A comprehensive understanding of prior research and theory is essential for generating novel, well-developed research questions. Locating and securing prior work, however, can often feel overwhelming as there are a seemingly infinite number of publications that may be relevant to your line of research. This article aims to reduce such unpleasant feelings by providing some helpful strategies for conducting efficient and thorough literature searches. 

First, it is important to formulate specific research questions to guide your search. Starting a search with very broad, vague goals (e.g., “I want to learn about bullying”) often produces thousands of search results, a substantial portion of which may focus on aspects of a topic that are not meaningful to you. Having specific questions about a topic provides a context for evaluating and integrating publications as you summarize prior work. Additionally, using specific questions will help you identify key search terms and parameters that will ultimately guide your search. For example, the question “What are the academic outcomes of bullied children?” generates the search terms “academic outcomes” and “bullied” and also provides the population parameter “children.” 

Once you generate your basic search terms, try to establish all word variations, synonyms and alternate terminologies that are typically associated with your key search terms. For instance, “academic outcomes” is synonymous with or related to “school performance,” “grades,” “GPA,” “SAT,” “college entrance exams,” “college admission” and “higher education” (among others). For “bullied,” you may produce word variations such as “bully,” “bullies” and “bullying,” and produce alternate terminology such as “victim,” “victims,” “victimized” or “victimization.” The population parameter “children” may be expanded to include terms such as “child,” “childhood” or “youth.” Generating additional search terms widens the span of your search and can produce relevant results that may not have been generated using only your original search terms.

PsycINFO is one of the most frequently used online psychological search services as it not only offers extensive access to articles but also provides search options and parameters that narrow results to those that are most relevant. Though numerous search options are offered in PsycINFO, the options presented below reflect those that are most frequently used and most helpful.

Using Boolean Operators

These include “and,” “or” and “not.” Including these operators between search terms can be especially helpful for reducing or increasing the breadth of search results.

• Including “and” between each search term will only return results that contain all search terms. For example, if you enter “bully and victim,” results will include works containing both “bully” and “victim.” Works containing only “bully” or “victim” will not be included in the search results.
• Including “or” between each search term will return results that contain at least one of the search terms. For example, if you enter “bully or victim,” results will include works that contain either “bully” or “victim”. This set of results will also include all works that contain both “bully” and “victim.”
• Including “not” before a search term will exclude any results containing the term. For example, if you enter “bully not victim,” results will include works that contain “bully” but that do not contain “victim.”

Parentheses and Boolean operators can be used to set apart search groups. If you are generally interested in how social support is related to depression, you may enter the following: “(family or romantic or peer) and (support or relationships) and (depression or depressive or depressed).” Using this method of searching can limit the number of searches needed to achieve your literature search goal.

Limiting and Expanding Search Terms

PsycINFO automatically searches for the plural forms of search terms; however, you can limit your results to exact words/phrases or expand your results to include word variations or synonyms using the following strategies.

• Placing a word or phrase in quotes will only return results that include the exact word or phrase that you entered. For example, if you enter “symptoms of depression” (in quotes) results will only include works that contain this exact phrase. Results will not contain works that simply contain the search terms in any capacity.
• Inserting an asterisk after the root stem of a search term will return results based on variations in the ending of the word. For example, if you enter “bull*” as your search term, results will be provided for the words “bully,” “bullies,” “bullied” and “bullying.” Be careful here as this option could produce results pertaining to unrelated words as well (e.g., bull).
• Selecting the “Apply related words” option in the Advanced Search screen of PsycINFO will produce results that include synonyms and plurals of your search term. Note that this search option is different from the asterisk strategy mentioned above in that variations of the word will not be included, only synonyms and plurals. The synonymous terms produced by this function may not include some of the key terms that you would prefer; as such, this option is mostly useful when you are unsure of what words may be synonymous with your primary search term.  

Search Limiters

You can limit additional search parameters on the advanced search screen of PsycINFO. Some of the more frequently used search limiters include:

• Checking the “peer reviewed” box will limit results to only include works that are published in peer-reviewed journals. This will exclude published works such as book chapters and dissertations, which is helpful if you are searching primarily for original articles for research studies.
• Selecting a specific “age group” can be very useful if you are primarily interested in results pertaining to a particular developmental period. Age groups are offered from early infancy through late adulthood.
• Selecting a preferred “population group” will provide results only for the population you select. Researchers who are primarily interested in either animals or humans can find more applicable publications by selecting their preferred population group.

Date Restrictions

Journals will want to see that you have incorporated recent work into the justification for your study and hypotheses. Limiting your search results to only papers in the past five or 10 years can give you some idea of the most recent research developments in your particular area of interest. Also, if you discover a recent review paper that summarizes a great deal of relevant work, you could search only for papers written after this review paper so that your search results are not redundant with the works cited in the review. 

Key Publications

During a literature search, you may find a publication that is especially relevant to your research questions. Sometimes, you can use such a publication as a springboard for finding both older and more recent publications that are relevant to your research questions. In search results on PsycINFO, many publications include “Cited References” and “Times Cited in this Database” links that can direct you to additional relevant publications. Clicking on the “Cited References” link will take you to a page that includes all of the works cited in the publication (some may be listed but not available in the database). This option can be especially helpful when searching for the origin of theories and seminal findings that provoked a particular line of research. Clicking on the “Times Cited in this Database” link takes you to other works in the database that cited the publication. Reviewing works that cited a publication offers perspective on how, or whether, research has advanced a particular topic since the work was published. 

Key Authors

As you review numerous articles, you will notice that certain authors appear repeatedly in search results. This is no surprise as many researchers conduct a program of research that aims to advance a particular topic or issue. Including key authors’ names in your search criteria can often provide you with a storyline for research in a certain area. For young psychological scientists, these storylines can be enlightening as they sometimes provide excellent examples of focused and directed research that define careers in psychological research.

Most of the strategies listed above are helpful for searching in other search engines as well (e.g., PubMed, Web of Knowledge, Google Scholar). For topics that cut across scientific areas (i.e., not just psychology), it is helpful to search in multiple databases as the PsycINFO database only includes articles with a strong psychological theme. Regardless of the search engine that you use, skim through the “Help” section on its website to see what search strategies are supported. It is easy to overlook this section, but doing so could save you a great deal of time as you conduct your literature search.

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Casey Calhoun is the clinical science representative on the APA Science Student Council. He is a fourth-year graduate student in the clinical psychology program at the University of North Carolina at Chapel Hill.