Though it remains unclear why we talk in our sleep, ongoing research seeks to unravel what we utter in our sleep, when this occurs and why certain people talk in their sleep while others sleep quietly. And also: do we inadvertently reveal secrets while sleep-talking?
If you were ever told that you were talking in your sleep, we regret to inform you: you are not special. Sleep talking is a common phenomenon that manifests in various ways: starting from meaningless mumbling, shouting or laughter and ending in long and coherent monologues that you conduct with yourself or someone else, without remembering anything in the morning. Although it can be embarrassing at times, this phenomenon is natural and normal, and generally harmless.
Until the 1950’s researchers believed that sleep was a passive state, during which most bodily and mental functions were disabled, to allow our systems to recover from the day’s activities. However, today we know well that sleep is an active, complex and involuntary process that plays a vital role in memory formation and processing, metabolic regulation, and brain toxin removal.
Speaking out loud while sleeping, also known as Somniloquy, is the most common sleep disorder. It is especially common in children: a study that included over 2,000 children between the ages of three and ten found that half of them sleep talked at least once per year, one in ten children sleep talk a few times per week and a little less of them sleep talk almost every night.
In adults it’s a different story. The American Academy of Sleep Medicine (AASM) reports that only five percent of adults, regardless of age, gender or socioeconomic status, say that they occasionally or regularly talk in their sleep. However, it’s worth noting that the data regarding the prevalence of this phenomenon may be inaccurate, as people’s awareness of whether or not they talk in their sleep is usually limited.
Sleep talking is particularly common in children. An illustration depicting a child mumbling in their sleep | Shutterstock, BNP Design Studio
A study conducted in Norway, which included interviews with roughly one thousand adult men and women, revealed surprisingly high rates of sleep talkers. Two out of every three study subjects (66 percent) indicated that they talked in their sleep at least once during their life, and over one sixth (17.7 percent) testified that they had talked in their sleep during the last three months.
Typically, people talk for only a short time and become quiet in a second or two. In rarer cases, the talking may continue for up to half a minute, but there are also “talkers” who may talk multiple times during one night. The subjects of these conversations vary. In certain cases they could be offensive and include cursing and shouting, but more often, the talking consists of senseless mumbling and even rolling laughter. In many cases the talking is loud enough to awaken sleeping partners, and sometimes even people sleeping in adjacent rooms.
Sleep talking is only one facet in a wide spectrum of sleep disorders. An exhausted woman | Shutterstock, The Faces
Speaking Out of a Dream?
The natural tendency of many of us is to assume that sleep talking originated from a dream. In practice, this connection is far from clear, and it is challenging to determine whether sleep talking is linked to dream sleep, or whether it is influenced by the depth of sleep. One thing that is relatively certain is that sleep talking can occur at any stage of the sleep cycle.
The sleep cycle is commonly divided into four stages, each distinguished by brain activity patterns and sleep depth. Together they form a cycle of about ninety minutes that repeats several times during the night. The first stage represents the lightest sleep, which we experience when we are midway between wakefulness and sleep, with relatively rapid brain electrical activity. In the second stage, brain waves slow down. Sleep talking during these stages is often coherent and comprehensible.
The third stage of sleep cycles is characterized by even slower brain wave activity, and the body enters deep sleep. The fourth and final stage of a sleep cycle is called Rapid Eye Movement (REM) sleep, as the eyes tend to move rapidly during this stage. This is the stage when we do most of our dreaming. During REM sleep, brain activity rises to levels similar to those of a fully awake person, and if we wake a person up during this stage there is a good chance that they will vividly remember the content of the dream they had. Sleep talking during these stages tends to be confused and unclear, often containing meaningless syllables or moans.
Sleep cycles are typically categorized into four stages, each characterized by distinct brain activity patterns. Electroencephalogram (EEG) recordings of the various sleep stages |
During REM sleep the brain is very active, while most of our voluntary muscles are paralyzed - except for the eye muscles. This is the reason we are able to remain lying down while we dream, without actually performing the movements we dream of. Since sleep talking requires complex muscle activation, it is reasonable to assume that we would speak less during this stage. However, the brain can have momentary lapses of regulation of the paralyzed muscles, and this is when people talk and move during REM sleep. In experiments that monitored the sleep of individuals who chronically sleep talk, it was found that almost a quarter of the participants talked during the REM stage, indicating that, at least in this group, there was no significant difference in the prevalence of sleep talking during this stage, compared to the other three stages.
While dreaming is strongly associated with REM sleep, we also dream in all other sleep stages, albeit to a lesser extent. The connection between these other sleep stages and sleep talking is far from conclusive. One study suggests that sleep talking reflects the content of a dream and may indicate the mental experience during the dream. In another smaller study, participants were recorded while sleeping for seven consecutive nights and were asked to document their dreams. It turned out that people who talk in their sleep felt their sleep quality was significantly worse than reported by others, and they experienced more frequent sleep interruptions. This suggests that sleep talking negatively impacts sleep quality. However, a different study showed a connection between sleep talking and processes of language and memory formation, suggesting that this phenomenon may help reinforce what was learned during the day.
The connection between dreaming and sleep talking remains inconclusive. Illustration of a man experiencing a dream in a sleep laboratory | Sam Falconer, Debut Art / Science Photo Library
Speaking (Almost) Naturally
Sleep talking is very similar to ordinary talking in its characteristics. In cases where sleep talking isn’t incomprehensible mumbling, the talker usually uses sentences with a correct grammatical structure, as well as semantic content, that is to say that the meaning of the words and expressions sounds correct. Often, it appears that the person is engaged in a conversation with themselves, but some people have been recorded having conversations with imaginary people, pausing as if waiting for a reply from the pseudo-speaker. Some even give direct answers to questions posed by someone else, presumably.
Thus, it appears that our brains continue to function while we sleep, in a mostly automatic process that combines states of consciousness, such that the brain’s sleep and wakefulness networks operate side by side. Electroencephalogram (EEG) tests, which measure electrical brain activity using sensors attached to the scalp, indicate that while we sleep talk, the activity in the speech areas in the brain is similar to that observed while awake.
During sleep talk, the activity in the speech areas in the brain is similar to that observed while awake.Image of a scientist studying the brain activity of a sleeping woman | Science Photo Library
Known Secrets
Over the years, very few studies have been conducted on sleep talking, possibly because for all we know it is a non-harmful phenomenon, except for some potential impact on sleep quality, daytime drowsiness, and disruption of the sleep of others. Nevertheless, there is one concern that troubles many people - that of accidentally revealing their deepest secrets while sleep-talking.
In practice it seems that there is no real cause for concern. While people do talk in their sleep about their experiences during the day, what is typically heard consists mostly of meaningless, incoherent syllables. Even when the words are decipherable, the speech is indeed correct, but tends to jump from one topic to another. More often than not speakers drift on the waves of their imagination and say things that bear no connection to reality. Therefore, it is difficult to trust what people say in their sleep.
And still, what do people talk about? A study conducted in France investigated speaking patterns of people who talk in their sleep. The study included 232 men and women, with 129 of them diagnosed with an increased tendency for sleep talking, 87 diagnosed as somnambulists - people who tend to walk in their sleep - or suffering from nightmares, one diagnosed with sleep apnea and the rest without any diagnosed sleep disorders. The participants were recorded during their sleep on multiple nights, and the recorded expressions were subsequently analyzed by the researchers. Out of 883 expressions, 60 percent were incomprehensible: a third of these included mumbling (32%), a quarter included shouting (26%) and nearly the same rate of whispering (24%). Additionally, there were also instances of laughter (15%), moaning (10%), or visible lip movement with no clear sound (8%). Few cases included humming or crying.
The most interesting findings pertained to the remaining 40 percent, who spoke more clearly. The sentences typically comprised around nine words on average, totaling 3,349 understandable words. Nearly half of these words were interjections such as “Ah” or “Oh La La” (the participants were French). Among the meaningful words, the most commonly uttered word was “No”. Most speakers addressed an invisible person in the third person form, and used the pronouns “You”, “Us”, and “I”. The subjects also frequently employed words that are commonly used in interpersonal interactions, such as “Fine”, “Hello”, “Please”, “Pay attention” or “But”.
The researchers also characterized the tone of voice. Generally, 24 percent of the expressions had a negative, vulgar and even rude tone, including humiliating or insulting remarks or curses used as interjections, like “Merde” (Crap). In contrast, the prevalence of polite expressions was much lower. Men talked in their sleep more frequently than women, and used more curse words.
Occasionally, individuals were recorded speaking in a language that was not their native tongue. One subject, who suffered from stuttering, also stuttered during sleep, and another subject was recorded singing in their sleep. The researchers concluded that the brain remains active during sleep, expressing thoughts about confrontations and conflicts, and potentially also allowing us to engage in intense imaginary conversations with others.
Our brain continues to function while we sleep. Image of a sleeping brain | Shutterstock, Oleg Erin
Stop the Chatter
Despite significant advancements in brain and sleep research in recent years, we still know very little about the mechanisms behind sleep talking. Some studies indicate that sleep talking may have a hereditary component. Studies show that sleep disorders are more common in certain families and that individuals with one sleep disorder often suffer from other concurrent sleep disorders, indicating a potential genetic link. A study involving eight-year-old twins found that many of them shared common sleep disorders, further reinforcing the hypothesis that these disorders have a genetic component. The genetic and environmental aspects of sleep disorders, along with their interconnections, are subjects of ongoing research.
Additionally, surveys indicate four main factors that might promote sleep talking. The primary factor is severe mental pressure, stress and anxiety. Following that, in a descending order of significance, we find increased alcohol consumption, medication side effects and other sleep disorders.
While sleep talking almost never stems from a medical condition and typically does not necessitate treatment, there are rare cases when its occurrence may signal a neurological problem or a health condition that requires attention. Extreme sleep disorders and nightmares, which lead to violent behavior, may be indicative of mental issues requiring treatment. For example, individuals who experience post traumatic stress disorder or similar psychiatric conditions, such as combat veterans with “shell shock”, tend to sleep talk twice as often as others.
A study examining the psychological consequences of firefighting found that many firefighters, whose work is characterized by heavy mental stress, danger and uncertainty, suffer from various sleeping disorders, including insomnia, nocturnal panic attacks and sleep talking.
Another study found that sleep talking is seven times more common in individuals who suffer from Parkinson’s disease. Often, this manifests as a direct portrayal of the content of unpleasant dreams, including vocalizations and limb movements while sleeping, sometimes in a frantic manner. In such cases, or when sleep talking becomes excessively frequent, it is recommended to seek evaluation by a family physician and consider undergoing sleep laboratory testing.
Since the causes of sleep talking remain unclear, we also don’t know how to prevent it. However, it may be reduced by practicing good sleep hygiene, which includes healthy sleep habits, such as regular sleep hours and avoiding late-day naps. Additionally, minimizing caffeine or other stimulant consumption in the afternoon or evening, and moderating alcohol intake, is recommended. Most importantly, it is always good to look for ways to reduce the level of pressure and stress in your life. If your sleep partner tends to talk in their sleep, consider using earplugs, and if nothing helps, consider sleeping in a separate room. Good night.