The dynamic grouping keyboard: a general keyboard optimization approach for users with motor impairment

An important feature of software keyboards is its ability to flexibly adapt the interface. In this paper, we present the Dynamic Grouping Keyboard, as a general approach to optimize text entry for users with motor impairments. Each time after a key is selected, the Dynamic Grouping Keyboard adapts the grouping of keys to optimize the interaction cost, such as the number of keystrokes and the distance of cursor movement, while maintaining the key locations to preserve keyboard layout. We identify the technical challenge, and propose a two-step algorithm for optimization: The first step estimates the amount of information that the current step should provide, while the second step minimizes the interaction cost by applying dynamic programming. Two lab studies with twelve able-bodied users were conducted, in which three keyboard cases for motor impairment were tested. Results showed that compared to an optimal static grouping (ambiguous) keyboard, the Dynamic Grouping Keyboard reduced interaction cost by 23–75%, and improved text entry rate by 16–71% across all tested cases. Subjective user feedback showed consistent preference for the Dynamic Grouping Keyboard due to its faster input speed and less fatigue.