Researchers and students often fail to master the specifics of APA style when writing psychology papers. In this article, we review common errors in writing and format that we regularly observe in student papers and provide several examples of how to conform to APA style. In addition, we discuss the rationale behind some of the stylistic guidelines to demonstrate to students that there is a reason for each aspect of APA style and to facilitate a more complete understanding of formatting rules. This article serves as a guide for instructors' grading adherence to APA style and for students and researchers writing in APA style.

Students regularly experience difficulty writing papers in psychology classes. A primary source of difficulty is a lack of mastery of American Psychological Association (APA) style. We intend this article as a guide both for instructors grading student adherence to APA style and for students and researchers writing in APA style.
     This article presents several common deviations from APA style. We compiled this list based on several years of teaching courses with extensive APA style writing requirements. This article is not a checklist for correct format or an exhaustive listing of all possible APA formatting errors; rather, it compiles what we view as the most commonly misunderstood elements of APA style and the most commonly committed stylistic errors.

Benefits and Use of APA Style
     APA style is central to student socialization into the discipline of psychology and is the standard formatting style used in many disciplines outside psychology (Madigan, Johnson, & Linton, 1995). For professionals, deviation from APA style results in a reduced likelihood of acceptance of papers (Smaby, Crews, & Downing, 1999), although there is considerable variability in the importance of correct format across journals (Brewer, Scherzer, Van Raalte, Petitpas, & Anderson, 2001). For students, deviations from APA style tend to lead to lower grades on papers.
     For the most part, undergraduate research methods courses in psychology introduce students to the elements of APA style (Smith & Eggleston, 2001). Coverage of APA style comprises over 10% of the material in psychology research methods textbooks (Jackson, Lugo, & Griggs, 2001). Despite the centrality of APA style to psychological writing, many students struggle with aspects of the format. For those faculty teaching the basics of APA style, there are many guides (e.g., Gelfand & Walker, 2001), techniques (e.g., Ault, 1991; Ware, Badura, & Davis, 2002), and checklists (e.g., Dunn et al., 2001) available. This article does not provide guidance in the basics of the format as these other sources do. Rather, we focus on common mistakes, with the goal of eliminating these errors and moving stylistic adherence from good to excellent. Before discussing errors, we define several terms that appear in the APA manual. In our experience, many students are unfamiliar with some of the terminology that the manual uses, resulting in misunderstandings that promote stylistic deviation.

Body
     The body of the paper refers to text starting at the introduction and running to the end of the discussion section.

Character
     A character is a single typed space. For example, the heading titled Basic Definitions includes 17 characters: the 16 letters plus the space between them. APA style limits the number of characters used in manuscripts, both to promote conciseness and to save journal space. Most word processors can count characters. Correct use of APA style eliminates extra spaces or lines between sentences or paragraphs.

Header
     A header (or page header) is a short title that consists of the first two or three words of the title and appears in the upper right hand corner of every page. By placing a short title and page number on each page, the pages can be easily put together in order if they become separated.

Heading
     Headings denote the beginning of a section or subsection of the paper; each of the terms in italics on this page denotes a heading (or subheading) as does the centered item titled Basic Definitions. 

Pagination
     Pagination refers to page numbering, usually either by issue or volume.

Running Head
     The running head is a short title that appears on the first page of the document. When published, the running head would reflect the title printed at the top of the pages of the article.

Titling the Introduction
     The introduction begins on the third page of the paper. Often students title the introduction section as Introduction. This section should have the same title as the paper itself, centered at the top of the page, followed immediately by the main body of the text.

Titling the Method Section
     Often students title the method section Methods. The correct title is Method and should be centered.

People are Participants Not Subjects
     In most cases, use the term participants rather than subjects to refer to individuals who take part in research, because the term participant acknowledges the consent to participate in the study (APA, 2001). Use the term subjects only when referring to nonhuman animals and statistics (e.g., within-subjects ANOVA).

Effect Sizes
     "For the reader to fully understand the importance of your findings, it is almost always necessary to include some index of effect size or strength of relationship in your Results section" (APA, 2001, p. 25). Despite a call from the APA to include effect size measures alongside significance test results and some progress in the field in this regard, there remain examples that do not include measures of effect. For example, the APA Publication Manual's sample paper and a prominent style guide (Szuchman, 2005) do not incorporate this information. These omissions suggest a failure to systematically follow through on effect size recommendations (Fidler, 2002). More practically, the lack of clear examples confuses students who may look to examples first for guidance. We present an example but encourage the reader to consult other resources on effect sizes (e.g., Kirk, 1996).

Incorrect presentation: Type of processor was found to be significant, F(1, 28) = 5.70, p = .02.

Correct presentation: Type of processor was found to be significant, F(1, 28) = 5.70, p = .02 η²= .20.

Decimal Places
     Students often present results using too many decimal places. Statistical packages often report results to several decimal places but all of these decimals may not be meaningful. For example, imagine you measured the self-esteem of 100 participants on a scale with scores ranging from 0 to 100. Your calculations yielded M = 70.5245 for scores on the self-esteem scale. Many students present this value as it was computed - to four decimals. Does stating M = 70.5245 transmit more meaningful information than reporting M = 70.5? In most cases, use of one or two decimal places is sufficient to provide needed information without sacrificing meaning. In most cases, statistical values reflecting correlations, inferential statistics (e.g., t, F, and χ²), and probabilities should be rounded two decimal places.

Probability Values
     The primary error we have observed regarding probabilities involves presentation of very small p values as p = .000. Several statistical packages report probability values to three decimal places. For a very small p value, statistical packages may round to p = .000. Reporting p = .000 suggests that drawing the observed sample from a population reflecting the null hypothesis is not just unlikely, but impossible. Instead, report these values as p < .01.

     Common formatting problems include beginning the method, results, and discussion sections on new pages; adding blank spaces between sections; or italicizing, bolding, or underlining the names of major section headings (e.g., Method, Results). Each of these sections should immediately follow the preceding section. For example, place the heading Results on the line immediately after the method section ends (of course, everything is still double spaced). Do not start a new page for each new section or add extra blank lines between sections.

Titles
     Figures and tables require descriptive titles that indicate their content in detail, often including the independent and dependent variables. For example, a title of "Means, Standard Deviations, and Correlations" does not indicate the variables in the table. A better title would be "Means, Standard Deviations, and Correlations for Attitudes Toward Driving Drunk as a Function of Gender."

Italics, Placement, and Special Rules for Figure Pages
     For tables, the title of the table appears in italics and one line below the term Table X, in which X refers to the table number; Table X is not italicized. Table titles use capitals for each major word, but figure titles have only the first word and proper nouns capitalized. Tables appear on a new page after the reference section of the paper with each table on its own page. For figure captions, the term Figure X appears in italics along with the title, which is not italicized and immediately follows Figure X. The rule for figures is the opposite of the format for tables. When using figures, the title for each figure goes on a page titled "Figure Captions" with the figures following on the next pages, one figure per page. This section begins on a new page after all tables. The page header and numbering appears on all tables and the captions page. The header and page numbers should, however, not appear on pages containing Figures. To identify the figure, on the back of the page, print by hand the word "Top" to indicate orientation, and the header and page number. Write the figure number in pencil on both the front and back of the figure.

Correct presentation of table title:

Table 1

Means, Standard Deviations, and Correlations for Attitudes Toward Driving Drunk as a Function of Gender

Correct presentation of figure caption:

Figure 1. Plot of attitudes toward driving drunk as a function of age.

     References often contain more errors than any other section. Before discussing specific issues, we note that students often mimic the printed format of references found in academic journals. APA style is for manuscripts; journals and books may or may not follow that format and may deviate from APA style prescriptions. Journals can use their own styles; authors of manuscripts should not deviate unless told otherwise by their editor or instructor. Thus, following APA style is important to avoid duplicating formats that are inconsistent with APA style.

Use of et al. With Multiple Author Papers
     APA style requires use of et al. to designate authorship for studies with three or more authors. There are two basic rules. First, for in-text citations to sources with three to five authors, cite all authors the first time you cite the source (e.g., Schultz, Shriver, Tabanico, & Khazian, 2004), but cite only the lead author's name followed by et al. for subsequent citations (e.g., Schultz et al., 2004). When a source has six or more authors, the correct format is to use the lead author's name followed by et al. for all in-text citations. For example, the correct citation for an article by Grusky, Marelich, Erger, Mann, Roberts, Steers, and Damesyn (2003) is Grusky et al. (2003) for all in-text citations. This rule applies only to in-text citations; list the first six authors and use et al. to represent the seventh and subsequent authors in the References section.

Direct Quotes
     We recommend limiting the use of direct quotes because using too many quotes tends to indicate a lack of synthesis of the quoted materials. To aid interested readers in finding the source of quotations, a page number must accompany each quotation.
     Example: "The interaction between group valence and legality begs for future investigation, especially as it relates to immigration attitudes" (Short & Magaña, 2002, p. 709).

Spacing, Commas, and Capitalization in the References Section
     The references section is very particular in regard to spacing, punctuation, and capitalization. A general rule to remember is that a single blank space must follow every period or comma (this rule applies to the main body of text as well). Regarding capitalization, capitalize the first word in an article or book title but not the remaining words unless they are proper nouns or follow a colon or dash. Capitalize the first letter of each word in a periodical title, except "small" words (e.g., for, and, of). Regarding author names, a comma appears after each name (and after each author's initials) cited except for the final author's initials, which are followed by a period.

Issue Numbers in References
     A common format error involves inclusion or exclusion of issue numbers. Include the issue number only if each issue of the journal begins with page 1 (i.e., is paginated by issue). Do not include the issue number if the journal is paginated by volume. If needed, the issue number appears in parentheses (but not in italics) after the volume number (which is in italics). In general, the issue number is not necessary, because it provides superfluous information. Pagination by issue is rare in psychology, but it is the writer's responsibility to determine whether this is in fact the case for a particular source.

Improper Format for References
     Students often cut and paste citations from databases such as PsychInfo or PsychArticles directly into the References section. These citations tend to deviate from APA style and should be retyped in proper APA style.

Reference Examples
     We provide two sample references. Note that for the first reference, there is a comma after the first author's initial. The comma is necessary even when there are only two authors. Nothing in the title of either article is capitalized except for the first word in the title, the first word after a colon, and proper nouns. All words in the journal titles (except the small word "of") are capitalized. The journal title and volume number are in italics. The references do not provide issue numbers, because both journals are paginated by volume. In the second reference, there is a single space after each period, including those between initials (e.g., W. D.).

Short, R., & Magaña, L. (2002). Political rhetoric, immigration attitudes, and contemporary prejudice: A Mexican American dilemma. Journal of Social Psychology, 142, 701-712.

Grusky, O., Marelich, W. D., Erger, J., Mann, T., Roberts, K. J., Steers, W. N., et.al. (2003). Evaluation of a brief low-cost intervention to improve antiretroviral treatment decisions. AIDS Care, 15, 681-687.

Grammar
     There are numerous grammatical and editorial suggestions included in the current APA publication manual. Please see Chapters 2 and 3 of the APA publication manual (APA, 2001) for a full explication of these rules. We suggest Bem (2004) for an excellent discussion of writing style and common grammar errors.

Capitalization
     There are several rules regarding what to capitalize and what not to capitalize. Most commonly, students incorrectly capitalize the names of theories and use capital letters to add emphasis. Generally speaking, capitalize only the first word in a sentence, headings, the first word after a colon, and proper nouns.

Spaces
     In APA style, there should be a single space following commas, periods, semicolons, and colons. There is no place in the text of a paper where more than one space should appear between characters.

Bold, Underlining, and Italics
     Student should never use bold or underlining font styles. Italics have designated uses in APA style, primarily for section subheadings, statistics (e.g., F, t, p), titles of books or periodicals, and volume numbers; avoid using italics for emphasis in the text.

Numbers Expressed as Words or as Figures
     There are a surprising number of rules regarding whether to write out a number or use a figure (numeral) to express a value. The most common error is using figures instead of words to represent values under 10 (e.g., 4 conditions rather than four conditions). In most cases, use words to represent values under 10 and numbers to represent values of 10 and above. An exception occurs when a sentence begins with a number; always spell a number if it is the first word in a sentence. Another exception is that all numbers in the abstract are presented as figures. Try to avoid beginning sentences with numbers. Another exception occurs when presenting two or more values that represent precise measurements, only one of which is less than 10. In such cases, use all numbers (e.g., 4 dogs and 12 horses). Of course, always present statistical results as numbers and never as words.

Abbreviations
     APA style limits use of abbreviations to specific scientific terms in common use and for terms used throughout a manuscript; for terms used only sparingly, or that are not in common use, it is probably best not to use an abbreviation. For example, a paper about affirmative action may use AA in places to save space. When using abbreviations, present the abbreviation in parentheses immediately after its first presentation, and thereafter always use the abbreviation, not the full term. Never use "vs." to replace "versus" or "&" to replace "and" (except in direct quotes and in the References section), and avoid use of the term "etc."

Correct abbreviation example: Rapid eye movement (REM) sleep is known to...

Incorrect abbreviation example: REM (rapid eye movement) sleep is known to...

Passive and Active Voice
     Passive voice refers to divorcing the verb (the action) from the subject (the actor). We view reducing passive voice as the best way to improve the clarity of writing, and APA style advocates active over passive voice whenever possible. Most word processors' grammar and spelling checkers check for passive voice.

Passive sentence example: Participants were provided with a pencil and a notebook.

Active sentence example: We gave participants a pencil and a notebook.

     Note that the active sentence makes clear who is carrying out the action, whereas the passive sentence does not.

Tense
     Because research papers represent completed research studies, the past tense is correct for most of a research paper. Exceptions include suggestions for future research or papers that serve as research proposals rather than final reports.

     In this article, we presented several common student errors. We believe that attention to these errors will improve student adherence to APA style. However, we caution students, instructors, and other writers and readers that this list of errors is not a substitute for use of primary materials such as the APA publication manual (APA, 2001). Rather, the most effective use of this article is in conjunction with that reference manual, and we hope that the combined use of these resources leads to clearer and more effective writing.

American Psychological Association. (2001). Publication manual of the American Psychological Association (5th ed.). Washington, DC: Author.

Ault, R. L. (1991). What goes where? An activity to teach the organization of journal articles. Teaching of Psychology, 18, 45-46.

Bem, D. J. (2004). Writing the empirical journal article. In J. M. Darley, M. P. Zanna, & H. L. Roediger III (Eds.), The compleat academic: A career guide (2nd ed., pp. 185-219). Washington, DC: American Psychological Association.

Brewer, B. W., Scherzer, C. B., Van Raalte, J. L., Petitpas, A. J., & Anderson, M. B. (2001). The elements of (APA) style: A survey of psychology journal editors. American Psychologist, 56, 266-267.

Dunn, J., Ford, K., Rewey, K. L., Juve, J. A., Weiser, A., & Davis, S. F. (2001). A modified presubmission checklist. Psi Chi Journal of Undergraduate Research, 6, 142-144.

Fidler, F. (2002). The fifth edition of the APA publication manual: Why its statistics recommendations are so controversial. Educational and Psychological Measurement, 62, 749-770.

Gelfand, H., & Walker, C. J. (2001). Mastering APA style: Student's workbook and training guide. Washington, DC: American Psychological Association.

Grusky, O., Marelich, W. D., Erger, J., Mann, T., Roberts, K. J., Steers, W. N., et al. (2003). Evaluation of a brief low-cost intervention to improve antiretroviral treatment decisions. AIDS Care, 15, 681-687.

Jackson, S. L., Lugo, S. M., & Griggs, R. A. (2001). Research methods textbooks: An objective analysis. Teaching of Psychology, 28, 282-288.

Kirk, R. E. (1996). Practical significance: A concept whose time has come. Educational and Psychological Measurement, 56, 746-759.

Madigan, R., Johnson, S., & Linton, P. (1995). The language of psychology: APA style as epistemology. American Psychologist, 50, 428-436.

Schultz, P. W., Shriver, C., Tabanico, J., & Khazian, A. (2004). Implicit connections with nature. Journal of Environmental Psychology, 24, 31-42.

Short, R., & Magana, L. (2002). Political rhetoric, immigration attitudes, and contemporary prejudice: A Mexican American dilemma. Journal of Social Psychology, 142, 701-712.

Smaby, M. H., Crews, J., & Downing, T. (1999). Publishing in scholarly journals: Part II - Is it an attitude or technique? It's a technique. Counselor Education and Supervision, 38, 227-236.

Smith, G. E., & Eggleston, T. J. (2001). Comprehending APA style through manuscript analysis. Teaching of Psychology, 28, 108-110.

Szuchman, L. T. (2005). Writing with style: APA style made easy (3rd ed.). Belmont, CA: Wadsworth.

Ware, M. E., Badura, A., & Davis, S. F. (2002). Using student scholarship to develop student research and writing skills. Teaching of Psychology, 29, 151-154.


Author Note. Christopher L. Aberson is Associate Professor of Psychology at Humboldt State University. David P. Nalbone is Assistant Professor of Psychology at Purdue University, Calumet.
     Send correspondence to Christopher L. Aberson, Department of Psychology, Humboldt State University, Arcata, CA 95521; e-mail: CLA18@humboldt.edu.