Starting in March, Nature and the monthly Nature research journals will experiment with an alternative to their time-tested method of traditional single-blind peer review, in which reviewers are anonymous but know the authors' identity. Authors will be able to choose double-blind peer review, in which both authors and reviewers are unknown to each other.

Double-blind and open peer review are often proposed as alternatives to the conventional single-blind process, with different strengths and limitations. Proponents of open peer review, where both authors and reviewers are unveiled to each other, see its transparency as a way to encourage more civil and thoughtful reviewer comments — although others are concerned that it promotes a less critical attitude. Advocates of double-blind peer review suggest that it eliminates ad hominem biases, such as those based on gender, seniority, reputation and affiliation1. How effectively either method can meet these aspirations while maintaining the necessary level of criticism remains a matter of debate.

Nature experimented with open peer review in 2006, but at the time, despite expressed interest, the uptake from both authors and reviewers was low and the open reviews were not technically substantive. Views about open peer review are probably still evolving, as several journals continue to experiment with variations on this practice. Opinions about double-blind review, however, are remarkably consistent.

In one of the largest studies on peer review — a 2009 international and cross-disciplinary survey of more than 4,000 researchers1 — 76% of respondents indicated that double blind was an effective peer-review system. (By comparison, open and single-blind peer review were considered effective by 20% and 45% of respondents, respectively.) More recently, our own reader survey confirmed the desire to have double-blind peer review as an option. Importantly, this sentiment is widely echoed in conversations with young scientists worldwide. These conversations illustrate a widespread perception that biases based on authorship affect the traditional single-blind peer review, and they have contributed greatly to us reconsidering this proposition.

Nature journals editors have traditionally not embraced double-blind peer review, for several reasons including scepticism of its efficacy, concern about the potential difficulty of recruiting referees, and the view that it is the editor's responsibility to mitigate biases addressed by double-blind review. All editors take, and will continue to take, this responsibility seriously by maintaining awareness of any potential predispositions when selecting reviewers and considering their comments. They will also continue to honour reasonable requests to exclude particular reviewers, regardless of the chosen method of peer review. But by definition, unconscious biases may be difficult to identify and to control. Several studies have detected involuntary biases, notably on the basis of gender, in other areas of the scientific enterprise, such as the hiring of laboratory staff, citation habits and speaker lineups at conferences. It is therefore difficult to guarantee a bias-free process.

Since June 2013, Nature Geoscience and Nature Climate Change have allowed authors to choose between double-blind and single-blind peer review at submission2. The reactions to the trial among surveyed authors have been sufficiently positive that Nature and the Nature monthly journals have decided to join the experiment. (Nature Communications will join at a later date.)

The responsibility for rendering the manuscript anonymous falls to the authors. Clearly, in some situations, maintaining anonymity will be impossible because of awareness of their work in the specialist community or because researchers wish to release data early and to discuss their work with their peers prior to publication, via conferences or preprint servers. Therefore, the double-blind process is optional on all titles. Some will choose it to assuage concerns about biases, others purely by principle.

We will keep this initiative under review, and we welcome comments from authors and reviewers.