Research Repository

# What Can I Say?: Effects of Discoverability in VUIs on Task Performance and User Experience

## Authors

Philipp Kirschthaler

Martin Porcheron

JOEL FISCHER Joel.Fischer@nottingham.ac.uk
Professor of Human-Computer Interaction

### Abstract

Discoverability, the ability for users to find and execute features through a user interface, is a recurrent problem with Voice User Interface (VUI) design that makes it difficult for users to understand what commands are supported by a newly encountered system. We studied the effects of two different discoverability strategies proposed in literature, one which provides informational prompts \textit{automatically} and one which provides help only when the user \textit{requests} it by asking What Can I Say?'. Our study adopted a Wizard of Oz approach that allowed users to order food delivery by voice. Through statistical analysis, we confirmed the beneficial nature of both discoverability strategies, with significantly better task performance and higher self-reported usability scores in comparison to a baseline. This suggests designers should consider the use of a discoverability strategy in the design of VUIs. While no significant differences were found between the strategies, a majority of the participants highlighted their preference for the What Can I Say?' strategy if they were to use the VUI more frequently. Finally, we reflect on the implications for the design of VUIs, highlighting the need to distinguish between initial use and longer-term use in the selection of a discoverability strategy.

### Citation

Kirschthaler, P., Porcheron, M., & Fischer, J. E. (2020). What Can I Say?: Effects of Discoverability in VUIs on Task Performance and User Experience. In CUI '20: Proceedings of the 2nd Conference on Conversational User Interfaces. https://doi.org/10.1145/3405755.3406119

Conference Name CUI '20: 2nd Conference on Conversational User Interfaces Jul 22, 2020 Jul 24, 2020 Jun 10, 2020 Jul 13, 2020 Jul 22, 2020 Jun 12, 2020 Jul 13, 2020 Association for Computing Machinery (ACM) CUI '20: Proceedings of the 2nd Conference on Conversational User Interfaces 9781450375443 https://doi.org/10.1145/3405755.3406119 Voice interfaces, Conversational interfaces, Dialogue design, Discoverability, Learnability, Wizard of oz, Usability, User study https://nottingham-repository.worktribe.com/output/4632840 https://dl.acm.org/doi/10.1145/3405755.3406119 https://cui2020.com/ Article no. 9.

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