That's not really true. There are always shades of grey between black and white. Sure, you have the drastic examples like heavy partiers and hermits. But then you also have to people (like me) who love both a good party and a nice quiet night alone. That's when you have to look at I vs. E in a way that isn't social. Do you need to be around people to recharge your "batteries"? or do you require private time for that? Basically do you get your energy from being involved in events and activities or do you get it from your inner world (the thoughts, pictures, and ideas in your head)?