Game researcher Jane McGonigal explains how introverts benefit from playing social games:

With introverts, their dopamine systems tend to work more with internal thought than with external, social stimulation. Whereas with extroverts, they have the dopamine receptors going off when someone smiles at them; for them, it’s like a hit of candy or crack cocaine, you know? And for introverts, that’s not happening.

But when we’re in game world, we do get motivated. We do get these dopamine hits from the game itself. When we’re getting them around other people, it can kind of shift our neurochemistry.

The whole interview is really interesting.