An evaluation of stylus-based text entry methods on handheld devices studied in different user mobility states

Effective text entry on handheld devices remains an important user input problem. On a personal digital assistant (PDA), text entry methods traditionally support stylus-based input performed by the user's dominant hand. In this paper, we present the design of a two-handed software keyboard for a PDA which specifically takes advantage of the thumb in the non-dominant hand. We compare our chorded keyboard design to other stylus-based text entry methods in an evaluation that studies user input in different user mobility states. Our study shows that users type fastest using the mini-qwerty keyboard, and most accurately using our two-handed keyboard. We also discover a difference in input performance with the mini-qwerty keyboard between stationary and mobile states. As a user walks, text input speed decreases while error rates and mental workload increases; however, these metrics remain relatively stable in our two-handed technique despite user mobility. (C) 2009 Elsevier B.V. All rights reserved.