"At its most extreme, introversion has been linked by experts to autism, or to schizoid personality disorder. And certainly those disturbances warrant being viewed as abnormal."

As a 59 year-old adult with Asperger's, I take umbrage at the above sentence. There is nothing abnormal about me, or my daughter (also diagnosed with Asperger's) or my grand-daughter (also diagnosed with Asperger's). If you met us, you would notice differences only if you have been educated to notice them; at most, you might think us a little strange or impatient. The differences are not always outward, but inward.

Lumping autism, regardless of where on the scale one might be, with schizoid personality disorder does a gross injustice to the thousands and thousands of us out here who are NOT mentally ill but who have sensory processing or other problems. You might want to rethink that sentence, particularly if it reflects your own beliefs.