And that sort of study is exactly why it’s silly to suggest that somehow Harvard (or wherever like that) is full of extroverts. Harvard’s “bias” (if there really is any) in favor of extroverts doesn’t mean anything like 80-90% of each class is made up of extroverts. It’s more like 35-40%, vs. the 25% you might get if 100% of the students were “gifted.”
Of course, @marlowe1 's bar for disqualification as an introvert is crazy low. The last of my many relatives who attended Harvard College is a total introvert. She can barely look someone in the eye as she is talking to them. Her social skills are negative. She is absolutely as nerdy as they come. (She was also the top student in her class at a famous high school, and was accepted at 100% of the colleges to which she applied, including MIT, Stanford, Princeton, and Yale. But she went to Harvard, where she was a third generation legacy, and therefore presumably unqualified.) She was a math concentrator at Harvard who wound up getting a PhD in a social-science field, and she is a tenure-track junior faculty member at a quality university.
Anyway, notwithstanding her high level of introversion and studiousness, in college she managed to play in the Gilbert & Sullivan orchestra (her academic work also focuses to some extent on music) and to be the librarian for a science fiction club. She picked up swing dancing in graduate school. Which probably qualifies her as an extrovert in @marlowe1 's taxonomy.
At the Yale I attended, hardly anyone could be said to “study and learn only what they need to know for another end.” That was so unusual as to be practically nonexistent, except maybe for a thin layer of helmet-sport recruits who truly struggled with academics and had to devote enormous effort to merely passing their classes and remaining eligible to play sports.