http://www.zotero.org/support/kb/given_name_disambiguation
you likely have a S. Baron-Cohen and a Simon Baron-Cohen in your database.

I recently started to encounter this same issue with one author.

Deleting the in-text citation in one instance fixed the issue, but in another instances it did not. Next verified that the authors name was consistently entered in all entries in my database. I found one instance that wasn't consistent. Fixed that and now all citations are working properly.

Thank you all for this discussion. Saved some manual editing headaches.

Only citations in the paper matter, your database is irrelevant.
Two possible causes for this:
1. There is another Duffy cited in the paper: Depending on the citation style it need not be the first author (though for most it would need to be).
2. You have a citation to a version of the Duffy paper that got somehow deleted from your database, so Zotero sees them as two separate papers. You'd see that when inserting a bibliography, as they'd appear as two entries.

Pretty sure those are the only two ways this can happen.
Which citation style?
You can test this out in a fresh document. What happens if you just insert the one Duffy paper?

I have just begun using Zotero, having become incredibly frustrated with this SAME problem (and others) in Refworks. I only have a couple of documents saved in my Zotero library -- but still, when I try to cite one of them in a Word document, I get the first initials added when they should not appear. I don't believe the 3 references I currently have in my library have shared authors. I'd sure like to see some suggestions for making a permanent fix on this. I'm getting ready to write a book and REALLY need a citation management system that works without requiring a lot of manual adjustment.

OK, I tried that, and it inserts incorrectly in the new document, too. So this means I can't count on Zotero to import author information correctly, right? I have to check every reference I save in the library to make certain it's correct? I don't mean to sound overly negative, but that's a serious flaw in the program. Is there some import option that is less likely to cause this problem? Is there any way to "teach" Zotero to import citation information correctly?

I've been importing with the document open in Chrome. Also, I just tried manually correcting a reference in my Zotero library so that the names appear in the library in this form -- Woolf, SH and Aron, LY. When I tried to enter that citation in a new document, it shows up just as I've written it above -- Woolf, SH and Aron, LY -- which is not correct for APA style. It should be Woolf & Aron. I don't understand why the program has to distinguish between authors when more than one document has authors with the same name. The difference should be obvious in the reference list. Also, I noticed when I went back to look at this reference in my library that there are errors in the title as well -- for instance, National Research Council appear all in lowercase letters.

I don't understand why the program has to distinguish between authors when more than one document has authors with the same name.

Also, you either misstated this or are misunderstanding it. It's about multiple authors with the same last name but different first names in the same document, not different documents. Zotero disambiguates authors as required by citation styles.

But that's not the even the issue you're facing now. As far as you've told Zotero, you currently just have an author with a literal name of "Woolf, SH" (as in, say, "Apple, Inc.").

Import this:
http://www.ncbi.nlm.nih.gov/pubmed/23307023
via URL bar icon as a template for how things should look.
This will give you the correct

(Woolf & Aron, 2013)

Woolf, S. H., & Aron, L. Y. (2013). The US health disadvantage relative to other high-income countries: findings from a National Research Council/Institute of Medicine report. JAMA: The Journal of the American Medical Association, 309(8), 771–772. doi:10.1001/jama.2013.91

(italics ommitted, they're in the original).
To restate what Dan is saying: what matters is not _how_ you're importing, but where you're importing from. Zotero uses data from publishers and databases. Some of it - like pubmed - is very good. Some of it is very bad. How much you need to check your references depends on where you import them from, though frankly, some degree of checking is going to be unavoidable. Reference managers help you with bibliographic tasks, but they don't at this point at least, remove you from the task entirely.

I didn't write in the commas myself in Zotero

OK, you said above you manually corrected it to that, so I'm not sure what you meant then.

the URL for the article mentioned above was: http://www.ncbi.nlm.nih.gov/books/NBK115854/pdf/TOC.pdf

That's just a PDF — you can't import from that (unless you used "Retrieve Metadata from PDF" on the PDF from within Zotero). We need the URL where you actually clicked the address bar icon, assuming that's what you did.

Hi, I am new to Zotero and I am also consistently having the problem of the first name being included in in-text citations. It is not a case of ambiguity as to the authors. I am using the Unified Style Sheet for Linguistics but even when I try another one like ASA or Chicago I still have the same problem. I have the problem on both of my computers, in different documents, with different authors, with all 3 of the styles mentioned above. In Zotero in the author field I enter the name as Last, First, so for example my own papers have the author field entered as Beam de Azcona, Rosemary G. I would expect in-text citations to come out as (Beam de Azcona 2012) but instead they come out as (Beam de Azcona, Rosemary G. 2012). Any advice?

I am having this issue now.

I cited three of Anna Tsing's papers/books. In-text citations were listing (A. L. Tsing 2017) and (A. Tsing 2015). So I fixed the entries in my Zotero Libary so that she was always listed as Anna Lowenhaupt Tsing. I figured that this would fix it and that they should all read (Tsing 2017), etc. However, now they are all listed as (Anna L Tsing 2017). I am having the same issue with another author that I cite more than once. Because he appeared once as Michael Coe and once as Michael A. Coe. I fixed the issue in the Zotero library so they are both consistent but it still refuses to take his first initial out of the in-text citation in word.

It seems that despite the zotero library being fixed, the word document remembers that I had previously cited a different A Tsing and A L Tsing. How can I reset the document so that it does not do this?

Thank you.

Yes, when I test in a new document the citations show up correctly. In the old document's bibliography they also show up correctly, it is just the in-text citations that continue to have the first name or initials. The in-text citations are updating, but it's my impression that they have somehow stored the author list somewhere in the document (which is not updating), so they don't recognize that now there is no longer a need to differentiate by first name/initial.

Sure. It's in Chicago author-date style.

Thanks for your quick response on my questions.

Tsing, Anna L. 2005. Friction: An Ethnography of Global Connection. Princeton, NJ: Princeton University Press.
———. 2009. “Beyond Economic and Ecological Standardisation.” The Australian Journal of Anthropology 20 (3): 347–68. https://doi.org/10.1111/j.1757-6547.2009.00041.x.
———. 2015. The Mushroom at the End of the World: On the Possibility of Life in Capitalist Ruins. Princeton and Oxford: Princeton University Press.

I did try switching citation style and it didn't fix the issue.

After looking at the link you sent I was able to solve this by just copying and pasting my entire document into a new word document and then refreshing the citations - not ideal, but it worked!

Thanks for your help!