Anyone know any usability or cognitive psychology research done on the optimum number of choices for menus/navigation?
I need some evidence to argue a case against a top level category menu of hundreds of options
While hundreds is likely a bit much, the answer tends to be 'as much as you need and not more'.
There's the old myth of 5-7, though that's not applicable at all to menus:
The best I've read on the subject is this report "the scent of information"
The basic premise is that users don't care how many times they have to click to get to the information they are looking for as long as they feel they are progressing to that point. So that's one argument for a deeper, but narrower navigation system, rather than a really shallow really wide system of 100 links on one page.
Historically the (mythical) argument has always been 7 +/- 2 because that's the sort of number of 'things' you can remember in short term memory. Unfortunately, many people then have taken this 'rule' verbatim, and restrict their menus to having 5-9 items in, and then created often deeply nested menus or navigation structures to compensate, which just makes the problem worse because content becomes hidden and you can't discover the items so easily.
So, now actually realizing the myth, and moving in the opposite direction particularly in website context, the movement has been actually to take a different approach and have lots of items in menus - mega drop down menus - which work well when neatly organized.
Some reading on mega drop downs: Econsultancy: http://econsultancy.com/uk/blog/3543-huge-drop-down-menus-good-for-usability-nielsen
Don't get me wrong - the 5-7-9 principle is still valid, but when the data does not fit sensibly around the rule, other approaches must be considered.
[Edit] made it clearer that I'm not at all suggesting menus are actully restricted to 7 +/- 2 items - the opposite in fact!
Agreed, the number of links in a menu depends on context. For example, the "scent of information" is greatly aided with good descriptive captions above menus lists of links. The better this caption is, the more links the menu can comfortably have, cognitively. That being said, less is better.
Captions like "Quick Links" are simply deadly, they practically mean "don't bother to read this list because it is an unorganized jumble".
Here is the summary of the research on this topic:
Go as broad as practical as early as possible in the menu structure where 'practical' means you have the space to:
Kent Norman is the researcher most often associated with research on menus.
This is from his 2008 summary of menu research.
"Small screens and slow transmission led designers of early systems to opt for menus with no more than eight alternatives at each level. Consequently, designers found it necessary to reduce the breadth of the tree and increase its depth.... However, other research in human factors suggested that human processing was not the limiting factor. People are quite able to read or scan long lists of items. Norman (1991) reviewed the assumptions concerning the rate of processing alternatives and the response time to make a decision and concluded that for lists of linearly organized arrays such as numbers, alphabetized lists, letters of the alphabet, and months of the year, one should increase breadth to the maximum practical level."
He also discusses organization and naming of items.
In 2002, a Wichita State student published research on breadth vs depth in hypertext structures which is related to this question. The broadest structure was 12x27. Compared to some of the deeper structures, participants using this structure found the target with fewer errors and in less time. While the 'deep' strucuture in that study is not comparable to a flat structure with hundreds of items, the paper is worth reading because it compares convex and concave structures too. If you convince your team to reduce the number of top level items, you'll need a proposal on organizing them. This research may help.