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PSYC 497 Resource Guide: Search Strategies

Practice Boolean Logic!

Research and Reference Help From a Librarian

Combining search terms and variables using Boolean operators

Once you have identified the keywords and major concepts from your research statement that you want to find, you can build a database query using  Boolean logic, which uses the combining operators AND, OR, NOT between search terms to sort them for the most effective results.

For example, consider the following search statements using the same variables with AND, OR, NOT:

  • differential diagnosis AND psychodiagnosis
    (AND narrows and focuses the search to retrieve only the data relating to both "differential diagnosis" and "psychodiagnosis")

  • differential diagnosis OR psychodiagnosis
    (OR widens the search to retrieve everything about either "differential diagnosis" or "psychodiagnosis," whether or not there is any correlation between the terms)

  • differential diagnosis NOT psychodiagnosis
    (NOT excludes the variable "positivity bias" to only retrieve data about "self-serving bias" but not where the variable "positivity bias" occurs)


Advanced Boolean searching: You can use AND, OR, NOT in combination. As a rule of thumb, when you want to search two related terms together in a longer Boolean search statement, connect the  with OR and group them in a set of parentheses.

Additionally you can put multi-word terms in quotation marks to make doubly sure the words are searched together as a phrase - but this is optional:

("differential diagnosis" OR psychodiagnosis) AND "major depression" AND adults NOT children


This video from the University of Auckland Libraries in Australia explains Boolean operators very well, and shows how they work in library catalogs, databases, and even Advanced Google.