A method of testing a subject for impairment includes presenting the subject with a display of a moving object, repeatedly moving over a tracking path and, while presenting the display to the subject, measuring the subject's measuring the subject's gaze positions. A computer system generates tracking error data corresponding to differences in the measured gaze positions and corresponding positions of the moving object, filters the tracking error data to remove data meeting one or more predefined thresholds so as to generate filtered tracking error data, and generates a representation (e.g., a visual representation) of the filtered tracking error data, the representation indicating frequency and amplitude of anticipatory saccades in subject's visual tracking of the moving object.
