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Many applications require the user to frequently switch between KeyboardMode and MouseMode. The more frequent this is required, the quicker the application approaches design failure. Switching from keyboard to mouse mode requires five steps:

  1. Lift hand from keyboard.
  2. Grope for mouse.
  3. Grab mouse.
  4. Wiggle mouse to locate cursor.
  5. Use mouse to perform an action.

Average time to switch modes ranges in seconds, which is enough of a discontinuity to be noticed.

On the other hand, drawing with a mouse requires fine precision movement. Unfortunately, a mouse is not designed to be used with fine precision. Consider that a human hand has three modes of operation: precision, power, and paw. Precision primarily uses the index finger and thumb; power uses the forearm; and paw just, well, paws at things. Using a screwdriver as an example, precision movement is used to operate a jeweler's screwdriver, to carefully pry gears from a watch casing. Power is used to drive a screw into the wall. Pawing is used to grab the screwdriver off the workbench.

Unfortunately, the mouse operates in paw mode. Even worse is that it doesn't use the most dextrous nor powerful parts of the hand-arm to operate (fingers, forearm respectively), but instead relies on the relatively weak lateral motions of the wrist and rotations of the elbow and shoulder.

That being said, most people take several months to learn how to use the mouse precisely (and this is what the game Minesweeper is meant to teach). Even then, with the constant switching of modes, precise use of the mouse is unlikely. Therefore, the user interface should be forgiving with respect to precision. For example, if a user wants to select a line in a paint tool, she should still grab the line even if she "missed" by a few pixels. The "snap to" feature in many graphics apps does this.

Another consider with the mouse is repetitive stress injury. A right-handed individual (80-90% of the population) can easily rotate their wrist only down and to the left. A left-handed individual can only rotate their wrist down and to the right. If a particular action, say dragging objects to "the trash", must be repeated often, it should be activated from a HotZone down and to the left. (It may be preferable to flip orientation for left-handed users.)

This is also why horizontally-oriented toolbars, ala Windows, are less usable than vertically-oriented toolbars on the left, ala early Macintosh programs. A right-handed individual can easily rotate his wrist to the left, in a precise way (by using his fingers to dextrously position the cursor), to select an object. It's harder to select something vertically, with only the thumb and wrist to guide the mouse.

That being said, the five "magic" pixels that can be accessed quickly without fail are (in decreasing order of ease):

  1. The pixel currently underneath the cursor. You just can't miss this one.
    1. actually, no. Look at a beginner using the mouse. They nearly always inadvertently nudge the mouse when trying to click, and completely miss.
  2. The bottom right corner.
  3. The top left corner.
  4. The top right corner.
  5. The bottom left corner.

Compare UsingTheStylus, PieMenu.


To avoid DominantHandBias, Microsoft has come to name the left mouse button the action button, and the right button the context button. Macintosh still calls their only mouse button, "the mouse." Of course, Macintosh users go through QuasiMode? acrobatics to use the mouse.

I hate to disagree, but those are typically the farthest pixels (or at least 3 of them are) from my pointer. And since I use a trackball, getting to them can be very slow (as many as 4 separate movements after I've positioned my hand on the trackball). On The Other Hand, anything within 5-600 pixels is quick and easy. Put an important UI element in a corner, and I will curse you for all eternity.

By FittsLaw, the corners are the easiest to reach for the mouse as they are infinite in extent in two dimensions. In other words, you just winge the mouse in those directions and it is almost impossible to miss them. On the other hand, if you winge a trackball, the cursor will actually crawl away from the corner near the end of its rotation due to frictional effects as the curve of its rotation changes. This makes the corners inappropriate for trackball usage, just as they are inappropriate for tablet or stylus usage. However, the vast majority of users have mice, not trackballs, so it becomes a trade off between universal ease of use (by researching, designing, and implementing multiple user interface systems) and cost effectiveness.

Actually, the problem comes with a large screen, and a trackball w/high resolution - you move the ball relatively large amounts to traverse the screen. I can hit the ball, have it spin and stop 4 times while crossing a 1600x1200 desktop diagonally. No problem once I hit the corner (mine stays in the corner, don't know where you've seen the crawl problem).

My point is merely that assuming all users use the same input devices is bad. Using techniques which are only beneficial to a single input device is bad. Taking things to extremes frequently causes more trouble than it's worth when your base assumptions turn out to be false (how about the X-Ray machine that lighted up the "on" and "off" buttons - so that "off" was lighted while it was turned on. German designers, U.S. users. Thank god for the safety interlocks on the door... and the best part was that doing it the other way would have caused problems in Germany.)

The solution is to replace all mice with trackballs. It was not obvious that the mouse was a poor choice because (obviously) before we had pointer-driven UIs, we had little experience with pointers. Ancient CAD systems had "pucks", which may (or may not) have encouraged Xerox and Apple to choose mice. But pucks were built with crosshaired windows, providing a rough-and-ready method of digitizing paper drawings; they were also often used with menu pads. (Still a bad idea, but then there were some reasons.) The original Mac mouse was cursed by graphic designers as "trying to draw with a pencil tied to a brick." And we all know how silly it was to dumb it down to one button.

Kensington (plug) has made a fine, ambidextrous, 4-button trackball for many years. A mouse is pretty much just an upside-down trackball; it was a stupid choice for a pointer, that's all. If manufacturers shipped this product instead of a 3-button mouse, volume would drive the cost down to current mouse costs.


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