From "A Theory of Theory of Mind," Michael Bérubé's American Scientist review of Lisa Zunshine's Getting Inside Your Head: What Cognitive Science Can Tell Us about Popular Culture:
Lisa Zunshine has a theory—a theory about theory of mind. It goes something like this (and in order to paraphrase it, I have to exemplify it, by getting inside her head as best I can):
Our brains evolved in such a way as to render us all eager but flawed mind readers. Whenever we see each other, we try to figure out what other people are thinking; it is a necessary skill in a deeply social species—or, rather, we are a deeply social species precisely because we have this skill. We try to read each other by look, posture, expression, gesture. And, to make things more complicated (and/or fun), we know this about each other, so we also try deliberately to produce certain readings in others by feigning certain looks, postures, expressions and gestures. All the world’s a stage—and the world we have created includes millions of actual stages, where actors embody the principle that all the world’s a (self-reflexive) stage.