One Apostrophe or Two?

punctuation-tip-4I have a quick tip for you today.  The question is, when you’re citing a study by multiple authors, do you put an apostrophe with all of the authors’ names, or just the last name? 

I came across a citation for the following study while editing today:

Akinola, Modupe, and Wendy Berry Mendes. “The Dark Side of Creativity: Biological Vulnerability and Negative Emotions Lead to Greater Artistic Creativity.” Personality and Social Psychology Bulletin. 34.12 (2008): 1677–86. Print.

The documentation style shown above is MLA style, for those who are new to it, but the punctuation principle in this post applies regardless of Chicago, APA, MLA, or other style.

If we want to cite without an apostrophe, it’s not too confusing (e.g., Akinola and Mendes). But if we want to use an apostrophe, do we put an apostrophe after both names, or just the second name? The correct usage depends on whether the authors collaborated on one study or wrote separate studies. In this case, we just have one study, so we use one apostrophe.

Tip: An easy easiest way to remember the rule is 1 Study = 1 Apostrophe, 2 Studies = 2 Apostrophes, etc.

As an example, in the text you might say,

Akinola and Mendes’s study provided evidence for a mediating effect of negative emotional changes (1683). (Note, if you’re wondering why the extra s is included, please see my previous post on citing authors with a name that ends in s).

Or, in APA we might have

Akinola and Mendes’s (2008) study provided evidence for a mediating effect of negative emotional changes.

Now let’s take an example if we are referring to separate studies.  Let’s say that both authors just published a study in 2013, one by Akinola and one by Mendes.  To use the possessive in this case, we might have something like this:

Akinola’s (2013) and Mendes’s (2013) studies show such and such.

As a final example, what if we have two studies, but multiple authors for each study? Remember the rule: the number of studies dictates the number of apostrophes.

So we might have something like this:

Milkman, Akinola, and Chugh’s (2012)  and Mendes and Koslov’s (2012) studies show such and such.  (2 Studies = 2 Apostrophes, 1 for Each Study)
For further reference, see the Chicago Manual of Style, section 7.22 (Joint versus Separate Possession). That section focuses on common nouns rather than author names, but the same principle applies. For instance,”Peter’s and Mary’s books” means that they each have their own books, and “Peter and Mary’s books” mean that they share ownership of the same collection of books.

Hope that clarifies the correct usage for some of you out there. Best wishes with your writing today!


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Rocky Citro

Hi, my name is Rocky, and I am a technical academic editor with over a decade experience editing for professors and graduate students in prestigious universities. I have also taught writing at the graduate and undergraduate level and have several years' TEFL teaching experience.