We will focus on examples using the OVID interface as it offers more search tools than the ProQuest interface. Please note that PsycINFO, MEDLINE and EMBASE all have rich thesauri. There are significant differences between them.
The OVID-based PsycINFO in the Advanced Search mode starts automatically with your keywords mapped to the closest thesaurus terms. (For the difference between keyword and thesaurus searching see the sidebar):
This is a good beginning, but the simple thesaurus term display generated this way shows all headings that contain the word you are looking for ("memory," in our case) without showing their relationships to each other, and without a preview of the result numbers:
To get a relational view of your term, locate the Search Tools in the main Ovid menu or on the top right of the screen in ProQuest. In OVID, this is where you look:
Select the Permuted Index. This will allow you to find all PsycINFO descriptors for the term you are interested in.
NOTE: In Permuted Index, you can only search for Descriptors matching a single search term. Below is the permuted idex display for the word "memory." Note specific headings like "implicit" or "explicit memory" and "serial recall," a term that does NOT contain the word we started with. Also note the somewhat larger heading of "cognitive processes":
In Ovid, you already know how many results you will get from each descriptor; just click on the box beside the retrieve option. Expolde will retrieve ALL the instances of your descriptor, broader and narrower; clicking right beside the exact thesaurus term will rerieve a narrower set of exact matches.
The ProQuest interface will match your search term to the nearest thesaurus subject heading match. The term "Descriptor" has been dropped. To use descriptors (i.e. thesaurus subject headings) in your ProQuest PsycINFO search, check boxes beside the descriptors you want and combine them using either the OR operator (for a broader, inclusive search) or the AND operator (for a very focused search). The option to Explode thesaurus terms is also included.
You can start with a keyword search, then construct a descriptor search as follows:
1. Do a keyword search on your topic.
2. Look at the descriptors attached to each article in your search results (far right, on the margin beside each record).
3. Find the descriptors that are most relevant to your topic.
4. Copy/paste the relevant descriptors back into your search window; limit to searching by descriptors.
NOTE: There are descriptors attached to each article record.
Keyword Searching: In keyword searching you are taking your best guess that the terms you are using will appear in articles that are about your topic. This can be a very effective way of searching. However, you may get a number of irrelevant results because the keywords you chose may not match those used in the field. You also won't know if you've found all the articles on your topic. Descriptor searching can help to alleviate these problems.
Descriptor Searching: Descriptors are the controlled vocabulary (or tags) used within a database to organize material. Descriptors are added to articles as they are being indexed. In theory, all the articles dealing with a certiain concept will get tagged with the same descriptor even if the terms used by authors actually drifted, or evolved, with time and even if they showed regional (geographic) variation. If you can find the right descriptors for your topic, you can focus your search on relevant articles and be sure that you've found everything on your topic.