This paper evaluates the performance of users with cerebral palsy (CP) using an inertial human-computer interface (HCI) based on head movements and a novel facilitation algorithm for users with mild to severe motor disorders that we named MouseField. Seventeen users from 3 centers specialized in CP participated in a series of tests that analyzed 10 measures of rapidity and accuracy in reaching tasks using an inertial interface with and without the MouseField algorithm. Cluster analysis was used to classify the users in three categories, C1-C3 ordered by rapidity. MouseField
improved rapidity in C2 and C3 and accuracy in C3. Although a loss of accuracy was detected for the least impaired (C1, MACS IV-V), MouseField proved to improve task performance of users with severe motor disorders (MACS V), with decrements of 33.3% and 65.5% in the movement times. Our experiments show that MouseField can be used to complement the inertial interface, ENLAZA, in order to facilitate navigation and minimize targeting errors, respectively, for users with severe motor impairments that are not able to use traditional mice or joysticks.