[Usability of Input Devices and Aids in the Field of Augmentative and Alternative Communication - An Experimental Study with People with and without Disabilities].

This study explored the usability of 15 different assistive input devices for persons with severe motor disabilities. Fifteen people without disabilities were asked to speak a predefined testsentence and then to write it using 15 different input aids. Ten persons with severe motor and communication disabilities wrote the same sentence using their own communication aid. The usability was evaluated in 3 dimensions: efficiency (speed as information transfer rate in bit per second), effectiveness (proportion of correct input over all input including errors and error correction), and user's satisfaction with an adapted version of the Quest II questionnaire. Participants without disabilities needed 40 to 140 times more time to write the sentence using the aid compared to speech, participants with disability between 13 to 500 times. The effectiveness was between 80 and 100 % for the participants without disabilities and between 73 and 100 % for the participants with disabilities. Satisfaction was between 3.4 and 5.0 (max.) for the participants without disability and between 2.8 and 5.0 for the participants with disabilities. Overall the input by standard devices such as keyboard and mouse had better usability than the more complex devices like eye gazing technology. Comparable types of control ( head control, eye control) also had similar usability. The usability dimensions of efficiency, effectiveness and satisfaction with input aids as examined in this study could be evaluated in the process of recommending communication and writing aids. The focus should however not only be on the input aids as such, but also include all optimization options such as word prediction and auto text.