Why do we sleep and why do we dream? Despite the fact that every human being spends roughly 1/3 of his or her life asleep, science has yet to crack the mystery of the phenomenon. Why do we sleep and dream? The answer for now is...we don't know. To learn more, we interview psychologist Richard Wiseman who has written a new book on sleep and dreaming that promises to help you get the most out of both based on what science has learned so far.