When it’s time to choose what classes to take next semester, many students hop on RateMyProfessors.com to find which teacher is the best. On the website, people anonymously rank teachers on a scale of one to five in terms of class difficulty, clarity, and helpfulness. Students can also write short blurbs about the class, the teacher, and the experience they had.

These reviews might reveal everyone’s favorite professor, but they also show unwarranted biases. An analysis of more than 14 million reviews found students use the words “brilliant” and “genius” more when describing white, male professors than for female or African American ones. The analysis, published in PLOS ONE, categorized the teachers in disciplines from the sciences, humanities, social sciences, and mathematics.

"Male professors were described more often as 'brilliant' and 'genius' than female professors in every single field we studied — about two to three times more often," said University of Illinois graduate student Daniel Storage, who led the study with psychology professor Andrei Cimpian, in a press release.

Reviews used the two words often when describing professors in physics and psychology, but women and African Americans are a minority in both of those fields, according to Storage. The analysis of the reviews gave researchers a deeper look into the attitudes and thoughts of the students writing them.

"What's valuable about spontaneous comments is that they provide an unvarnished reflection of how people evaluate others in their field, and what they look for in other people in that field," Cimpian said in the release.

The study also aimed to determine why women and African Americans are underrepresented in various academic fields. The researchers looked at teachers’ math scores on the GRE test, how strongly they wanted to avoid working long hours, and their ability to think systematically. They also weighed how picky each academic field was. None could account for the groups’ low numbers. “The only thing that was explaining the proportions of women and African Americans in a particular field was that field's emphasis on the importance of brilliance and genius," Storage said.

Cimpian said both women and African Americans suffer from the stereotype that their intellectual abilities are weaker than those of white males. This may bias students’ perception of brilliance in the classroom, leading to less enthusiastic reviews of female and African American professors. Cimpian said even women and African Americans may regard themselves as inferior due to this stereotype.

In 2015, Cimpian conducted a similar study which asked graduate students, professors, and faculty to describe the attributes needed to succeed in their field. Those who responded with an emphasis on brilliance or genius were more than likely a part of academic fields where women and African Americans are underrepresented.

Source: Storage D, Cimpian A.The frequency of 'brilliant' and 'genius' in teaching evaluations predicts the representation of women and African Americans across fields. PLOS ONE. 2016.