http://www.ribbonfarm.com/2011/04/07/extroverts-introverts-aspies-and-codies/

At 106 Miles events there are a fair share of introverts and extroverts.

I like this article's definition of the way they interact...

Introverts are transactional in their approach to social interactions; they are likely to walk away with their “share” of the energy generated by any exchange, leaving little or nothing invested in the relationship itself. This is like a deposit split between two individually held bank accounts. This means introverts can enjoy interactions while they are happening, without missing the relationships much when they are inactive. In fact, the relationship doesn’t really exist when it is inactive.

Extroverts are more likely to invest most of the energy into the relationship itself, a mutually-held joint account that either side can draw on when in need, or (more likely) both sides can invest together in collaboration. This is also why extroverts miss each other when separated.

...which explains some of the more unusual interactions I've seen, in which some people "take" while others are "giving".