[dgreensp]

I don't think extraverts need any feeling of obligation to go to a party, that's just their version of curling up alone with a book.

In my experience, the most striking difference between extraverts and introverts is that extraverts enjoy the stimulation of being around people (whether it's a party, a small group, or one on one), potentially from the moment they get up to the moment they go to sleep. They might live with three housemates, meet someone for breakfast, have a phone call with a friend just to chat, and on and on, and they don't feel drained, they feel energized. It's as natural as being alone all day is for an introvert.