Usability: Understanding Cross References, Part I

Cross references — those little notes that tell a reader to look elsewhere in the index for information — are a much-loved tool for many indexers (Hans Wellisch gives them 10 pages in Indexing from A to Z). They’re quiet instructions, helping readers get acquainted with the author’s word choices. They neatly connect bits and pieces of the index, highlighting threads that run through the text. But they are also surprisingly misunderstood, or not understood at all.

There aren’t many index usability studies available, but one finding that several studies have in common is that users find cross references — particularly See also references — confusing. Even when, as Liddy and Jorgenson in their oft-cited 1993 Syracuse study* found, users get faster and better results when an index contains cross references.

So what’s going on? According to Wellisch, cross references should only be used when needed to lead a user from words that are “not used, incomplete, or different in form or content” to a  term that is more appropriate or relevant. Users seem to understand the straightforward instructions to See a different term, and be tripped up by See also, though that doesn’t mean See is always correctly used or even necessary.

My hunch is users can handle See references easily simply because they aren’t presented with any other options:

canines. See dogs

There are no page numbers (locators), and nowhere else to go. Common mistakes when using See include presenting locators and the dreaded circular cross reference, where the user, on turning to dogs is faced with this conundrum:

dogs. See canines

See references serve mainly two purposes: to tell the reader which term is used by the author, and to save space. In the first instance, terminology changes over time, people’s (and companies’) names change, there are pseudonyms, there are acronyms. See references can lead from generic to specific, or the other way around. In a book about many different animals, specific dog breeds might not be mentioned, and readers need to know that.

golden retrievers. See dogs

But in a book with significant portions about dogs, in order to put all the information under dogs would mean using sub-subheadings, which is space intensive and not ideal. So we see:

dogs. See hounds; retrievers; terriers. (Or, to muddy the waters, the general cross reference: dogs. See specific types.)

It’s also not uncommon — especially in multi-authored works — for the same concept to be expressed by many different words. Teenagers, adolescents and young adults are terms that can be used interchangeably, and while variety makes for a better read, it’s best in an index to keep all references to the concept of humans between the ages of 13 and 19 in one spot. How frustrating would it be to have three different entries in the index to only the pages on which the specific term was used? As in:

adolescents, 2–7, 14, 33, 99

teenagers, 15, 82, 98, 100–101

young adults, 3, 17–19, 56, 78–83

Better put ’em all in one spot, then tell the reader which one you chose. (Usually, indexers choose the one the author uses the most.) And while we’re at it, note that by combining all three of these collections of page numbers under, say, adolescents, we’ll end up with too many locators and need subheadings. That brings me to the other common reason for using a See reference: to save space.

Now we have this entry:

adolescents

brain development, 2–7, 98–101
education, 14–15, 17–19, 78–83
sleeping habits, 33, 56

If there’s loads of room in the index, it’s possible to duplicate (double-post) those subheadings under both teenagers and young adults. Readers find what they need wherever they look. That’s not always possible, so, enter the See reference.

teenagers. See adolescents

What if there were only 3 locators in total? An error I see often with beginner indexes is the unnecessary See reference. The index is supposed to be an information-retrieval tool. That is, it exists for the sole purpose of helping readers get what they need to know. It needs to be precise, accurate, and eliminate unnecessary page turning. If the user wants to spend all day flipping pages, she’d just read the book and dispense with the index altogether. An unnecessary See reference points the reader from one synonym to another, only to discover a handful of locators.

For something as ostensibly straightforward as a See cross reference, there’s a lot going on under the surface. In a future post (or two), I’ll take a look at See also cross references.

I owe much to Kate Mertes’s excellent usability studies literature review in the Fall 2016 issue of ASI’s Key Words journal, and her excellent presentations on index usability.

*“Reality check! Book index characteristics that facilitate information access.” Elizabeth D. Liddy and Corinne L. Jörgensen, Proceedings of the American Society of Indexers 25th Annual Meeting, 1993, pp. 125–38. Port Aransas, TX: American Society of Indexers.