Reviewers' and editors' perceptions of submitted manuscripts with different numbers of authors, addresses and funding sources

The results of an experiment are described in which manuscripts submitted to a medical journal were each sent to two reviewers, One was blinded to the details of authorship, addresses and funding acknowledgements; the other was not. The intention was to see whether papers with larger numbers of these parameters would be more favourably reviewed, either because the reviewers were directly influenced by these factors or because the papers were really of higher quality. it turned out that the differences between the reviewers' marks for each paper were not correlated with the parameters, but that the sums of the two were so correlated. This suggests that the tendency of papers with more authors, etc, to be published in higher-impact journals is actually due to their perceived quality and not to the numbers of authors per se.