I’d have to agree with JHS, introvert/extrovert is way too simplistic. I would look more at a scale from socially inept to socially gifted. I have three daughters and two fall in the middle, but one is in the gifted area. She is a top 10% student but not top 1%, but if she gets to an interview then she becomes a top .1%. (e.g. if she makes it to the interview she always gets an offer no matter what the competition). There in lies the value of the socially gifted, but as far as Harvard can discern this from an application, it has little to go on.