Peer review (known as refereeing in some academic fields) is a process of subjecting an author's scholarly work or ideas to the scrutiny of others who are experts in the field. It is used primarily by publishers, to select and to screen submitted manuscripts, and by funding agencies, to decide the awarding of monies for research. The peer review process is aimed at getting authors to meet the standards of their discipline and of science generally. Publications and awards that have not undergone peer review are likely to be regarded with suspicion by scholars and professionals in many fields.

A rationale for peer review is that it is rare for an individual author or research team to spot every mistake or flaw in a complicated piece of work. This is not because deficiencies represent needles in a haystack, but because in a new and perhaps eclectic intellectual product, an opportunity for improvement may stand out only to someone with special expertise or experience. Therefore showing work to others increases the probability that weaknesses will be identified, and with advice and encouragement, fixed. The anonymity and independence of reviewers is intended to foster unvarnished criticism and discourage cronyism in funding and publication decisions.

In addition, since the reviewers are normally selected from experts in the fields discussed in the article, the process of peer review is considered critical to establishing a reliable body of research and knowledge. Scholars reading the published articles can only be expert in a limited area; they rely to some degree on the peer-review process to provide reliable and credible research which they can build upon for subsequent or related research. As a result, significant scandal ensues when an author is found to have falsified the research included in an article, as many other scholars, and the field of study itself, has relied upon that research. (See below peer review and fraud.)

A publisher sends advance copies of an author's work or ideas to one or more others who are experts in the field. These referees each return an evaluation of the work, including suggestions for improvement, to an editor or other intermediary (typically, most of the referees' comments are eventually seen by the author as well). Evaluations usually include an explicit recommendation of what to do with the manuscript or proposal, often chosen from a menu provided by the journal or funding agency. Most recommendations are along the lines of the following:

• to unconditionally accept the manuscript or proposal,
• to accept it in the event that its authors improve it in certain ways,
• to reject it, but encourage revision and invite resubmission
• to reject it outright.

During this process, the role of the referees is advisory, and the editor is under no formal obligation to accept the opinions of the referees. Furthermore, in scientific publication, the referees do not act as a group, do not communicate with each other, and typically are not aware of each other's identities. There is usually no requirement that the referees achieve consensus. Thus the group dynamics is substantially different from that of a jury. In situations where the referees disagree about the quality of a work, there are a number of strategies for reaching a decision.

Traditionally reviewers would remain anonymous to the authors, but this is slowly changing. In some academic fields most journals now offer the reviewer the option of remaining anonymous or not; papers sometimes contain, in the acknowledgments section, thanks to (anonymous or named) referees who helped improve the paper.

At a journal or book publisher, the task of picking reviewers typically falls to an editor. When a manuscript arrives, an editor solicits reviews from scholars or other experts who may or may not have already expressed a willingness to referee for that journal or book division. Granting agencies typically recruit a panel or committee of reviewers in advance of the arrival of applications.

In some disciplines there exist refereed venues (such as conferences and workshops). To be admitted to speak, scholars and scientists must submit papers (generally short, often 15 pages or less) in advance. These papers are reviewed by a "program committee" (the equivalent of an editorial board), who generally requests inputs from referees. The hard deadlines set by the conferences tend to limit the options to either accept or reject the paper.

Typically referees are not selected from among the authors' close colleagues, relatives, or friends. Referees are supposed to inform the editor of any conflict of interests that might arise. Journals or individual editors often invite a manuscript's authors to name people whom they consider qualified to referee their work. Authors are sometimes also invited to name natural candidates who should be disqualified, in which case they may be asked to provide justification (typically expressed in terms of conflict of interest). In some disciplines, scholars listed in an "acknowledgments" section are not allowed to serve as referees (hence the occasional practice of using this section to disqualify potentially negative reviewers).

Editors solicit author input in selecting referees because academic writing typically is very specialized. Editors often oversee many specialties, and may not be experts in any of them, since editors may be full time professionals with no time for scholarship. But after an editor selects referees from the pool of candidates, the editor typically is obliged not to disclose the referees' identities to the authors, and in scientific journals, to each other. Policies on such matters differ between academic disciplines.

Scientific journals observe this convention universally. The two or three chosen referees report their evaluation of the article and suggestions for improvement to the editor. The editor then relays the bulk of these comments to the author (some comments may be designated as confidential to the editor), meanwhile basing on them his or her decision whether to publish the manuscript. When an editor receives very positive and very negative reviews for the same manuscript, the editor often will solicit one or more additional reviews as a tie-breaker.

As another strategy in the case of ties, editors may invite authors to reply to a referee's criticisms and permit a compelling rebuttal to break the tie. If an editor does not feel confident to weigh the persuasiveness of a rebuttal, the editor may solicit a response from the referee who made the original criticism. In rare instances, an editor will convey communications back and forth between authors and a referee, in effect allowing them to debate a point. Even in these cases, however, editors do not allow referees to confer with each other, and the goal of the process is explicitly not to reach consensus or to convince anyone to change their opinions. Some medical journals, however (usually following the open access model), have begun posting on the Internet the pre-publication history of each individual article, from the original submission to reviewers' reports, authors' comments, and revised manuscripts.

After reviewing and resolving any potential ties, there may be one of three possible outcomes for the article. The two simplest are outright rejection and unconditional acceptance. In most cases, the authors may be given a chance to revise, with or without specific recommendations or requirements from the reviewers.

Recruiting referees is a political art, because referees are not paid, and reviewing takes time away from the referee's main activities, such as his or her own research. To the would-be recruiter's advantage, most potential referees are authors themselves, or at least readers, who know that the publication system requires that experts donate their time. Editors are at a special advantage in recruiting a scholar when they have overseen the publication of his or her work, or if the scholar is one who hopes to submit manuscripts to that editor's publication in the future. Granting agencies, similarly, tend to seek referees among their present or former grantees. Serving as a referee can even be a condition of a grant, or professional association membership.

Another difficulty that peer-review organizers face is that, with respect to some manuscripts or proposals, there may be few scholars who truly qualify as experts. Such a circumstance often frustrates the goals of reviewer anonymity and the avoidance of conflicts of interest. It also increases the chances that an organizer will not be able to recruit true experts – people who have themselves done work like that under review, and who can read between the lines. Low-prestige journals and granting agencies that award little money are especially handicapped with regard to recruiting experts.

Finally, anonymity adds to the difficulty in finding reviewers in another way. In scientific circles, credentials and reputation are important, and while being a referee for a prestigious journal is considered an honor, the anonymity restrictions make it impossible to publicly state that one was a referee for a particular article. However, credentials and reputation are principally established by publications, not by refereeing; and in some fields refereeing may not be anonymous.

The process of peer review does not end after a paper completes the peer review process. After being put to press, and after 'the ink is dry', the process of peer review continues in journal clubs. Here groups of colleagues review literature and discuss the value and implications it presents. Journal clubs will often send letters to the editor of a journal, or correspond with the editor via an on-line journal club. In this way, all 'peers' may offer review and critique of published literature.

Peer review can be rigorous, in terms of the skill brought to bear, without being highly stringent. An agency may be flush with money to give away, for example, or a journal may have few impressive manuscripts to choose from, so there may be little incentive for selection. Conversely, when either funds or publication space is limited, peer review may be used to select an extremely small number of proposals or manuscripts.

Often the decision of what counts as "good enough" falls entirely to the editor or organizer of the review. In other cases, referees will each be asked to make the call, with only general guidance from the coordinator on what stringency to apply.

Very general journals such as Science, Nature have extremely stringent standards for publication, and will reject papers which report good quality scientific work that they feel are not breakthroughs in the field. Such journals generally have a two-tier reviewing system. In the first stage, members of the editorial board verify that the paper's findings -- if correct -- would be ground-breaking enough to warrant publication in Science or Nature. Most papers are rejected at this stage. Papers that do pass this 'pre-reviewing' are sent out for in-depth review to outside referees. Even after all reviewers recommend publication and all reviewer criticisms/suggestions for changes have been met, papers may still be returned to the authors for shortening to meet the journal's length limits. With the advent of electronic journal editions, overflow material may be stored in the journals online Electronic Supporting Information archive.

A similar emphasis on novelty exists in general area journals such as the Journal of the American Chemical Society (JACS). However, these journals generally send out all papers (except blatantly inappropriate ones) for peer reviewing to multiple reviewers. The reviewers are specifically queried not just on the scientific quality and correctness, but also on whether the findings are of interest to the general area readership (chemists of all disciplines, in the case of JACS) or only to a specialist subgroup. In the latter case, the recommendation is usually for publication in a more specialized journal. The editor may offer to authors the option of having the manuscript and reviews forwarded to such a journal with the same publishers (e.g., in the example given, Journal of Organic Chemistry, Journal of Physical Chemistry, Inorganic Chemistry,...). if the reviewer reports warrant such a decision (i.e., they boil down to "Great work, but too specialized for JACS: publish in ..."), the editor of such a journal may accept the forwarded manuscript without further reviewing.

Some general area journals, such as Physical Review Letters, have strict length limitations. Others, such as JACS, have Letters and Full Papers sections: the Letters sections have strict length limits (two journal pages in the case of JACS) and special novelty requirements.

More specialized scientific journals such as the aforementioned chemistry journals, Astrophysical Journal, and Physical Review A/B/C/D/E/... use peer review primarily to filter out obvious mistakes and incompetence, as well as (borderline) plagiarism, overly derivative work, and straightforward applications of known methods. Different publication rates reflect these different criteria: Nature publishes about 5 percent of received papers, while Astrophysical Journal publishes about 70 percent. The different publication rates are also reflected in the size of the journals.

Screening by peers may be more or less laissez-faire depending on the discipline. Physicists, for example, tend to think that decisions about the worthiness of an article are best left to the marketplace. Yet even within such a culture peer review serves to ensure high standards in what is published. Outright errors are detected and authors receive both edits and suggestions.

To preserve the integrity of the peer-review process, submitting authors may not be informed of who reviews their papers; sometimes, they might not even know the identity of the associate editor who is responsible for the paper. In many cases, alternatively called "masked" or "double-masked" review, the identity of the authors is concealed from the reviewers, lest the knowledge of authorship bias their review; in such cases, however, the associate editor responsible for the paper does know who the author is. Sometimes the scenario where the reviewers do know who the authors are is called "single-masked" to distinguish it from the "double-masked" process. In double-masked review, the authors are required to remove any reference that may point to them as the authors of the paper.

While the anonymity of reviewers is almost universally preserved, double-masked review (where authors are also anonymous to reviewers) is not always employed. Critics of the double-masked process point out that, despite the extra editorial effort to ensure anonymity, the process often fails to do so, since certain approaches, methods, notations, etc., may point to a certain group of people in a research stream, and even to a particular person. Proponents of the single-masked process argue that if the reviewers of a paper are unknown to each other, the associate editor responsible for the paper can easily verify the objectivity of the reviews. Single-masked review is thus strongly dependent upon the goodwill of the participants.

One of the most common complaints about the peer review process is that it is slow, and that it typically takes several months or even several years in some fields for a submitted paper to appear in print. In practice, much of the communication about new results in some fields such as astronomy no longer takes place through peer reviewed papers, but rather through preprints submitted onto electronic servers such as arXiv.org.

In addition, some sociologists of science argue that peer review makes the ability to publish susceptible to control by elites and to personal jealousy. The peer review process may suppress dissent against "mainstream'" theories. Reviewers tend to be especially critical of conclusions that contradict their own views, and lenient towards those that accord with them. At the same time, elite scientists are more likely than less established ones to be sought out as referees, particularly by high-prestige journals or publishers. As a result, it has been argued, ideas that harmonize with the elite's are more likely to see print and to appear in premier journals than are iconoclastic or revolutionary ones, which accords with Thomas Kuhn's well-known observations regarding scientific revolutions.

However, others have pointed out that there is a very large number of scientific journals in which one can publish, making control of information difficult. In addition, the decision-making process of peer review, in which each referee gives his opinions separately and without consultation with the other members, is intended to mitigate some of these problems.

While some believe passing the peer-review process is a certification of validity, those who study that process often hold a far more skeptical view. Drummond Rennie, deputy editor of Journal of the American Medical Association is an organizer of the International Congress on Peer Review and Biomedical Publication, which has been held every four years since 1986 [4]. He remarks, "There seems to be no study too fragmented, no hypothesis too trivial, no literature too biased or too egotistical, no design too warped, no methodology too bungled, no presentation of results too inaccurate, too obscure, and too contradictory, no analysis too self-serving, no argument too circular, no conclusions too trifling or too unjustified, and no grammar and syntax too offensive for a paper to end up in print." [5]

Obviously, for those who continue to have their essays rejected, this simply isn't the case. Solidly written, well researched ideas are not seeing their way into "mainstream" journals. Consider, for example, the papers of Professor Tom Van Flandern [[6]] who disagrees with Special and General Relativity or those who do not support Stratfordians in their belief that a rustic hempen homespun wrote the works of "William Shakespeare," a belief based solely on the attribution to him in an advertisement placed in the First Folio [[7]] in 1623, seven years after the rustic's death.

A Folio which contained, for example, several plays, including Othello (1622)that had been modified on the face of editions published AFTER the actor's death, with said changes universally taken to be the Author's. This advertisement has been proven false in every other particular. Moreover the FF certifies to a literary canon of 36 plays only, and which therefore explicitedly excluded all of Shakespeare's poems and many of the plays now claimed as his by Stratfordians, such as Periclies and Two Noble Kinsmen.

For scholars suffering from this sort of ostracism, peer review is best thought of as a process of reviewing papers from a dock or a "pier." Perhaps it should be defined as a having a member of the "peerage" review one's paper?

This would be bad news for Stratfordians, since it was Sir Hugh Trevor Roper who wrote that the state of present scholarship on the connection between the rustic Stratfordian and the Author is not only subject to question, but scholarly doubt. Roper, perhaps the leading academic historian of the 20th Century, was created a life peer in 1979.

Sir Hugh noted, "of all the immortal geniuses of literature, none is personally so elusive as William Shakespeare." He continued: "It is exasperating and almost incredible that he should be so. After all, he lived in the full daylight of the English Renaissance, in the well-documented reigns of Queen Elizabeth and King James I…Since his death, and particularly in the last century, he has been subjected to the greatest battery of organized research that has ever been directed upon a single person. Armies of scholars, formidably equipped, have examined all the documents that could possibly contain at least a mention of Shakespeare's name. One hundredth of this labor applied to one of his insignificant contemporaries would be sufficient to produce a substantial biography. And yet the greatest of all Englishmen, after this tremendous inquisition, still remains so close to a mystery that even this identity can still be doubted."

And that's not all Sir Hugh Trevor Roper had to say about what should be a wide open question:

"During his lifetime nobody claimed to know him. Not a single tribute was paid to him at his death. As far as the records go, he was uneducated, had no literary friends, possessed at his death no books, and could not write. It is true, six of his signatures have been found, all spelt differently; but they are so ill-formed that some graphologists suppose the hand to have been guided. Except for these signatures, no syllable of writing by Shakespeare has been identified. Seven years after his death, when his works were collected and published, the other poets claimed to have known him, a portrait of him was painted. The unskillful artist has painted the blank face of a country oaf." ("What's in a Name," Realities [November 1962] 41.)

Unfortunately "peer review" is a process that suffers from abuse by established "cliques." Worse it is not a process that assures future success. Ideas, discoveries and research should be evaluated on merit, not on whether or not they have been approved of by a disinterested circle of experts in any give field. That merit will only become apparent over time, when the ideas, discoveries and research has had an opportunity to work itself into the fabric of intellectual life and/or technology, as Schopenhauer [[8]] pointed out several centuries ago. Academics and corporations who fear the publication of alternative views or technologies generally have good reasons for that fear. Reasons that are either anti-intellectual or anti-competitive. As Charles Darwin [[9]]pointed out it is "false evidence," not "false ideas" that are counterproductive.

Peer review failures are common but are not usually acknowledged by journal editors.^{[citation needed]} Editors seldom publish retractions or corrections for flawed articles. However, they often allow readers to point out an article's flaws in a letters section. In some cases, they refuse to even publish letters in order to avoid embarrassment to the author, journal, and peer reviewers. Corrections in published letters are often ineffective.

Acknowledged deviations from the idealized outcome of the peer review process are readily observable at both extremes: successful without peer review prior to publication on the one hand; and unsuccessful despite peer review on the other extreme. Among the widely known examples of work later acknowledged to be successful without peer review prior to publication is that of Watson and Crick's 1951 paper on the structure of DNA published in Nature. A widely known example of the other extreme is the Jacques Benveniste affair, where peer review was exercised prior to publication in the journal Nature and the published results appear to have been unable to be replicated by other researchers.

A famous peer review failure was the 1977 Science article on the dodo and seed germination that among other major flaws, lacked the required control treatment for its main experiment.^[1] Another glaring peer review failure involved a 1993 Bioscene article^[2] on Jan Baptist van Helmont with no references for its many historical facts.^[3] Bioscene not only refused to publish a letter pointing out the factual errors but would not consider publishing another article correcting the original article.

In 2006, a group of UK academics launched the online journal Philica, which tries to redress many of the problems of traditional peer review. Unlike in a normal journal, all articles submitted to Philica are published immediately and the review process takes place afterwards. Reviews are still anonymous, but instead of reviewers being chosen by an editor, any researcher who wishes to review an article can do so. Reviews are displayed at the end of each paper, and so are used to give the reader criticism or guidance about the work, rather than to decide whether it is published or not. This means that reviewers cannot suppress ideas if they disagree with them. Readers use reviews to guide what they read, and particularly popular or unpopular work is easy to identify.

Another approach that is similar in spirit to Philica is that of a dynamical peer review site Naboj. Unlike Philica, Naboj is not a full-fledged online journal, but rather it provides an opportunity for users to write peer reviews of preprints at arXiv.org. The review system is modeled on Amazon and users have an opportunity to evaluate the reviews as well as the articles. That way, with a sufficient number of users and reviewers, there will be a convergence towards better quality of the review process.

In June 2006, Nature launched an experiment in parallel open peer review - some papers that have been submitted to the regular confidential process will also be available for open, identified public comment on the web.[10]

Peer review of scholars' work has existed at least since it was known as "The Inquisition of the Holy Roman and Catholic Church"; a principal task of which was to investigate "suspected novelties". Although the Inquisition's reach did not extend to protestant England at the time, The Royal Society was founded in 1660 to escape similar peer review from established University Aristotelian scholars by substituting experiment for such authority. As the motto of the society stated in flat repudiation of such peer review, its members were to be beholden to "the words of no one", but only to the evidence.

Peer review has been a touchstone of modern scientific method apparently only since in the middle of the twentieth century.[11] Before then, its application was lax. For example, Albert Einstein's revolutionary "Annus Mirabilis" papers in the 1905 issue of Annalen der Physik were not peer-reviewed. The journal's editor in chief (and father of quantum theory), Max Planck, recognized the virtue of publishing such outlandish ideas and simply had the papers published; none of the papers were sent to reviewers. The decision to publish was made exclusively by either the editor in chief, or the co-editor Wilhelm Wien—both certainly ‘peers’ (who were later to win the Nobel prize in physics), but this does not meet the definition of "peer review" as it is currently understood. At the time there was a policy that allowed authors much latitude after their first publication. In a recent editorial in Nature, it was stated that "in journals in those days, the burden of proof was generally on the opponents rather than the proponents of new ideas."

Peer review, in scientific journals, assumes that the article reviewed has been honestly written, and the process is not designed to detect fraud. The reviewers usually do not have full access to the data from which the paper has been written and some elements have to be taken on trust (except perhaps in subjects such as mathematics).

The number and proportion of articles which are detected as fraudulent at review stage is unknown. Some instances of outright scientific fraud and scientific misconduct have got through review and were detected only after other groups tried and failed to replicate the published results.

An example is the case of Jan Hendrik Schön, in which a total of fifteen papers were accepted for publication in the top ranked journals Nature and Science following the usual peer review process. All fifteen were found to be fraudulent and were subsequently withdrawn. The fraud was eventually detected, not by peer review, but after publication when other groups tried and failed to reproduce the results of the paper.

More recently the norwegian scientis Jon Sudbø published fraudulent articles in The Lancet. He is currently under investigation.

An example of what can happen within academic publications without peer-review is that of NYU Physics Professor Alan Sokal's publication of Transgressing the Boundaries: Toward a Transformative Hermeneutics of Quantum Gravity in the journal Social Text. The submission for publication by Sokal was a hoax that became known as the Sokal Affair.

While no public data exist concerning how frequently this occurs, sometimes reviewers detect cases of likely plagiarism and bring this to the attention of the editor. Since reviewers generally lack access to raw data but do see the full text of the manuscript, they are perhaps in a better position to detect plagiarism of prose than out-and-out fraudulent data.

A related form of professional misconduct that is sometimes reported is a reviewer using the not-yet-published information from a manuscript or grant application for personal or professional gain. The frequency with which this happens is of course unknown, but the United States Office of Research Integrity has sanctioned reviewers who have been caught exploiting knowledge they gained as reviewers.

See software peer review.

The technique of peer review is also used to improve government policy. In particular, the European Union uses it as a tool in the 'Open Method of Co-ordination' of policies in the fields of employment and social inclusion.

A programme of peer reviews in active labour market policy started in 1999, and was followed in 2004 by one in social inclusion. Each programme sponsors about eight peer review meetings in each year, in which a 'host country' lays a given policy or initiative open to examination by half a dozen other countries and relevant European-level NGOs. These usually meet over two days and include visits to local sites where the policy can be seen in operation. The meeting is preceded by the compilation of an expert report on which participating 'peer countries' submit comments. The results are published on the web.

• Academic conference
• Academic journal
• Abstract management
• Adversarial review
• Code review
• Journal Club
• Objectivity
• Open Peer Commentary
• Publication bias
• Scholarly method
• Sokal affair
• Wikipedia:Peer review

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• The end of the Peer Show - scientists’ misguided attempt to solve a non-existent problem
• The philosophical basis of peer review and the suppression of innovation
• Peer review is broken.
• Suppressing Dissent in Science
• Hampering the progress of science by peer review and by the 'selective' funding system
• A Case Study of Data Suppression and Misrepresentation
• "A Difficult Balance: Editorial Peer Review in Medicine"
• A STUDY IN SUPPRESSION OF INFORMATION
• Suppression of Dissent in Science
• Refereed Journals: Do They Insure Quality or Enforce Orthodoxy? Frank J. Tipler
• Stevan Harnad:
  • 2003: PostGutenberg Peer Review
  • 2002: Self-Selected Vetting vs. Peer Review: Supplement or Substitute?
  • 2001: A Note of Caution About "Reforming the System"
  • 1999: Peer Review Reform Hypothesis-Testing
  • 1998: The Invisible Hand of Peer Review Nature version; Exploit Interactive version
  • 1997: Learned Inquiry and the Net: The Role of Peer Review, Peer Commentary and Copyright
  • 1996: Implementing Peer Review on the Net: Scientific Quality Control in Scholarly Electronic Journals
  • 1985: Rational disagreement in peer review
  • 1984: Commentaries, opinions and the growth of scientific knowledge
  • 1982: Peer commentary on peer review: A case study in scientific quality control
  • 1979: Creative disagreement
• 1978 Behavioral and Brain Sciences (BBS) editorial