Eye-gaze word processing

Erica is a personal computer operated by eye-gaze. By looking at menu options displayed at different locations on the computer monitor, a disabled user can invoke commands without the need for standard input devices. The design of test entry software for Erica´s gaze word processor is described. A basic encoding is accomplished through a static tree-structured menu system, which associates the 85 most common ASCII characters with unique sequences of menus and eye-gaze picks. The expected length of the pick sequences is minimized based on the approximate frequencies of individual characters determined from a 55882 character corpus of English language text. Text entry speeds are further enhanced by adding context-sensitive nodes to the static tree. The menu screens corresponding to these nodes contain the five characters most likely to follow the last two characters entered, based on character transition probabilities derived from the sample corpus