NYC freelancer Shiela Spencer, a student of the personality tests beloved by career counselors, tells a public-speaking audience that there are not only introverts and extroverts but also "shy extroverts," outwardly-directed yet self-aware folks who would be willing group participants were they more at ease.
But why stop there? This article does not square the Myers-Briggs circle by looking for the shy extrovert's opposite. A biography of Herbert Hoover describes him as an "aggressive introvert" -- sure in his beliefs but blind to their effect. Certainly we know the loquacious sort performing for his or her own amusement, or the curmudgeon heedless of social cues. A few Toastmasters evaluations would test at least some of their closely held notions.
The fact is, none of us is a pure introvert or extrovert, and success often involves coaching to move us somewhere else on the continuum.