Well, this is going to be something of a first for me: a post relating to a sociological / psychological aspect of gaming. Not a topic which I normally have much insight into, or even much interest in generally, but this just occurred to me and I realised that it's something I've actually never seen explicitly discussed before, so would be very interested to hear other people's input.
For the sake of discussion, let's say there are three (very broad) types of people: introverts, extroverts, and people who are either somewhere in the middle or who can switch / go both ways.
I am the classic introvert. Quietly spoken, often blending into the background in groups unless specifically involved, preferring small intimate situations to big open ones, and so forth. (This is a personality trait for which I've inwardly criticised myself for much of my life, and have only in recent years come to accept as both normal and ok, but that's another topic...)
My gaming group also tends (I would say) towards the introverted end of the spectrum. My regular group has a mix of introverted and "in the middle" people, but no one whom I would immediately and unreservedly describe as an extrovert.
Thinking about other people I've played RPGs with over the years, I can see a strong pattern: I favour other players who are on the introverted end of the spectrum. Indeed, the fellow gamers whom I've gotten on least well with over the years were all strong extroverts.
Of course, as I am almost always on the DM's side of the screen, the fact that my group is on my preferred end of the intro/extroversion spectrum is likely no coincidence -- I've probably selected such players in order to form a group to my tastes.
Noticing this pattern and preference is the first interesting thing.
The second thing, however, is the (to me) somewhat radical idea that there must almost certainly be gaming groups out there which are composed of people on the extroverted end of the spectrum! It's really something I've never given any thought to.
So what I'm now really interested to hear is what other people think about this. To me the typical role-player is the quiet / nerdy type, but I know there are extrovert role-players out there -- I've met them! To what proportion and in which combinations they exist is something I find quite fascinating.