PLOS Biology relies on members of the scientific research community to assess the validity of articles under consideration through peer review.

Invitation to Review

PLOS Biology editors select potential reviewers based on their expertise in research areas relevant to the manuscript under consideration. Reviewer invitations are sent by email from the journal's Editorial Manager submission system. Use the links in the invitation email to accept or decline, or check the “New Reviewer Invitations” folder on your Reviewer Main Menu screen in Editorial Manager. Accept an invitation only if you have the knowledge, time and objectivity necessary to provide an unbiased assessment of the research. In agreeing to complete a review, you also give permission to publish your review under a Creative Commons Attribution CC BY license.

Our Peer Review Process

PLOS Biology practices single-anonymized peer review by default, but offers opportunities for authors and reviewers to participate in signed and published peer review.

Our peer review model

	Single-anonymized peer review During the peer review process you will know the authors’ names, but your name will not be shared. Your review will appear in the editorial decision letter where it can be read by the authors and other reviewers.
	Signed peer review You can choose to sign your name to your review when you submit it. Remember, if you sign your name the authors and other reviewers of the manuscript will see it. If the authors choose to publish their peer review history your name will accompany your comments alongside the published article.
	Reviewer cross-commenting Once a full set of reviewer reports has been received, we will circulate it anonymously among the reviewer panel to give you the chance to see and comment on your peers' reports before a decision is made. You will be given 2 working days to comment, so as not to delay the decision-making process.
	Portable If the authors subsequently choose to transfer their manuscript to another PLOS journal your review will accompany it. You may hear from editors at another PLOS journal for re-review. Reviewers for any PLOS journal should be willing to have their reviews considered by the editors of another PLOS journal. In addition, PLOS Biology has partnered with the Neuroscience Peer Review Consortium to help ensure that the time and expertise that reviewers devote to assessing a manuscript is not lost if authors decide to submit to another journal. As such, PLOS Biology may transmit reviews to other NPRC journals at the request of the authors. We will contact individual reviewers for permission to transmit their names to the recipient journal and will otherwise transmit the reports anonymously. Beyond the Neuroscience Peer Review consortium, PLOS Biology will transmit reviews to other journals at the request of the authors. We will contact individual reviewers for permission to transmit their names to the recipient journal and will otherwise transmit the reports anonymously.
	Published peer review history If the authors decide to publish their peer review history, the editorial decision letter, including your review, will appear alongside the published article. Your name will not appear unless you choose to sign your review.

Best practices for reviewers

	Declaring competing interests A competing interest is anything that interferes with or could be perceived as potentially interfering with, a thorough and objective assessment of a manuscript. Common examples of competing interests may include:   A recent or current collaboration with any of the authors Direct competition or a history of scientific conflict with any of the authors An opportunity to profit financially from the work Do not accept a review assignment if you have a competing interest, or don’t feel able to give an objective assessment. If you’re unsure whether your relationship qualifies as a competing interest, contact the journal office for advice. If we ask you to complete the review anyway, be sure to declare the competing interest when you submit your review.
	Crediting collaborators If you had help completing the review you must share your collaborator’s name with the journal when you submit the review, either by entering it In the question labeled "Did you prepare this review with someone else?", or via email. Be careful not to include your collaborator’s name in the text of the review itself.
	Confidentiality Keep manuscripts and correspondence confidential and do not share information about submissions with any one else unless previously agreed with the editor. We expect that reviewers will not make use of any material or take advantage of any information they gain through the peer review process.   Read the PLOS Confidentiality Policy.
	Reviewing a manuscript you’ve previously reviewed If you reviewed the article at another journal, let the editor know via email. Consider the manuscript as a new submission unless instructed otherwise. Keep in mind that it may have been revised since the last time you evaluated it, and PLOS Biology’s criteria for publication may differ from those of the other journal.
	Time to review Aim to complete your review within 10 days. If you need more time to perform the review, please email us as soon as possible.

Receiving credit

In choosing to volunteer as a peer reviewer for PLOS, you are helping to support free and open access to rigorous research. We couldn’t be more grateful!

	Reviewer Credit with ORCID and Publons Link your PLOS reviewer account to your ORCID or Publons record. Set up syncing to have reviewer activity automatically posted to your ORCID profile review activity. This record will confirm that you completed a review for the journal, but won’t publish the content of your review.

What to Assess

To be eligible for publication manuscripts must meet our criteria for publication and comply with our editorial and publishing policies. The following guidance relates to articles reporting the results of original research. If you are reviewing another article type see the other article types page and check your invitation letter for guidance on what to consider in your review.

Criteria for publication

In addition to being ethically conducted and scientifically valid, research published in PLOS Biology should be exceptional in the following ways:

1. Originality
2. Importance to researchers in its field
3. Interest to scientists outside the field
4. Rigorous methodology and substantial evidence for its conclusions

Writing the review

The purpose of the review is to provide the editors with an expert opinion regarding the validity and quality of the manuscript under consideration. The review should also supply authors with explicit feedback on how to improve their papers so that they will be acceptable for publication in PLOS Biology. As you write, consider the following points:

• What are the main claims of the paper and how significant are they for the discipline?
• Are these claims novel? If not, please specify papers that weaken the claims of originality of this one. If a similar paper was recently published, the current manuscript may still be eligible for publication under our complemetary research policy.
• Is this paper outstanding in its discipline? If yes, what makes it outstanding? If not, why not?
• Who would find this paper of interest? Why?
• Are the claims properly placed in the context of the previous literature? Have the authors treated the literature fairly?
• Do the data and analyses fully support the claims? If not, what other evidence is required?
• Would additional work improve the paper? How much better would the paper be if this work were performed and how difficult would it be to do this work?
• If the paper is considered unsuitable for publication in its present form, does the study itself show sufficient potential that the authors should be encouraged to resubmit a revised version?
• Are original data deposited in appropriate repositories and accession/version numbers provided for genes, proteins, mutants, diseases, etc.?
• Is the manuscript well organized and written clearly enough to be accessible to non-specialists?
• Are details of the methodology sufficient to allow the experiments to be reproduced?
• PLOS Biology encourages authors to publish detailed protocols and algorithms as supporting information online. Do any particular methods used in the manuscript warrant such treatment? If a protocol is already provided, for example for a randomized controlled trial, are there any important deviations from it? If so, have the authors explained adequately why the deviations occurred?

Any remarks that might help to strengthen the paper should be directed to the authors themselves. If you have any concerns pertaining to publication ethics, research ethics, or data availability please raise those directly with journal staff at plosbiology@plos.org.

Reviewing Preregistered Research Articles

Preregistered Research Articles are a form of empirical article offered at PLOS Biology in which the methods and proposed analyses are peer reviewed prior to conducting experiments, data collection or analysis. Peer review takes place in two stages:

Stage 1: Protocol

You’ll review a protocol describing the research question, rationale, study design, proposed methodology for data collection and analysis, and plans for ethical approval. Peer review aims to ensure that the proposed research addresses a meaningful and important question, and that the study design and methodological approach are sound. Consider the following points in your review:

• The importance of the research question(s).
• The logic, rationale, and plausibility of the proposed hypotheses (does the manuscript provide a valid rationale for the proposed study, with clearly identified and justified research questions?)
• The soundness and feasibility of the methodology and analysis pipeline (including statistical power analysis where appropriate). Is the protocol technically sound and planned in a manner that will lead to a meaningful outcome and allow testing of the stated hypotheses? 
• Whether the clarity and degree of methodological detail is sufficient to exactly replicate the proposed experimental procedures and analysis pipeline.
• Whether the authors have pre-specified sufficient outcome-neutral tests for ensuring that the results obtained are able to test the stated hypotheses, including positive controls and quality checks.

Stage 2: Preregistered Research Article

Once the research is complete, you’ll review the complete article that includes the results of the study outlined in the Stage 1 protocol. Peer review focuses on adherence to the Stage 1 protocol, the appropriateness of any deviations, and the accuracy of the conclusions. Consider the following points in your review:

• Whether the introduction, rationale and stated hypotheses are the same as the approved Stage 1 Protocol submission (required).
• Whether the authors adhered precisely to the approved Stage 1 experimental procedures.
• Whether the data are able to test the authors’ proposed hypotheses by satisfying the approved outcome-neutral conditions (such as quality checks, positive controls).
• Whether the authors’ conclusions are justified given the data.
• Whether any post-hoc analyses added by the authors are justified, methodologically sound, and informative.
• Whether, in accordance with the PLOS’ data availability policy, data has been made freely available in a public repository. Data files should be appropriately time stamped to show that data was collected after Stage 1 Protocol approval and not before.

Editorial decisions will not be based on the perceived importance or novelty of the Stage 2 results. Significance of the research question was assessed during Stage 1.

At each stage of review you’ll have the option to sign your comments. If the final article is accepted for publication, the authors will have the option to publish their peer review history. 

Revisions

We often ask the original reviewers to evaluate revised manuscripts and the authors’ response to reviewer comments. We hope that you’ll make yourself available for re-review and questions from the editors.

Editing reviewers’ reports

The editors and PLOS staff will not change any reviewer comments that are intended for authors to read, except with reviewer approval prior to the decision letter being sent. For example, we may request changes if language is deemed inappropriate for professional communication, or if the comments contain information considered confidential, such as competing interest declarations.

Reviewing Magazine Submissions

The review process for our magazine section articles is slightly less formal than peer review for research articles but we nevertheless expect the science and logic of the articles to be rigorous and precise. 

Perspectives

Perspectives address issues at the interface between science and policy or science and society; present a policy position aimed at influencing policy decisions; or examine and make recommendations on scientific and publishing practices. Because Perspectives are opinion pieces, the authors are given more latitude in expressing their views than would be allowed in standard scientific articles or reviews. Nevertheless, we expect the articles to be grounded in scientific reality. In addition to providing feedback on the soundness of the science and coherence of the argument presented, we would appreciate your general reaction to the article. In particular: do you think the piece is interesting? Do you feel that it deals with an important or significant issue? Is the point of view well-argued and scientifically supportable? If you have any comments or suggestions to improve the piece or increase its scope or interest, we would be grateful for specific suggestions.

Community Pages

Community Pages provide individuals, networks, and organizations with the opportunity to highlight resources, tools, or initiatives of benefit to the scientific community and beyond (including science education and public engagement in science). All resources, tools, and the outputs of initiatives must be open and accessible to all. In addition to providing feedback on the soundness of the science and coherence of the article, we would appreciate your general reaction to it. In particular: do you think the piece is interesting? Do you feel that it deals with an important or significant issue? Does the piece avoid self-promotion? If the article is considered unsuitable for publication in its present form, does it show enough potential that the authors should be encouraged to revise the article? If you have any comments or suggestions to improve the piece or increase its scope or interest, we would be grateful for specific suggestions.

Essays

An Essay should offer a provocative or novel perspective on a specific topic of interest to scientists and, in most cases, to a broader audience. Author(s) should outline the topic, clearly state and argue their viewpoint, and provide a selected number of specific examples where applicable. Because Essays should convey the author’s point of view, more latitude is allowed than would be in standard scientific articles or reviews. Nevertheless, we expect the articles to be firmly grounded in scientific reality. In addition to providing feedback on the soundness of the science and coherence of the argument presented, we would appreciate your general reaction to the article. In particular: do you think the piece is interesting? Do you feel that it deals with an important or significant issue? Is the point of view well-argued and scientifically supportable? If the article is considered unsuitable for publication in its present form, does it show enough potential that the authors should be encouraged to revise the article? If you have any comments or suggestions to improve the piece or increase its scope or interest, we would be grateful for specific suggestions.

Unsolved Mysteries

As the name implies, an Unsolved Mystery should discuss a topic of biological or medical importance that is poorly understood and in need of research attention (e.g., an unexplored, challenging or persisting question, an emerging opportunity, or a recent puzzling phenomenon with potentially devastating consequences). The articles are intended to stimulate scientists to think about future research possibilities outside their areas of expertise. In addition to providing feedback on the soundness of the science and coherence of the argument presented, we would appreciate your general reaction to the article. In particular: do you think the piece is interesting? Do you feel that it deals with an important or significant issue? Is the point of view well-argued and scientifically supportable? If the article is considered unsuitable for publication in its present form, does it show enough potential that the authors should be encouraged to revise the article? If you have any comments or suggestions to improve the piece or increase its scope or interest, we would be grateful for specific suggestions.

Consensus Views

Consensus View articles present a comprehensive analysis by an independent and usually multidisciplinary panel of experts who make specific recommendations on important scientific, publishing or policy issues. Because Consensus Views give guidance or recommendations to the community, we expect the articles to be firmly grounded in scientific reality and balanced. In addition to providing feedback on the soundness of the science and coherence of the arguments presented, we would appreciate your general reaction to the article. In particular: do you think the piece is interesting? Do you feel that it deals with an important or significant issue? Is the point of view well-argued and scientifically supportable? If the article is considered unsuitable for publication in its present form, does it show enough potential that the authors should be encouraged to revise the article? If you have any comments or suggestions to improve the piece or increase its scope or interest, we would be grateful for specific suggestions.

The Editorial Process

Decision process

The editors make the final decision on whether to publish each submission based on the reviewers’ comments, the PLOS Biology criteria for publication, and their own assessment of the manuscript.

Conflicting reviews

If reviewers appear to disagree fundamentally, the editors may choose to share all the reviews with each of the reviewers and request additional comments that may help the editors to reach a decision. Decisions are not necessarily made according to majority rule. Experts may disagree, and it is the job of the Editor to make a decision. Editors evaluate reviewer recommendations and comments alongside comments by the authors and material that may not have been made available to reviewers. Please know that your recommendation has been duly considered and your service is appreciated, even if the final decision does not accord with your review.

More on our Editorial Process.

Help

For more tips on peer review go to the Peer Review Center, and sign up to the Peer Review Toolbox.

If you have questions or concerns about the manuscript you are reviewing, or if you need assistance submitting the review, please email us plosbiology@plos.org.