I currently have a paper submitted to PNAS. We had two rounds of revisions, and following detailed suggestions from one reviewer, we have improved our proposed algorithm a lot: its complexity is now significantly lower, and the idea he suggested makes the overall method more robust in handling noisy signal.
I feel that this reviewer's contribution extend far beyond his original role, so much that I feel it would be ethically honest to have him as a co-author. To be crystal-clear: if he was not a reviewer, but a colleague with whom I had discussed this before submitting the paper, he would clearly be entitled to authorship, no question.
But… he is a reviewer, so I am wondering how (if at all) we should ask him to join as co-author. Right now, I am ready to submit the twice-revised manuscript, and I have no doubt that it will be accepted (second review was “minor revisions”). The options I can see are:
- In my cover letter for the revised manuscript, explain the situation to the editor and ask him if he could (with the reviewer's agreement) lift anonymity and allow the authors' list change.
- Wait for the manuscript to be formally approved, and only then write to the editor asking for the same thing.
- Do nothing, for example because it is frowned upon. This would pain me greatly, because the reviewer really contributed very significantly to the algorithm, and I believe he should be able to claim authorship for this contribution (if he sees it fit).
So, what are accepted practices? How should I handle this matter?