Reviewer 1 vs. Reviewer 2: Why Does One Manuscript Have Two Different Fates? A Comprehensive Analysis of Ethics, Biases, and the Future of Double-Blind Peer Review

Peer review is the backbone of validation for modern scientific knowledge. Among various peer review models, the double-blind model has received widespread attention in leading journals such as Nature, JAMA, PNAS, and BMJ as an approach to reduce biases arising from author identity. This review article, with a special focus on the double-blind model and an analysis of the roles of two simultaneous reviewers ("Reviewer 1" and "Reviewer 2"), first examines the evolutionary history of peer review from the 17th century to the era of generative artificial intelligence, then provides an empirical comparison of single-blind, double-blind, triple-blind, and open models. The large-scale analysis by Tomkins and colleagues (2017) in PNAS and the study by Squazzoni and colleagues (2021) in Science Advances on 145 journals including 1.7 million authors form the evidentiary framework. In a special section, the substantive, cognitive, and behavioral differences between Reviewer 1 and Reviewer 2 (including the cultural phenomenon of "Reviewer 2," the hostile second reviewer) are analyzed. The article also addresses gender, nationality, and institutional prestige biases; peer review ethics based on COPE and ICMJE guidelines; conflict of interest; the role of artificial intelligence; and emerging challenges such as "paper mills" and "reviewer fatigue." Finally, practical recommendations are provided for researchers intending to submit manuscripts to Q1 journals.