The following biases can influence how a reviewer assesses a paper and impacts their conclusion regarding the paper they are reviewing.

• Gender bias

• Racial / ethnic bias
• Geographical bias
• Seniority bias

Gender bias

Gender bias refers to the differential treatment or evaluation of individuals based on their gender. In peer review, gender bias can manifest in several ways:

• Implicit bias: Unconscious stereotypes and assumptions about gender may lead reviewers to evaluate work by authors of different genders differently.

• Author identification: Knowing the gender of the author can affect how a reviewer interprets and critiques the research.
• Language use: Biased language choices in a manuscript may lead reviewers to make subjective judgments about the author's competence.

Gender bias in peer review can result in disparities in acceptance rates, funding, and recognition for researchers of different genders. It is essential for reviewers to consciously assess manuscripts based on their scientific merits, not the gender of the author.

Example: A study by Budden et al. (2008) found that manuscripts with female first authors were 7.6% less likely to be accepted for publication in high-impact journals compared to manuscripts with male first authors. This demonstrates the presence of gender bias in peer review, where female authors face disparities in acceptance rates.

Reference: Budden, A. E., Tregenza, T., Aarssen, L. W., Koricheva, J., Leimu, R., & Lortie, C. J. (2008). Double-blind review favours increased representation of female authors. Trends in Ecology & Evolution, 23(1), 4-6.

Racial bias

Racial/ethnic bias occurs when reviewers unintentionally favour or disadvantage authors based on their racial or ethnic background. This bias can be subtle but impactful:

• Cultural perspective: Reviewers may misinterpret or undervalue research conducted from different cultural perspectives.

• Stereotyping: Implicit biases about the abilities or expertise of authors from certain racial/ethnic backgrounds can affect the review process.

Addressing racial/ethnic bias requires reviewers to assess manuscripts objectively, focusing solely on the research's quality and contribution.

‍Example: A study by Ginther et al. (2011) revealed significant racial disparities in research funding from the National Institutes of Health (NIH). African American applicants were 10 percentage points less likely to receive NIH R01 research awards compared to white applicants, even after controlling for variables such as educational background and publication record. This racial bias can extend to the peer review process, where similar disparities may exist.

Reference: Ginther, D. K., Schaffer, W. T., Schnell, J., Masimore, B., Liu, F., Haak, L. L., & Kington, R. (2011). Race, ethnicity, and NIH research awards. Science, 333(6045), 1015-1019.

Geographical bias

Geographical bias involves favoring or discriminating against research based on the location or affiliation of the authors. This bias can lead to:

• Preference for Prominent Institutions: Research from well-known institutions may receive more favorable reviews than equally valid work from lesser-known institutions.

• Neglect of Underrepresented Regions: Valuable research from underrepresented geographical areas may be overlooked.

Peer reviewers must evaluate research based on its scientific merit rather than the geographic location of the authors' affiliations.

Example: A study conducted by Smith and Ebrahim (2019) analyzed the distribution of publications across countries and found that research from high-income countries receives disproportionately more citations than research from low-income countries, irrespective of the quality of the research. This geographical bias in citation rates may reflect biases in the peer review process, where researchers from high-income countries may receive preferential treatment.

Reference: Smith, E., & Ebrahim, G. (2019). Citation impact of research sponsorship. PLoS ONE, 14(7), e0219186.n of the authors. This bias can lead to:

Seniority bias

Seniority bias occurs when reviewers treat junior and senior researchers differently, often giving undue weight to the latter's work. This bias can result in:

• Undervaluing Emerging Talent: Reviewers may dismiss innovative work from junior researchers in favor of established researchers.

• Reluctance to Challenge Senior Authors: Reviewers may hesitate to critique work by senior authors, even when warranted.

Impact of biases on peer review

The biases discussed above can significantly impact peer review, leading to unequal opportunities and distorted assessments of research papers. Some common consequences of biases in peer review include:

• Unequal Access: Researchers from underrepresented groups may face additional barriers to publication, funding, and career advancement.

• Underrepresentation: Research from marginalized groups may receive less attention and recognition, leading to a lack of diversity in academic discourse.
• Inaccurate Assessment: Biases can result in inaccurate evaluations of research quality, affecting the credibility of the peer review process.