## 4 Experiments
### Procedure  
First, the dialog aspect of the experiment was explained to the participants. The participants were instructed to interact with the dialog system according to the dialog state. An example of the dialog conditions between the user and dialog system is displayed in Table 2. During this experiment, the user and dialog system were of the same age, had similar interests, and had met for the first time. However, participants in the experiment were told that the dialog partner was not a human but a dialog system. This instruction was based on the guidelines for the Situation Track of the Dialog System Live Competition [42; 43]. Both this study and the aforementioned competition aimed to develop a dialog system capable of engaging in natural, human-like dialog. Some evaluation methods, such as the Turing test, do not explicitly state who the dialog partner is. However, in this study, aiming to create a society where humans and dialog systems interact symbiotically, we consider evaluating dialog systems as a service crucial. To this end, we specifically considered contexts where the human user is aware that the dialog system is not human. Then, we asked the participants to register as users of Telegram [44], which is a social networking service. The participants interacted with the dialog system using Telegram. Finally, the participants evaluated their impressions of the dialog system, at which point the experiment ended. During the experiment, the dialog states were set with reference to the Dialog System Live Competition 2 [42; 43]. The questionnaire consisted of 10 items that were designed to investigate the human-like nature of the dialog system, the recognition of changes in the speech level of the dialog system by the participants, their evaluation of the breakdown of the dialog, and their overall impression of the dialog. The participants responded to each item on a 7-point Likert scale (1 = strongly disagree, 4 = neither agree nor disagree, and 7 = strongly agree). The content of each question is presented below:  
* Q1: The dialog system behavior was like a human being. * Q2: The dialog system behaved in such a way that it maintained an appropriate social distance from me. * Q3: The utterances of the dialog system considered the social relationship with me. * Q4: There was a change in the wording of the dialog system (e.g., formal or informal style). * Q5: I felt that the utterances of the dialog system were a mixture of formal and informal styles. * Q6: I decided on my own wording with the wording of the dialog system in mind. * Q7: The dialog with the dialog system was not broken down. * Q8: The sentence endings of the dialog system were appropriate for the aforementioned situations (e.g., age and relationship between the user and system). * Q9: The dialog with the dialog system was enjoyable. * Q10: The dialog system was approachable. Among these 10 items, Q1 to Q3 aimed to investigate the human-like nature of the dialog system, Q4 to Q6 were established to investigate whether or not the participants in the experiment were cognizant of the speech level of the dialog system, Q7 and Q8 aimed to investigate their evaluation of the dialog breakdown, and Q9 and Q10 were designed to evaluate their overall impression of the dialog. While Q2 and Q3 do not directly assess human likeness, a key aspect of human likeness considered in this study is the ability to dynamically adapt one's attitude in response to one's relationship with the dialog partner. Therefore, Q2 and Q3 were included as evaluation indicators of human likeness. We createdthe questionnaire items for Q2, Q3, Q4, Q5, and Q6 because no existing literature providing similar scales was available. For the other questionnaire items, we prepared each item with reference to existing evaluation scales for interactive robots and dialog systems [45; 46; 47] in order to comprehensively evaluate the dialog system.