Researchers analysed more than 14 million reviews on RateMyProfessors.Com, where students write anonymous reviews of their professors.
"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 Daniel Storage from University of Illinois in the US.
"Students also used 'brilliant' and 'genius' to describe their professors most often in academic fields such as philosophy and physics, in which women and African-American students are a distinct minority," said Storage.
"While there are correlations between some of these factors and the presence or absence of women and African-Americans in some fields, we consistently found that 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," said Storage.
"The people in certain fields might not see that quality in women and African-Americans. Women and African-Americans themselves may be conditioned to not see these qualities in themselves," said Cimpian.
The findings were published in the journal Science.