I'm not sure I believe in this whole introvert / extrovert divide. Is there science, or is it just personality tests?
How do you mean? I think it is a real thing based on personality traits and personal preferences but there's a lot of misunderstanding about it, especially introversion. You can be both and you don't have to live in a cave shut off from the world to be an extrovert.
I would love to tell you, and everyone you know, about my thoughts on this matter... but I can't while you're trying to maintain eye contact with me, or while I suspect that a few other people might judge me for my opinion, but I'll go right ahead and post this anyway, because I'm at the far end of a keyboard and safe from immediate judgment, except that this is the internet and everything I post will be kept forever like some sort of creepy, invasive electronic memorial, which I'm actually okay with because I like the idea of future generations knowing that I was a genius before my time - but I can't fathom the idea that someone I might actually have to smile at in person could know that I once held an opinion about something.
(It's bullshit - putting labels on yourself at that level is one step removed from setting up a tumblr page and posting every 20 minutes about how you don't want anyone to know how you're feeling...)