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EgoChat Agent                                                     97


                                       virtualized-ego(A)         virtualized-ego(B)
                                          liquor       brandy         liquor
                                                                                  sake



                                                 beer                       wine



                                               Figure 11.3.  Example of a flow-of-topics set


                              Story structure: A stream of messages reflects social relationships between
                                   community members. The frequency of exchange between community
                                   members on mailing-lists and between a user and a VE on EgoChat
                                   is recorded in each VE. For example, when community member (a) is
                                   inclined to talk with member (b) more than with community member (c)
                                   and the VE of member (b) has talked in the previous turn, the VE of
                                   member (a), not that of member (c), goes first in the present turn.
                              Coherence: A VE that selects the following message after a message men-
                                   tioned just before goes first so that messages are exchanged coherently.
                                    The summaries in a personal memory are labeled with key words that
                                   represent the contents of the summaries. A message is regarded as the
                                   one that follows the previous message when its keyword matches the
                                   previous one.
                              Fairness: A VE that speaks little goes before one that speaks a lot for the sake
                                   of fairness.

                              4.     Experiment

                                We carried out a basic experiment to ascertain the usability of the EgoChat
                              system and investigate the effects of voice interaction between humans and
                              agents. The experimental system was implemented in Java and Java3D API on
                              a MS-Windows OS. The voices of VEs were not generated by text-to-speech
                              software. Instead, they were recorded human voices. The body of a VE consists
                              of a spherical head and a cone-shaped torso, and the head nods while talking.

                              4.1     Method
                                We created four VEs and generated their personal memories from a humanly
                              summarized log of a mailing list about liquor where participants exchanged
                              ideas about how to market brandy. Each VE represents a mailing-list partici-
                              pant. The subjects were three postgraduate students in our laboratory who have
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