From Jonathan Rauch, "Caring for Your Introvert: The habits and needs of a little-understood group."

How can I let the introvert in my life know that I support him and respect his choice? First, recognize that it's not a choice. It's not a lifestyle. It's an orientation.

Second, when you see an introvert lost in thought, don't say "What's the matter?" or "Are you all right?"

Third, don't say anything else, either.