In the 2017 article, researchers analyzed over 200 French-speaking adults who experienced sleep talking on a regular basis. Some participants had additional sleep disorders including REM sleep behavior disorder (RBD), sleepwalking, or night terrors. The researchers conducted patient interviews and used video and sound recordings to track patient sleep. The study team made note of any verbalizations made while sleeping, including whispering, mumbling, crying, whistling, and yelling, as well as non-verbal lip movements.
In analyzing which words were most commonly uttered by sleeping patients, the researchers also looked at the use of profanity during sleep. While cursing was detected during both REM and non-REM sleep phases, it was more common during non-REM sleep and more often seen in men than women. There were also differences in the types of swear words used during the two sleep stages. “F***” and “s***” came up predominantly during non-REM sleep; but louder, more nasty words were more common during REM sleep.