The fundamental distinction between primary and secondary sources involves the difference between original data and later analysis. In various academic majors, this takes on distinct forms. For example, in fields such as , biology or psychology the original data often take the form of experiments. The primary sources in these fields are the sources in which that data is reported and analyzed by the researcher -Usually, these take the form of peer-reviewed journal articles.
In the humanities and history, the original data sources are typically the cultural artifacts produced at the time of the person, place, event, or other historical happening being studied. Journal articles are typically secondary sources, a very important place for interpretation of the data.