Perspective sharing by body-orientation matching
between a user and an embodied agent
Satoshi V. Suzuki
Tokyo Institute of Technology
Department of Computational Intelligence and Systems Science,
Interdisciplinary Graduate School of Science and Engineering
P.O.Box 226–8502
J2–53, 4259 Nagatsuta, Midori-ku Yokohama, Japan
Email: ssv@ntt.dis.titech.ac.jp
Hideaki Takeda
National Institute of Informatics
P.O.Box 101–8430
2–1–2, Hitotsubashi Chiyoda Tokyo, Japan
Email: takeda@nii.ac.jp

Abstract
People often try to discover and solve problems by accepting others' perspectives in daily life. In computersupported environments, a user should be able to accept the perceived mental perspective of an embodied agent
in the same way. In this study, mental perspective change by body-orientation correspondence between a user
and an embodied agent was examined through a psychological experiment. When a participant (N=48) was
solving a problem, two embodied agents, one of which always agreed with the participant's opinion, and anotherof which always disagreed with it, appeared face-to-face and discussed the problem in this experiment. The
location of the virtual perspective of the participant depended on experimental conditions. After the problem
solving, the participant evaluated each embodied agent based on his/her impression. The results of theexperiment imply that the embodied agent’s mental perspective that was different from the user’s was acceptable
to the user if the body orientation of the embodied agent corresponded with that of the user, although the abrupt
body orientation correspondence of the user with the embodied agent can induce a negative social influence on
the user. Considering the results of the experiment, how the design principle of human-agent body-orientation
correspondence can be refined and applied in real situations is discussed.
INTRODUCTION
Considering others' thoughts to solve problems around them is an important practice for people, but some biases
exist to make others' thoughts obscure in human cognitive processes. For example, in user interface design
process, when developing a personal view (Norman, 1991) of a target user, a user-interface designer tends tounconsciously overlook situations around the target user. In group discussion, it is hard to compel majority's
opinion since people unconsciously tend to conform to the majority's opinion (Janis, 1982). These facts imply
that the human decision-making process often excessively focuses on easily available information around a
person. Thus, a user interface for “persuading” (Fogg, 2003) a user to voluntarily accept a perspective fromothers can contribute to solving this problem. This study investigated the possibility of changing thoughts byperspective sharing with others, through designing body orientation of embodied agents.
This study attempts to reveal that an arrangement of the embodied agent’s body orientation triggers the user’s
perspective sharing with the embodied agent. Studies on embodied agents have shown that a user regards
embodied agents as voluntary thinking social entities when interacting with them. Moreover, embodied agentscan visually appeal to a user’s intuitive thought particularly with their body expression (Takeuchi, Watanabe, &Katagiri, 2005). However, most studies on embodied agents in a user interface have not considered bodyorientation of embodied agents. Embodied agents’ body orientation is therefore focused on as a means to induce
the user’s perspective sharing with an embodied agent.
In this paper, first, the argument for focusing on perspective sharing by body-orientation matching between auser and an embodied agent is explained based on related works of perspective sharing and social response to theembodied agent's body expression. Second, a psychological experiment to examine the influence of perspective
sharing with body-orientation matching between the user and the embodied agent is described based on thisargument. Then, based on the results of the psychological experiment, how body-orientation matching between

the user and the embodied agent influence the user's perspective sharing and contribute to problem solving is
discussed.
PERSPECTIVE SHARING BETWEEN A USER AND AN EMBODIED AGENTIn this study, two terms are introduced, virtual perspective (VP) and mental perspective (MP). These terms arenecessary because the meaning of the term “perspective” changes depending on context. VP refers to a user’s oran embodied agent’s perspective in virtual space, while MP refers to the mental state of the user and theperceived mental state of the embodied agent.
This study intends to investigate the possibility of MP sharing between a user and an embodied agent by VP
sharing. The VP sharing between them is accomplished by body-orientation matching as shown in Figure 1.
Seeing the embodied agent that shows its back, the user should imagine what the agent sees and perceive thecircumstance around it, and then inspect what the agent will think. This study attempts to examine the hypothesisthat VP sharing by body-orientation matching between the user and the embodied agent causes MP sharing
between them.

What is it seeing, andwhat is it thinking...
Embodied agent

User

Figure 1: VP sharing caused by body-orientation matching between a user and an embodied agent
RELATED WORKSIn this section, through discussion of studies regarding cognitive limitations of perspective sharing among people
and the social influence of the body orientation both of people and of embodied agents, the existence of a
relation between the user’s perception of the perspective of embodied agents and the arrangement of bodyorientation of the user and the embodied agents.
Problems in Perspective Sharing
The human cognitive system has limitations that impede people from trying to understand others' MP. This isbecause a mechanism to save cognitive resources exists in human cognitive processes used in considering other'sthought. For example, some human social actions appear under certain rules without one's consideration andconscious thought (Bargh, 1997). Besides, people will tend to try to understand others unfamiliar to them withlimited information such as appearance and tone of speech, because they unconsciously attempt to make adecision with limited information under uncertainty (Tversky & Kahneman, 1982). Furthermore, one tends tounconsciously regard what he/she knows as what others know (Birch & Bloom, 2004). In fact, these limitations
were observed in estimating how long novice took to learn novel interface both in novices and experts (Hinds,
1999). This evidence implies that attempts to let people understand others' thought consciously will be needed.
Nevertheless, some attempts to enable people to consider others' MP exist. One of the famous examples is a userinterface design process with personas (Cooper & Reimann, 2003; Pruitt & Grudin, 2003). In this process,personas are designed to represent typical target users and a user scenario is created based on defined personas.
Such a process can let interface designers consider the possible activities of the target users. Although the userinterface design process with personas can solve problems of considering others' thought, such an attempt byinterface design itself does not exist. To put it differently, what kind of interface design enables users to take into
account others' MP remains unclear. In this study, the body orientation is focused on to examine the potential ofusing it in interface design to let users inspect others’ thoughts.
Sharing Embodied Agent's Mental Perspective with a User
Some studies have attempted to share MP by assigning a certain social role to an embodied agent to let a user
perceive this agent as his/her peer. For example, Fogg (2003) introduced such social roles with the results ofpsychological experiments. According to his findings, an agent whose perceived characteristics are similar to theuser's should be perceived as the user's peer, and also the user may regard the agent as a peer if the user is told
explicitly that the agent is his/her “teammate.” The strategy that a “co-learner agent” shows empathic facial
expressions to a user (learner) in an e-learning system (Morishima, Nakajima, Brave, Yamada, Maldonado, Nass,

& Kawaji, 2005) can be regarded as the same approach to enable the user to perceive the agent as his/her peer.
However, these studies did not mention the influence of the body orientation of embodied agents on the user's
perception.
Moreover, some applications have attempted to express the agent's VP by showing the agent's back to the user.
For example, in another e-learning system, user's VP in virtual classroom is set at the back of student agents
which show their back (Watanabe, 2003). Furthermore, Okamoto, Okamoto, Nakano, and Nishida (2005)
claimed that an embodied agent that showed its back to a user should provoke empathy from the user toward theembodied agent. None of these studies, however, used empirical evidence to argue that the correspondence ofbody orientation of an embodied agent with that of a user triggers the user to accept the opinion of the embodied
agent.
With the lack of study on the potential for body-orientation matching to induce shared MP, this study sought toexamine, through a psychological experiment, whether the body-orientation matching between the user and theembodied agent can express that the agent is the user's peer, and whether the user can accept perceived MP fromthe agent.
EXPERIMENTThe prediction for the experimental results was that the degree of the user’s perception of the same social
relationship with an embodied agent would be reflected in how much the user accepted the opinion of theembodied agent. The degree of acceptance of the embodied agent by the user was measured in an experimentconducted as follows.
Purpose of the Experiment and Predictions
Based on the hypothesis that the opinions of an embodied agent regarded as a social entity that shares MP witha user tend to be accepted by the user, the results of the experiment were predicted as follows:
P1 A user will change his/her opinion considering the perceived thought of an embodied agent whose bodyorientation matched with his/her own.
P2 A user will evaluate an embodied agent whose body orientation matches with his/her own as better thanother agents whose body orientation does not agree with his/hers.
Experimental Design

Figure 2: Con-agent (left) and Pro-agent (right)

Figure 3: Arrangement of body orientation of two embodied agents: Con-behind (left), Square (center), Probehind (right)
In this experiment, the two embodied agents shown in Figure 2 appeared as represented in Figure 3. One of theembodied agents, which appeared on the right side of each figure, is called Pro-agent, and the other one is calledCon-agent in this article. The Pro-agent always agreed with the participant’s opinion, while the Con-agent
always disagreed with it. They were standing face-to-face over a table, but the perspective that the participant
could take was different dependent on the condition to which he/she was assigned. In the Con-behind condition(left side in Figure 3) and the Pro-behind condition (right side in Figure 3), the participant took the perspectivefrom behind the Con-, or the Pro-agent, respectively. The participant took the perspective from between the two
embodied agents so that he/she could see side of each agent's body in the Square condition (centre in Figure 3).
Participants were assigned one of these conditions randomly. Then, one independent variable (the VP that theparticipant could take, between-participant factor) existed.
Procedure
Forty-eight Japanese undergraduate and graduate students (24 males and 24 females, mean age: 24.3 (SD: 4.46)
years old) participated in this experiment. All of the participants had been using PCs and browsing the WWW
for at least 2 years. They were randomly assigned to one of the three experimental conditions. Thus, for eachcondition, there were 16 participants (8 males and 8 females).
First of all, each participant solved the desert survival problem (Lafferty & Eady, 1972). We used this task
because it has been used in other studies (Fogg, 2003) and we thought that it could easily produce a difference of
opinion between the two embodied agents without crucial noise factors. The participant ranked each of the 14
items (flashlight, jackknife, sectional air map, raincoat, magnetic compass, compress kit, pistol, parachute, salt
tablets, water, book entitled Edible Animals of the Desert, vodka, top coat, and cosmetic mirror) depending
his/her opinion of how important they were for survival. The participant input the rank of each item in a laptop
PC and then the Pro-agent ranked the items the same as the participant, while the Con-agent ranked the items sothat the rank of each item was different from that which the participant chose. The ranking of the Con-agent wasdetermined automatically. For example, if the participant ranked item A as number 2, A’s ranking by the Conagent was number 8 regardless of what item A was. Based on the ranking decided in this process, for each item,the embodied agents suggested why they had ranked the item higher (or lower) than the other in randomizedorder. The speech of the embodied agents was shown to the participant solely with text in speech balloons; no
acoustic medium was used in this experiment. The speech balloons for the embodied agents did not appear
simultaneously. One of the balloons appeared first with animation in which the embodied agent that was
speaking nodded. Then the other speech balloon appeared with animation in which the embodied agent that was
speaking shook its head. Which of the embodied agents started to speak first was decided randomly, but thefrequency with which each agent spoke first was the same. That is, for 7 items randomly chosen, the Pro-agent
was first to suggest its opinion about the item’s rank, and for the others, the Con-agent was first to tell its opinion.
The participant could change the ranking of the items if he/she wanted to do so after considering the two
embodied agents’ opinion. The two embodied agents were implemented with Macromedia Flash and embedded
in a Web page displayed with Mozilla Firefox (full screen mode), and experimental data were collected via the
WWW with the CGI program. After finishing modifying the item ranking, the participant evaluated theimpression of the two embodied agents with a paper-and-pencil questionnaire. Finally, the participant wasdebriefed, thanked for his/her participation, and dismissed. The experiment took around 30–40 minutes for eachparticipant.
RESULTSIn this section, based on analyses of the results of the experiment, the data is discussed in detail.
MeasuresFirst, as measures of attitude change, we classified the participants’ ranking of items in the following manner.
For example, any item ranked as number 3 by a participant and the Pro-agent was ranked as number 6 by theCon-agent. In this case, if the participant modified the rank of this item higher than number 2, this item wascounted on number of items whose ranking were changed with the Pro-agent’s opinion; if he/she modified therank lower than number 4, it was counted on number of items whose ranking were changed with the Con-agent’s
opinion. On the contrary, for the case that an item ranked as number 10 by a participant and Pro-agent andranked as number 7 by Con-agent, if the participant modified ranking of this item higher than number 9, thisitem was counted on number of items whose ranking were changed with the Con-agent’s opinion; if he/she
modified the ranking of this item lower than number 11, it was counted on number of items whose ranking werechanged with the Pro-agent’s opinion. Any items for which the participant did not modify the ranking, the items
were counted on number of items whose ranking was not changed.
Evaluation of each embodied agent’s impression consisted of twenty-nine 7-point scale questions. The
questionnaire was made taking into account previous studies (Nass, Fogg, & Moon, 1996; Suzuki & Yamada,2004). Then, these three indices suggested by factor analysis were adopted:

Perceived similarity This represented the user’s perception of the embodied agent's similarity to him/her. It
was an index of ten items: perceived similarity of final rankings to the embodied agent’s hypothetical final
ranking, relevance of thought, acceptance of the embodied agent’s advice, perceived similarity of approach,perceived similarity of interaction style, perceived similarity of final ranking to the embodied agent’s initialranking, perceived similarity of initial rankings, receptivity to the embodied agent’s suggestions, degree of
empathy to the embodied agent, and perceived similarity of suggestions (Cronbach’s α = .945).
Perceived intelligence This expressed the user’s perception of the intelligence of the embodied agent. This
index was made from eight items: capability of the embodied agent, trust in the embodied agent’s information,
helpfulness of the embodied agent’s information, articulateness of the embodied agent’s suggestions,
intellectuality of the embodied agent, insightfulness of the embodied agent’s information, dependence on theembodied agent’s suggestions, and cleverness of the embodied agent (α = .896).
Friendliness This regarded the user’s perception of the friendliness of the embodied agent. It consisted of two
items: warmth, and kindness of the embodied agent (Pearson’s r = .909).
Attitude Change
Table 1: Frequency of change direction of each item's ranking for each condition
Total number of items whose ranking
were changed with the were not changed
Pro-agent's opinion

were changed with the Total
Con-agent's opinion

Con-behind (n = 16)

77

52

72

201

Square (n = 16)

91

131

109

331

Pro-behind (n = 16)

56

41

43

140

Total

224

224

224

672

Table 1 indicates the number of items for which each agent did and did not change the participants’ rankings.
The result of a χ2-test revealed that there was significant difference in the distribution of the variables of ranking
change among these three conditions (χ2 (4) = 15.34, p < .01). Moreover, the number of items whose rankings
were changed with the Pro-agent’s opinion was significantly highest in the Con-behind condition (adjusted
residual: z = 1.79, p < .10), and lowest in the Square condition (z = − 2.68, p < .01) among the three conditions.
The number of items whose ranking were not changed was significantly lowest in the Con-behind condition (z =− 3.16, p < .01) and highest in the Square condition (z = 3.38, p < .01) among three conditions. Additionally, in
the Con-behind condition, the number of items whose ranking changed with Con-agent’s opinion was
significantly higher than other conditions (z = 1.88, p < .10).
Evaluation Based on Impression of Two Embodied Agents
Table 2: Mean (SD in parentheses) for variables about evaluation based on participant's impression of embodied
agentsCon-behind (n = 16) Square (n = 16) Pro-behind (n = 16)
Perceived similarity
Pro-agent 5.319 (0.917)
Con-agent 3.054 (0.921)
Perceived intelligence
Pro-agent 4.492 (0.948)
Con-agent 4.136 (0.877)
FriendlinessPro-agent 4.469 (1.271)
Con-agent 2.531 (1.231)

5.150 (0.992)
3.186 (0.699)

5.144 (1.228)
3.068 (0.833)

4.273 (0.757)
4.195 (0.906)

4.422 (1.135)
4.086 (0.870)

4.063 (0.793)
3.438 (1.153)

4.093 (1.129)
3.188 (1.031)

Table 2 shows the results of evaluation based on participants’ impressions of the embodied agents. To analyze
these results, we applied a split-plot design that consisted of two independent variables: embodied agents (Proagent and Con-agent; within-participant factor) and experimental conditions (Pro-behind, Square, and Conbehind; between-participant factor) when conducting two-way analysis of variance for each dependent variable.
First, for each condition, the evaluation of the similarity of the Pro-agent was higher than that for the Con-agent.
Indeed, according to 2 × 3 two-way analysis of variance, the main effect of the embodied agents was significant(F (1, 45) = 97.90, p < .001). However, there was no interaction between the experimental condition factor andthe embodied agents factor, thus no influence from the experimental conditions should appear. Second, while
Table 2 shows that the evaluation of the intelligence of the Pro-agent was slightly higher than that of the Conagent, this difference was not significant (F (1, 45) = 1.862, n.s.). Finally, according to Table II, on theevaluation of the friendliness of the Con-agent, the participants in the Con-behind condition evaluated the Conagent lower than did those in other condition, despite the fact that there seemed to be little difference in theevaluation of the friendliness of the Pro-agent among the three conditions. Actually, interaction between theexperimental conditions and the embodied agents was significant (F (2, 45) = 2.957, p < .10). Thus, examining
the significance of difference of the Con-agent among the experimental conditions by testing the simple main
effect with Tukey’s HSD test, a significant difference between the Con-behind and the Square condition was
found (p < .10).
DISCUSSION
Considering the results of our psychological experiment, the user’s MP change by VP sharing with the embodied
agent and the change of the impression that the user has of each embodied agent are discussed in this section,with mentioning future works.
Induction of Perspective Sharing by Body-orientation Matching
In this experiment, participants in the Con-behind condition changed their opinions more often than did those in
the Square condition, and the participants in the Pro-behind condition also changed their opinions (notsignificantly, nevertheless) more than those in the Square condition. That is, a tendency was observed for theparticipant to change his/her opinion with the embodied agent whose body orientation corresponded withhis/hers and had different opinions from him/her. Then, the prediction P1 was partially supported. This result
suggests that an embodied agent that shares VP with the user and has a perceived different MP from the user's
can share MP with the user. The Con-behind condition showed a salient tendency since the perceived differenceof MP between the participant and the Con-agent was larger than that between the participant and the Pro-agent.
Furthermore, three of the participants in the Square condition did not change their opinions at all in spite of theembodied agents’ interaction. This may be because body arrangement in the Square condition can induce theuser's interest in agents' interaction less than in the other two conditions. Consequently, body-orientation
matching between a user and an embodied agent can induce the user's acceptance of the perceived MP of theagent.
Nonetheless, how long the influence of body orientation correspondence between a user and an embodied agent
continues is still unknown. If the user interacts with an environment where embodied agents appear and some ofthem match with the user in body orientation for a long time, whether the influence of body orientation
correspondence between them is reinforced or diminished cannot be judged with a psychological experimentinside a laboratory in the limited time of half an hour. Therefore, observation of interaction between the user andan environment in which embodied agents appear for a long time is needed to consider body-orientation
matching in practical application.
Role of an Embodied Agent as User's Peer
Despite the fact that body-orientation matching between a user and an embodied agent can promote the user's
acceptance of the perceived MP of the agent, greater difference in the perceived MP between the user and theagent may let the user feel proportionately less friendly toward the agent. The experimental results indicated thatthe evaluation of the friendliness about the Con-agent by the participants in Con-behind condition was lower
than that by the participants in the Square condition. This result contradicts the prediction P2. Additionally,
regardless of body orientation, the participants perceived similarity of thought with Pro-agent. This result also
does not support the prediction P2, and contradiction between the result and the prediction occurred in the Conbehind condition. Taking into account these results, corresponding VP between a user and an embodied agent
whose perceived MP is largely different from the user can give the user a negative impression of the agent.
To avoid negative influence of the embodied agent on the user by VP corresponding, the agent should haveperceived similarity in its features other than the body-orientation matching adopted in this experiment andperceived MP. Even if the perceived MP is different, the user can be influenced from another perceived
similarity and a positive impression of the agent, as shown in related works; as a result, the user can accept theopinion of the agent that is different from his/hers (Fogg, 2003). The user abruptly encountered two embodied
agents in this experiment and no other social cues than VP and perceived MP of the agents were given in thisexperiment. If the participant had the chance to understand other social cues and find something in common with
the Con-agent, he/she would have felt more similar and friendly with that agent. The design of the encounter anddevelopment of the relationship between a user and an embodied agent should be important in MP sharing
between them.

Possible Application of Body-orientation Matching
MP sharing has an important role in problem discovery and solving. MP sharing between a prospective user andan interface designer should contribute to improving user interface design, and MP sharing between minority
and majority in group discussion may help with finding problems in the majority's solution. Taking the MP of ateacher can help a student with finding how to derive the correct answer in a mathematical problem (Morita &Miwa, 2003). Although there are problems of encounter and relationship development design between a user andan embodied agent, body-orientation matching between them can cause the user's acceptance of the perceived
MP of the embodied agent. Then, considering a real situation of problem discovering and solving, MP sharing
by body-orientation matching between the user and the embodied agent should be examined.
CONCLUSION
In this study, mental perspective change by the virtual perspective correspondence between a user and anembodied agent was attempted. The result of a psychological experiment suggested that a perceived mental
perspective of an embodied agent that was different from the user’s perspective was acceptable to the user when
the body orientation of the embodied agent corresponded with that of the user, compared to the environment inwhich the body orientation of the embodied agent and the user did not match, though the abrupt body orientation
correspondence of the user with the embodied agent can give the user a negative social influence. The designprinciple of human-agent body-orientation correspondence should be further refined in human-agent encounterand social relationship development, and must be examined in real problem discovering and solving situation. In
the future, we aim to discover design principles of embodied agents’ body expression that can let a user
understand others’ mental perspectives that are different from his/her own.
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ACKNOWLEDGEMENTS
We would like to express our gratitude to those who participated in our psychological experiment in this study,
and those who cooperated in recruiting the participants and offered a space for the experiment.