Back when you were a child of 2 or so, you were virtually mindless, at least compared to how you are now. In the first few years of life, your primary focus was you: You wanted food, comfort, a colorful toy -- and you were willing to cry very loudly to get it. In return, you offered nothing but potential quiet. You were egocentric. You can hardly be blamed for this, however; you hadn't developed to a point where you could look past your own needs.Then, at about age 3 or 4 -- if you're neurotypical, meaning your mental development was comparatively normal -- you underwent what seemed like a magical transformation. You became a genius at mind reading. You suddenly were capable of looking past yourself and taking into account others' wants, needs, knowledge and mental states. You had developed what is called folk psychology, an ability to think of the mind states of others. Some researchers think that you are able to pull off this nifty trick through theory of mind. To recap: Folk psychology is our ability to make predictions about what's on others' minds, and theory of mind is one explanation for how we carry out that ability.