Suggested reviewers: friends or foes?

Peer review, a core element of the editorial processing of manuscripts submitted for publication in scientific journals, is widely criticized as being flawed. One major criticism is that many journals allow or request authors to suggest reviewers, and that these 'preferred reviewers' assess papers more favorably than do reviewers not suggested by the authors. To test this hypothesis, a retrospective analysis was conducted of 162 manuscripts submitted to the Journal of Comparative Physiology A between 2015 and 2021. Out of these manuscripts, 83 were finally rejected and 79 were finally accepted for publication. In neither group could a statistically significant difference be detected in the rating of manuscripts between reviewers suggested by the authors and reviewers not suggested by the authors. Similarly, pairwise comparison of the same manuscripts assessed by one reviewer suggested by the authors and one reviewer not suggested by the authors did not reveal any significant difference in the median recommendation scores between these two reviewer types. Thus, author-suggested reviewers are not necessarily, as commonly assumed, less neutral than reviewers not suggested by the authors, especially if their qualification and impartiality is vetted by the editor before they are selected for peer review.