There is a fundamental asymmetry that exists in contemporary peer review of scientific papers. Most scientific journals do not hide the identity of the authors of a submitted manuscript. The scientific reviewers, on the other hand, remain anonymous. Their identities are only known to the editors, who use the assessments of these scientific reviewers to help decide whether or not to accept a scientific manuscript. Even though the comments of the reviewers are usually passed along to the authors of the manuscript, the names of the reviewers are not. There is a good reason for that. Critical comments of peer reviewers can lead to a rejection of a manuscript, or cause substantial delays in its publication, sometimes requiring many months of additional work that needs to be performed by the scientists who authored the manuscript. Scientists who receive such criticisms are understandably disappointed, but in some cases this disappointment can turn into anger and could potentially even lead to retributions against the peer reviewers, if their identities were ever disclosed. The cloak of anonymity thus makes it much easier for peer reviewers to offer honest and critical assessments of the submitted manuscript.

Unfortunately, this asymmetry – the peer reviewers knowing the names of the authors but the authors not knowing the names of the peer reviewers – can create problems. Some peer reviewers may be biased either against or in favor of a manuscript merely because they recognize the names of the authors or the institutions at which the authors work. There is an expectation that peer reviewers judge a paper only based on its scientific merit, but knowledge of the authors could still consciously or subconsciously impact the assessments made by the peer reviewers. Scientific peer reviewers may be much more lenient towards manuscripts of colleagues that they have known for many years and who they consider to be their friends. The reviewers may be more critical of manuscripts submitted by rival groups with whom they have had hostile exchanges in the past or by institutions that they do not trust. A recent study observed that scientists who review applications of students exhibit a subtle gender bias that favors male students, and it may be possible that similar gender bias exists in the peer review evaluation of manuscripts.

The journals Nature Geoscience and Nature Climate Change of  the Nature Publishing Group have recently announced a new “Double-blind peer review” approach to correct this asymmetry. The journals will allow authors to remain anonymous during the peer review process. The hope is that hiding the identities of the authors could reduce bias among peer reviewers.  The journals decided to implement this approach on a trial basis following a survey, in which three-quarters of respondents were supportive of a double-blind peer review. As the announcement correctly points out, this will only work if the authors are willing to phrase their paper in a manner that does not give away their identity. Instead of writing “as we have previously described”, authors write “as has been previously described” when citing prior publications.

The editors of Nature Geoscience state:

From our experience, authors who try to guess the identity of a referee are very often wrong. It seems unlikely that referees will be any more successful when guessing the identity of authors.

I respectfully disagree with this statement. Reviewers can remain anonymous because they rarely make direct references to their own work in the review process. Authors of a scientific manuscript, on the other hand, often publish a paper in the context of their own prior work. Even if the names and addresses of the authors were hidden on the title page and even if the usage of first-person pronouns in the context of prior publications was omitted, the manuscript would likely still contain multiple references to a group’s prior work. These references as well as any mentions of an institution’s facilities or administrative committees that approve animal and human studies could potentially give away the identity of the authors. It would be much easier for reviewers to guess the identity of some of the authors than for authors to guess the identity of the reviewers.

But even if referees correctly identify the research group that a paper is coming from, they are much less likely to guess who the first author is. One of our motivations for setting up a double-blind trial is the possibility that female authors are subjected to tougher peer review than their male colleagues — a distinct possibility in view of evidence that subtle gender biases affect assessments of competence, appropriate salaries and other aspects of academic life (Proc. Natl Acad. Sci. USA 109, 16474–16479; 2012). If the first author is unknown, this bias will be largely removed.

The double-blind peer review system would definitely make it harder to guess the identity of the first author and would remove biases of reviewers associated with knowing the identity of first authors. The references to prior work would enable a reviewer to infer that the submitted manuscript was authored by the research group of the senior scientist X at the University Y, but it would be nearly impossible for the reviewer to ascertain the identity of the first authors (often postdoctoral fellows, graduate students or junior faculty members). However, based on my discussions with fellow peer reviewers, I think that it is rather rare for reviewers to have a strong bias against or in favor of first authors. The biases are usually associated with knowing the identity of the senior or lead authors.

Many scientists would agree that there is a need for reforming the peer review process and that we need to reduce biased assessments of submitted manuscripts. However, I am not convinced that increasing blindness is necessarily the best approach. In addition to the asymmetry of anonymity in contemporary peer review, there is another form of asymmetry that should be addressed: Manuscripts are eventually made public, the comments of peer reviewers usually are not made public.

This asymmetry allows some peer reviewers to be sloppy in their assessments of manuscripts. While some peer reviewers provide thoughtful and constructive criticism, others just make offhanded comments, either dismissing a manuscript for no good reason or sometimes accepting it without carefully evaluating all its strengths and weaknesses. The solution to this problem is not increasing “blindness”, but instead increasing transparency of the peer review process. The open access journal F1000Research has a post-publication review process for scientific manuscripts, in which a paper is first published and the names and assessments of the referees are openly disclosed.  The open access journal PeerJ offers an alternate approach, in which peer reviewers can choose to either disclose their names or to stay anonymous and authors can choose to disclose the comments they received during the peer review process. This “pro-choice” model would allow reviewers to remain anonymous even if the authors choose to publicly disclose the reviewer comments.

Scientific peer review can play an important role in ensuring the quality of science, if it is conducted appropriately and provides reasonably objective and constructive critiques. Constructive criticism is essential for the growth of scientific knowledge. It is important that we foster a culture of respect for criticism in science, whether it occurs during the peer review process or when science writers analyze published studies. “Double blind” is an excellent way to collect experimental data, because it reduces the bias of the experimenter, but it may not be the best way to improve peer review. When it comes to peer review and scientific criticism, we should strive for more transparency and a culture of mutual respect and dialogue.