Evaluating Touch and Crown Interactions on a Linear QWERTY Soft Keyboard on Smartwatches

Typing on a smartwatch presents significant challenges due to several factors, including the small size of these devices, the lack of tactile feedback, and the fat finger problem. This study presents an empirical analysis of two distinct text-entry methods for a one-line QWERTY keyboard: a traditional touch-based interaction and an input technique that leverages the rotary-crown, a feature commonly found on a substantial number of smartwatch devices. Interaction via the rotating crown enables text entry even when touch input is impractical - such as when wearing gloves, in wet conditions, or in cases of reduced precision like the 'fat finger' problem. By rotating the rotary-crown, the user can navigate to and select the desired character, which is then input by pressing the corresponding key to confirm the selection. The method was evaluated in comparison to the touch-interaction: the results demonstrated that participants achieved higher accuracy with the rotary-crown input, with a Total Error Rate of 9%; conversely, participants exhibited faster performance with the touch-interaction, achieving a typing speed of 9.3 words per minute.