When the eye does not know what the hand does

The most important flaws in computer systems arise from the HMI (human machine interface), in particular from the combination of pointing devices such as computer mice as input on one hand and computer screens as display on the other : users control with their hands the mouse's movement which is then translated into an equivalent movement of an arrow on the computer's screen. Consequently, the user's eyes focus only on that image instead of the hands. The result is a non neglectable non-collocation (or dislocation) between haptical focus (the motoric focus of the hands) and the optical focus (the visual focus of the eyes, where the intellectual focus lies). There are some inherent negative consequences to this fact.

If one considers the common way of working on some paperwork or artist's work, whether it is drawing, writing, painting or another creative activity, one is usually focused on the oeuvre in front of oneself, with the eyes following the tool in use. In particular, this tool, e.g. a pencil or a pen, is in most cases very close to the fingers, the actuators. It's a very fine-tuned and high precision closed loop for motoric control, a loop of vision and action, where the eyes focus on both the result of the tool's movement, e.g. a line, and on the hands or even fingers themselves. Even a non-active pen will guide the intellectual focus on ordinary paper when proof-reading in a conventional way. Hence, there is a collocation of intellectual, optical and haptical focus which constitutes the traditional working paradigm.

In contrast, computer aided work suffers from a long control loop, from the vision to action, involving the mouse, the computer's processor, software, video board and screen, i.e translations, delays and non-collocation compensation in the human brain. Because it's the brain which tries to compensate unconciously, in order to make collocate haptical and optical, hence intellectual focus. The result is to consider the mouse as prolongated finger or arm. Working in that way must be learned and probably stems from the typewriter paradigm, where a keyboard is used to input text tinto a machinem but the result apears dislocated, on a piece of paper or now on a screen. Since there is more intellectual work involved, it vannot reach the natural performance. It's probably for this reason why most people cannot proof-read text on an ordinary computer screen. Of course if the compensation is fast enough, the length of the control loop would not play a role, but there is another reason: the lack of sensivity.

The mouse is usually controlled by the hand. The muscels to control the hand are located in the arm, and they are not fine-motoric muscels. In contrast, the finger muscels (even though they are also in the lower arm) are used to carry out fine-motoric movements, as they do to control fingers to play a piano, to make fine drawings, etc. A computer mouse driven by arm muscels cannot compete with them. As final consequence, creative work is nearly impossible when using mice. Or give it a try: mount a 20inch lever on your wrist, then mount a pencil on the outer end of it, and try to make a fancy drawing.


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Copyleft, Peter Wurmsdobler.
Created on June 16 2007,
Last modified on July 1 2007.