The eyes have it

The text entry system, called Dasher, designed by David MacKay and David Ward in the University's Department of Physics, can be controlled by an eyetracker - a camera that tracks where on the screen the user is looking.

"The software works like a video game in which the user steers ever deeper into an enormous library," explained Dr MacKay. "A language model is used to shape this library in such a way that it's quick and easy to select probable sequences of characters and hard to make spelling mistakes."

The system, which is described in today's Nature (22 August 2002), is much faster than any alternative writing systems driven by an eyetracker. Experiments show that with practice, Dasher can produce up to 25 words per minute. Users writing with other eyetracker-based techniques, using on-screen keyboards, can produce only 15 words per minute.

"Not only is this faster than any alternative writing system driven by an eyetracker, the frequency of spelling mistakes is about five times smaller - and the new system is also less stressful to use," added Dr MacKay.

Dasher is distinctive because it is controlled by continuous pointing gestures, so it uses humans' natural ability to make high-precision analogue movements. A keyboard, where the hands use all-or-nothing movements to produce text, wastes this ability.

Dasher also makes no distinction between word completion and ordinary writing. Other writing systems will suggest completed words in a separate part of the display and the user has to point or stare at them to choose them. Dasher's suggestions are integrated seamlessly into the writing process. The language model adapts to an individual user's writing style, so that sometimes several words can be written with a single glance.

Dasher will be particularly useful for computer users who are unable to type using a conventional keyboard. Because it can be driven using any pointing device - mouse, rollerball, touchpad, or eyetracker - it is also useful for handheld computers or mobile phones where there is no space for a keyboard. It also has potential as an input system for other languages, such as Japanese.

David MacKay and David Ward plan to develop Dasher as an 'Open Source' software project, like Linux.

For further information on Dasher, go to the Dasher website at:
http://www.inference.org.uk/dasher/