Somniloquy or sleep-talking is a parasomnia that refers to talking aloud while asleep. It can be quite loud, ranging from simple mumbling sounds to loud shouts and long frequently inarticulate speeches, and can occur many times during a sleep cycle. As with sleepwalking and night terrors, sleeptalking usually occurs during the less-deep delta-wave NREM sleep stages or during temporary arousals therefrom.
It can also occur during the deeper REM sleep stage, at which time it represents what sleep therapists call a motor breakthrough (see sleep paralysis) of dream speech: words spoken in a dream are spoken out loud. Depending on its frequency, this may or may not be considered pathological. All motor functions are typically disabled during REM sleep thus, motoric, i.e., verbal elaboration of dream content, could be considered an REM behavior disorder (see below).
Sleep-talking can occur by itself or as a feature of another sleep disorder such as:
Sleep-talking is very common and is reported in 50% of young children, with most of them outgrowing it by puberty, although in rare cases it may persist into adulthood (about 4% of adults are reported to talk in their sleep). It appears to run in families. In 1966, researchers worked to find links between heredity and somniloquy. Their research suggests the following:
Sleep-talking by itself is typically harmless; however, it can wake others and cause them consternation—especially when misinterpreted as conscious speech by an observer. If the sleep-talking is dramatic, emotional, or profane it may be a sign of another sleep disorder (see above). Sleep-talking can be monitored by a partner or by using an audio recording device; devices which remain idle until detecting a sound wave are ideal for this purpose. Polysomnography (sleep recording) shows episodes of sleep talking that can occur in any stage of sleep.
In literature
Sleep-talking appears in Shakespeare's Macbeth. Lady Macbeth, in a "slumbery agitation," is observed by a gentlewoman and doctor to walk in her sleep and wash her hands, and utter the famous line, "Out, damned spot! out, I say!" (Act 5, Scene 1)
Sleep-talking also appears in The Childhood of King Erik Menved, a 19th century historical romance by Danish author Bernhard Severin Ingemann. In the story, a young girl named Aasé has the prophetic power of speaking the truth in her sleep. In an 1846 English translation, Aasé is described thus:
She is somewhat palefaced; and, however blithe and sprightly she may be, she is, nevertheless, now and then troubled with a kind of dreaming fit. But that will wear off as she gets older. Her mother was so troubled before her; and I believe it runs in the family as I am not entirely free from it myself. I do not give much heed to such dreaming now; but she has never yet said anything, while in this state, that has not proved in a manner true; though she can discern nothing, by night or day, more than others may do when they are in their senses.
Walt Whitman wrote a now-lost novel based on Ingemann's romance, which he titled The Sleeptalker.