I found a link to this youtube clip on Social Sound Design, a great audio forum, and it has kind of blown my mind.
Take a minute to watch this and see if you can make your brain overcome the McGurk Effect.
Sound is just as important as picture to making a movie work, and since I make a living providing sound to support and enhance moving pictures I know it to be true. I love making the argument sound completely effects the way the same scene is felt. Yet this McGurk effect proves that it works both ways and sound can be heard completely differently depending on the picture it is paired with. Never thought of it that way.