When I read this, I mentally said, "Aha! I understand now! I can explain it!"
Well, in fact, I can't, because extroverts don't get it, but this article makes it a little easier. After handing a copy to my mother and my sister (both extroverts on crack) they both have calmed down some about my crappy ability to respond to phone calls and email.
http://www.theatlantic.com/doc/200303/rauch********excerpt***********
Do you know someone who needs hours alone every day? Who loves quiet conversations about feelings or ideas, and can give a dynamite presentation to a big audience, but seems awkward in groups and maladroit at small talk? Who has to be dragged to parties and then needs the rest of the day to recuperate? Who growls or scowls or grunts or winces when accosted with pleasantries by people who are just trying to be nice?
If so, do you tell this person he is "too serious," or ask if he is okay? Regard him as aloof, arrogant, rude? Redouble your efforts to draw him out?
If you answered yes to these questions, chances are that you have an introvert on your hands—and that you aren't caring for him properly. Science has learned a good deal in recent years about the habits and requirements of introverts. It has even learned, by means of brain scans, that introverts process information differently from other people (I am not making this up). If you are behind the curve on this important matter, be reassured that you are not alone. Introverts may be common, but they are also among the most misunderstood and aggrieved groups in America, possibly the world.