*8.2. Effects on the Elderly with Dementia*

The caregivers who observed the trial remarked, during an interview after the trial, that participants with dementia appeared to have really enjoyed the dialogue. To comprehend their opinion, we grouped the results of the following question posed to the caregivers, "Did the participant talk with the robot more positively, comparing to when he or she talk with staffs?" at the level of dementia (Figure 12). Although two-way ANOVA showed no interaction between groups and scenarios, the graph appears to suggest the trend that participants with severe dementia spoke more

actively than usual, in accordance with the observation caregivers made during the trial and confirmed during the interview after the trial.

**Figure 12.** Averages of the scores of the question to the caregivers, grouped by dementia levels of the participants.

Furthermore, we grouped the participant utterance times precisely as we did for the caregiver impressions (Figure 13). This graph shows that some of the participants were talking for more than 5 min (i.e., Participants 2, 15, 18, 19, and 20). Especially, there were three participants with severe dementia in the two-robot scenario. Although we cannot conclude with certainty based on such small data, this result appears to provide a new hypothesis that some elderly people with severe dementia may actively speak when placed in a two-robot scenario.

**Figure 13.** Utterance time of each participant grouped by dementia levels.

Further research are required to investigate whether using multiple robots is better for elderly people with severe dementia.
