I've always found it interesting that a social interaction fuses an extrovert with energy while the same level of interaction can deplete an introvert's energy. But the division between the two types can seem too black and white. According to this study, scientists are now dividing extroverted people in two categories—one type is motivated to be social as part of a goal-oriented reward system while the other type is all about socializing to get the warm fuzzies and to feel connected. What I think we're talking about is social climbers versus social networkers, who, like the research points out, can often be one and the same. Also interesting is the greater volume in the area of the brain for extroverts, the medial orbitofrontal cortex, where stimulus-reward associations are made. Meanwhile, according to a 2012 study at Harvard, introverts had more gray matter in the prefrontal cortex, the area known for abstract thought, anticipating outcomes and moderating social behavior. Are you an extrovert or an introvert? What kind of extrovert are you? Tell us in the comments.