Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!uflorida!ukma!rutgers!bellcore!faline!thumper!rdh
From: rdh@thumper.bellcore.com (Ralph Hill)
Newsgroups: comp.cog-eng
Subject: Re: consistency
Summary: Reaction to Grudin's Anti-Consistency talk.
Keywords: consistency, desktop metaphor, interfaces, computing environments
Message-ID: <1465@thumper.bellcore.com>
Date: 8 Feb 89 04:53:06 GMT
References: <714@cogsci.ucsd.EDU>
Organization: Bell Communications Research
Lines: 74

In article <714@cogsci.ucsd.EDU>, norman@cogsci.ucsd.EDU (Donald A Norman-UCSD Cog Sci Dept) writes:
> In an earlier article I cited some research of Jonathan Grudin that
> demonstrated that the common interface design rule of "be consistent"
> was sometimes best violated.
> ...
> The paper was presented at a recent workshop on
> HCI at which it received a controversial hearing.
> ...
> don norman

I was in the audience at this "controverial hearing."  I, and many of the
audience, are sympathetic to what Jonathan is saying, but there are
some tricky issues here...

I think the problem is not with "consistency", but the simple guideline
"be consistent."

Quoting Jonathon's summary:
> For example, in abbreviating a set of two dozen command names, which
> is the best algorithm: truncation, vowel deletion, or single-letter-at-
> all-costs (even if it doesn't match the first letter of the command)?
> As explained in the paper, any of these could be the best design solution,
> it depends on aspects of the users' tasks.

Notice that each is a different form of consistency.  The question is not
"to be consistent or not to be consistent?" it is "which consistency is best?"

Continuing the quote:

>    More importantly, consistency
> is often not desirable at all. A recent proposal for an international
> standard suggested placing the arithmetic function keys on numeric keypads
> across the top row in the order +, -, x, / because "that is consistent
> with the way we learn and remember these functions." True, but the most 
> frequently used keys are generally the zero, ENTER, and plus keys,
> and this placement would maximize the distance from the plus key to the
> other two, thus maximizing the keying time and the likelihood of errors.
> A better solution is the more standard arrangement, with the plus key
> above the ENTER key, but this has nothing to do with "consistency," it
> is based on knowledge of the hand, motor control, and the data entry task.


And here we get into an agrument about consistency:  I claim Jonathon's
"better solution" is better because it is consistent with common
usage of the keys.

Again the question is "which consistency is best?":
consistency with learning order (the proposed standard) or
usage (the "better solution")?

In this case (an over-learned task) usage is believed to be a better 
consistency.  In other cases, say, recently learnt tasks,
learning order may be better.

I think Jonathon is giving half the argument: he is against bad
consistency.  So am I.  He left out (or minimized) the argument
for good consistency.

And then, there is the really hard part:  What is good consistency?  How do
you recognize it?  Where do you look for it?

I think Jonathon has made a good start in the right direction.  Unfortunately
(for all of us), we have a long way to go.

My opinion:
Consistency is not bad, it is simple application of simple rules like
"be consistent" that is bad.  If good interfaces good be designed by
simply following simple rules, why are there so few good interfaces?

Ralph D. Hill
Bellcore
rdh@thumper.bellcore.com

Don't blame other members of the audience for things I have said.