Validation of Fitts' law adapted for upper limb motor impairment on software keyboards

Abstract

The aim of this paper is to make a validation of the Vella's model based on Fitts's law on several virtual keyboard layouts to prove its validity. Firstly, we have obtained this model through an experiment in three populations (able-bodied, suffering myopathy and tetraplegia). The Vella's model takes into account the motor behaviour variability inside of a population. We have observed a more important variation for the motor impairment than for the able-bodied. In second time, we have compared to the keyboard performance with the different models based on Fitts's law. Then we have evaluated the Vella's model on suffering myopathy subject. This one has used two virtual keyboards: Annie and AZERTY. Theoretical results have been compared with experimental results. The Vella's model is more efficient for suffering myopathy participants than for able-bodied participants . These results show that there are still strong needs to adapt the Fitts's law to accurately model the user's behavior.