# The Reviewer's Request for More Experiments: When to Comply, When to Push Back ## Quick Answer - Evaluate each requested experiment against its necessity for the study's core claims, the availability of existing data, and the feasibility of completion within a reasonable timeline. - Comply when the request addresses a genuine methodological gap or strengthens a central conclusion, and push back with a clear, evidence-based rationale when the request is redundant, impractical, or beyond the study's scope. - Remember that peer review is a negotiation process, and a well-reasoned response letter that explains why an experiment is unnecessary can be as persuasive as performing the experiment itself. ## Understanding the Peer Review Process and Your Rights as an Author Peer review serves as a quality control mechanism for scientific publishing, but it operates within a framework of ethical standards that protect both authors and reviewers. The Committee on Publication Ethics (COPE) Core Practices establish expectations for peer review that include fair treatment of authors and clear communication about editorial decisions. These practices recognize that peer review should be a constructive process, not an open-ended demand for unlimited work. When you receive a request for more experiments, you are not obligated to comply with every suggestion. The editor, not the reviewer, makes the final decision about whether your manuscript is acceptable for publication. Your response letter is your primary tool for communicating with the editor about which requests are reasonable and which are not. The peer review system depends on the assumption that reviewers provide feedback that improves the quality of published research. However, reviewers can make mistakes, misunderstand your methods, or request experiments that are not feasible within your resources. Understanding your rights as an author helps you navigate these situations with confidence. Your rights include the ability to disagree with reviewers, to explain why a suggested experiment is unnecessary, and to propose alternative approaches that address the same concern. The editor serves as the arbiter who weighs your arguments against the reviewer's concerns. A respectful, evidence-based response is more likely to succeed than either silent compliance or defensive resistance. ## At a Glance: Decision Framework for Responding to Experiment Requests | Request Type | Recommended Response | Rationale | | --- | --- | --- | | Addresses a central claim or methodological flaw | Comply or provide equivalent evidence | The study's conclusions depend on this evidence, and the editor will likely require it | | Requests redundant validation of established methods | Push back with citations and existing data | Repeating published protocols wastes resources without adding scientific value | | Requires resources beyond your capacity | Negotiate a reduced version or timeline extension | Editors may accept a partial response if you demonstrate good faith effort | | Falls outside the study's stated scope | Explain the scope limitation and suggest future work | Studies cannot address every related question, and reviewers should respect stated boundaries | This framework helps you categorize each request before deciding how to respond. The key distinction is whether the requested experiment would change the interpretation of your results or merely add supporting detail. ## Core Principles for Evaluating Experiment Requests ### Distinguish Essential from Optional Experiments Essential experiments are those that directly test your central hypothesis or address a methodological weakness that could invalidate your conclusions. Optional experiments provide additional context, explore secondary questions, or confirm findings through alternative methods. When you receive a request, ask yourself whether the experiment would change the answer to your research question. Consider whether the requested experiment addresses a gap that reviewers identified in your study design. If the experiment would fill a critical gap that undermines your conclusions, you should seriously consider performing it. If the experiment would merely add another data point to an already complete story, you can reasonably decline with explanation. ### Assess the Feasibility of the Request Feasibility includes technical difficulty, time requirements, cost, and access to necessary equipment or expertise. A request that requires a technique your laboratory does not have, a tissue sample you cannot obtain, or a timeline that would delay publication by years may be unreasonable even if the science is sound. When assessing feasibility, consider whether you can complete the experiment within a reasonable timeframe, whether you have the funding to support it, and whether you have the technical expertise to perform it correctly. If you cannot meet these requirements, you should explain the constraints in your response letter. ### Consider the Source of the Request Requests from the editor carry more weight than requests from individual reviewers. The editor makes the final decision about publication, so you should prioritize addressing the editor's concerns. If the editor specifically asks for an experiment, you should either perform it or provide a very strong justification for why it is unnecessary. Requests from reviewers are suggestions that the editor may or may not endorse. If only one reviewer requests an experiment and the editor does not mention it in the decision letter, you have more latitude to decline. If multiple reviewers request the same experiment, the editor is more likely to require it. ## The Reviewer Response Letter: Your Primary Negotiation Tool ### Structure Your Response for Clarity A well-organized response letter helps the editor evaluate your arguments efficiently. Begin with a summary of the major changes you made in response to the reviews, then address each comment individually. Number your responses to match the reviewer's comments so the editor can easily cross-reference your replies. For each comment, state whether you complied, partially complied, or declined the request. Then explain your reasoning. If you performed the experiment, describe what you did and where the results appear in the revised manuscript. If you declined, explain why the experiment is unnecessary, infeasible, or outside the scope of your study. ### Use Evidence to Support Your Arguments When you decline a request, you need to support your position with evidence. This evidence can include citations to published literature that establishes your methods, data from your existing experiments that already address the reviewer's concern, or explanations of technical limitations that make the experiment impossible. The EQUATOR Network provides reporting guidelines that help authors demonstrate their research meets established standards for transparency and completeness. Citing the appropriate reporting guideline in your response letter shows the editor that your study follows accepted practices for your field. ### Maintain a Professional Tone Your response letter should be respectful even when you disagree with a reviewer. Avoid defensive language, personal attacks, or dismissive comments about the reviewer's expertise. Focus on the science and explain your reasoning clearly. Remember that the editor may send your response back to the original reviewers for additional comment. A professional tone increases the likelihood that reviewers will accept your arguments and recommend publication. ## Practical Workflow for Handling Experiment Requests ### Step 1: Inventory All Requests Create a table listing every comment from every reviewer and the editor. For each comment, note whether it requests new experiments, requests clarification of existing methods, identifies errors, or makes suggestions for improvement. This inventory helps you track your responses and ensures you address every concern. ### Step 2: Categorize Each Request Apply the decision framework from the At a Glance table to categorize each request. Mark each request as essential, optional, or unreasonable. Essential requests require compliance or equivalent evidence. Optional requests can be addressed with explanation. Unreasonable requests can be declined with justification. ### Step 3: Plan Your Response Strategy For essential requests, plan the experiments you will perform and estimate the time and resources required. For optional and unreasonable requests, draft your explanations and gather supporting evidence. Consider whether you can propose alternative approaches that address the reviewer's underlying concern without performing the exact experiment requested. ### Step 4: Execute the Essential Experiments Perform the experiments you have committed to completing. Keep detailed records of your methods and results so you can describe them accurately in your response letter and revised manuscript. If an experiment fails or produces unexpected results, document what happened and explain the outcome in your response. ### Step 5: Draft Your Response Letter Write your response letter following the structure described above. Address every comment from your inventory, state your response for each, and provide evidence for your decisions. Review your letter for completeness and professionalism before submitting it with your revised manuscript. ### Step 6: Submit and Follow Up Submit your revised manuscript and response letter through the journal's submission system. If you do not receive a decision within a reasonable timeframe, contact the editorial office to inquire about the status of your submission. ## Records and Measurements: Documenting Your Response Process ### Maintain a Comment Response Log Create a spreadsheet or document that tracks every reviewer comment, your response, and the outcome. Include columns for the reviewer number, comment number, comment summary, your response category, your response text, and the manuscript location where you addressed the comment. This log helps you ensure completeness and provides a record if questions arise later. ### Track Time and Resources Record the time and resources you spend responding to reviewer requests. This information helps you estimate the cost of compliance and provides evidence if you need to explain why a request is infeasible. It also helps you plan future submissions by anticipating common reviewer requests in your field. ### Document Technical Limitations If you decline a request because of technical limitations, document the specific reasons. This documentation might include correspondence with equipment manufacturers, quotes from service providers, or records of failed attempts to perform the experiment. This evidence strengthens your response letter and demonstrates good faith effort. ## Common Failure Patterns in Responding to Experiment Requests ### Complying with Every Request Without Evaluation Some authors comply with every reviewer request because they fear rejection or lack confidence in their ability to negotiate. This approach wastes time and resources, delays publication, and can introduce new problems if the additional experiments produce conflicting results. Evaluate each request on its merits before deciding to comply. ### Declining Requests Without Adequate Justification The opposite failure pattern involves declining requests without providing evidence or reasoning. Editors are unlikely to accept a response that simply states an experiment is unnecessary without explaining why. Always provide specific reasons and supporting evidence for your decisions. ### Ignoring the Editor's Specific Concerns The editor's decision letter often contains guidance about which reviewer comments are most important. Ignoring this guidance and focusing only on reviewer comments can lead to rejection. Prioritize the editor's concerns and address them thoroughly. ### Submitting a Disorganized Response Letter A response letter that is difficult to follow, incomplete, or poorly organized creates a negative impression and makes the editor's job harder. Take the time to structure your response clearly and address every comment systematically. ## Welfare and Safety Context in Animal Research ### Ethical Oversight of Animal Experiments When reviewer requests involve animal experiments, you must consider whether the proposed work falls within your approved animal care and use protocols. Institutional Animal Care and Use Committees (IACUC) review and approve all animal research before it begins. Performing additional experiments outside your approved protocol violates ethical standards and may be illegal. If a reviewer requests an animal experiment that is not covered by your existing protocol, you must obtain IACUC approval before proceeding. This process takes time and may require justification of the scientific necessity for the additional work. In your response letter, you can explain that the requested experiment requires IACUC approval and describe your plan to obtain it. ### The Three Rs Framework The principles of Replacement, Reduction, and Refinement guide ethical animal research. Replacement means using non-animal methods when possible. Reduction means using the minimum number of animals necessary to achieve statistical power. Refinement means minimizing pain and distress for the animals used. When a reviewer requests additional animal experiments, consider whether the request aligns with these principles. If the requested experiment would require more animals than necessary or could be replaced with a non-animal method, you can decline the request on ethical grounds. The National Library of Medicine's Research Methods Resources provide guidance on designing studies that meet ethical standards while maintaining scientific rigor. ### Data Management for Animal Studies The NIH Data Management and Sharing Policy establishes expectations for sharing data generated from NIH-funded research. If your animal study is NIH-funded, you must comply with this policy by including a data management plan in your application and sharing your data according to that plan. Additional experiments requested by reviewers may generate new data that falls under this policy. Consider how reviewer-requested experiments affect your data management obligations. You may need to update your data management plan or allocate additional resources for data sharing. The NIH Grants and Funding website provides information about the requirements for NIH-funded research. ## Limitations and Professional Escalation Criteria ### When to Escalate to the Editor If a reviewer makes demands that are clearly unreasonable, unethical, or beyond the scope of your study, you may need to escalate the issue to the editor. Examples include requests that would require falsifying data, requests that violate ethical standards, or demands for experiments that are technically impossible. When you escalate to the editor, explain the situation clearly and provide evidence for your position. The editor has the authority to overrule reviewer demands and make a final decision about your manuscript. The COPE Core Practices support the editor's role in ensuring fair and ethical peer review. ### When to Consider Withdrawing Your Submission In rare cases, reviewer demands may be so unreasonable that continuing the peer review process is not in your best interest. If the editor supports demands that you believe are scientifically unjustified or ethically problematic, you may choose to withdraw your manuscript and submit it to another journal. Before withdrawing, consider the costs and benefits. Withdrawal delays publication and requires you to start the review process over at a new journal. However, submitting to a journal with a more reasonable review process may ultimately lead to faster publication and a better outcome. ### Seeking Institutional Support If you face unreasonable demands related to your research, your institution may provide support. Research offices, ombudspersons, and department chairs can advise you on how to handle difficult peer review situations. They may also advocate on your behalf if the situation involves ethical concerns or disputes about research conduct. ## Practical Options and Tradeoffs for Common Request Types ### Requests for Additional Replicates Reviewers often request additional replicates to strengthen statistical power. Before complying, assess whether your existing sample size is adequate for your study design. If your power analysis shows sufficient power, you can decline the request with an explanation of your statistical approach. If you decide to add replicates, consider the cost and timeline. Additional replicates may require new animal subjects, additional reagents, or extended experimental timelines. Weigh these costs against the benefit of satisfying the reviewer. ### Requests for Mechanistic Experiments Reviewers may request experiments that explore the mechanism underlying your observations. These requests can be valuable if they strengthen your conclusions, but they can also expand the scope of your study significantly. Consider whether the mechanistic experiment is necessary to support your claims or whether it addresses a question that goes beyond your study's purpose. If you decline a mechanistic experiment, explain that the mechanism is an interesting question for future research and that your current study was designed to address a different question. Suggest the specific future experiments that would address the reviewer's concern. ### Requests for Clinical or Field Validation For translational research, reviewers may request validation in clinical samples or field conditions. These experiments can be expensive, time-consuming, and difficult to arrange. If you cannot perform the requested validation, explain the barriers and describe any preliminary evidence that supports the generalizability of your findings. Consider whether you can provide alternative evidence that addresses the reviewer's concern. For example, you might provide data from a related model system or cite published studies that support your conclusions. ### Requests for Additional Analyses of Existing Data Some reviewer requests can be satisfied by reanalyzing data you already have. Before declining a request, consider whether you can address it through additional statistical analyses, subgroup analyses, or data visualization. These approaches are often faster and less expensive than new experiments. If you perform additional analyses, describe them clearly in your response letter and revised manuscript. Explain how the new analyses address the reviewer's concern and where the results appear in the manuscript. ## The Role of Reporting Guidelines in Responding to Reviewers ### Using Reporting Guidelines to Justify Your Methods Reporting guidelines provide checklists of items that should be included in research reports for specific study types. When a reviewer requests information or experiments that are not required by the relevant reporting guideline, you can cite the guideline to support your position that your manuscript meets established standards. The EQUATOR Network maintains a comprehensive database of reporting guidelines for various study types. Consult the appropriate guideline for your study design and use it to structure your response to reviewer comments about missing information or methods. ### Transparency as a Defense Against Unnecessary Requests Transparent reporting of your methods, data, and limitations reduces the likelihood that reviewers will request unnecessary experiments. When reviewers understand exactly what you did and why, they are less likely to demand additional work. The EQUATOR Network emphasizes that transparent reporting is essential for research quality and reproducibility. In your response letter, emphasize the transparency of your reporting and explain how your manuscript provides sufficient detail for readers to understand and evaluate your methods. This approach demonstrates that your study meets professional standards and that additional experiments are not needed. ## Building a Professional Network for Peer Review Support ### Consulting Colleagues and Mentors When you receive challenging reviewer requests, consult colleagues and mentors who have experience with peer review. They can provide perspective on whether a request is reasonable, suggest alternative approaches, and help you draft your response letter. Their experience can help you avoid common mistakes and navigate difficult situations. ### Learning from Published Response Letters Many journals publish response letters or provide examples of successful responses. Studying these examples can help you understand what editors expect and how successful authors handle difficult requests. Your colleagues may also share examples from their own experience. ### Maintaining Your Researcher Identity The ORCID system provides a persistent identifier that links your research activities across publications, grants, and other outputs. Maintaining your ORCID record helps you document your publication history and demonstrate your expertise when responding to reviewers. It also supports the transparency and integrity of the research enterprise. ## Common Scenarios and Recommended Responses ### Scenario 1: The Reviewer Requests an Experiment You Have Already Performed If you have already performed the requested experiment but did not include the results in your manuscript, you can comply easily by adding the data and describing it in your response letter. If the experiment was performed but the results were not significant or were excluded for other reasons, explain this in your response and describe why the data were not included. ### Scenario 2: The Reviewer Requests an Experiment That Requires a Technique You Do Not Have If the requested experiment requires a technique that is not available in your laboratory, you have several options. You can collaborate with a laboratory that has the necessary expertise, decline the request with an explanation of the technical limitation, or propose an alternative approach that addresses the same question. If you choose to collaborate, consider the timeline and cost of establishing the collaboration. If you decline, explain the specific technical barriers and describe any alternative evidence that addresses the reviewer's concern. ### Scenario 3: The Reviewer Requests an Experiment That Would Take Years to Complete Longitudinal studies can require years of data collection. If a reviewer requests a longitudinal experiment that would delay publication significantly, explain the timeline and propose alternatives. You might offer to present preliminary data, describe the study as future work, or suggest that the question be addressed in a separate publication. ### Scenario 4: The Reviewer Requests an Experiment That Conflicts with Your Conclusions If a reviewer requests an experiment that you believe would produce results conflicting with your conclusions, consider whether the experiment is scientifically valid. If the experiment is valid and would provide important information, you should consider performing it even if the results might complicate your story. If the experiment is not scientifically valid, explain why in your response. ## Frequently Asked Questions ### How do I decide whether to comply with a reviewer's request for more experiments? Evaluate whether the experiment addresses a central claim or methodological flaw in your study. If the experiment would change the interpretation of your results, you should comply or provide equivalent evidence. If the experiment would merely add supporting detail or address a question outside your study's scope, you can decline with explanation. ### What should I include in my response letter when declining a requested experiment? Explain why the experiment is unnecessary, infeasible, or outside the scope of your study. Provide specific evidence, such as citations to published literature, data from your existing experiments, or documentation of technical limitations. Maintain a professional tone and focus on the science. ### Can I propose an alternative experiment instead of the one the reviewer requested? Yes, you can propose an alternative approach that addresses the reviewer's underlying concern. Explain how the alternative experiment provides equivalent or better evidence and describe the specific advantages of your proposed approach. ### How long should I take to respond to reviewer requests for additional experiments? There is no standard timeline, but you should respond as quickly as possible while ensuring the quality of your work. If you need additional time, contact the editorial office to request an extension. Explain the reasons for the delay and provide a realistic timeline for completion. ### What if the editor requires an experiment that I believe is unnecessary? The editor has the final authority over publication decisions. If the editor requires an experiment, you should either perform it or provide a very strong justification for why it is unnecessary. If you cannot reach an agreement with the editor, you may consider withdrawing your manuscript and submitting to another journal. ### How do I handle requests for experiments that require IACUC approval? Explain in your response letter that the requested experiment requires IACUC approval and describe your plan to obtain it. Note that the approval process takes time and that you will need to submit a protocol amendment or new protocol before proceeding. ### Should I share my data when responding to reviewer requests? Data sharing is increasingly expected in scientific publishing. The NIH Data Management and Sharing Policy requires data sharing for NIH-funded research. Sharing your data can address reviewer concerns about reproducibility and reduce the need for additional experiments. ### What are my rights if a reviewer makes unethical demands? The COPE Core Practices establish ethical standards for peer review that protect authors from unfair treatment. If a reviewer makes unethical demands, such as requesting falsified data or demanding unreasonable concessions, you should escalate the issue to the editor and document the situation. ## Using the Evidence | Source | Best use in this topic | Important limitation | |---|---|---| | [Research Methods Resources](https://www.ncbi.nlm.nih.gov/books) | official guidance | Check the linked page for current local requirements | | [EQUATOR Network](https://www.equator-network.org/) | official guidance | Check the linked page for current local requirements | | [Core Practices](https://publicationethics.org/core-practices) | official guidance | Check the linked page for current local requirements | ## Related Articles - [RT-qPCR Experiments: Design Choices That Affect Interpretation](/blog/guides/rt-qpcr-experiments-design-choices-that-affect-interpretation) - [Avoiding Pseudoreplication: A Guide to True Replication in Experiments](/blog/guides/avoiding-pseudoreplication-a-guide-to-true-replication-in-experiments) - [Randomized Experiments: Why Randomization Matters](/blog/guides/randomized-experiments-why-randomization-matters) - [Adapter Contamination in Sequencing Reads: How to Diagnose and Respond](/blog/guides/adapter-contamination-in-sequencing-reads-how-to-diagnose-and-respond) - [Control Groups in Experiments: How to Choose and Use Them](/blog/guides/control-groups-in-experiments-how-to-choose-and-use-them) ## References and Further Reading - [Research Methods Resources](https://www.ncbi.nlm.nih.gov/books). National Library of Medicine. - [EQUATOR Network](https://www.equator-network.org/). EQUATOR Network. - [Core Practices](https://publicationethics.org/core-practices). Committee on Publication Ethics. - [NIH Grants and Funding](https://grants.nih.gov/). National Institutes of Health. - [ORCID for Researchers](https://info.orcid.org/researchers). ORCID. - [Data Management and Sharing Policy](https://sharing.nih.gov/data-management-and-sharing-policy). National Institutes of Health. - [NCBI Literature Resources](https://www.ncbi.nlm.nih.gov/). National Center for Biotechnology Information. - [PubMed](https://pubmed.ncbi.nlm.nih.gov/). National Library of Medicine. > This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.