Peer review: How this fundamental part of the scientific method actually works – Professor Eleanor Riley

Among the phrases that have entered the Covid-19 lexicon in the last year, “peer review” may not be the most iconic and may be one of the least well understood.

The term has been taken up by journalists and commentators primarily in the negative – “not yet peer reviewed” – as precautionary shorthand for preliminary or unconfirmed data given the sheer volume of research being published online prior to formal review.

This “pre-print” trend emerged a few years ago but has come to the fore during the pandemic due to the urgent need to share potentially life-saving discoveries.

Peer review is the process by which a scientific community discusses new research findings and comes to a consensus regarding the reliability of the data, the validity of the conclusions, and the novelty, significance and likely impact of the research.

It has been the basis for evaluation of scientific advances for centuries. It became embedded in the scientific process more than 350 years ago with the founding of learned societies, such as The Royal Society, that provided a lively forum where practising scientists could debate the strengths and weaknesses of a particular piece of work.

However, it was in the early 20th century, with increasing investment in scientific research as a publicly funded endeavour for public benefit, that peer review began to be a formal, and formalised, component of scientific evaluation.

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Today, peer review comes into play at the very start of the research cycle, when a researcher seeks funding to carry out a piece of work, and again when the data are presented for publication.

The peer review process was born out of the forums from debate about science, such as the Royal Society, that emerged from the 17th century and scrutinised the landmark research of Charles Darwin and many, many others (Picture: Peter Macdiarmid/Getty Images)

Research projects can last anything from a few weeks to decades and cost anything from a few hundred pounds to many millions. Typical grants funded by the main UK government funder, UK Research and Innovation, last three to five years and cost up to £3 million, although the cost of some major research initiatives far exceeds this.

Applications are sent, in confidence, to members of the relevant scientific community who comment on the expertise of the applicants, the quality of the work proposed, its importance and the likelihood that it can be delivered with the resources requested.

Peer reviewers frequently offer suggestions for improvement. Applicants are able to respond to the comments (which are anonymised) before the original application, the peer review comments and the applicant’s response are discussed by an expert committee that decides whether or not to provide the funds requested.

When research results are ready for publication, journal editors also appoint expert reviewers. Authors will revise their manuscript in light of the comments received.

This is an iterative process, with one or more rounds of comment and revision taking weeks or months, until the editor decides that the paper is either ready for publication or fails to meet the standard for that journal.

Peer review depends upon the expertise and goodwill of (overwhelmingly, unpaid) reviewers. It is far from perfect – mistakes are sometimes made and professional rivalries can intrude – but the vast majority of problems are identified and resolved prior to publication. Importantly, publication is merely the start of an ongoing peer review process. The real debate is only just beginning.

Eleanor Riley is professor of immunology and infectious diseases at the University of Edinburgh

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