Objective Many anecdotes suggest that including citations to the works of potential reviewers is a good (albeit unethical) way to increase the acceptance chances of a paper. However, previous attempts 1,2 to quantify this effect (citation bias) had low sample sizes and unaccounted confounding factors, such as paper quality (stronger papers had longer bibliographies) or reviewer expertise (cited reviewers had higher expertise). In this work, the question of whether positive comments from reviewers are associated with their work being cited in the papers that they review was investigated.

Design The study used data from 2 top-tier computer science conferences: the 2021 Association for Computing Machinery Conference on Economics and Computation (EC) and 2020 International Conference on Machine Learning (ICML). Both conferences received full-length papers that underwent rigorous review (similar to top journals in other areas). The study analyzed anonymized observational data, and consent collection was not required. The dependent variable of the analysis was the overall score given by a reviewer to a paper (between 1 and 5 in EC and 1 and 6 in ICML; higher meant better). To investigate the association between the citation of a reviewer and their score, parametric (linear regression for EC and ICML) and nonparametric (permutation test with covariate matching for ICML) tests at significance level α = .05 were combined, circumventing various confounding factors, such as paper quality, genuinely missing citations, reviewer expertise, reviewer seniority, and reviewers’ preferences in which papers to review. The approach comprised matching cited and uncited reviewers within each paper and then carefully analyzing the differences in their scores. In this way, the aforementioned paper quality confounder was alleviated as matched cited and uncited reviewers reviewed the same paper. Additionally, various attributes of reviewers (eg, their expertise in the paper’s research area) were used to account for confounders associated with the reviewer identity (eg, reviewer expertise). Finally, the genuinely missing citation confounder was accounted for by excluding papers in which an uncited reviewer genuinely decreased their evaluation of a paper because it failed to cite their own relevant past work.

Results Overall, 3 analyses were conducted, with sample sizes ranging from 60 to 1031 papers and from 120 to 2757 reviewers’ evaluations. These analyses detected citation bias in both venues and indicated that citation of a reviewer was associated with an increase in their score (approximately 0.23 point on a 5-point scale). For reference, a 1-point increase of a score by a single reviewer would improve the position of a paper by 11% on average.

Conclusions To improve peer review, it is important to understand the biases present and their magnitude. This work 3 studied citation bias and raised an important open problem of mitigating the bias. The reader should be aware of the observational nature of this study when interpreting the results.

References 1. Beverly R, Allman M. Findings and implications from data mining the IMC review process. ACM SIGCOMM Computer Communication Review. 2012;43(1):22-29. doi:10.1145/2427036.2427040

2. Sugimoto CR, Cronin B. Citations gamesmanship: testing for evidence of ego bias in peer review. Scientometrics. 2013;95(3):851-862. doi:10.1007/s11192-012- 0845-z

3. Stelmakh I, Rastogi C, Liu R, Echenique F, Chawla S, Shah NB. Cite-seeing and reviewing: a study on citation bias in peer review. arXiv. Preprint posted online March 31, 2022. doi:10.48550/arXiv.2203.17239

Conflict of Interest Disclosures Ivan Stehlmakh reported interning for Google. Charvi Rastogi reported interning for IBM. No other disclosures were reported.

Funding/Support Ivan Stehlmakh, Charvi Rastogi, Ryan Liu, and Nihar B. Shah were supported by a National Science Foundation (NSF) CAREER award (1942124), which supports research on the fundamentals of learning from people with applications to peer review. Federico Echenique was supported by NSF grants SES 1558757 and CNS 1518941. Charvi Rastogi was partially supported by a J. P. Morgan artificial intelligence research fellowship.

Role of the Funder/Sponsor The funders did not play a role in any of the following: design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the abstract; and decision to submit the abstract for presentation.

Acknowledgement We appreciate the efforts of all reviewers involved in the review process of the 2021 Association for Computing Machinery Conference on Economics and Computation and 2020 International Conference on Machine Learning. We thank Valerie Ventura, PhD, Carnegie Mellon University, for useful comments on the design of the analysis procedure.

Additional Information Nihar B. Shah is a co–corresponding author.