I put introvert because I seriously enjoy time alone (with a good internet connection) and because I am socially MUCH better one-on-one than in larger groups. However, like so many of the responses above, I don't think I am consistently in either category. It depends on the other people present, the nature of the group and the event in question, the topic(s) being discussed, my mood that particular day, my goal in the situation, how long it has been since I had sex, whether or not it is a Thursday etc etc. I can also choose which I prefer (for whatever reason) and do both pretty well/authentically. I routinely find myself both the most introverted and the most extroverted person in the room depending on all those variables.
Two categories just don't catch the range of human personalities, not even roughly.
-Ww