The use of headers and subheadings informs readers about what to expect from the article and guides the flow of debate. Each portion of the paper is divided and defined by these elements. Based on the amount of subordination, the APA proposes a five-level heading structure. These are independent, associated, subassociated, subsubassociated.
Independent heads are the most important parts of an article and can be identified by capital letters. They deal with different topics or issues. Examples include "How we developed the atomic bomb" and "Reasons for believing in God's existence." Independent heads should be introduced with the word "THEN" or "NOW," to indicate that additional information is to follow.
Associated heads connect two or more subjects together. They are represented by lowercase letters and are often followed by a list. For example, after discussing how we developed the atomic bomb, the writer might want to discuss reasons people believe in God's existence. To do this, he or she would need to explain why others think it is worthwhile to create such theories. APA Style Guide
Subheaded sections are further subdivisions of an article or section. They are indicated by numbers following the header letter. Subheads can be used to highlight parts of the article that may not be clear until later in the text.
In APA Style, there are five levels of heading. Level 1 is the most important or highest level of heading. Level 2 is a subsection of Level 1, and so on through Levels 4 and 5. Level 3 headings are called indents. They are used to identify parts of a chapter, section, or paragraph.
Level 1 headings are found at the beginning of a sentence. Examples: name, date, page number, publication, address, etc. Use these when they will help to identify the paragraph or figure more easily.
Use level 2 headings when you want to divide an article into sections or topics. For example, if you were writing about "America's Cup victories," you could name the sections "History of the America's Cup" and "Recent Events."
Use level 3 headings when you need to identify parts of a larger idea. For example, if you were writing an essay about "the importance of reading fiction," you could name the sub-sections "for education" and "for enjoyment."
Use level 4 headings when you want to identify individual items such as facts, definitions, or quotations.
Use level 5 headings for minor details.
Sections 2.26 and 2.27 of the APA Publication Manual, Seventh Edition cover headings.
Level 1 headings are used to divide an article into different parts. They are also used to introduce major sections of the article. These headings should be Level 1 captions that identify the subject being discussed in the article. They should not include references or citations. Examples of appropriate Level 1 headings include: Introduction, Body, Conclusion.
Level 2 headings are used to group together items that are related or belong together. For example, an author might group articles about a particular topic by year in a series. These headings should be Level 2 captions that identify a subtopic within the main topic of the article. Authors should not use references or citations for Level 2 headings. Examples of appropriate Level 2 headings include: 1986, 1987, 1988, etc.
Level 3 headings are used to refer to parts of chapters or books. They are not used to divide articles. Level 3 headings should be used only to identify specific pages in a book or article. Authors should not use references or citations for Level 3 headings. Examples of appropriate Level 3 headings include: Page 21, Paragraph 3, Line 9.