The proposed research involves the development of assistive technology that is based upon a force-feedback joystick. The Barron Associates Joystick Appliance (BAJA) is targeted at individuals with neuromuscular problems in their arms and/or hands and will compensate for many deficiencies in the operator's own movement capabilities, including lack of strength, coordination, range of motion limitations, and physiologic noise (e.g., tremors). The BAJA's corrective action can provide tactile and proprioceptive stimuli that many users find to be more satisfying and effective than indirect solutions that are based exclusively on software. Unlike other human-computer interface devices, the BAJA can adapt quickly and robustly to a wide variety of different disabilities, including manifestations of spasticity, dystonia, and rigidity, as well as spinal cord injury and muscular weakness. Adaptability is particularly important because no single solution works well for all types of disabilities. Adapting the BAJA for an individual user, as well as quantifocation of the performance improvement realized with its use, is achieved through a novel method that captures the information processing capacity of the human motor system.