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Cognitive load and the rule of seven (or how many is too many)

Nick Finck

September 3, 2004 at 12:14 PM

Ok, so I have done some deep researching about "how many is too many" (as far as links and information bits on a page) and I thought I would share some of this with the Digital Web Magazine readership. Most of my research pointed to this paper, The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information by George A. Miller, published in 1956 mind you.

To summarize, "The span of absolute judgment and the span of immediate memory impose severe limitations on the amount of information that we are able to receive, process, and remember." Therefore the number of links or bits of information should be kept below seven.

However, my esteemed colleague, Christina Wodtke, was quick to point out that there is much proof on the contrary to this theory: Web Page Design: Implications of Memory, Structure and Scent for Information Retrieval and The Myth of quot;Seven, Plus or Minus 2", etc. Upon her advice I spoke with Victor Lombardi, known expert in the field of Information Architecture, User Experience and Research. He summarized his findings in this area for me quite nicely:

  1. Breadth vs. depth is the wrong question to ask, it's irrelevant to the user experience
  2. The number of links and density of links is what people experience
  3. Different audiences and applications will want different a different number and density of links
  4. Once you find the number and density (guess + usability testing) you just prioritize information:
    1. some things will fall naturally into taxonomies
    2. some will fall naturally into task-based navigation
    3. the rest is probably all about priority, so as you reach your number and density limit, push lower priority stuff to the next level down

Keith also has some pretty good information on this subject in his article The One Magic Rule of Web Design.

Comments

Tony

September 4, 2004 at 10:33 AM

So I guess "It Depends". It's quite amazing how often you can fall back upon that answer.

Nick Finck

September 4, 2004 at 1:54 PM

Yes, I know. The interesting part was that I was really trying to find a definiative answer here, but I guess that idea is out. It all depends on your site: the users, the amount of information, the design, the relavance, the structure.

Michael Almond

September 5, 2004 at 9:28 AM

My understanding was that the "magic number 7" referred mainly to our telephone system (seven digits and then an area code...so actually 10). I was under the impression that this range, around 7-10 items, was an "ideal" to shoot for when designing a Web site's top navigation level or global navigation, however you refer to the first set of items a user encounters. Again, I was informed that this is only a guideline and not a rule. It does seem to play out whenever I am working with clients on the assessment phase of a project. They seem to always point out examples of sites within this "magical" range and say "Oh, I want a site like that!" I might add that they tend to say the exact same thing when we look at sites that use fluid design with no limit to line length (Alert box, for example) and then look sites with a "semi-fluid" layout; that is, sites with fixed centered content that are fluid within the browser area (A List Apart, for example). They always prefer the former want "one just like that" as well. Makes my job just a little easier when I listen to my clients.

Henrik Olsen

September 5, 2004 at 1:34 PM

Hi Nick Here

Nick Finck

September 7, 2004 at 12:59 PM

Henrik, both links seem to point to the same location. I this the post you intended to link to?

orecipe

March 10, 2005 at 9:32 AM

what is the formula for the rule of seven?

Nick Finck

March 10, 2005 at 10:17 AM

It is "Seven, Plus or Minus Two". See the link in the post for the details.

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