it's either a pregnant lady or a peanut butter and jelly sandwich

This morning I participated in a psychology grad student's research. Basically it consisted of me being psychoanalyzed. First, he asked me some simple questions like "how old are you" and "are you in a romantic relationship". Then he showed me about 12 different ink blots and asked me to tell him what I saw in each one. With each one, I found myself going into great detail about what I saw in these smears of ink on paper. Not only did I describe the objects that I saw within the blots, but I also found myself explaining what these objects were doing and why they were doing it and for whom. It was like my mind automatically made up a story for this imaginary object that I found hidden in the ink blot.
I was thinking about it on the way home and I began to wonder how this effects the ways that I see people. If I, without even trying, make up a story about the girl I see looking at herself in the mirror that I saw in an ink blot (there was one that, to me looked like a girl looking at her butt in the mirror), how much more so must I do this with actual people that I see. I realize that this isn't a strange concept because obviously everyone forms opinions about people whether they mean to or not as soon as they see them. We all have preconceived notions. I don't know...it just really hit me how much I must actually do this without even realizing it. I look at a person and automatically decide whether they are someone that I would want to get to know or not. I wonder how much I miss out on because of this behavior.