PLOS One is a peer-reviewed, open-access mega-journal published by the Public Library of Science (PLOS) that accepts original research articles spanning all disciplines of science, engineering, medicine, and related social sciences and humanities, evaluating submissions primarily on methodological soundness rather than novelty, theoretical impact, or perceived importance.^[1][2] Launched in December 2006 as the first multidisciplinary open-access journal of its kind, it was established to accelerate scientific progress by removing traditional barriers to publication, such as subjective assessments of a study's potential influence, thereby enabling broader dissemination of rigorous findings.^[3][1] The journal pioneered the "mega-journal" model, which relies on article processing charges to fund operations and has resulted in high publication volumes, including over 23,000 articles in 2012 alone, making it one of the largest scientific journals by output.^[4][1] With a 2024 impact factor of 2.6 and coverage of more than 200 subject areas, PLOS One has advanced open science principles, promoting accessibility and reuse under Creative Commons licenses, though its scale has drawn scrutiny for occasional lapses in peer-review integrity, including manipulated reviews that prompted over 100 retractions in 2022 and further concerns about retraction-prone editorial practices identified in 2025.^[5][6][7][8]

History

Founding and Launch (2000-2006)

The Public Library of Science (PLOS) was established in 2000 through an open letter initiated by biomedical scientists Harold Varmus, Patrick O. Brown, and Michael Eisen, which called for the creation of a free online public library providing unrestricted access to the full text of peer-reviewed scientific journal articles in medicine and the life sciences.^[9] The letter, circulated with a deadline for action in September 2001, garnered signatures from over 34,000 scientists across 180 countries, reflecting widespread frustration with subscription-based models that restricted access to research funded largely by public sources.^[9] PLOS's founding principles emphasized returning control of scientific publishing to the research community, prioritizing accessibility and integration of knowledge over proprietary barriers imposed by commercial publishers.^[9] Following its inception, PLOS secured a major grant from the Gordon and Betty Moore Foundation to launch its first journals, beginning with PLOS Biology in October 2003 and PLOS Medicine in 2004, both operating under an open-access model funded by article processing charges (APCs) while adhering to selective editorial criteria focused on novelty and broad interest.^[10] These early ventures demonstrated the viability of nonprofit open-access publishing but highlighted challenges in financial sustainability due to limited submission volumes, as high selectivity constrained revenue.^[11] In response, PLOS conceived PLOS ONE (initially stylized as PLoS ONE) as a broader platform to publish methodologically sound research across all scientific disciplines, irrespective of perceived impact or novelty, thereby increasing throughput and APC income to support the organization's open-access mission.^[11] This shift aimed to accelerate scientific progress by evaluating papers solely on validity, ethics, and rigor during peer review, decoupling publication from subjective judgments of significance that often delayed or rejected valid work in traditional journals.^[11] PLOS ONE opened for manuscript submissions in August 2006 and published its inaugural articles on December 20, 2006, as a beta version featuring community commenting and annotation tools to foster post-publication discussion.^[3] By late 2006, the journal was receiving over 100 submissions per month, signaling early interest in its inclusive model, which licensed content under a Creative Commons Attribution (CC-BY) framework to maximize reuse while requiring authors to cover APCs of approximately $1,350 (with waivers available).^[11] Founders like Eisen positioned PLOS ONE as a radical departure from conventional publishing, arguing it empowered researchers by prioritizing empirical validity over market-driven appeal, though it initially faced skepticism regarding quality control without traditional filters.^[11]

Growth in Output and Influence (2007-2015)

Following its launch in late 2006, PLOS One experienced rapid expansion in publication output during the subsequent years. In 2007, the journal received approximately 2,500 submissions and published around 1,200 articles.^[12] By 2010, submissions had surged to nearly 13,500, with 6,800 articles accepted and published, reflecting an annual growth rate exceeding 50% in its early phase driven by its broad scope and inclusive editorial criteria that prioritized scientific validity over perceived novelty or impact.^[12] This trajectory continued, culminating in 23,464 articles published in 2012, establishing PLOS One as the world's largest academic journal by volume at that time.^[4] Output peaked in the mid-2010s, with 31,496 articles in 2013 and 30,040 in 2014, before a modest decline to 28,114 in 2015 amid increasing submissions and tighter quality controls.^[13] The journal's acceptance rate, initially around 50%, supported this scale by accommodating diverse fields from biology to social sciences, contrasting with traditional journals' selectivity.^[14] This volume growth was fueled by open-access appeal, article processing charges that covered costs without subscription barriers, and a peer-review process emphasizing soundness over groundbreaking significance, attracting researchers seeking faster publication timelines.^[4] In terms of influence, PLOS One received its first Journal Impact Factor of 4.4 in 2010 from Thomson Reuters (now Clarivate), signaling recognition in citation-based metrics despite its non-selective model.^[4] The factor rose to 4.411 the following year before stabilizing around 3.5–3.7 through 2015, reflecting high citation rates from sheer output volume rather than exclusivity.^[13] By 2012, the journal's articles amassed citations at rates competitive with established multidisciplinary outlets, influencing the rise of "mega-journal" formats and demonstrating that broad dissemination could amplify collective scientific impact without traditional prestige filters.^[4] Indexing in major databases like PubMed further enhanced visibility, with PLOS One articles comprising a growing share of open-access citations in biomedicine and beyond.^[15]

Recent Developments and Challenges (2016-2025)

In 2016, PLOS One's publication output decreased by more than 13% from the previous year, totaling around 19,000 articles, as part of a broader effort to address concerns over rapid growth and perceived dilution of quality in its high-volume model.^[16] This decline continued into 2017, with submissions falling due to factors including the journal's lack of a formal proofreading stage, which led to frequent typographical and formatting errors in published papers, eroding author confidence.^[17] In response, the journal reduced its acceptance rate to approximately 50%, aiming to prioritize methodological soundness over novelty while tightening editorial oversight.^[17] The journal's impact factor reflected these shifts, dropping from 2.806 in 2016 to 2.766 in 2017 and further to 2.6 by 2024, amid competition from specialized outlets and scrutiny of megajournal metrics.^[13][5] A significant challenge emerged in 2022 when an investigation uncovered manipulated peer reviews in over 300 submissions received since 2020, primarily involving suggested reviewers with fabricated identities or affiliations, resulting in the retraction of more than 100 papers.^[7] This incident exposed vulnerabilities in the single-blind review process for handling high submission volumes, where incentives tied to article processing charges (APCs) may have pressured efficiency over rigorous verification. To mitigate such issues, PLOS One implemented procedural enhancements, including in 2024 the introduction of an author proofing step prior to publication to catch errors missed in prior workflows, alongside plans to issue corrections for approximately 1,000 existing papers affected by inaccuracies in figures, data, or metadata.^[18] Persistent integrity concerns persisted into 2025, as evidenced by expressions of concern issued in August for four papers from a Japanese research team, citing substantial overlaps in control samples, data, and study designs across publications.^[19] These developments underscore the tension in PLOS One's business model, where reliance on APC revenue from broad-scope publishing has amplified risks of misconduct and errors, necessitating ongoing investments in detection tools and staff training despite reduced output.^[7][18]

Publication Model

Scope and Editorial Standards

PLOS ONE operates as a multidisciplinary open-access journal, accepting original research submissions across more than 200 subject areas spanning the natural sciences, medicine, engineering, and related social sciences and humanities.^[1] Unlike traditional journals that prioritize novelty, impact, or perceived significance, PLOS ONE evaluates manuscripts solely on the basis of scientific validity, including methodological rigor, data analysis, and ethical compliance, without regard for expected broader implications or alignment with prevailing trends.^[20] This broad scope aims to disseminate technically sound research irrespective of field-specific thresholds for excitement or priority, provided the work advances knowledge through reproducible methods and transparent reporting.^[2] The journal's editorial standards emphasize technical soundness over subjective assessments of importance, with decisions resting on whether the study meets criteria such as originality (not previously published in full), completeness of results, and adherence to ethical guidelines like those from the Declaration of Helsinki for human subjects or ARRIVE for animal research.^[20] Manuscripts must include all necessary data, code, and materials for verification, aligning with PLOS's commitment to reproducibility, though enforcement relies on author compliance and reviewer scrutiny rather than mandatory deposition in all cases.^[21] Editorial screening occurs prior to peer review to filter for basic fit and plagiarism, ensuring only viable submissions proceed.^[22] Peer review at PLOS ONE employs a single-blind model, where reviewers assess technical validity, ethical integrity, and clarity, but not novelty or potential citations, with editors making final accept/reject calls after typically 1-3 rounds of revisions.^[22] Reviewers are selected for expertise matching the manuscript's domain, and the process targets a decision within 30-60 days post-submission, prioritizing rigor to uphold publication standards amid the journal's high volume—over 20,000 articles annually as of recent years.^[23] While this framework promotes inclusivity for valid but non-groundbreaking work, it has drawn scrutiny for potentially diluting selectivity compared to impact-focused outlets, though official policies maintain that acceptance hinges on verifiable soundness rather than prestige.^[24]

Peer Review Process

PLOS One utilizes a single-anonymized peer review process, wherein reviewers are aware of the authors' identities, but authors remain unaware of the reviewers' identities.^[22] Manuscripts undergo an initial editorial screening by the journal staff to verify adherence to submission guidelines, ethical standards, and basic scientific merit before assignment to an Academic Editor, an independent expert in the relevant field.^[22] The Academic Editor then solicits reviews from typically two or more external experts, who evaluate the submission within a 10-day timeframe, with journal follow-ups for delays.^{[23] [22]} Reviewers assess manuscripts primarily for scientific soundness and validity, focusing on the appropriateness of study design, methodological rigor, data analysis quality, ethical compliance, and whether conclusions logically follow from the results, rather than on novelty, perceived impact, or appeal to a niche audience.^[23] This criterion aligns with the journal's broad-scope model, aiming to publish technically valid research regardless of its potential citation impact.^[22] The Academic Editor synthesizes reviewer feedback to recommend one of four decisions: accept, minor revision, major revision, or reject, with the journal editor making the final call.^[22] Revised manuscripts may undergo additional review rounds if substantive changes are required.^[22] The average time to first editorial decision is about 43 days from submission, though this varies based on reviewer responsiveness and complexity.^[22] Independent data indicate a median first review round of around 3.1 months and total handling time for accepted papers of 4.6 months.^[25] PLOS One encourages transparency by offering authors the option to publish the anonymized peer review history, including reviewer comments and author responses, alongside the accepted article.^[22] Reviewers must declare conflicts of interest, maintain confidentiality, and provide constructive, evidence-based critiques.^[23]

Open Access Policies and Licensing

PLOS One operates under a fully open access model, making all published articles freely available to readers worldwide immediately upon publication without embargo periods or subscription barriers. This approach aligns with the Public Library of Science (PLOS) mission to accelerate scientific progress by removing paywalls and promoting unrestricted dissemination of research findings.^[1][26] Articles in PLOS One are licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license, which permits users to copy, distribute, display, and perform the work, as well as make derivative works, for any purpose, including commercial uses, provided that appropriate credit is given to the original authors and source. Authors retain copyright ownership of their work but grant PLOS and the public a perpetual, worldwide, non-exclusive license to publish and disseminate the article under this framework. This licensing policy explicitly allows reuse of article content in whole or in part, fostering maximal reusability while requiring proper attribution to prevent misrepresentation.^[27][28][1] The open access model is sustained primarily through article processing charges (APCs) paid by authors or their institutions upon acceptance, with standard fees set at $2,382 for most article types as of 2023, though reduced rates apply to specific formats like Registered Reports ($1,780 for protocols). PLOS One offers fee assistance programs, including full waivers for corresponding authors from low- or middle-income countries based on Research4Life eligibility criteria, and participates in transformative agreements with institutions to cover APCs collectively. Supplementary materials, such as figures and data, are also made openly available under compatible licenses no more restrictive than CC BY, ensuring comprehensive accessibility.^[29][21][30]

Operations and Business Model

Funding via Article Processing Charges

PLOS One operates as an open-access journal, with its primary funding derived from article processing charges (APCs) paid by authors or their institutions upon acceptance of manuscripts. These charges cover the costs of peer review, editorial management, production, hosting, and long-term archiving, eliminating reliance on subscription fees and enabling immediate free access to published content.^[29] The APC model aligns with PLOS's mission to promote open science by shifting costs from readers to producers of research.^[31] As of 2025, the standard APC for most research articles in PLOS One is $2,382 USD, with reduced fees for specific article types such as Registered Report Protocols at $1,780 and Lab Protocols at $1,477.^{[29] [32]} This fee structure has evolved over time; for instance, earlier amounts were lower, around $1,695 in the early 2010s, reflecting increases tied to operational costs and inflation.^[33] APC revenues have historically subsidized PLOS's broader portfolio, including higher-cost journals, though PLOS One's high volume—publishing tens of thousands of articles annually—makes it a key revenue driver.^[33] To mitigate financial barriers, PLOS One provides waivers and discounts through programs like Research4Life, which fully or partially waives APCs for corresponding authors from eligible low- and middle-income countries, and the PLOS Fee Assistance (PFA) program for those unable to pay.^{[29] [32]} Institutional partnerships, such as read-and-publish agreements or flat-fee models, further reduce or eliminate APCs for affiliated authors; for example, under Community Action Publishing (CAP), participating institutions pay an annual membership fee to cover unlimited publications without per-article charges.^{[29] [34]} These alternatives, introduced experimentally around 2020, aim to address equity issues in APC-based funding while maintaining journal sustainability, with adoption growing since 2021.^[35] In 2024, PLOS received a $3.3 million grant from the Gates Foundation to accelerate transitions toward APC-free models for certain funders, though APCs remain central to PLOS One's operations.^[36] Critics of the APC model, including some in scholarly publishing, argue it can incentivize volume over rigorous quality control, as revenue depends on acceptance rates rather than selectivity; PLOS One's broad scope and non-rejection-for-lack-of-novelty policy exemplify this approach, which has drawn scrutiny despite empirical evidence of maintained peer review standards.^[37] Nonetheless, APC-funded open access has enabled PLOS One to publish over 200,000 articles since 2006, democratizing access while generating revenues exceeding $100 million annually across PLOS journals by the early 2020s.^[38]

Editorial Structure and Management

PLOS One's editorial leadership is headed by Editor-in-Chief Emily Chenette, who oversees the journal's overall editorial direction and operations, supported by Deputy Editor-in-Chief George Vousden.^[39][40] A team of staff editors manages specific divisions, including Laura Kelly for Behavioral and Social Sciences and Neuroscience, ensuring coordinated handling of submissions across disciplines.^[39] The journal relies on a large cadre of volunteer Academic Editors—approximately 7,000 active members—who are established principal investigators and group leaders with extensive publication records.^[14][41] These editors are assigned manuscripts based on expertise, overseeing the peer review process, including reviewer selection, evaluation of reports, and rendering final publication decisions.^[22][41] Section Editors provide additional oversight within specialized fields, while the system incorporates Editorial Manager software for workflow management, allowing editors to track invitations, reviews, and decisions.^[41][42] Management emphasizes scalability for a high-volume megajournal, with initial editorial screening for completeness and scope fit preceding assignment to Academic Editors.^[22] However, the decentralized structure has faced challenges, including anomalous editor activity and decision biases detected through statistical analysis of handling patterns, prompting calls for enhanced oversight mechanisms like activity monitoring and editor performance documentation.^[14] In August 2025, an investigation identified retraction-prone editors among the volunteer pool, underscoring the difficulties of managing thousands of academics with limited central staff support—around 22 full-time employees.^[8] PLOS addresses these through policies on ethical publishing, conflict-of-interest declarations, and periodic board rotations, though the model's reliance on distributed expertise prioritizes volume over centralized control.^[43][14]

Indexing, Metrics, and Performance Indicators

PLOS One is indexed in major scientific databases, including Science Citation Index Expanded (Web of Science), Scopus, PubMed Central, MEDLINE, and Directory of Open Access Journals (DOAJ), facilitating broad discoverability of its articles.^[1][44] It is also covered by multidisciplinary services such as AGRICOLA and Biological Abstracts, though coverage varies by discipline.^[1] The journal's 2024 Journal Impact Factor (JIF), as reported by Clarivate Analytics, stands at 2.6, with a 5-year JIF of 3.2; these metrics reflect citations to recent articles relative to citable items published in the prior two or five years, respectively.^[45] In Scopus metrics, PLOS One has a CiteScore of 5.6 (covering 2018–2023 citations) and a SCImago Journal Rank (SJR) of 0.803, placing it in Q1 for multidisciplinary sciences based on normalized citation impact.^[46][15] Its h-index is 467, indicating 467 articles each cited at least 467 times, underscoring cumulative influence since its 2006 launch.^[15] Performance indicators reveal high output volumes, with PLOS One publishing a peak of 23,464 articles in 2012 and exceeding 200,000 total articles by 2017, though annual submissions and acceptances have since moderated amid editorial tightening.^[4] Recent acceptance rates hover around 48–49%, down from historical highs near 70%, reflecting a focus on methodological soundness over novelty; desk rejection rates without peer review are approximately 23%.^[1] Median time from acceptance to publication is 11–13 days, prioritizing rapid dissemination in its open-access model.^[1]

Reception and Impact

Achievements in Scientific Accessibility

PLOS One's adoption of an immediate open access model upon its launch on December 11, 2006, eliminated subscription paywalls, enabling unrestricted global access to full-text articles and supplementary materials for researchers, educators, and the public alike.^[1] Content is distributed under a Creative Commons Attribution (CC BY) license, which permits copying, redistribution, and adaptation for any purpose, including commercial use, provided proper attribution is given, thereby supporting educational reuse, meta-analyses, and innovation in under-resourced fields.^[47] This approach has sustained a high publication volume, reaching the milestone of its 100,000th article by June 2014, creating an expansive, freely available archive spanning over 200 subject areas in science, engineering, medicine, and social sciences.^[48][1] Comprehensive indexing in major databases such as PubMed, Scopus, and Web of Science ensures broad discoverability, while article-level metrics track views, downloads, citations, and altmetrics, revealing widespread engagement; for example, in 2022, PLOS journals collectively received over 100,000 media mentions, amplifying real-world dissemination.^[1] Open access in PLOS One yields an 8.6% citation advantage over non-open access equivalents, driven by enhanced visibility and reduced access barriers, particularly for authors and readers in low- and middle-income countries.^[49] The journal's open science mandates further bolster data and process accessibility: since March 2014, data availability statements are required, with 93.7% of 21,793 articles in 2018 including them and many providing links to reusable datasets in public repositories, facilitating reproducibility and secondary analyses.^[50] Public peer review histories, available for thousands of articles, promote transparency in editorial decisions.^[51] High-performing articles demonstrate robust public interest, with download-to-view ratios reaching 49.8% in select cases, underscoring the model's efficacy in bridging academic and non-academic audiences.^[52] These elements collectively prioritize empirical dissemination over prestige-driven selectivity, enabling smaller research communities to contribute and access validated findings without institutional privilege.^[53]

Criticisms of Methodological and Quality Standards

Critics have argued that PLOS One's criterion of assessing manuscripts solely for technical soundness and methodological validity, rather than novelty or broader significance, enables the publication of research with limited scientific advancement, thereby compromising overall journal quality. This approach, while intended to democratize access, has been linked to a historically high acceptance rate—approximately 70% in earlier years, stabilizing around 48-50% by 2023—which exceeds that of more selective journals and raises concerns about insufficient filtering of subpar work.^[1][54] Empirical analyses have identified irregularities in the peer review process, including anomalous editor activity where a small subset of highly active editors exhibit decision biases favoring acceptance, with some manuscripts accepted in as little as seven days, potentially indicating lax oversight.^[14] A study of over 88,000 PLOS One articles found that reliance on author-suggested reviewers substantially inflates acceptance probabilities—by up to 20 percentage points compared to editor-suggested panels—suggesting systemic incentives for leniency that undermine methodological rigor.^[55] Further quality concerns stem from documented failures in detecting manipulated peer reviews, culminating in PLOS One's 2022 decision to retract over 100 papers due to fabricated reviewer comments and conflicts of interest, exposing vulnerabilities in verification protocols.^[7] A 2025 PNAS analysis of open datasets estimated that at least 2% of PLOS One's published articles may involve fraud or papermill activity, higher than in some comparator journals, attributing this to scalable peer review rings exploiting the journal's volume-driven model.^[56] Reproducibility audits of PLOS One papers, such as those employing multilevel modeling, have revealed inconsistent reporting of data and code, hindering verification of methodological claims despite journal policies mandating transparency.^[57] These issues have prompted accusations of editorial stringency erosion, with investigations identifying retraction-prone editors whose handling correlated with higher rates of subsequent withdrawals, pointing to inadequate initial quality controls.^[8] While PLOS One maintains a multi-stage screening process, critics contend that the emphasis on rapid throughput over exhaustive scrutiny—evidenced by desk rejection rates below 25%—prioritizes quantity, fostering a repository of variable methodological depth rather than a bastion of elite standards.^[1][14]

Broader Influence on Open Science

PLOS ONE's launch in December 2006 marked a pivotal shift in scholarly publishing by establishing the mega-journal model, which prioritizes scientific rigor over novelty or perceived impact, thereby broadening the criteria for publication and accelerating the adoption of open access across disciplines. This approach demonstrated that high-volume, multidisciplinary open access journals could sustain operations through article processing charges while making research freely available, influencing the creation of subsequent mega-journals such as Scientific Reports in 2011. By 2013, PLOS ONE had published over 50,000 articles, underscoring the scalability of this model and pressuring traditional subscription-based publishers to experiment with hybrid and fully open access formats.^[58][59] The journal advanced open science by implementing early and stringent data sharing mandates, requiring authors to include data availability statements starting March 1, 2014, which facilitated greater transparency and reproducibility. This policy, applied to all PLOS journals including PLOS ONE, correlated with increased data deposition in repositories and higher citation rates for compliant articles, as evidenced by analyses showing articles with shared data receiving up to 69% more citations. Such requirements set precedents for other publishers, contributing to widespread adoption of data policies in high-impact journals and fostering a cultural shift toward routine data reuse in research validation.^[60][61] Beyond direct policies, PLOS ONE's parent organization developed tools like Open Science Indicators (OSIs) to quantify practices such as data sharing and preregistration at scale, enabling systematic evaluation of open science adoption across the literature. In 2023, PLOS collaborated with 80 stakeholders from 20 biomedical institutions to define 19 key open science practices, providing a framework for global monitoring and incentivization. These initiatives have informed funder mandates and institutional assessments, promoting equitable access and reducing barriers in under-resourced regions, though challenges like uneven compliance persist.^[62][63]

Controversies

Peer Review Manipulation and Retractions

In August 2022, PLOS ONE initiated retractions of more than 100 published papers after investigations revealed manipulations of the peer review process, including the use of peer review rings and fake reviews.^[7] The action began with the retraction of 20 articles on August 3, 2022, stemming from an editor's detection of an unusual spike in submissions—primarily in agricultural research from authors in Iran—among over 300 manuscripts received since 2020, approximately 100 of which had been published.^{[7] [8]} These manipulations involved coordinated efforts to suggest or impersonate reviewers, compromising the integrity of the evaluation process.^[64] A 2025 analysis of retraction notices at PLOS ONE found that nearly one-third of all retracted papers could be traced to decisions by just 45 editors, with all such notices citing peer-review integrity concerns and potential manipulation.^[8] This pattern highlighted vulnerabilities in handling high submission volumes, where organized fraud networks exploited editorial workflows, including brokerage roles in fake paper production and review rigging.^[65] PLOS ONE responded by conducting prior investigations into paper mill activities and peer review fraud, implementing enhanced safeguards such as improved reviewer verification and detection of anomalous submission patterns.^{[56] [66]} While PLOS ONE's retraction rate reflects its scale as a megajournal processing thousands of papers annually, these incidents underscore broader challenges in peer review scalability, with manipulation tactics evolving to include AI-assisted fraud and coordinated author-editor collusion.^[8] The journal has since added measures like author proof steps for corrections and expressions of concern for suspicious data overlaps linked to review flaws, though critics note that systemic reliance on voluntary editorial oversight amplifies risks from bad-faith actors.^[18][19]

Handling of Ideologically Sensitive Papers

In April 2015, PLOS One faced public scrutiny following the disclosure of a peer review containing remarks perceived as sexist toward the manuscript's female authors, Fiona Ingleby and colleagues, whose submission examined sex-biased gene expression in Drosophila melanogaster. The anonymous reviewer suggested that the paper's perceived shortcomings might stem from the authors' gender and youth, stating, "Perhaps it is because they are young female scientists that they fail to understand...," and recommended adding a male co-author to enhance credibility.^[67] The review's tone, including patronizing comments on the authors' competence, sparked widespread condemnation on social media and in scientific outlets, amplifying concerns over gender bias in peer review processes.^[68] PLOS One responded swiftly by permanently barring the reviewer from future contributions and prompting the resignation of the academic editor, who had recommended rejection partly based on the review despite its unprofessional elements.^[67] The journal then expedited a re-review by new referees, leading to the paper's acceptance and publication in June 2015.^[69] This handling underscored PLOS One's policy against ad hominem or discriminatory comments in reviews, aligning with its editorial guidelines emphasizing objective scientific assessment, though critics argued the response prioritized public perception over substantive debate on the review's validity. Beyond this incident, PLOS One has published numerous papers exploring ideologically charged topics, such as innate sex differences in cognition, personality, and occupational aspirations, without documented retractions attributable to ideological opposition. Examples include studies documenting greater male variability in cognitive abilities across 65 nations^[70] and global sex differences in Big Five personality traits.^[71] These publications reflect the journal's "sound science" criterion, which prioritizes methodological rigor over alignment with prevailing social narratives, potentially mitigating biases observed in more specialized outlets. No verified cases exist of PLOS One retracting articles solely for challenging orthodox views on gender, race, or related sensitivities, in contrast to its retractions for data fabrication or peer review fraud, which number over 100 in some batches.^[7] This approach occurs amid broader academic environments where surveys indicate self-censorship among researchers on topics like sex differences due to anticipated backlash, with 58% of social psychologists in one study avoiding politically sensitive hypotheses.^[72] PLOS One's open-access model and decentralized editorial structure may facilitate publication of heterodox findings if empirically supported, though reliance on volunteer reviewers—often from ideologically homogeneous fields—raises untested risks of implicit filtering. Mainstream media amplification of the 2015 case, framing it unequivocally as sexism without equivalent scrutiny of analogous biases against male-centric or conservative-leaning submissions, highlights selective outrage patterns in scientific discourse.^[73]

Responses to Criticisms and Policy Reforms

In response to widespread criticisms regarding peer review manipulation, PLOS One implemented batch retractions, including over 100 articles in 2022 linked to compromised review processes, primarily in agricultural research submissions.^[7] To address systemic vulnerabilities such as paper mills, the journal introduced a policy in February 2023 explicitly targeting manipulation of the publication process, which includes fabrication or sale of content, authorship irregularities, and peer review interference; violations result in rejection or retraction, with investigations guided by confidentiality to protect ongoing inquiries.^[74] Complementing this, a parallel policy on standards for professional conduct was enacted, mandating respectful interactions among authors, reviewers, and staff, with sanctions for abusive behavior or excessive resubmissions.^[74] Following an audit revealing a backlog of minor errors, PLOS One announced in March 2024 plans to issue corrections to approximately 1,000 published papers for issues like author affiliations, references, and data statements, attributing the accumulation to resource prioritization rather than lapses in quality control.^[18] As a reform, the journal added a mandatory author proofing step prior to publication—the first such requirement in its history—to preempt similar oversights, despite potential delays in high-volume output.^[18] In handling specific incidents of unprofessional peer review, such as a 2015 case involving sexist comments recommending male co-authors for female researchers, PLOS One removed the reviewer from its database, dismissed the review, reassigned the manuscript, and requested the academic editor's resignation, while publicly condemning the remarks.^[67] Addressing broader critiques, including a 2025 PNAS study and Nature analysis identifying 45 editors linked to nearly one-third of the journal's retractions, PLOS One highlighted preemptive measures like enhanced submission screening since 2021, algorithmic editor assignments, and collaborations with bodies such as COPE and STM Integrity Hub, which facilitated prior editor removals and article retractions before the studies' release.^[56] These reforms underscore ongoing refinements to editorial integrity, including vetting processes and rapid misconduct probes, without altering the journal's core criterion of scientific validity over novelty.^[56]