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PICO: Combining Keywords

Describes the PICO interface and how to use it effectively.

Tutorials

View brief video tutorials via YouTube (closed captioned):

Exact Phrase

Most search automatically look for all the keywords you enter. But they don't have to be in any particular order, or next to each other.

But what if you really need to find a phrase--multiple words that mean something specific when you put them together?

Generally, put your keywords inside quotation marks to search for them as an exact phrase: those words, in that order, next to each other.

Examples of phrase searching:

"obsessive compulsive disorder"

"academic achievement"

"animal rights"

"business planning"

Boolean Logic

How do keyword searches work? There are three basic operations, involving Boolean logic. Boolean operators to tell the computer whether you want to:

  • find all the words (AND)
  • find any of the words (OR)
  • exclude a word (NOT)

Today, most databases automatically search for all the keywords you typed (AND), because it's the most common and useful way to narrow a search.

But you may still encounter some advanced search forms that require you to use Boolean operators. Advanced search forms usually will display a choice of operators, so that you can see them at work.

Practiced searchers can also construct their own Boolean search statements. Remember that they are mathematical statements, not normal sentences, and have special syntax rules. If you combine AND and OR in a search, you must put parentheses around the OR terms.

Example:

(smoking or cigarettes or tobacco) and (teens or adolescents) and legislation

Truncation

What if you need to find multiple forms of the same word? For example:

teen
teens
teenaged
teenager
teenagers

To do this use truncation, also known as stemming or wildcarding.

Truncation uses a symbol, usually an asterisk (*), to substitute for all the letters that might follow a word stem.

Example:

teen*

finds all the word forms above.

Putting it Together

You can combine Boolean operators, phrase searches, and trucation, but you must very precise with the syntax and punctuation!

Here's an example:

(drink* or alcohol) and (teen* or adolescents) and "academic achievement"

Boolean Logic: Examples

Here’s a visual example of how Boolean logic works:

Venn diagram: X and Y

The small shaded area is the result; results must have both terms.

Example: zoos and animal welfare

Venn diagram: X or Y

The shaded area now covers everything, because results can have either term.

Example: men or males

Venn diagram: X not Y

The shaded area is smaller again; only results that have X, but don't have Y.

Example: Titanic not movie