I came across an interesting article from NBC News about dreams. The article talks about a researcher from Hong Kong who believes his research shows that body posture during sleep can affect your dreams.

Calvin Kai-Ching Yu, of Shue Yan University, studied 670 people and most of them reported that sleeping face down gave them intense dreams -- including feeling of "being tied up," being "unable to move," and even "sex."

He believes laying on your stomach provides more intense physical stimulus, like making it tougher to breathe, for example, which makes our bodies feel more constricted. He goes on to say he believes sleeping face down provides our genitals with more stimulation from the sheets and bedding, therefore allowing our minds to wander in that "sexier" direction!