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PSYC 497 Resource Guide

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

  • differential diagnosis OR depression
    (OR widens the search to retrieve everything about either "differential diagnosis" or "depression," whether or not there is a correlation between the variables)

  • differential diagnosis NOT depression
    (NOT excludes the variable "depression" to retrieve data about "differential diagnosis" but not where the variable "depression" occurs)


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.