I have always believed that it's actually a physical impossibility to "wake up screaming" from a nightmare - apparently the salivary glands radically slow production while you're asleep, in order to stop you (sorry if you're eating) drowning in your own spit. This explains why you can tell if somebody is pretending to be asleep because you can hear them swallow, and why you often wake up with a dry mouth. I have had my share of nightmares, and more often than not wake up wheezing rather than screaming - more like the noise of a cat dealing with a furball than a full-throated Hollywood AAAAAIIIEEEEEEE. Imagine my surprise when the other night I was woken by an almost Niles Crane style of shriek ("No, Daphne, that wasn't your mother screaming...") from the slumbering Mr Fishwife. It later transpired he had had a nightmare in which Esther Rantzen was chasing him, with a spear, down a long corridor which also happened to be his grandmother's back garden. Just when he thought it was safe and was hiding behind a shed, she emerged again, this time with a pair of shears. Now what this experience has taught me is (a) the logic of nightmares is random to say the least, (b) maybe I'm wrong about the salivary thing, and (c) people who scream in your ear at 4 in the morning can really disturb your sleep.