Chances are we’ve all experienced sleep-talking at some point, either by being the person speaking or the person at the receiving end. In fact, according to a 2010 research study, approximately two-thirds of people have experienced sleep talking at least once as an adult. It can be confusing or hilarious, but what’s the science behind it?
Sleep talking, formally known as somniloquy, is a parasomnia in which one talks aloud during sleep. It can range from entire dialogues or monologues to inarticulate gibberish or mumbling. Unlike most parasomnias, which only occur during specific parts of the sleep cycle, sleep talking can happen during either rapid eye movement (REM) or non-REM sleep.
Sleep talking is more common in children, with almost 50 percent of children talking in their sleep at least once a year and around 25 percent exhibiting this behavior at least once a week. Most children grow out of these episodes, though they may emerge later in life, brought on by stress or lack of sleep.
About half of the words said during a sleep-talking episode are incoherent, according to a 2017 study. Of the 3,349 comprehensible recordings analyzed in this study, “no” was most commonly heard.
Scientists remain uncertain as to what exactly causes sleep talking, but studies measuring brain activity may offer some insight. Sleep talking may have links to memory consolidation – when the sleeping brain reviews the day’s experiences and commits important ones to long-term memory. One 2018 review suggests it could be a verbal replay of memories the brain is going through at the time.
Sleep talking may have a genetic component, with some studies finding that it can run in families. Sleep talking also has links to conditions like obstructive sleep apnea.