Re: The semi-magic number 7? Not for lists.

Subject: Re: The semi-magic number 7? Not for lists.
From: David Cramer <dacramer -at- VIDEON -dot- WAVE -dot- CA>
Date: Tue, 11 May 1999 00:45:20 -0500

I've been holding off on jumping in on this thread up till now, but now I
have to yield to temptation.

Regardless of what Miller may or may not have intended to say, the "no more
than 7" rule has taken on a life of its own. I vote to exterminate it now,
please. I've had to put up with enough turkeys preaching this rule in
inappropriate circumstances already. The last time "no more than 7" reared
its ugly head was in end-user computer training manual writing conventions
which mandated that no procedure could consist of more than 5 steps (they
liked to be conservative), because research showed that more steps would
confuse users.

Well, if we're talking about creating mail merge, I guess we're out of
luck. And arbitrarily chopping necessarily longer procedures into smaller
bits tended to create an alternate problem, in that it took a continuous
operation into separate chunks, losing the overall context and continuity.

So my stand was that the context of the number of steps for a procedure was
an inappropriate application of the "no more than 7" rule. Sorry, research
proves it, so there :-(

And I just happen to have an irrefutable research experiment of my own to
blow the "no more than 7" rule out of the water. Anyone can do it in under
15 minutes. All that's required is a paper and pencil and a willing partner.


1) Have your partner read make up a list of 20 words for things (e.g.,
"carpenter", "cloud", "lion", "toaster", etc.) and read them aloud to you
at an interval of about 15 seconds each while you try to memorize them.

2) Write down as many of the things as you can.

If you can remember all 20, then you have already proven the rule of 7
wrong. For a challenge, try listing them in reverse order.


1) Now have your partner make up another list and read it as before. But
this time visualize a distinct location in you home for each thing. (e.g.,
imagine the "carpenter" on the front steps, the "cloud" in the front
hallway, and so on. If you can work out a set of 20 locations that you can
traverse in order, you can demonstrate some even more fascinating memory

2) Write down the list as before. If you have managed to imagine 20
sequential locations, you should find that you can also just as easily
write down the 20 things in reverse order, in order skipping every other
item, and so on.

This is not just a memory trick. I believe it's a fundamental feature of
human thought. The point seems to me to be that we are necessarily spatial
beings. You may notice that you have no difficulty remembering hundreds of
locations every day. If we can't remember more than 7 items in one go, how
come we don't all get lost on the way to the bathroom? Spatial memory. And
if we can bring spatial memory into the equation whenever we have to
remember anything, we enlist the resources of an incredible power that's at
the heart of human memory in each one of us.

Good user interfaces for all sorts of tools, from cars to computer
programs, succeed to a large extent to the degree to which they can harness
spatial memory, and provide reasonable, predictable locations for the
controls that operate them. This is just basic ergonomics.

The problem with the "no more than 7" rule, as others have pointed out, is
that its original context was the memorization of bits without
significance, in the absence of spatial relationships (including
hierarchical relationships).

And the moment you bring significance and spatial relationships into the
equation, basically all bets are off. Rules need no longer apply.



David Cramer, Process Innovation Evangelist 87-1313 Border Street
PBSC Computer Training Centres (an IBM company) Winnipeg MB R3H 0X4
Corporate Office Research & Development Canada

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