USER INTERFACE DESIGN UPDATE - September, 2000

Insights from Human Factors International, Inc. (HFI)
Providing consulting and training in software ergonomics.
(http://www.humanfactors.com/home/)

Every month HFI reviews the most useful developments in
UI research from major conferences and publications.
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In this issue Dr. Bob Bailey reviews:

How to improve design decisions by reducing reliance on superstition.
Let’s start with Miller’s “Magic 7”
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Probably the most well-known article in the fields of usability, user
interface design and user experience is Miller’s 1956 paper entitled
“The magical number seven, plus or minus two.” It is incredible
how this article has lasted for over 40 years, and still seems to
influence many design decisions. More recent, better research is
available, but not being used.

I recently re-read the 16-page article, and have concluded that
there is absolutely nothing in his paper that can still help us develop
better systems. I am not attacking George Miller. Miller was an
excellent researcher and added much to our knowledge in the field.
I am addressing the unfortunate, continued success of this one paper.

At least partially because of the success of Miller’s paper, the
number “seven” is now almost universally and erroneously accepted
as the human capacity limit for a wide range of issues. I have had
people tell that the “Magic 7” paper is the reason why the local
telephone number has seven numbers. This is not true. I have had
others tell me that the “Magic 7” paper is the reason they:

   - place only seven items on the menu bar,
   - place only seven items in a pull-down menu,
   - have only seven bulleted items in a list,
   - never have more than seven radio buttons or check boxes together, and
   - place only seven tabs at the top of a website page.

These are all silly decisions, and I suspect that Miller’s “Magic 7”
paper continues to cause many other poor design decisions to be made.
For example, a designer thinking that it is okay for people to remember
a few items shown on one Web page while waiting for another page to
load; after all (the designer reasons), “the research shows that people
easily can remember seven items for a little while.” More recent
research indicates that people can remember closer to 3 or 4 items
for a short period of time.

When Miller published his paper in 1956, most scientists believed
that there was only one human memory system. The idea of a
separate “short-term memory” system was not generally known or
accepted, and there was no understanding of short-term memory’s
characteristics, uses or limitations. This gradually changed in the next
couple of years with the work of Brown (1958) in England and
Peterson and Peterson (1959) in the United States.

In the early 1970s, investigators began broadening their view of
short-term memory to a more useful one that became known as
“working memory.” The current concept of working memory
describes a memory system that does more than just temporarily
store small amounts of information. For example, having a greater
working memory capacity is positively related to increased reading
comprehension, drawing inferences from text, learning technical
information and reasoning skill (Baddeley, 1992).

Even though the field has systematically moved from Miller’s
“immediate memory,” to “short-term memory,” and currently to
“working memory,” many practitioners are still back in the 1950s.
Even Miller’s original “seven” has been shown to be untrue.
For example, Broadbent (1975) suggested that the working
memory capacity was actually 4-6 items, MacGregor (1987)
reported that it was only four items, and LeCompte (1999)
argued that it was actually about three items.

The next time you read or hear someone refer to Miller’s “Magic 7”
paper as the justification for their argument, quietly say to yourself,
“Oh-oh, the amateurs are at it again.”
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References:

Baddeley, A. (1992), Working memory, Science, 255, 556-559.

Broadbent, D.E. (1975), The magic number seven after fifteen years.
In A. Kennedy and A. Wilkes (eds.), Studies in Long-Term Memory,
New York: Wiley, 3-18.

Brown, J. (1958), Some tests of the decay theory of immediate memory,
Quarterly Journal of Experimental Psychology, 10, 12-21.

LeCompte, D. (1999), Seven, plus or minus two, is too much to bear:
Three (or fewer) is the real magic number, Proceedings of the Human
Factors and Ergonomics Society, 289-292.

MacGregor, J.N. (1987), Short-term memory capacity: Limitation or
optimization? Psychological Review, 94(1), 107-108.

Miller, G.A. (1956), The magical number seven, plus or minus two:
Some limits on our capacity for processing information, The
Psychological Review, 81-97.

Peterson, L.R. and Peterson, M.J. (1959), Short-term retention of
individual items, Journal of Experimental Psychology, 58, 193-198.
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3-day 1999 Annual User Interface Update Seminar presented by
Dr. Robert Bailey.
http://www.humanfactors.com/training/annualupdate.asp.
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REGISTER for UI Update Seminar:

San Francisco, CA - October 11-13, 2000
https://www.humanfactors.com/training/registration/AUregister8.asp
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Suggestions, comments, questions?
HFI editors at mailto:hfi@humanfactors.com.

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