8 March 2005. One of the secrets of long-time online searchers is a technique that is sometimes called "pearl culturing." This is how it works: My client asked me to find recent discussions of the possible correlation between early childhood vaccinations and the subsequent diagnosis of autism. One of the sources I used was PsychINFO, a database that includes summaries of articles -- but not the full text -- along with keywords and standardized subject terms, called descriptors.
 

You start with a small set of relevant records, and then add to your search with additional subject terms as you go.

I did not know what the descriptors were for autism and vaccinations; nor did I have a copy of the PsychINFO thesaurus handy. Instead, I looked for truncated versions of the words "autism" and "vaccination," and limited my search to articles in which those words appeared in the title. This was a narrow search, but my assumption was that all the retrieved articles would be right on point. And, sure enough, they were.

Then I looked at the descriptors assigned to those records and saw that they used "Autism" and "Immunization." A subsequent search for recent articles with those two descriptors turned up exactly what my client wanted.

This technique is called pearl culturing because you start with a small set of relevant records (e.g., the ones with my search terms in the title), and then add to your search with additional subject terms as you go.

Pearl culturing works well in the world of value-added online services such as Dialog. But how can you use this technique in Web searching, when no one has applied descriptors to Web pages? As a matter of fact, they have, in a sense. Any human-built Web directory, such as the Open Directory Project, Librarians' Index to the Internet, or Zeal, consists of Web sites that have subject categories assigned to them by human editors.

So, how would you conduct pearl culturing on the Web? Continuing my search for discussions of autism and childhood vaccinations, I noted that one of the most vocal groups on this subject is the Cure Autism Now Foundation. So I went to Zeal and searched for the phrase "cure autism now". Sure enough, I found not only the Cure Autism Now Foundation, but the search results pointed me to an entire category devoted to autism research organizations. It would have taken me a while to have drilled down through the Zeal categories to find these listings. I would have had to select Personal > Health > Conditions & Illnesses > Mental Conditions > Autism > Assocs & Support > Guides & Directories. Whew!

Of course, one of the limitations of this technique is that you are only retrieving sites that a human has identified, evaluated and included in the directory you are searching. But for many research projects, that is exactly what you want. You are not looking for every site on a topic, just the best ones. And that is when pearl culturing can be a powerful tool.

© 2004, 2005 Mary Ellen Bates all rights reserved.

Mary Ellen Bates is the principal of Bates Information Services, a research and consulting business based in Boulder, CO.