# Effects of Voice and Lighting Color on the Social Perception of Home Healthcare Robots
## 4 Discussion
In the present study, the overall acceptance of the adopted robot was lower when it had an adult female voice and warm lighting than when it had an adult male voice. When the healthcare robot's voice and lighting color did not match (e.g., the use of warm lighting and an adult male voice), feelings of discomfort were evoked in the participants. This finding suggests that robots' social cues should be paired with consistency to prevent discomfort in users. Many studies on the uncanny valley effect have reported that the humanlike nature and realism of a robot's appearance are the key to inducing this effect [69; 70; 71]; however, these studies have ignored the potential influence of multimodal interaction on the aforementioned effect [72]. The discomfort evaluation conducted in this study indicates that even when using lighting as visual feedback, users experience discomfort if the lighting does not match the robot's voice. The results of the present study are similar to those of [PERSON] [73], who determined that a mismatch between a robot's face and voice considerably increased a user's feelings of discomfort when interacting with the robot. [PERSON] et al. [74] found that a mismatch between robots' facial texture and voice can cause the perception of uncanniness among children. The influence on HRI of matching robots' social cues is not completely clear and must be investigated in future studies. To a certain extent, this study provides insights on the influence of verbal cue-visual cue matching for robots on overall user acceptance. The participants of this study rated the warmth of the adopted robot highly when it had an adult female voice or a child voice, and they rated the robot's competence highly when it had an adult male voice. When robots have an adult male voice, stereotypes about men are activated. Therefore, robots that have an adult male voice are perceived to have high competence but low warmth. Stereotypes about children, such as innocence and harmlessness, are activated when a robot has a child voice; thus, users perceive a robot with a child voice to have high warmth but low competence. In the discomfort evaluation in this study, use of an adult male or female voice caused considerably more discomfort than did use of a child voice. This result may have been due to the stereotype of a child's voice, which is associated with harmlessness, unlike adult male and female voices. Robots that have a child's voice make people comfortable, which explains the current use of children's voices in many commercial robots. From the social perception perspective, people generally prefer competent and warm people; however, an evaluation of warmth takes precedence over an evaluation of ability. Therefore, robots that evoke warm feelings in people make them feel comfortable [75]. Similar results were obtained by [PERSON] et al. [67], who found that people favor robots with high-pitched adult female voices because they consider these voices to be more attractive than low-pitched adult male voices. [PERSON] et al. [76] reported that users generally perceive robots with an adult male voice to be more capable than robots with an adult female voice or a child voice [77]. This result appears to confirm another golden rule in HRI; that is, robots should conform to users' social stereotypes. Similar results were acquired by [PERSON] et al. [13], who found that robots' social cues can trigger gender stereotypes with respect to occupation [78]. Their results suggest that robots with an extroverted personality and adult female voice are perceived by users to be suitable for healthcare occupations, whereas robots with an introverted personality and adult male voice are considered to be suitable for security-related tasks. This phenomenon may be attributable to the amount of information transferred during HRI. Some social cues--especially social categorization-related information, such as gender--can trigger a social perception during an interaction.