Primary, secondary, and tertiary sources

Introduction

Your professor has instructed you to get primary or secondary materials for your research project.  So what's the difference, and how do you find them? 

Three basic types of resources

Sources of information are considered primary, secondary, or tertiary depending on their originality (did the writer do the original work, or are they commenting on the work of others?) and their proximity or how close they are to the source (is this a first-hand account, or somewhat after the fact?)

Here is a very general overview of how information is produced.  Note that these distinctions are not rigid; the same resource can overlap categories.

• Primary - Direct, uninterpreted records of the subject of your research project. Thus, a primary source can be almost anything, depending on the subject and purpose of your research.  Examples of primary sources.
   
• Secondary - Books, articles, and other writings by scholars and researchers build on primary sources by interpreting, analyzing, and assessing primary information.  Secondary materials often have a persuasive, analytical aim not characteristic of primary material.  Examples of secondary sources.
   
•  Tertiary - Encyclopedias, indexes, textbooks, and other reference sources which present summaries of or introductions to the current state of research on a topic, summarize or condense information from primary and secondary sources, or provide a list of primary and secondary sources of more extensive information.  Examples of tertiary sources. 

How do you tell the difference?

It's not always easy to distinguish primary and secondary sources.  The distinction between primary, secondary, and tertiary sources can differ between subjects and disciplines, particularly between the sciences and the humanities.  (If a source does not fit the description of a primary source, it is most likely a secondary source.) 

• In the sciences, research findings may be communicated informally through email, then presented at meetings before being formally published as a primary source.  Once published, they will be commented on by other scholars (secondary sources) and professionally indexed in a database or printed index (tertiary sources.)  
• In the humanities, primary sources for the cultural history of the 1950s might include the paintings, novels, and films of the period.
• A newspaper article is a primary source if it is reporting the news or the views of the day, but may be a secondary source to the extent that it includes analysis and research based on other sources.

Research tip:  Work backwards.

• Start with tertiary sources (reference sources, databases, etc.)
  Find background information on your topic by consulting reference sources and web pages for introductions and summaries, and to find bibliographies or citations for secondary and primary sources.
• Then go to secondary sources
  Find articles, books, web pages, and other sources providing more extensive and in-depth analysis of a topic.  Check to see what other scholars and experts have to say about your topic.
• Then try primary sources
  Once you have some background knowledge on your topic, you will be better able to understand, interpret, and analyze the primary source information.  See if you can find primary source evidence to support or refute what other scholars and experts have said about your topic, or try an interpretation of your own and look for more primary sources to confirm or refute your thesis.  When you present your conclusions, you will have produced another secondary source to assist others in their research.

Adapted, with permission, from materials from Wesleyan University Library.