Designers Characterize Naturalness in Voice User Interfaces: Their Goals, Practices, and Challenges

This work investigates the practices and challenges of voice user interface (VUI) designers. Existing VUI design guidelines recommend that designers strive for natural human-agent conversation. However, the literature leaves a critical gap regarding how designers pursue naturalness in VUIs and what their struggles are in doing so. Bridging this gap is necessary for identifying designers’ needs and supporting them. Our interviews with 20 VUI designers identified 12 ways that designers characterize and approach naturalness in VUIs. We categorized these characteristics into three groupings based on the types of conversational context that each characteristic contributes to: Social, Transactional, and Core. Our results contribute new findings on designers’ challenges, such as a design dilemma in augmenting task-oriented VUIs with social conversations, difficulties in writing for spoken language, lack of proper tool support for imbuing synthesized voice with expressivity, and implications for developing design tools and guidelines.