A few days ago I got into a lively debate about the merits of graphical user interfaces (GUIs) versus command-line user interfaces (CLUIs), specifically in regards to the just-released MacOS X beta, which includes a command-line interface for those who want to use it. My standpoint, of course, was that each is faster/better for different tasks, and for different people, and that a choice is the best option, especially when having both doesn't detract from having either.

One of the points in favor of a CLUI is that you don't have to keep moving your hand from the keyboard to the mouse and back. With this in the back of my mind, I came across a paper presented in HCI 96 on a study performed at the University of Toronto, about using existing full keyboards as half-keyboards for people who only had one hand to type with (by design or circumstance).

The model they used for typing with one hand was a simplified chording system where the hand types characters on its side of the keyboard naturally, but holds the space bar down as a modifyer to type the other keys, mirroring those keys to keys on the hand-s side of the keyboard. The idea is that the brain maps keys to fingers, not positions, and as such, people would quickly adapt to typing, say, the letter 'i' with their left middle finger instead of their right middle finger.

It's a great piece, with good strong data. I don't know if follow-up work was done on this, or if software was released to the public, but it's definitely worth a read nonetheless, especially as there are more and more applications for one-handed typing, and any system that leverages off of what the user already knows will be more readily accepted than a new system, such as chording.

Pictures of an IBM prototype based on this system can be found here.