Why do people sometimes put authors with equal contribution in non-alphabetical order?

Question

I've seen papers (e.g., in Science) where the first two authors are listed in non-alphabetical order, and yet there are asterisks behind their names to say that they contributed equally.

It seems strange to me, because if the two authors are in alphabetical order, then it could be that the first author contributed more or the two contributed equally, and this can be made clear with asterisks in the paper if it's the latter case. When they're in non-alphabetical order, however, if someone only sees the author list without seeing the paper, they will likely assume that the first author contributed most.

So my question is: Are there particular reasons why people do that? (This question is related, but I don't think the answers there get to my question.)

Answer 1

There are some requirements for funding¹², a degree³, tenure and similar for which literal first authorship counts. If one of the equally contributing authors gains an advantage from being the first author due to this while the other one doesn’t or has a smaller advantage, it can make sense to have the order deviate from the alphabetic one.

Another conceivable scenario would be that the first authors is well-known in the respective field and was made first author to attract a little bit more attention to the paper.

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^{¹ For example several faculties in Germany have schemes for evaluation and publication-based funding that assign special value to first-author publications. Some of those do not mention joined first authorships and do not make sense with multiple first authors, which indicates that first authorship is meant literal (example in German, search for Erstautor).}

^{² This journal, e.g., lists a handful of funding organisations that will pay the publication costs, if the first author is funded by the respective organisation. Joined first authorship is not mentioned. Even if this may be dealt with on a per-case basis, just flipping the first authors may be easier.}

^{³ For example, for a publication-based PhD thesis, it may required that the included publications be first-author publications (example, again in German) without the case of joined first authors being considered. While the latter may be allowed on a per-case basis, flipping the authors may be much easier and avoid a lot of bureaucracy.}

Answer 2

There are a couple reasons for doing this - most of which are rooted in the idea that the "first first" author still has an advantage. Some folks will still refer to the paper by "Adams et al." In fields where first authorship carries weight, some people "don't believe" in co-firsts. There's some ambiguity about whether a co-first author can put their name first on their own CV, which will be important for quick reads by people evaluating said CV.

Given that, there are a couple reasons:

1. "Alphabetical ordering" inherently privileges one of the authors. They may, in the interest of fairness, "flip for it", or in a series of papers just alternate.
2. "First first" might also be the one willing to field some of the post-writing effort behind a paper - actually submitting, fielding press inquiries, etc.
3. There may be someone that benefits more. For example, a postdoc for whom this is a big deal publication may be put first so that they can reap any little residual benefit from those who don't pay attention to the note, instead of an established researcher who doesn't need it as much.
4. Not all journals accept a co-first designation. So the order may be "If it comes down to it, and we can't share, it should be you" decision, even if it does make it into a co-first compatible journal.

One publication I'm on has a author order that involved 2-4.

Answer 3

Two authors who regularly collaborate may have a rotation scheme going (with footnotes about equal contribution). That is, they take it in turns to be first author on any of the papers that is about their joint research. This avoids building up a substantial difference in first authorship, which can be important on CVs where the footnotes are not visible.

Answer 4

Many factors may affect order in a list of authors. And this is field-dependent. In mathematics, one usually considers that all authors contributed equally, and use the alphabet order.

In addition to @Wrzlprmft, one may for instance ask whether Do age and professional rank influence the order of authorship in scientific publications? Some evidence from a micro-level perspective.

I have experienced three other cases, with globally equal contributions between authors. "Globally equal" is a very complicated concept, illustrated thereafter.

In an overview four-author paper (A panorama on multiscale geometric representations, intertwining spatial, directional and frequency selectivity), we (the three other authors) decided to put as "first author" the one who had not a permanent position at the time of submission, and who did a great job in gathering article pieces and assembling contributions. In a five-author paper (CHOPtrey: contextual online polynomial extrapolation for enhanced multi-core co-simulation of complex systems), the first one was the (sole) woman author, and the youngest. This concept took us about 5 years to develop, with people moving in and out, and she did the final programming. And last, we swapped places in a two-author paper (Lapped transforms and hidden Markov models for seismic data filtering), because the alphabetical order put a too-heavy birth advantage on one of us.

All because of this "silly" thinking that the first author did more work, and since in some disciplines (biology, medicine), the citations are often in the shape "Author 1 et al., Year, Journal". And sometimes there is a strange feeling that, in order or importance, there is some hidden hierarchy like:

• first author
• last author
• second author
• penultimate or second-to-last author
• third author
• while other authors could be straw people.

So, my three rules of bibliometrics:

1. authors' list should be agreed on among authors (sounds odd, but sometimes one guy really does not belong),
2. authors should agree on an order,
3. for the rest, do not let bibliometrics rule the above. Scientific integrity and honesty should prevail.

Linked stories:

• Not listed as author despite doing statistical work
• Publish the paper without letting know one of authors?
• Is it appropriate to add a co-author at the stage revise & resubmit?

Answer 5

In Brazil, the order of authors defines fellowships and fundings. There are some fellowships that you cannot apply for if you don't have at least 2 publications as first author.

Answer 6

At the Collaborative Institutional Training Initiative, there is an interesting article on "Authorship" by Stephanie J. Bird, which basically boils down to the fact that practices are completely variable on the issue between different disciplines:

The significance of the order of authorship is also variable within fields and sub-fields. Again, universal, definite rules for author order are generally lacking. The order may reflect the extent or nature of one's contributions, for example, who did the "most" work, who had the primary or key idea, or who wrote the first draft of the manuscript. Historically, the head of the research team, normally the most senior researcher, was listed first. This practice is still somewhat common but more recently, that individual may be listed last, especially in the life sciences.

In some physical sciences, particularly experimental physics, authorship is typically alphabetical. An alphabetical listing is also used by some journals, and in some research groups, alphabetical (or a version of it) may be standard practice. For example, contributions may be listed alphabetically except for the head of the research group who is listed first or last. When a research team produces several related papers derived from the same project, the order of authors may rotate.

... In many fields, the first author is the individual who earns the most credit by having taken primary responsibility for the intellectual core of the work. (On occasion, the last author is primarily responsible for the work's intellectual core.) This individual may also be known as the "lead" or "primary" author. This convention has developed in part because of the practice of referencing relevant, related work in the literature by the last name of the first author followed by "et al." when there are more than two or three authors depending on the journal. Thus, while a paper by Sandra Dunn and Jonathan Thomas would be cited as "Dunn and Thomas", a paper authored by Sandra Dunn and three other individuals would be cited as "Dunn et al."

... In spite of the emphasis and attention paid to author order and the designation of corresponding author, the actual significance of any particular order of authors can be opaque and open to misunderstanding and misinterpretation. A reader's assumptions may not be consistent with the assumptions and intentions of the authors themselves. The recognition of individual authors is most likely to reflect their reputations, the reliability of their work, the reputation of the colleagues with whom they choose to work and of their trainees, and their cumulative contributions to the field.

Because of the complexities with determining what a particular author list means, some journals use an asterisk, or another similar strategy, attached to each author's name as a means for more specifically spelling out the relevant person's specific contribution to a project. At times, it can be used to indicate that the authors contributed equally to the work either as co-first authors or as corresponding authors.

A sampling of Bird's references that seem on-topic:

• Claxton, Larry D. 2005. "Scientific Authorship: Part 2. History, Recurring Issues, Practices, and Guidelines." Mutation Research 589(1):31-45.
• Bebeau, Muriel J., and Verna Monson. 2011. "Authorship and Publication Practices in the Social Sciences: Historical Reflections on Current Practices." Science and Engineering Ethics 17(2):365-88.
• Borenstein, Jason. 2011. "Responsible Authorship in Engineering Fields: An Overview of Current Ethical Challenges." Science and Engineering Ethics 17(2):355-64.
• Macrina, Francis L. 2011. "Teaching Authorship and Publication Practices in the Biomedical and Life Sciences." Science and Engineering Ethics 17(2):341-54.

Answer 7

I do not know if Science has a convention for this, but let me tell you about the convention in Economics and Finance journals. The most common way to reference articles is to cite by authors-date and in alphabetical order, for instance: Kahneman and Tversky (1979). In Economics or Finance, the order of the authors does not usually indicate any seniority or importance in the contributions.

If the non-alphabetical order of authorship indicated anything, the authors would usually explain it in a footnote. For instance, I have seen authors indicate that the order reflected the winner of a particular game of chess, but I do not recall which article it was.

Authors who publish quite a bit together occasionally swap the order of the authors, e.g. Tversky and Kahneman (1991). This can be done for a variety of reasons and it is up to the authors to decide to do that. The journals would not (as far as I know) make any such request. A common reason for non-alphabetical listing of authors is that the authors have two papers published together in the same year and they find it clearer to use the reference style Tversky and Kahneman (1991) rather than Kahneman and Tversky (1991b).

Examples of References:

Kahneman, Daniel & Tversky, Amos, 1979. "Prospect Theory: An Analysis of Decision under Risk," Econometrica, Econometric Society, vol. 47(2), pages 263-91, March.

Tversky, Amos, and Daniel Kahneman. 1991. "Loss Aversion in Riskless Choice: A Reference-dependent Model". The Quarterly Journal of Economics 106 (4). Oxford University Press: 1039–61.

Answer 8

I'm years late, but having at least discussed a similar situation - one axis of contribution is the "work" and "experiments". Another measure is doing the logistics / shepherding to get a paper through rebuttals and formatting styles for conference submissions, correspsondences, making sure all contributors work on the assigned tasks before deadlines, etc. This almost always falls on on the first author, because you need a designated person.

You can have equal contribution to the scientific work, but one author may take on more contribution to this "sheep herding" and the responsibility to make sure the paper gets through, and that makes them the "first author".

YMMV, its very case by case and not a universal truth.

Answer 9

'All co-first authors are equal, but some are more equal than others'

While in some fields they are really equal, in many fields it is not, and the first co-first author is usually considered to do more works, but second author do also did quite a number of work that more than second author, and in this case they may decide to get the second author to co-first author.

In many fields collaboration is necessary, say one lab have the samples, and one lab have the analysis skills. Both are important to a paper, without any of them the paper is not possible. In this case, they may put one people in a lab to co-first. Of course there are co-corresponding author as well. Exactly orders of first and second co-first may vary. For example, it can be taking terms for the series of this collaborations.