Take the QUIZ : http://lonerwolf.com/introvert-or-extrovert-test/
Interesting. I'd never heard the term "Ambivert" before.
I'm often accused of "going hermit", because I'm capable of being alone for long stretches of time. I could spend days on end painting, writing, or puttering around in my garden and be as happy as a pig in mud.
But when I party, I turn into Chatty Kathy. I've always thought that it was odd that I could swing wildly back and forth - Going both ways, LOL.
Ambivert. That must be it :) More here : http://lonerwolf.com/ambivert/