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Subject:Keyboard vs. Mouse: What we know from user tests From:"Jared M. Spool/User Interface Engineering (508)975-4343" <SPOOL -at- NEU -dot- EDU> Date:Mon, 6 Nov 1995 00:05:41 -0500
There has been discussion on this list recently about the relative speed
of using a keyboard versus a mouse. The following is some data that we've
observed in our testing of dozens of products.
AFFORDANCES MAKE A DIFFERENCE
An affordance is how a function (such as "Cut" or "Next Field") communicates
how it is to be controlled. Think of it as a clue. Mouse operations, by
nature, have affordances, whereas most keyboard operations do not. Users
have to already know that the Tab key will move to the next field. (To that
end, they have to have a sense of what the next field is.)
Our testing shows that functions which have affordances are faster for users
who are new or infrequent users of the function. (They might be frequent
users of the application, but not have used this particular function before.)
When a designer puts an underline under a field label, that is an affordance
for those people who know what the underline means and is not an affordance
for the rest of the population. This means that knowing whether an affordance
will work for your users means having to know something about what your users
There is a phenomena known as "Kinestetic Memory". It is how touch typists
type and how pianists play piano. Instead of thinking about the specific
muscle movement, the individual thinks of the result and the muscles "remember"
how to do that. It is a learned skill.
While observing people who use Emacs, a very keyboard intensive text editor,
we observed that most of the frequent commands were, in fact, memorized by
the user's fingers. (We would ask user's what commands performed certain
functions and they often would not be able to answer without putting their
fingers on a keyboard or moving them across an imaginary keyboard.)
Kinestetic Memory is by far the fastest way of controlling a device. It
seems to require less thinking on the part of the user, allowing them to
concentrate on the result (such as the data they are entering or the music
they are making).
We've conducted extensive testing of a variety of people using spreadsheets.
We observed experience 1-2-3 For DOS, Excel and Quattro Pro For Windows users
using a variety of spreadsheet products with the intent of learning if one
product was different from another, even though they had the same functionality.
In speed of use, we noticed that one population of individuals stood out amongst
the rest. Those people were experienced 1-2-3 For DOS users while using 1-2-3
for Windows. These users could execute commands, such as changing column widths
or copying a range of numbers, significantly faster than any other individuals
in any of the products.
THE OLD SLASH COMMAND TRICK
The difference was that experienced 1-2-3 For DOS user's fingers have memorized
the commands, such as /WCW10 for change a column width to 10 characters wide.
In the testing, they actually typed these commands so fast that we had to go
and watch the videotape in slow motion to see what they actually typed! They
would complete command oriented tasks 50% faster than other users.
Because all the other populations didn't have these sequence memorized, they had
to use the mouse. (There are no affordances for these sequences.) The act of
moving the mouse to the top left of the column, waiting for the cursor to change
to a double arrow, dragging the cursor to widen the column, seeing the result,
deciding if it was wide enough, and repeating it all over again, took signifi-
cantly longer than the keyboard equivalent.
Should users learn /WCW10 for changing columns or Shift-Control-Insert for Copy?
One has to look at the costs of learning. With affordance-driven activities,
cost is low. You only have to learn what affordances to look for and the
application does the rest. As demonstrated with touch typing classes or piano
lessons, kinestetic memory takes a lot of training and practice to payoff. This
cost is high, but the payback is high.
RETURN ON INVESTMENT
For actions that users are going to do day-in and day-out, it makes sense to
provide the most efficient way for them to use. For actions that users are
going to do infrequently, it might be more efficient to provide affordances
for easy learning.
Understanding how the operations are going to be used and their frequency and
speed requirements is critical to knowing whether to make users invest in
training to develop sufficient kinestetic memory to succeed.
BUT WAIT, THAT'S NOT ALL
If you decide to go the finger memory route, you've only solved part of the
problem. The next step is figure out how to train your users. Touch typing
and piano lessons are deliberate, time intensive activities with no immediate
benefit to the learner. The only benefit comes with time and practice effort.
Training users to use an application is a long topic to itself, but there are
a couple of things that we've observed work best. First, applications that
have a designed learning path that is inherent tend to work best. Second,
frequent observation of users to see if they are learning the keyboard
commands will tell you if the learning path is working.
Finally, people need some way to learn that keyboard commands exist. Making
clues as explicit as possible will encourage users to use them.
As with all of our observations, these are based on users we selected to
test specific applications. We did not choose your users with your appli-
cation. Therefore, the results that we have observed may not be true for
your users using your application. Use this data accordingly.
User Interface Engineering is a consulting firm specializing in product
usability issues. We offer training, consulting and informational services.
Contact me for more information about our upcoming courses and our
newsletter, Eye For Design.
Jared M. Spool
User Interface Engineering
800 Turnpike St, #101
North Andover, MA 01810
fax: (508) 975-5353
Spool -dot- CHI -at- Xerox -dot- Com