the perceived feelings inhaptic interactions. In the experiment, only one
participant reported that Pepper glanced up at his face
while it looked at his hand.
We only investigated the touches between the hands ofpeople and the robot. Past research work reported thatpeople felt different feelings due to which part of therobot’s body they touched [43]; our research work only
investigated the effects of touching a hand. If the robot
touched a different part of the interaction partner’s body,
it would also influence the perceived feelings of the robot.
Moreover, if the robot touched a different body part,
appropriate touch behaviors, touch trajectories, and thetouch’s force would be modified.
The perceived gender of the robot is another factor thatmight change impressions of its touch. We used Pepper’s

Hirano et al.

default text-to-speech function that produces a neutral
gender voice, but people have different feelings when the
robot used specific female/male voices. Since past
research reported that the genders of the toucher andreceiver are related to perceived feelings of touch [44],our future work must investigate the effects between theperceived robot’s gender and communication cues.
Another limitations is a simple settings in touch
interaction, because intention and scenario would be
important to the perceived impressions. Moreover,definitions of natural interaction are also different
depending on contexts. For example, Chen et al.,investigated the touch effects in nursing contexts [23]; insuch situations, roles of robots and meaning of touches
would have important roles for touch interaction. In
addition, active touch from a care robot in nursing
contexts would be natural, but our results showed thatsuch touch style was negatively evaluated at a simple
touch interaction context. Gharb et al. reported thatlooking at an object is essential to realize naturalinteraction for both humans and robots in hand-oversituations [27], but in our results showed that looking at a
hand is negatively evaluated, too. Also, different touch
interactions such as a handshake, a pat and/or a high fivewould provide more positive impressions to people. In
this study we focused on the touch style and gazebehaviors without specific settings due to focusing on
simple situations to investigate their effects withoutbiased assumptions, but we should consider suchintentions and scenarios to apply these knowledge tohuman-robot touch interaction.
7 Conclusion

We reported the effects of communication cues
(combining gaze behaviors and touch styles) toward theperceived feelings to a robot in haptic interaction. Basedon related works, we employed two gaze behaviors
during touch (face-only: looking at the face of aninteraction partner, and face-hand-face: looking at theface, the hand, and returning to the face) and the touchstyles (touch-to-robot: a person touching a robot,
touched-by-robot: a robot touching a person, and mutualtouch: a person and robot touching each other). To
investigate the effects of gaze behaviors, touch styles,
and gender effects, we conducted a mixed-design
experiment in which a robot interacts with participants
through touch.
The experimental results indicated that our participantspreferred face-only gaze behaviors more than face-handface gaze behaviors. They also preferred touch-to-robot
more than touched-by-robot and mutual-touch. Even
though a part of our experimental results showed
contradictory phenomenon compared to past research, we
still believe such knowledge will help robotics

How Do Communication Cues Change Impressions of Human-Robot Touch Interaction?

researchers who are designing communication cues in
haptic interaction with social robots.
Acknowledgements: This research work was supported
by JSPS KAKENHI Grant Numbers JP15H05322, JP
16K12505, and JP 15K16075.
Conflict of Interest: The authors declare that they haveno conflict of interest.
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Takahiro Hirano received B.Eng. degree from Doshisha
University, Kyoto, Japan, in 2016. He is currently a M.Eng.
student at Doshisha University and an internship student at
the Intelligent Robotics and Communication Laboratories(IRC), Advanced Telecommunications Research InstituteInternational (ATR).His research interests include humanrobot interaction.

How Do Communication Cues Change Impressions of Human-Robot Touch Interaction?

Masahiro Shiomi received M. Eng. and Ph.D. degrees inengineering from Osaka University in 2004 and 2007. From2004 to 2007, he was an intern researcher at the Intelligent
Robotics and Communication Laboratories (IRC). He iscurrently a group leader in the Agent Interaction Design
department at IRC, Advanced Telecommunications
Research Institute International (ATR). His researchinterests include human-robot interaction, haptic interaction,
robotics for childcare, and multiple social robots.

Takamasa Iio received his M. Eng. and Ph.D degree from
Doshisha University, Kyoto, Japan, in 2009 and 2012. From2012 to 2014, he was a researcher at the Intelligent Robotics
and Communication Laboratories in the Advanced
Telecommunications Research Institute International (ATR).
He is currently a specially appointed assistant professor at
Osaka University, Osaka, Japan. His research interests
include human-robot interaction, group conversation
between humans and multiple robots and social behaviors ofrobots.

Mitsuhiko Kimoto received his M. Eng. degree from
Doshisha University, Kyoto, Japan, in 2016. He is currently
a Ph.D. student at Doshisha University and a Student Internat the Intelligent Robotics and Communication Laboratories(IRC), Advanced Telecommunications Research InstituteInternational (ATR), Kyoto, Japan. His research interests
include human-robot interaction.

Ivan Tanev was born in 1964 in Simeonovgrad, Bulgaria.
He earned M.S. (with honors) and Ph.D. degrees from SaintPetersburg State Electrotechnical University, Russia in 1987
and 1993, respectively, and Dr. Eng. degree from MuroranInstitute of Technology, Japan in 2001. He has been with the
Bulgarian Space Research Institute (1987), Bulgarian
Central Institute of Computer Engineering and Computer
Technologies (1988-1989), Bulgarian National Electricity
Company (1994-1997), Synthetic Planning Industry Co.
Ltd., Japan (2001-2002), and ATR Human Information
Science Laboratories (2002-2004), Japan. Since 2013 he has
been a professor at Doshisha University, Japan. Dr. Tanev’s
research interests include evolutionary computations,evolutionary robotics and multi-agent systems.

Katsunori Shimohara received the B.E. and M.E. degrees
in Computer Science and Communication Engineering andthe Doctor of Engineering degree from Kyushu University,
Fukuoka, Japan, in 1976, 1978 and 2000, respectively. From2001 to 2006, he was Director of the Network Informatics
Laboratories and the Human Information Science
Laboratories, Advanced Telecommunications ResearchInstitute (ATR) International, Kyoto, Japan. He is currently

11

a Professor at the Department of Information Systems
Design, Faculty of Science and Engineering, ant theGraduate School of Science and Engineering, Doshisha
University, Kyoto, Japan. His research interests include
human communication mechanisms, evolutionary systems,
human-system interactions, and socio-informatics.

Norihiro Hagita received B.S., M.S., and Ph.D. degrees inelectrical engineering from Keio University, Japan in 1976,
1978, and 1986. From 1978 to 2001, he was with the
Nippon Telegraph and Telephone Corporation (NTT). He
joined the Advanced Telecommunications ResearchInstitute International (ATR) in 2001 and established the
ATR Media Information Science Laboratories and the ATRIntelligent Robotics and Communication Laboratories in
2002. His current research interests include communication
robots, networked robot systems, interaction media, andpattern recognition. He is a fellow of the Institute ofElectronics, Information, and Communication Engineers,
Japan as well as a member of the Robotics Society of Japan,
the Information Processing Society of Japan, and The
Japanese Society for Artificial Intelligence. He is also a cochair for the IEEE Technical Committee on Networked
Robots.