You guys seem to me to be denying the obvious, but admittedly sometimes the seemingly obvious proves not to be the true. There must be research on the question of what type of personality best correlates with spending lots of time alone with books and what type correlates with trying out for the glee club and running for student council. If I discover anything on this, I may weigh in again.
@JHS , on parsing further your comments, I take this from them: Whether or not there is a correlation in the general population between studiousness and introversion (which you deny), there would definitely not be any such correlation in the gifted class of kids who have a chance of getting accepted at Harvard. That’s an interesting distinction, though again it seems counter-intuitive. One would expect it to be the case that excellence in any activity (the study of a subject matter or matters in this case) correlates with time spent in that activity (as well as with natural aptitude, of course). And behind time spent there must lie (if that time is to be effective) deep emotional commitment to the activity itself. That’s in fact the way I remember the enthusiasms and manias of both high school life and college life. You seem to be suggesting that the kids who are capable of really excelling in their studies would be more, not less, likely to be ones with time and emotional energy left over to excel in those non-studious social activities that consume time and emotional energy in their own right. It would be nice to think that humans are that versatile and polyvalent. But even Leonardo with all his talents and interests had little of these left to spare for social life. Shakespeare sounds like he was also cut from that cloth. And don’t get me started on Newton. Maybe the subset of kids applying to Harvard transcends all such limitations.