the singing frog

I wish I knew why I get so uncomfortable in certain situations. Why do I have such a hard time being social? What is it with my brain that puts me in some kind of "lock down" mode when I'm around people. I've always made the analogy that I'm like that old Warner Brothers cartoon with the singing frog. The guy that finds the frog is the only one that ever sees the frog sing and dance. That's me! To most of the world I'm just an emotionless freak that they want no part of. Yet, I can be witty, funny, outgoing...you get the idea.

Is there some key inside the brain that makes one person an extrovert and another an introvert? Are we just hard wired this way?