"A growing body of experimental evidence suggests that, on the whole, we know significantly less about our friends, colleagues, and even spouses than we think we do. This lack of knowledge extends far beyond embarrassing game-show fodder -- we’re often completely wrong about their likes and dislikes, their political beliefs, their tastes, their cherished values. We lowball the ethics of our co-workers; we overestimate how happy our husbands or wives are.
...
Whatever the cause, such findings challenge our idea of what friendship is. Friends and spouses are people to whom we are supposed to be able to confide anything -- we draw support and a sense of well-being from the thought that our friends know us better than anyone else in the world, and like us nonetheless. Instead, it appears that there are whole regions of our personalities that they miss entirely, and we do the same with them.
The news is not all grim. Other researchers argue that people are pretty good at seeing at least the building blocks of their friend’s personalities. And in certain realms, like judging intelligence and creativity, there’s evidence that our friends are actually more perceptive about us than we are, if only because any illusions they may have about us are dwarfed by the illusions we have about ourselves."
-What you don't know about your friends-
