2. Participants in the experimental group will be given the visual tracking game application for home use. The game software automatically logs reference and head cursor coordinates (gaze performance) during the visual tracking task and saves the data to a coded and time stamped computer file (anatomized). Participants will be asked to play the tracking task (in standing at the beginning of every training session. This will involve three short tests of 45 seconds at three tracking speeds. The application automatically saves the logged data file, and the clients can either e-mail the files to the investigator, or save on a flash drive provided and return at a follow-up visit.