*6.3. Scenarios*

To achieve the purpose, it was desirable to design an experiment that could clarify two basic research questions: Whether or not the system has the question–answer–response dialogue model, and whether a single robot or two robots engage in a dialogue. However, without the question–answer–response dialogue model, it was obvious that the elderly could not continue a dialogue with the system. The reasons are as follows: the chatbot model commonly used in non-task-oriented chat systems generates responses based on the results of speech recognition. When speech recognition fails, the chatbot model generates a response that does not match the context of the dialogue. Since speech recognition frequently fails during a dialogue with elderly people, the system with the chatbot model would give unrelated responses in the dialogue in most cases. Therefore, we designed scenarios depending on whether only a single robot or two robots participate in a dialogue, which are as follows:


The field trial was a between-participant design. The participants were assigned to each scenario in such a way as to balance the dementia level of participants in of each scenario as shown in Table 2.


**Table 2.** Distribution of participants' cognitive capacities.

#### *6.4. Procedure*

The procedure was as follows: A caregiver escorted a participant to a place of trial (Figure 5). The caregiver had the participant sit down on a chair in front of the robot. If the participant was using a wheelchair, the caregiver put the participant with the wheelchair in front of the robot. After escorting, the caregiver moved to a position behind the participant. Thus, the caregiver was invisible to the participant during the trial. Then, a controller greeted the participant and explained the task. The instruction was as follows: "This robot starts to talk to you in a little while. Please talk with it." After the instruction, the controller started the system and the robot started a dialogue. As the participants were native Japanese speakers, the field trial was conducted in the Japanese language. The procedure that a caregiver takes an elderly person to the robot, encourages him or her to talk with the robot, and watches him or her from behind would be reasonable at least in the phase of introducing the robot system.

The dialogue continued following the flowchart of Figure 6. The robot said the introduction first. Next, the robot started a dialogue. In every 5 min during the dialogue, the robot asked the participant whether to continue the dialogue or not. When the participant gave a positive answer, the robot continued the dialogue. Otherwise, a negative answer ended the dialogue.

Here, we should note an inappropriate case caused by speech recognition errors. If the robot recognized that the participant answered positively even though the participant actually answered negatively, the robot would have continued the dialogue. Because such a situation must be avoided, an experimenter force-quit a program for a dialogue as soon as possible.

Considering the burdens of a participant, we limited the dialogue time to 15 min even if the participant would like to continue. The dialogue was recorded by video cameras.

The caregiver had observed the dialogue and filled out in a questionnaire about the participant behavior. When the dialogues ended or were force-quit, the caregiver took the participant to a place away from the robot. Then, an interviewer asked the participant a simple question. After that, the caregiver took the participant back to his or her room, and then escorted the next participant to the place of trial.

**Figure 5.** Twin-Robot dialogue system that talks with an elderly person.

**Figure 6.** Flowchart of a dialogue in the trial.
