STEM vs non STEM creates a false dichotomy. In the Duke study, Arcidiacono found not just the natural sciences and engineering, but also economics are “more difficult, associated with higher study times, and are more harshly graded”. In an earlier quote of mine, it seems like MBB consulting firms put analytical philosophy into the hard group as well. (It is no co-incidence that these are the very same subjects that are associated with high standardized test scores, btw).
I have no reason to doubt him because the Wellesley study also found the same thing: some departments give easier grades than others, and a change in grading practice create changes in student behaviour-choice of subsequent courses and major, faculty evaluation, and what have you. Here is a nice summary:
“Based in part on grades, students make choices about how hard to work (Babcock 2009), courses (Sabot and Wakemann-Linn 1991), majors, and careers. ……, graduate schools make choices about whom to admit (Wongsurawat 2009), and employers make choices about whom to hire (Chan, Hao, and Suen 2007)”.
As far as I can see, “passion” has little to do with it.
@bernie12 You may find the study interesting. It confirms a lot of what you are saying: