Customised text entry devices for motor-impaired users.

The standard QWERTY keyboard is the principal text entry device for word processing and computer-based communications. For many motor-impaired individuals, and in particular those without intelligible speech, the low text entry rates they can typically achieve is a major problem. For some, the QWERTY design is completely inappropriate. Alternative designs that can appreciably increase these rates would greatly enhance their ability to communicate. This paper considers and compares several approaches to the design of text entry devices for motor-impaired users. A general method for customising (i e, optimising) these designs is employed, and consideration is given to designs requiring significantly fewer input switches than the 26 or more keys required by QWERTY. Use is made of language statistics in the design procedure, and the increased availability of inexpensive, powerful computers is directly exploited.