This is what I mean when I call myself an extreme introvert. There are varying levels of introversion, and I guess I'd place myself at more of a "medium-well" to "well done" level.
This is from the article at Psychology Today:
... Grimes posits that introversion is not the opposite of extroversion, but that they are two different traits altogether. And she proposes something that has come up here from time to time: That introversion actually is on the autism scale.
Grimes' thesis explains that if you take each of the factors this new model proposes and follow it along a continuum to their most extreme expressions, they correlate with the widely used Baron-Cohen Autism Spectrum Quotient.
Depending on how much we have of each factor (and how they interact with other personality traits), we can be simply introverted or, moving along the continuum, have Asperger's syndrome or, moving further yet, have autism.
A Compelling Theory About Introversion, Extroversion, and Autism
from the blog, The Introvert's Corner
It's an interesting theory. And, even better, it fits in nicely with my tagline!