I propose to add a third kind of "vert" to the two standard categories - introverts and extraverts.

That's the "adapted introvert," who masquerades as an extravert at times, and then "re-verts" to introversion when the situation no longer demands it. I know, because I am one, and many of my colleagues in my occupation show the same pattern.

In a thirty-year career as a management consultant, seminar presenter, and conference speaker, I'm often mistaken for an extravert. People ask, "How can you stand up in front of 5,000 people and give an impassioned speech about leadership, and not be an extravert?" The answer is: it's not easy.

Most of the star "motivational" speakers, so far as I've been able to determine, are high-energy extaverts. However, many of the topic experts - people who speak about the future, business strategy, leadership, economics, technology, and organizational performance, seem to be driven by their inner achievement needs, not their needs to connect with other people. They have to get themselves "up" for intensive interactions with others, and when the mission is done they retreat to the comfort of their private interior worlds.