Because MIT is a STEM heavy school, I know the number of humanities majors is incredibly low. However, I heard that you get more personal attention by the professors because of the reduced class size.
There is no definite answer to this, but generally speaking: applying to a less competitive major should increase your chances. I would not just rely on the scarcity of your major though, as there is no guarantee, and even if it does help it would be minorly (unless it is a very rare major in general). Still focus on being a strong applicant in general!
I think MIT claims that major doesn't impact decisions, like many colleges. Of course, we can't know if that's true, you could get rejected for literally any reason. Your admissions officer could be having a bad day or a bias for/against humanities majors (not that they're supposed to).
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