Although it may seem counterintuitive, AND is used to narrow the number of sources you retrieve from a database. You can visualize the search of a large academic database or library catalog using the following diagram:

{ linguistics AND cognitive AND childhood }

In the search depicted above, a student has requested articles that contain the subjects cognitive, linguistics, and childhood. This particular search will only retrieve articles that contain all three terms. This small subset of the larger subject sets is referenced by the arrow. All the information represented by the other portions of the three circles will be excluded. Thus, even if an article contains two of the three search terms, it will be excluded from the results.

Unlike the AND operator, OR seeks to broaden a search, as in this example:

{ Virginia OR Ohio }

In the search depicted above, a student has searched for the subjects Virginia OR Ohio. This search will return every article having the subject of Virginia as well as every article with the subject of Ohio. Unlike the AND search, where only articles containing both terms are returned in the search results, the OR search yields every source on both subjects regardless of whether those subjects appear together in the same source. As a consequence, the OR search will produce far more results.

• Since the OR operator lacks precision, it is most often used in parenthetical searches, described below.

The Boolean operator NOT is used to subtract or screen out topics or keywords that are unwanted within the search results.

{ “alternative energy” NOT solar }

In the search depicted above, a student is researching alternative energy and wants to exclude any information dealing with solar energy. To remove all references to solar energy, the student has searched for “alternative energy,” but has removed any articles from the search results that contain the subject solar using the operator NOT.

The NOT operator is helpful when you find your search results are polluted with unwanted items. This is often a problem when two distinct things share the same name. For example, if you were researching the Norse explorers known as the Vikings, you might discover that your search results include unwanted information about the Minnesota Vikings football team. You can subtract these unwanted results by searching for Vikings NOT Minnesota or Vikings NOT football, for example.

This search uses quotation marks to form an exact phrase search, described below.

You can also use the various Boolean search terms in tandem using parenthetical constructions:

• (Ohio OR Virginia) AND unemployment

• (cognitive AND linguistics) NOT childhood

Such parenthetical searches follow the order of operations, like in math equations. In the first example, the search will first combine all the articles with the keyword of Ohio to all the articles with the keyword Virginia, creating a large collection of search results. Afterward, the keyword unemployment will be applied to that collection using the AND operator, yielding the final search results that look for sources dealing with unemployment in either Virginia and Ohio. Similarly, the second example creates a large collection of results that share the subjects cognitive and linguistics, then all the items having the term childhood are removed from the results using the NOT operator.

Most Internet search engines and library catalogs default to the AND operator when multiple terms are entered, even if it has not been typed by the user. For example, if you search for artificial intelligence, the search algorithm will actually use the search string artificial AND intelligence to produce your results. In some circumstances this may produce undesirable results. For example, we might imagine an article about the “intelligence” of using certain “artificial” sweeteners in food for children. This is not an article that is relevant for your project.

To avoid this problem, you can instruct your search engine to perform what is known as an exact phrase search. This is performed by placing quotation marks around the exact words you are searching for:

• “artificial intelligence” AND apocalypse

By searching for “artificial intelligence” your search results will only contain items that have that exact phrase within the document or title.

• manufact* (truncation)

• wom?n (wild card)

If you search for the terms steel AND manufacturing, your search results may not include results with the terms manufacturer, manufacture, manufactured, or manufactures. As a result, you may not discover articles or books that are important to your research. By truncating the word with an asterisk, however, you will gather all the relevant search results.

Similarly, if you only search for woman, you will potentially miss out on the all the texts that mention women or womyn. Or imagine that you are doing research on a certain type of organization. It would be wise to search for organi?ation, since much of the English-speaking world spells the word with an “s” instead of a “z” as we do here in the US. Without this, your research may become skewed to favor the literature on US-based institutions. However, using the wild card ? you will search all spellings simultaneously, gathering all the relevant results. The question mark wild card should be used to replace a single letter only.

To illustrate, look at these two searches on the JSTOR database:

• Iraq AND manufacturing (19,188 results)

• Iraq AND manufact* (39,444 results) 👀️