While I'd have a difficult time pinning myself as either introvert or extrovert, I notice when I'm with a comfortable crowd, ideas will fall out of my mouth with so little processing that many sentences end with "... wait, nevermind, scratch that." I'll use my close aquaintences as easy parallel processing or to quickly look at ideas from obvious viewpoints that I tend to easily overlook.

When I'm in an unfamiliar group or setting, I'll often spend so long revising what I want to say that the conversation moves on and I've hardly said a word for 20 minutes.