Vulture: a mid-air word-gesture keyboard

Word-gesture keyboards enable fast text entry by letting users draw the shape of a word on the input surface. Such keyboards have been used extensively for touch devices, but not in mid-air, even though their fluent gestural input seems well suited for this modality. We present Vulture, a word-gesture keyboard for mid-air operation. Vulture adapts touch based word-gesture algorithms to work in mid-air, projects users ’ movement onto the display, and uses pinch as a word delimiter. A first 10-session study suggests text-entry rates of 20.6 Words Per Minute (WPM) and finds hand-movement speed to be the primary predictor of WPM. A second study shows that with training on a few phrases, participants do 28.1 WPM, 59 % of the text-entry rate of direct touch input. Participants ’ recall of trained gestures in mid-air was low, suggesting that visual feedback is important but also limits performance. Based on data from the studies, we discuss improvements to Vulture and some alternative designs for mid-air text entry. Author Keywords Word-gesture keyboard; shape writing; text entry; mid-air interaction; in-air interaction; freehand interaction. ACM Classification Keywords I.3.6 Methodology and Techniques: Interaction technique