Four o'clock in the morning, and the lights are on and still there's no way we're going to sleep, not after the film we just saw. The book we just read. Fear is one of the most primal human emotions, and one of the hardest to reason with and dispel. So why do we scare ourselves? It seems almost mad that we would frighten ourselves for fun, and yet there are thousands of books, films, games, and other forms of entertainment designed to do exactly that....