Und selbst dann: Ich sehe nicht, wieso das ein eigener Typus sein soll, der im Gegensatz zu den anderen beiden steht.

Gute Frage.

Wenn man diese Definition von Introvertiertheit in den Worten des Psychiaters C.G. Jung, der den Begriff begründete nimmt, ist das was in dem taz Artikel beschrieben wird, vielleicht, anders als ich dachte, schon darin enthalten:

He holds aloof from external happenings, does not join in, has a distinct dislike of society as soon as he finds himself among too many people. In a large gathering he feels lonely and lost. The more crowded it is, the greater becomes his resistance. He is not in the least “with it,” and has no love of enthusiastic get-togethers. He is not a good mixer. What he does, he does in his own way, barricading himself against influences from outside. He is apt to appear awkward, often seeming inhibited, and it frequently happens that, by a certain brusqueness of manner, or by his glum unapproachability, or some kind of malapropism, he causes unwitting offence to people…

For him self-communings are a pleasure. His own world is a safe harbor, a carefully tended and walled-in garden, closed to the public and hidden from prying eyes. His own company is the best. He feels at home in his world, where the only changes are made by himself. His best work is done with his own resources, on his own initiative, and in his own way…

Crowds, majority views, public opinion, popular enthusiasm never convince him of anything, but mere make him creep still deeper into his shell.

Nur: Ich habe nicht den Eindruck, dass man heutzutage selbst starke Introvertiertheit noch so definiert. Was der Begriff heute meint, scheint doch deutlich anders zu sein.