Sleep talking is one of those weird, embarrassing and often hilarious things that we can’t really explain (do yourself a favor and check out Sleep Talk Recorder, which allows people to upload their hilarious nocturnal mutterings—one woman whispers, “We have a tiny Tom Hanks to split between us,” and another man mumbles, “Hercules, Hercules”).
But now, a new French study on sleep talking published in the journal Sleep has tackled the subject matter and come up with some pretty fascinating results. As it turns out, most words spoken during sleep talk are often negative and um, pretty vulgar (almost 10 percent of all recorded sleep talk included swearing). And according to the researchers, the most commonly used word sleep talkers say is “no.”
The scientists hypothesize that this happens because sleep talk occurs while we’re in REM sleep, which is when we’re more likely to have intense and emotional dreams. These dreams may also involve threatening situations, which might explain the negative language.
Interestingly enough, researchers found that most sleep talk was grammatically correct. Huh. Our sleep brains care about verb agreement (even if those verbs are surrounded by a ton of swearing). Good to know.