A Hug from a Robot Encourages Prosocial Behavior
Masahiro Shiomi Member, IEEE, Aya Nakata, Masayuki Kanbara, Norihiro Hagita, Member, IEEE

Abstract—This paper presents the effects of being hugged bya robot to encourage prosocial behaviors. In human-humaninteraction, touches including hugs are essential forcommunication with others. Touches also show interesting
effects, including the “Midas touch,” which encourages
prosocial behaviors from the people who have been touched.
Previous research demonstrated that people who touched arobot experienced positive impressions of it without clarifying
whether being hugged by a robot causes the Midas touch effect,i.e., positively influences engagement in prosocial behaviors. We
developed a huge, teddy-bear-like robot that can give reciprocalhugs to people and experimentally investigated its effects on
their behaviors. In the experiment, a robot first asked
participants to give a hug and then asked them to makecharitable donations in two conditions: with or without areciprocated hug. Our experiment results with 38 participants
showed that those who were hugged by a robot donated moremoney than those who only hugged the robot, i.e., without areciprocated hug.

I.

INTRODUCTION

Robots can physically interact with people, which is an
essential difference from computer-graphic-based agents. In
fact, past research has reported that the physical presence ofrobots influences interactions with people differently or morestrongly than computer-graphic-based agents [1-4]. For
example, Bainbridge et al. investigated different responses to arequest to throw a book by comparing humans, agents, androbots [2]. Shinozawa et al. concluded that people are more
likely to follow a robot’s opinion than the opinion of acomputer-graphic agent [4].
Physical existence enables robots to communicate withpeople through haptic interaction. In human science literature,
the positive effects of haptic interaction have already beenbroadly investigated, and both the mental and physicalbenefits have been unveiled [5-10]. An interesting
phenomenon known as the “Midas touch” effect, which
encourages prosocial behaviors, has also been reported [11].
Following these results, robotics researchers also investigatedthe positive effects of a robot's haptic interaction [1, 12, 13].
For example, touching a robot positively affected the mental
health of seniors [14]. Hugs, another kind of touch, are also aninteresting research topic in the human-robot interaction
research field, and researchers have started to investigate theireffects. For example, Sumioka et al. reported that a voice callto another person through a huggable robotic device decreased
stress levels more than with a common smartphone [15].

* This research work was supported by JSPS KAKENHI Grant Number
JP15H05322 and JP16K12505.
M. Shiomi, A. Nakata, M. Kanbara and N. Hagita are with ATR, Kyoto,
6190288, Japan. (e-mail: m-shiomi@atr.jp)
A. Nakata, M. Kanbara and N. Hagita are also with NAIST, Nara,
6300192, Japan.

Figure 1. Participant being hugged by a robot

However, in research that focused on hug interaction withrobots, the robots did not reciprocate the hugs because of the
difficulties of hug behaviors or their size and shape. Moreover,the literature in human-human interaction showed several
contradictory (positive and negative) effects of reciprocal
haptic interaction. For example, reciprocal touch lends support
and generally binds the affective relationship more tightly
together [16]. But other works reported that nonreciprocal
touch evokes dominance, status, and power [17-20]. Anotherwork concluded that a non-reciprocal touch expresses warmthor love and rarely dominance or control [21]. Therefore, there
is room to uncover the effects of reciprocated hugs by a robot.
A question arises: how does being hugged by a robot (Fig. 1)
influence people to change their behaviors?
This paper addresses this question by investigating theeffects of being hugged by a robot. We developed a robot
named “Moffuly” (Fig. 1) that resembles a large teddy bearand implemented a simple structure with which it hugs aninteracting person. We compared the effect of being huggedby it by investigating responses to prosocial behaviors(donations) requested by the robot. We also discussed both
positive and negative perspectives on the effects of being
hugged by a robot based on our experiment results.
II.

RELATED WORKS

A. Human’s touch effects
Touching, including hugging, increases happiness andhealth through both mental and physical benefits. For example,
past research confirmed that the act of hugging reduces bloodpressure and protects against heart rate increases understressor events [5]. Hugs also provide stress-buffering social
support and protection against the infectious virus that causes
the common cold [6]. Such tactile stimulation as back-rubbing
and hugs induces the release of oxytocin, a hormone thatfacilitates social bonding and trusting behaviors [22]. Even if
touch is imagined, buffers stress and pain better than verbal
support [7]. Burgoon et al. investigated how touchinginteractions affect impressions in human-human interaction[23], such as intimacy and immediacy.
Touching also influences prosocial behaviors, not only
health status. Researchers investigated touch effects for
positive impressions [24], and higher compliance to requests[25, 26]. This phenomenon was dubbed the “Midas touch,”which is one famous effect of touching in human science
literature.
B. Human-robot haptic interaction
In human-robot interaction research fields, touching
including hugs with robots provides positive effects [12-15,
27-29], as in the case with human interaction. For example,
touching a seal robot (Paro) provided mental health benefits
for elderly people [14]. Being touched by a robot increased
people’s motivation during monotonous tasks and improved
their impressions of it [13]. Chen et al. investigated theinfluence of a combination of a robot’s touches and verbal
communication cues on robot impressions [30]. Conversations
through huggable devices decreased stress levels more thanwith a smartphone in an investigation of cortisol levels [15].
Hug interactions are preferred by interacting people who are
observing their reactions in real environments [31, 32].
Midas touch effects in human-robot interaction are broadly
investigated because they are a commonly used measurementof the behavioral effects of touches in the human interaction
research field. For example, Fukuda et al. measured them froma robot’s touch by analyzing Medial Frontal Negativity by
EEG [33]. Haans et al. investigated whether tactile stimulation
with vibration motors influenced the helping behaviors ofpeople [34]. Another viewpoint investigated Midas touch
effects through telepresence robot negotiation [35].
These research works thoroughly investigated the effects
of touch with a robot and the Midas touch in human-robot
interaction. However, the hug interactions with robots in themwere a one-way hug interaction; due to the limited capabilitiesof the robots, only the people hugged them, not the other way
around. Some research implemented a reciprocal hug behavior
for robots [31, 32]. But since these behaviors were part of aninteraction, the scrutiny of reciprocated hugs remains
inadequate.
We believe that reciprocated hugs from a robot willprobably have a stronger influence than one-way hug
interactions from people. In this study, we unveil the effects ofreciprocated hugs from a robot by measuring both prosocial
behaviors and the interactions of people, both of which arecommonly used to investigate behavioral effects inhuman-robot interaction.

the robot gives a hug, we covered its frame with
polypropylene cotton and used weak motors that can be easily
resisted if needed. We addressed sanitation concerns byattaching a washable cover to its face part that makes contact
with the faces of participants during the hugs (Fig. 1). Itsutterances were generated using speech synthesis software[37]. The robot was placed in a room with three cameras andthree microphones. Speech recognition was performed by anoperator who chose from among pre-determined rules tocontrol it.
We prepared several chat contents and reply behaviors forconversations, including such self-introductions as “Hello,
I’m Moffuly! Even though I look like a bear, my favorite foodis electricity, not honey.” We also prepared self-disclosure
contents because they are important for friendly
human-computer and human-robot interactions [38, 39].
During conversations, the robot asks to chat with people andsimply replies to them: “I see,” “you did your best,” and so on.
Appropriate reply behaviors are chosen by the operator basedon the conversation contexts. Since we designed the robot as alistener in this study, to prevent complex conversations about
itself, the robot politely refused to answer most questions:“Sorry, I don’t know much about that. But I’d like to hearmore about your story!”
B. Hug behaviors
We prepared two hug behaviors for the experiment: ahug-request in which the robot asks for a hug, and areciprocated hug behavior in which the robot hugs theparticipants who hugged it.
For safe reciprocated hugs from the robot, we followed asimilar experiment procedure from a past research work [13];we designed it to ask the person for a hug first, which it thenreturns. The following are the details of these behaviors:
Hug-request behavior: The robot opens its arms and says,“Before we start talking, would you please give me a hug?”(Fig. 2-a). The robot says, “Hug me longer, please” when the
person seems to stop the hug or to leave the robot.
Reciprocated hug behavior: After the person grants its
hug-request behavior and hugs the robot, it moves both of its
own arms (which are controlled by the operator) until it
touches the person’s body. Then the robot pats the person on
the back (Fig. 2-b); the timings of the pats are based on two
rules. First, while the robot is talking, the timing is based on
the end of its contents. Second, when the person is talking to
the robot, the timing is either based on the end of their contents
or on 30-second periods.

III. SYSTEM CONFIGURATION
Our system is designed for Wizard-of-Oz studies [36] inwhich we systematically tele-operated it. This enables us toconcentrate on user interactions in ideal situations where therobot always responds correctly.
A. Robot
For this study, we developed “Moffuly,” a robot that
resembles a large teddy bear (Fig. 1). It is 200-cm tall with two
elbows (1*2 DOF) and a speaker. Its arms are 80 cm long,which is adequate to reciprocate a hug. To ensure safety when(a) Hug-request behavior(b) Reciprocated hug behavior

Figure 2. Hug behaviors of robot

IV. EXPERIMENT
A. Hypothesis and prediction
Hugs are basically reciprocal. A reciprocated hug conveys
acceptance and positive impressions. We believe thatreciprocated hugs from a robot can also more strongly convey
positive impressions to the person who hugged the robot than
non-reciprocated hugs and would probably influence his/herbehavior.
To investigate the effects of reciprocated hugs from a robot,
we focused on behavior changes: the Midas touch effect. In
human-human interaction, touch encourages such prosocial
behaviors as donations and helping the person who wastouched [11, 24-26]. Such effects are also observed inhuman-robot interaction [33, 34]. Therefore, a hug from arobot, which is one typical touch behavior, might influence
prosocial behaviors in the interacting persons. Based on thesereasons, we make the following hypothesis:
Prediction: People who were hugged by a robot will
donate more money to charity than people who only hugged it(i.e., without a reciprocated hug).
B. Participants
Thirty-six Japanese people (18 women and 18 men, whose
average ages were 35.49, S.D 10.13) were paid for their
participation.
C. Environment
In the experiment environment, we fixed the robot to awall and installed two cameras and microphones on the ceilingand one camera/microphone near it. We used this information
to analyze the experiment and to control the robot by anoperator who manipulated it from another room.
D. Condition
The study had a between-participant design with thefollowing two conditions. For each condition, nineteen
subjects (nine women and ten men) participated. In bothconditions, the conversational and the replay behaviors wereidentical, and the operator controlled the robot based on thesame pre-defined rules in both conditions.
Hug-request only: The robot requests a hug from theparticipants and then chats. It did not hug the participants.
Reciprocated hug: The robot requests a hug from theparticipants, hugs them back, and then starts to chat. During
the chats, it pats them on the back based on pre-defined rules.
E. Procedure
Before the experiment, the participants were given a brief
description of our experiment’s purpose and procedure. In this
explanation, we only asked the participants to interact and talkwith the robot by hugging without mentioning the donations.
We explained the nature of their interaction with the robot andliterally demonstrated how to hug it (Fig. 2-b). We also
explained that the robot’s face part with which theparticipants’ faces make contact during hugging was
replaceable for sanitation concerns. We also explained thatsince the robot’s conversation capabilities are limited,
complex conversations are difficult. We stressed that the robot
likes listening to stories and encouraged them to talk with it.

After the above explanations, the experimenter left theparticipants in the experiment room and started the firstsession. During this session, only the participants and therobot were in the room.
After starting the experiment, the robot introduced itself tothe participants and made its hug-request behavior. Afterbeing hugged, the robot talked with them using theself-disclosure contents and asked for stories or just offered tolisten to them. In the reciprocated hug condition, the robot
hugged the participants and started patting them on the backbased on the pre-defined rules. All the participants interactedwith the robot for ten minutes per session. At the end, the robot
said, “By the way, I’m collecting donations for earthquake
victims. Would you like to give? There’s a donation box in theroom where you’ll answer a questionnaire after theexperiment.” Then the experimenter entered the room and led
the participants to another room that held a desk, a chair, and a
donation box. The experimenter paid the participants andasked them to complete questionnaires. The experimenter
again left the participants in the room for ten minutes. At thistime, they could freely donate some money. After ten minutes,
the experimenter returned and interviewed them.
In debriefing sessions after the interviews, we explained
the purpose of this experiment and calculated the amount of
their donations. We offered to return their donation to them (ifthey wanted) and promised to donate the same amount ofmoney ourselves even if they wanted their donation back. But
all of the participants declined our offer, i.e., they wanted to
donate money. Therefore, we donated the participants’ money
to the earthquake charity.
This research was approved by our institution’s ethics
committee for studies involving human participants. Written,
informed consent was obtained from all of them.
F. Measurement
To investigate whether the reciprocated hug behavior
encouraged prosocial behavior, i.e., donations for earthquake
victims, we measured both the number of people who donatedand the amount of their donations.
Although our main interests are in the behavioral changes,
we additionally measured one subjective impression of theparticipants by a questionnaire that their total impressions of it.
They answered a questionnaire on a 1-to-7 point scale where 7
is the most positive and 1 is the most negative.
V. RESULTS
A. Verification of prediction
Table 1 and Fig. 3-left show the numbers of people who
donated and the average donation by all 36 participants. For
the number of people, we conducted a Chi-square test, which
did not show any significant differences between theconditions (x2(1) = 0.446, p=n.s, φ=0.111).
We also conducted a t-test for the donation amount. The
results showed significant differences between the conditions(t(34)=2.391. p=0.022, r=0.38). Even if we conducted a t-test
for the average donation by only those participants who
donated (hug-requests only: 8 participants, reciprocated hugs:
11 participants), we still identified a significantly different
level (p <.05). Thus, the prediction was partially supported.

TABLE I.

NUMBER OF PEOPLE WHO DONATED

Did not donate

Donated

Hug-requests only

10

8

Reciprocated hugs

7

11

Yen

Donated money
140
120
100
80
60
40
20
0

*

* : p < .05

Total impression
7
6

5
4
3
2
1

its name (Moffuly) was derived from “mofumofu” (fluffy inJapanese). Other participants asked about its favorite foods,
birthplace, and first love. The robot answered simple questions
using yes or no, but refused complex questions that needed
explanations or reasons.
D. Interview results of hug impressions
In the interviews, first we asked the participants about theirfavorite robot interaction. 5/18 participants (the hug-request
only condition) and 14/18 participants (the reciprocated hug
condition) positively evaluated their hug experiences with therobot. The remaining participants positively evaluated theirchats with the robot, but they did not mention their huginteractions.

Figure 3. Average and S.E. of donated money and total impression

We also asked the participants in the reciprocated hug
condition whether their impressions of the reciprocated hugs
from the robot were positive or negative. 17/18 participants
positively evaluated the reciprocated hugs, and only 1/18
participant criticized it because the hugging wasn’t smooth.
Most positively evaluated their hug interactions with the robot
in the reciprocated hug condition.

Figure 4. Participant who smiled after being hugged

E. Interview results about why people donatedIn the interviews, we asked the participants whether the
robot’s requests and/or interactions were related to their
donation behaviors. In the hug-request only condition, 3/8
participants who donated said that the robot’s request did not
influence their decision; 6/8 participants who donated said thatthe robot’s request did influence their decision. As in thereciprocated hug condition, 3/11 participants who donatedsaid that the robot’s request did not influence their decisions;
8/11 participants who donated said that the robot’s request
influenced their decision. The results suggest that the robot’s
reciprocated hug did not influence their donation decisions.

Hug-requests Reciprocated
only
hugs

Hug-requests
only

Reciprocatedhugs

B. Questionnaire results
Figure 3-right shows the questionnaire results of the total
impressions of the participants. We also conducted a t-test that
did not show any significant differences between theconditions (t(34)=0.278, p=0.782, r=.13). The donation
amounts were different between the conditions, but the total
impressions were not different between them in this study.
C. Observations
In both conditions, typical interaction pattern was that theparticipants talked about themselves while hugging the robot.
Most seemed surprised by the robot’s hug-request behavior,even though we did explain it to them. In the reciprocated hug
condition, sometimes participants even smiled the first timethat they were hugged by the robot (Fig. 4).
Participants listened to the robot and often responded bynodding. After finishing its self-introduction andself-disclosures, the robot asked the participants to talk about
themselves. They mainly chose to talk about their families,
holidays, or school/work. For example, several participants
described their most recent trips: “Every year, I go on acycling tour with my friends. This was our fourth year. Every
year we’ve had trouble, such as heatstroke, leg cramps, and soon. This year, we again had a problem; my friend took a spilland broke his bicycle during the tour.” Another participant
described her job at which she works hard outside on hot
summer days, and the robot said, “I see, you’re working very
hard.” She thanked the robot and smiled.
Some participants asked the robot about itself, even though
we had already explained that its conversation capabilities
were very limited. For example, a participant asked whether

Also, we asked participants whether they usually donate
during such charity drives/opportunities. 12/18 participants in
the hug-request only condition and 12/18 participants in thereciprocated hug condition reported that they often donated.
From these results, the number of people who often donate did
not seem biased between the conditions.
We additionally investigated the average ages of those
who donated because age is probably related to theirdisposable income (we did not ask about their income in thisstudy), which might influence donation behaviors/habits. The
average ages of those who donated were 33.29 (S.D: 10.36) inthe hug-request only condition and 38.78 (S.D: 8.39) in thereciprocated hug condition; there were no statisticaldifferences between the conditions.
VI. DISCUSSION
A. Positive and negative perspectives
Our experiment results revealed that reciprocated hugs
from a robot influenced people’s prosocial behaviors,
although the reciprocated hug mechanism was relatively
simple without rich chat contents. Interestingly, some people
wanted hugs without verbal communication. Thisphenomenon happens in human-human interaction too, e.g.,when we silently hug an intimate friend or family member.
Touching including hugs is essential to construct social
relationships in human-human interaction [8], where thecapabilities of reciprocated hugs are useful to construct social
relationships with robots, especially for long-term interaction.
Past research implemented physical interactions to develop arapport between a robot and people [31, 32]. Moreover,huggable robots are already being used to investigate haptic
interaction effects and for such daily supports in real settings
as elderly care [14, 40]. Reciprocating hugs from a robot
might facilitate social relationships in such contexts.

comparing touch and non-touch [45]. We assume that non-hug
condition would show similar results with the hug-request
only condition because Shiomi et al. have also compared
between non-touch, passive touch (human touch only) andactive touch (reciprocated touch) and reported that there is nodifference between non-touch and passive touch [13].
Comparing non-touch conditions might provide richer
knowledge about hug interaction with a robot.

On the other hand, the effects of reciprocated hugs on
prosocial behaviors, i.e., donations, are related to ethicalissues. In this study, we conducted an experiment under anacademic context and donations from participants forearthquake victims in Japan, but we need to carefully design
reciprocated hug behaviors in real-world contexts. We areconcerned about how to touch people [41], e.g., since a robot
must avoid touches that brazenly solicit contributions.
Moreover, if the robot’s reciprocated hug could contribute to
the construction of social relationships, as described above, we
also need to design robot behaviors that avoid beseeching
requests from robots by exploiting such relationships. A
worldwide social movement has emerged called the “free hugs
campaign” whose events are sometimes related to donations
or charity events [42]. Such a context is another possible
application with our robot because it can reciprocate a hug.

C. Limitations
Since our experiment was conducted with our developed
robot, which has a huggable appearance and size, robot
generality is limited. We cannot ensure that our findings canbe applied to all interactive robots because size and feelings
about being touched are essential for hug interactions. To
generalize reciprocated hug effects, we must investigate themwith different kinds of robots, especially non-huggable robots.

B. Future work
Even though our results revealed that reciprocated hugs
from a robot encouraged prosocial behaviors, it remains
unknown why such effects occurred because our questionnaire
results did not show significant differences between theconditions. We must investigate further relationships via othermeasurements to discuss the effects of reciprocated hugs.

The meaning of touching differs by culture. For example,
in Japan, hug interactions are less common than in suchcountries as Italy [8]. Japanese people might have strong
positive impressions toward hugs because they are relatively
rare in their daily lives. Even though past worldwide researchon hugging has identified positive effects, we cannot
generalize our results yet. Cross-cultural experiments are
critical to scrutinize the effects of reciprocated hugs.

One potentially interesting trial is to investigate suchphysiological measurements as cortisol, which indicates thestress levels of people, because in human science literature,such physiological measurements are commonly investigated.
A past research already investigated huggable medium effects,
which decrease stress levels through conversations [15], but it
did not address reciprocated hugs from a robot. If being
hugged by a robot further decreases stress levels, it mightserve as evidence for the effects of reciprocated hugs, andapplications might be useful for therapy. Other physiologicalmeasures, such as brainwaves, might also help understand thereciprocated hug effects. A past research work analyzed
robot’s touch effects through EEG analysis, which shows thatthey affect Medial Frontal Negativity, whose amplitude iscorrelated with feeling of unfairness [33].
From the psychological perspective, one possible
measurement is the Big Five personality traits that investigate
the relationships between personal characteristics andbehavior changes. Earlier works demonstrated several
measurements toward robots such as negative attitudes toward
robots scales (NARS) and the robot anxiety scale (RAS) [43,44]. Measuring them might deepen our understanding of theeffects of reciprocated hugs.
Another possible future work is to compare the effects of
non-hug. In fact, past research investigated touch effects bycomparing them with non-touch conditions [13, 45]. For
example, Tai et al. showed how touching a doll or a teddy bear
impacts the effect of social exclusion on prosocial behavior by

Since the robot’s hug interaction was relatively simple, wemust also investigate more effective hugs. Investigating
different hug-style situations is another potentiallyenlightening approach, e.g., a hug while standing face-to-face,instead of sitting on the floor. However, we believe that our
setting offers essential knowledge for researchers who areinterested in hug interactions with interactive robots.

VII. CONCLUSION
We focused on the effects of reciprocated hugs from arobot on people’s prosocial behaviors. Even though previous
research investigated the positive effects of hug interactions
with robots, such works focused less on being hugged by arobot during the interactions. To investigate the effects ofreciprocated hugs from a robot, we developed a large,
teddy-bear type robot that can reciprocate hugs from people
and conducted a between-subjects experiment in which it
asked participants for donations (i.e., prosocial behaviors)with a reciprocated hug.
Our experiment results showed significant differences
about the amount of donations among participants who were
hugged or not hugged by the robot. On the other hand, thenumbers of people who donated was not significantly different
between the conditions. This study showed that a reciprocatedhug from a robot influences people’s behavior, even though
impressions toward it did not different between conditions.
REFERENCES[1] J. Li, “The benefit of being physically present: A survey of experimental
works comparing copresent robots, telepresent robots and virtual
agents,” International Journal of Human-Computer Studies, vol. 77, pp.
23-37, 2015.
[2] W. A. Bainbridge, J. Hart, E. S. Kim, and B. Scassellati, “The effect ofpresence on human-robot interaction,” in RO-MAN 2008-The 17th
IEEE International Symposium on Robot and Human Interactive
Communication, pp. 701-706, 2008.

[3] A. Powers, S. Kiesler, S. Fussell, and C. Torrey, “Comparing a computer
agent with a humanoid robot,” in Human-Robot Interaction (HRI), 2007
2nd ACM/IEEE International Conference on, pp. 145-152, 2007.
[4] K. Shinozawa, F. Naya, J. Yamato, and K. Kogure, “Differences in effectof robot and screen agent recommendations on humandecision-making,” International Journal of Human-Computer Studies,vol. 62, no. 2, pp. 267-279, 2005.
[5] K. M. Grewen, B. J. Anderson, S. S. Girdler, and K. C. Light, “Warmpartner contact is related to lower cardiovascular reactivity,”
Behavioral medicine, vol. 29, no. 3, pp. 123-130, 2003.
[6] S. Cohen, D. Janicki-Deverts, R. B. Turner, and W. J. Doyle, “Doeshugging provide stress-buffering social support? A study ofsusceptibility to upper respiratory infection and illness,” Psychologicalscience, vol. 26, no. 2, pp. 135-147, 2015.
[7] B. K. Jakubiak, and B. C. Feeney, “Keep in touch: The effects ofimagined touch support on stress and exploration,” Journal of
Experimental Social Psychology, vol. 65, pp. 59-67, 2016.
[8] A. Gallace, and C. Spence, “The science of interpersonal touch: an
overview,” Neuroscience & Biobehavioral Reviews, vol. 34, no. 2, pp.
246-259, 2010.
[9] K. C. Light, K. M. Grewen, and J. A. Amico, “More frequent partner
hugs and higher oxytocin levels are linked to lower blood pressure andheart rate in premenopausal women,” Biological psychology, vol. 69, no.
1, pp. 5-21, 2005.
[10] T. Field, “Touch for socioemotional and physical well-being: A
review,” Developmental Review, vol. 30, no. 4, pp. 367-383, 2010.
[11] A. H. Crusco, and C. G. Wetzel, “The midas touch the effects ofinterpersonal touch on restaurant tipping,” Personality and Social
Psychology Bulletin, vol. 10, no. 4, pp. 512-517, 1984.
[12] R. Yamazaki, L. Christensen, K. Skov, C.-C. Chang, M. F. Damholdt, H.
Sumioka, S. Nishio, and H. Ishiguro, “Intimacy in Phone
Conversations: Anxiety Reduction for Danish Seniors with Hugvie,”
Frontiers in Psychology, vol. 7, pp. 537, 2016.
[13] M. Shiomi, K. Nakagawa, K. Shinozawa, R. Matsumura, H. Ishiguro,
and N. Hagita, “Does A Robot’s Touch Encourage Human Effort?,”International Journal of Social Robotics, pp. 1-11, 2016.
[14] R. Yu, E. Hui, J. Lee, D. Poon, A. Ng, K. Sit, K. Ip, F. Yeung, M. Wong,and T. Shibata, “Use of a Therapeutic, Socially Assistive Pet Robot(PARO) in Improving Mood and Stimulating Social Interaction andCommunication for People With Dementia: Study Protocol for a
Randomized Controlled Trial,” JMIR research protocols, vol. 4, no. 2,
2015.
[15] H. Sumioka, A. Nakae, R. Kanai, and H. Ishiguro, “Huggablecommunication medium decreases cortisol levels,” Scientific Reports,
vol. 3, pp. 3034, 2013.
[16] A. Montagu, “Touching: The human significance of the skin,” 1971.
[17] D. L. Summerhayes, and R. W. Suchner, “Power implications of touchin male—Female relationships,” Sex Roles, vol. 4, no. 1, pp. 103-110,
1978.
[18] J. F. Deethardt, and D. G. Hines, “Tactile communication andpersonality differences,” Journal of Nonverbal Behavior, vol. 8, no. 2,
pp. 143-156, 1983.
[19] B. Major, and R. Heslin, “Perceptions of cross-sex and same-sex
nonreciprocal touch: It is better to give than to receive,” Journal of
Nonverbal Behavior, vol. 6, no. 3, pp. 148-162, 1982.
[20] C. Forden, “The influence of sex-role expectations on the perception oftouch,” Sex Roles, vol. 7, no. 9, pp. 889-894, 1981.
[21] M. D. Pisano, S. M. Wall, and A. Foster, “Perceptions of nonreciprocal
touch in romantic relationships,” Journal of Nonverbal Behavior, vol.
10, no. 1, pp. 29-40, 1986.
[22] J. A. Bartz, J. Zaki, N. Bolger, and K. N. Ochsner, “Social effects ofoxytocin in humans: context and person matter,” Trends in cognitive
sciences, vol. 15, no. 7, pp. 301-309, 2011.
[23] J. K. Burgoon, D. B. Buller, J. L. Hale, and M. A. Turck, “Relational
messages associated with nonverbal behaviors,” Human
Communication Research, vol. 10, no. 3, pp. 351-378, 1984.
[24] J. D. Fisher, M. Rytting, and R. Heslin, “Hands Touching Hands:
Affective and Evaluative Effects of an Interpersonal Touch,”Sociometry, vol. 39, no. 4, pp. 416-421, 1976.
[25] N. Guéguen, “Touch, awareness of touch, and compliance with arequest,” Perceptual and Motor Skills, vol. 95, no. 2, pp. 355-360, 2002.
[26] N. Guéguen, C. Jacob, and G. Boulbry, “The effect of touch oncompliance with a restaurant's employee suggestion,” International

Journal of Hospitality Management, vol. 26, no. 4, pp. 1019-1023,
2007.
[27] C. DiSalvo, F. Gemperle, J. Forlizzi, and E. Montgomery, “The Hug: an
exploration of robotic form for intimate communication,” in Robot andhuman interactive communication, 2003. Proceedings. ROMAN 2003.
The 12th IEEE international workshop on, pp. 403-408, 2003.
[28] H. Cramer, N. Kemper, A. Amin, B. Wielinga, and V. Evers, “‘Give mea hug’: the effects of touch and autonomy on people's responses toembodied social agents,” Computer Animation and Virtual Worlds, vol.
20, no. 2-3, pp. 437-445, 2009.
[29] K. Nakagawa, M. Shiomi, K. Shinozawa, R. Matsumura, H. Ishiguro,
and N. Hagita, “Effect of Robot’s Whispering Behavior on People’s
Motivation,” International Journal of Social Robotics, vol. 5, no. 1, pp.
5-16, 2012.
[30] T. L. Chen, C.-H. A. King, A. L. Thomaz, and C. C. Kemp, “AnInvestigation of Responses to Robot-Initiated Touch in a Nursing
Context,” International Journal of Social Robotics, vol. 6, no. 1, pp.
141-161, 2013.
[31] F. Tanaka, A. Cicourel, and J. R. Movellan, “Socialization between
toddlers and robots at an early childhood education center,”Proceedings of the National Academy of Sciences, vol. 104, no. 46, pp.
17954-17958, 2007.
[32] T. Kanda, R. Sato, N. Saiwaki, and H. Ishiguro, “A two-month field trial
in an elementary school for long-term human–robot interaction,” IEEE
Transactions on Robotics, vol. 23, no. 5, pp. 962-971, 2007.
[33] H. Fukuda, M. Shiomi, K. Nakagawa, and K. Ueda, “‘Midas touch’in
human-robot interaction: Evidence from event-related potentials during
the ultimatum game,” in Human-Robot Interaction (HRI), 2012 7th
ACM/IEEE International Conference on, pp. 131-132, 2012.
[34] A. Haans, and W. A. IJsselsteijn, “The virtual Midas touch: Helping
behavior after a mediated social touch,” IEEE Transactions on Haptics,
vol. 2, no. 3, pp. 136-140, 2009.
[35] C. Bevan, and D. Stanton Fraser, “Shaking hands and cooperation intele-present human-robot negotiation,” in Proceedings of the Tenth
Annual ACM/IEEE International Conference on Human-Robot
Interaction, pp. 247-254, 2015.
[36] N. Dahlbäck, A. Jönsson, and L. Ahrenberg, “Wizard of Oz studies:
why and how,” in Proceedings of the 1st international conference onIntelligent user interfaces, Orlando, Florida, USA, pp. 193-200, 1993.
[37] H. Kawai, T. Toda, J. Ni, M. Tsuzaki, and K. Tokuda, “XIMERA: A
new TTS from ATR based on corpus-based technologies,” in ISCA
Speech Synthesis Workshop, pp. 179-184, 2004.
[38] T. W. Bickmore, and R. W. Picard, “Establishing and maintaining
long-term human-computer relationships,” ACM Transactions on
Computer-Human Interaction (TOCHI), vol. 12, no. 2, pp. 293-327,
2005.
[39] T. Kanda, M. Shiomi, Z. Miyashita, H. Ishiguro, and N. Hagita, “Acommunication robot in a shopping mall,” Robotics, IEEE Transactions
on, vol. 26, no. 5, pp. 897-913, 2010.
[40] K. Kuwamura, S. Nishio, and S. Sato, “Can We Talk through a Robot
As if Face-to-Face? Long-Term Fieldwork Using Teleoperated Robot
for Seniors with Alzheimer's Disease,” Frontiers in Psychology, vol. 7,
pp. 1066, 2016.
[41] J. B. Van Erp, and A. Toet, “How to touch humans: Guidelines forsocial agents and robots that can touch,” in Affective Computing andIntelligent Interaction (ACII), 2013 Humaine Association Conferenceon, pp. 780-785, 2013.
[42] "Free Hugs Campaign "; http://freehugscampaign.org/[43] T. Nomura, T. Suzuki, T. Kanda, and K. Kato, “Measurement ofnegative attitudes toward robots,” Interaction Studies, vol. 7, no. 3, pp.
437-454, 2006.
[44] T. Nomura, T. Suzuki, T. Kanda, and K. Kato, “Measurement of anxiety
toward robots,” in ROMAN 2006-The 15th IEEE International
Symposium on Robot and Human Interactive Communication, pp.
372-377, 2006.
[45] K. Tai, X. Zheng, and J. Narayanan, “Touching a teddy bear mitigates
negative effects of social exclusion to increase prosocial behavior,”
Social Psychological and Personality Science, pp. 1948550611404707,
2011.