A pair of sociologists think they may have an answer: typecasting. Conjure up the classic image of a humanities or social sciences professor, the fields where the imbalance is greatest: tweed jacket, pipe, nerdy, longwinded, secular — and liberal. Even though that may be an outdated stereotype, it influences younger people’s ideas about what they want to be when they grow up…

The academic profession “has acquired such a strong reputation for liberalism and secularism that over the last 35 years few politically or religiously conservative students, but many liberal and secular ones, have formed the aspiration to become professors,” they write in the paper, “Why Are Professors Liberal?” That is especially true of their own field, sociology, which has become associated with “the study of race, class and gender inequality — a set of concerns especially important to liberals.”

What distinguishes Mr. Gross and Mr. Fosse’s research from so much of the hubbub that surrounds this subject is their methodology. Whereas most arguments have primarily relied on anecdotes, this is one of the only studies to use data from the General Social Survey of opinions and social behaviors and compare professors with the rest of Americans.