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Keyboard vs. The Mouse, pt 3

From SunWorld Magazine, September, 1992

Dear Tog: I've been flipping through Tog on Interface at semi-random and stumbled across the section in which you state categorically that mousing is faster than keyboarding. I know this to be false in some important cases from my own experience—specifically, for cursor positioning when editing variable-pitch text smaller than about 12-point, especially sans-serif. I implemented the Emacs local cursor positioning control combinations for Smalltalk, and I challenge you or anyone else with a stopwatch to demonstrate that they are slower than the mouse for an experienced user, especially with a cursor that obscures half of what you're trying to select and for a user over 40 whose fine motor control is slower.

Peter Deutsch
Sunsoft Corporation

My stopwatch is armed and ready...

The test I did I did several years ago, frankly, I entered into for the express purpose of letting cursor keys win, just to prove they could in some cases be faster than the mouse. Using Microsoft Word on a Macintosh, I typed in a paragraph of text, then replaced every instance of an "e" with a vertical bar (|). The test subject's task was to replace every | with an "e." Just to make it even harder, the test subjects, when using the mouse, were forbidden to just drop the cursor to the right of the | and then use the delete key to get rid of it. Instead, they had to actually drag the mouse pointer across the one-pixel width of the character t o select it, then press the "e" key to replace it.

The average time for the cursor keys was 99.43 seconds, for the mouse, 50.22 seconds. I also asked the test subjects which method was faster, and to a person they reported that the cursor keys were much, much faster. This was a classic example of the difference between subjective time (the passage of time the user experiences) and objective time (the passage of time the clock experiences). Put simply, the more mentally engaging the task, the shorter the time appears.

One can argue that the only thing important is that a task seem shorter—after all, if we don’t experience the longer time, why worry about it. To an extent, I am sympathetic with this view, one of the reasons I was such a loud clamorer for adding cursor keys to the original, cursor-key-less Macintosh.

Consider, though, the primary goal of making people more productive. How can someone spending twice as long at a given task be more productive? They can’t, particularly when one considers the reason the subjective time seems so short: the intensity of the user’s total mental engagement in performing the manipulation. Under such circumstances, the user must set aside the original task of writing or editing a document in favor of figuring out what key to press and how many times to press it. While the mouse users are dragging and pressing away, they are figuring out what kind of edits they will be performing next. The cursor-key user is stuck in the here-and-now.

On the other hand, Peter, I have seen some mouse implementations that were slow enough that cursor keys might very well outperform them. I’m particularly suspicious of a "cursor that obscures half of what you're trying to select." I also assume you implemented a cursor scheme that would enable you to travel by word-at-a-time and sentence-at-a-time. Such schemes will increase the speed of cursor travel, although the decision-making necessary to select the most effective key combination can increase the mental burden—and time—even more.

Cursor key navigation is vital to a large population of people with impaired motor skills. I have never seen it outperform the mouse, however, under circumstances where users have good motor skills and the mouse interface is peppy, responsive, and cleanly implemented.

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