Reviewer selection biases editorial decisions on manuscripts.

Many journals, including the Journal of Neurochemistry, enable authors to list peer reviewers as 'preferred' or 'opposed' suggestions to the editor. At the Journal of Neurochemistry, the handling editor (HE) may follow recommendations or select non-author-suggested reviewers (non-ASRs). We investigated whether selection of author-suggested reviewers (ASRs) influenced decisions on a paper, and whether differences might be related to a reviewer's, editor's or manuscript's geographical location. In this retrospective analysis, we compared original research articles submitted to the Journal of Neurochemistry from 2013 through 2016 that were either reviewed exclusively by non-ASRs, by at least one ASR, by at least one reviewer marked by the author as 'opposed' or none. Manuscript outcome, reviewer rating of manuscript quality, rating of the reviewers' performance by the editor (R-score), time to review, and the country of the editor, reviewers and manuscript author were analyzed using non-parametric rank-based comparisons, chi-square (χ2 ) analysis, multivariate linear regression, one-way analysis of variance, and inter-rater reliability determination. Original research articles that had been reviewed by at least one ASR stood a higher chance of being accepted (525/1006 = 52%) than papers that had been reviewed by non-ASRs only (579/1800 = 32%). An article was 2.4 times more likely to be accepted than rejected by an ASR compared to a non-ASR (Pearson's χ2 (1) = 181.3, p < 0.05). At decision, the editor did not simply follow the reviewers' recommendation but had a balancing role: Rates of recommendation from reviewers for rejection were 11.2% (139/1241) with ASRs versus 29.0% (1379/4755) with non-ASRs (this is a ratio of 0.39 where 1 means no difference between rejection rates for both groups), whereas the proportion of final decisions to reject was 24.7% (248/1006) versus 45.7% (822/1800) (a ratio of 0.54, considerably closer to 1). Recommendations by non-ASRs were more favorable for manuscripts from USA/Canada and Europe than for Asia/Pacific or Other countries. ASRs judged North American manuscripts most favorably, and judged papers generally more positively (mean: 2.54 on a 1-5 scale) than did non-ASRs (mean: 3.16) reviewers, whereas time for review (13.28 vs. 13.20 days) did not differ significantly between these groups. We also found that editors preferably assigned reviewers from their own geographical region, but there was no tendency for reviewers to judge papers from their own region more favorably. Our findings strongly confirm a bias toward lower rejection rates when ASRs assess a paper, which led to the decision to abandon the option to recommend reviewers at the Journal of Neurochemistry. Open Data: Materials are available on https://osf.io/jshg7/.