A couple of months ago Micah J. Marty and I had a twitter conversation and subsequent email exchange about how citations worked with preprints. I asked Micah if I could share our email discussion since I thought it would be useful to others and he kindly said yes. What follows are Michah’s questions followed by my responses.

Right now, I am finishing up a multi-chapter Master’s thesis and I plan to publish a few papers from my work. I may want to submit a preprint of one manuscript but before I propose this avenue to my advisor, I want to understand it fully myself. And I have remaining questions about the syntax of citing works when preprints come into play. What happens to a citation of a preprint after the manuscript is later published in a peer reviewed venue?

At the level of the journal nothing happens. So, if you cite a preprint in a published ms, and that preprint is later published as a paper, then the citation is still to the preprint. However, some of the services indexing citations recognize the relationship between the preprint and the paper and aggregate the citations. Specifically, Google Scholar treats the preprint and the published paper as the same for citation analysis purposes. See the citation record for our paper on Best practices for scientific computing which has been cited 49 times, but the vast majority of those are citations to the preprints.

Here’s an example with names we can play with: Manuscript 1 (M1) may require some extra analysis, but it presents some important unexpected results that I would like to get out on the table as soon as possible. M1 is submitted to PeerJ Preprints and accepted (i.e., published online as a preprint with a DOI). M2 is submitted to Marine Ecology Progress Series (MEPS) for peer review, and M2 cites the PeerJ Preprint M1.

Just a point related to vocabulary, I wouldn’t typically think of the preprint as being “accepted”. Any checking prior to posting is just a quick glance to make sure that it isn’t embarrassingly bad, so as long as it’s reasonably written and doesn’t have a title like “E is not equal to mc squared” it will be posted almost immediately (within 48 hours on most preprint servers).

1)  Are preprints considered “grey literature”? That is, is it illegitimate for M2 to cite a work that has not been peer reviewed?

Yes, in the sense that they haven’t been formally peer reviewed prior to posting they are similar to “grey literature”. Whether or not they can be cited depends on the journal. Some journals are happy to allow citing of preprints. For example, this recent paper in TREE cites a preprint of ours on arXiv. Their paper was published before ours was accepted, so if it wasn’t for the preprint it couldn’t have been cited.

2)  Is there a problem if M1 is eventually published in a peer reviewed journal but the published article of M2 cites only the PeerJ Preprint of M1?

I would say no for two reasons. First, assuming that M2 is published before M1 then the choice is between having a citation to something that people can read, science can benefit from, and that can potentially be indexed (giving you citation credit) vs. a citation to “Marty et al. unpublished data”, which basically does nothing. Second, all preprint servers provide a mechanism for linking to the final version, so if someone finds the preprint via a citation in M2 then that link will point them in the direction of the final version that they can then read/cite/etc.

In short, I think as long as you aren’t planning on submitting to a behind the times journal that doesn’t allow the submission of papers that have been posted as preprints (and the list of journals with this policy is shrinking rapidly) then there is no downside to posting preprints. In the best case scenario it can lead to more people reading your research and citing it. The worst case scenario is exactly the same as if you didn’t post a preprint.