I've been reading about the theory of multiple intelligences with interest and it makes reference to introversion.
It falls under the rubric of "Intrapersonal intelligence". I love this description of introversion.

Intrapersonal

This area has to do with introspective and self-reflective capacities. Those who are strongest in this intelligence are typically introverts and prefer to work alone. They are usually highly self-aware and capable of understanding their own emotions, goals, and motivations. They often have an affinity for thought-based pursuits such as philosophy. They learn best when allowed to concentrate on the subject by themselves. There is often a high level of perfectionism associated with this intelligence.

Careers which suit those with this intelligence include philosophers, psychologists, theologians, and writers.

Take the test:

www.bgfl.org/bgfl/custom...ose_lang.cfm