"I Can Feel Your Empathic Voice": Effects of Nonverbal Vocal Cues in Voice User Interface

Active use of voice assistant highlights the importance of interpersonal relationships with the conversational voice agent. When the agent evaluates a user's task performance, empathic feedback is needed to prevent the user's negative feelings. Voice reflects emotions through its nonverbal voice features that can either strengthen or lessen the feeling of empathy. Our study investigated the effect of nonverbal vocal cues in speech interaction on the user's perception toward the agent. 39 university students participated in the experiment, and MANOVA was tested to analyze their responses regarding intimacy, similarity, connectedness, enjoyment, and ease of use. The study result showed that using nonverbal vocal cues on empathic feedback contributes to establishing an interpersonal relationship with the agent, which gives implications to the fields of human-centered agent design.