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Basic Research Concepts (Sciences)

Primary vs. Secondary Sources


Why does this matter?

Many college research assignments require you to use mostly primary sources. For that reason, let’s look at the purpose of primary and secondary scientific sources and how to tell the difference between them.


Primary Sources / Original Research

In the sciences, a primary source is also called “original research” or an “original research article.” This means that the author of the article is reporting the findings of original research, an original experiment, or an original study that she performed herself. An “original research article” is the first time that these findings have been shared.

In the sciences, most original research articles have the following outline:

  1. Introduction
  2. Methods
  3. Results
  4. Discussion
  5. Conclusion
  6. References

Sometimes the Methods section is towards the end of the article instead of towards the beginning, but the Methods section is a required piece of an original research article. If an author is sharing the findings of an original experiment or study, she needs to tell us exactly how she designed and performed her study.


Secondary Sources / Review Articles

In the sciences, a secondary source is usually called a review article, systematic review, or a meta-analysis. It is called a “secondary source” because the author(s) did not perform any original experimentation or studies--they only read other people’s studies.

The purpose of a review article is to review all of the research articles that have been published on a particular topic. After reviewing all of the research that has been done on this topic, the author(s) of a review article will summarize all of this research to inform the audience of things like:

  • How many studies had similar findings
  • How many studies had different findings
  • Which questions need to be answered by further research

Review articles identify where we’ve been and where we need to go in researching a particular topic.


How to Tell the Difference

The best way to tell the difference between an original research article (primary) and a review article (secondary) is to look at the Methods section.

  • Original research articles must have a Methods section. This section describes the study design, including who/what was the subject of the study, what was done to the subjects and how, how long the study lasted, and how the study data was analyzed afterwards.
  • Review articles aren’t required to have a Methods section, because no original experiment or study was performed. If you find an article that is peer-reviewed (has a References list) but it doesn’t have a Methods section, it’s probably a review article. IF a review article has a Methods section, it only describes how the authors searched for the articles they used in the review: which databases were searched, which search words were used, and other criteria for including or excluding an article from the review.
Example 1: Original Research Article (Primary)

Article: Association of Caffeine Intake and Caffeinated Coffee Consumption with Risk of Incident Rosacea in Women

Take a look at the Methods section. The authors describe in detail how they designed their study, including what was being measured, the groups being measured, and how they evaluated their statistical data.

This article also follows the usual outline of an original research article: Introduction, Methods, Results, Discussion, Conclusion, References.

Example 2: Review Article (Secondary)

Article: Estrogenic Activity of Coffee Constituents

This article has a list of references at the end, so it's definitely peer-reviewed. But look at the outline of the article. Do you see a Methods section? When you find a peer-reviewed article without a Methods section, it's a secondary source, not a primary source.

Notice that the rest of the article also does not follow the usual outline of an original research article.

Test Yourself!