I just did a search for that phrase on google and got the following:
Why do we cry while watching movie even though we know that it's not real?
While watching a movie we know that all that is happening in front of our eyes is not real and yet we get scared at times and at times we cry as if somebody really died. Here we are treating patterns of color on a white screen as if they are people. This is because our brains have the ability to equate one thing with something, which that thing is not. But for this ability we would never be able to learn or understand anything. Imagine you don’t know English. Then the words you are reading right now would simply look like some squiggly lines. But once you learn English you no longer see them merely as black curves on white background. You see words, sentences, and meaning. Underlying all this is our brain’s ability to treat one thing as something else by forming connections between different neurons representing different things.
Funny, because that's sort of exactly what I was looking for. I just finished watching A Walk to Remember. I think this was my second-and-a-half time. I have a version of it on my pc, but i've only seen pieces of it here. Hence the half. But every time, at certain scenes, this movie makes me cry. This is all coming from a person who thinks (I still do) that he is far less emotional than most others. Maybe I could see myself in that sort of situation? Ah.. who knows...
Anyway. It's a good movie. If you haven't seen it, you should. And if after you watch it, you don't like it.. Well, no one's perfect ;-)