A lot can happen when you're busy catching some Z's. Dreams, sleepwalking, that thing where you are nodding off but jerk back awake, and, perhaps the most common of them all, sleep talking.
If you've ever shared a bed or a room with a sleep talker, you'll be familiar with the concept of random nocturnal mutterings (see one woman's hilarious account of her husband's habits here). But why exactly do people do it? And what secrets are you giving away while fast asleep?
Thankfully, according to St. Vincent's Hospital sleep specialist, Dev Banerjee, you're not likely to be giving away your computer password any time soon.
"Sleep talking is just one of those nighttime anomalies that are very common," Banerjee told The Huffington Post Australia.
"Sleep is not completely passive. You do lots of things -- burping, farting, turning, talking -- it's just one of those. Sleep talking is not regarded as a sleep disorder as such. It's just a nuisance.
"I get asked a lot what people are likely to say, but the fact of the matter is it's just a lower abstract vocalisation -- usually mumbling -- though many men, in particular, think they are going to give the names of ex-girlfriends or their credit card pin numbers and the like."
In actual fact, Banerjee says it's more likely you'll spout complete nonsense than actually articulate anything that makes sense.
"Thankfully when most people sleep talk, it’s usually gibberish and it's not going to give away the names of your ex-partners or anything like that.
"In my experience, blokes tend to be more worried about what they are saying [than women]. That's something they worry about, that they are going to yell ‘oh Julie!' or something in their sleep.
"In reality, it's more likely to be monosyllabic words. You're definitely not going to have someone to recite Shakespeare."
Banerjee says sleep talking can occur in any phase of sleep, and therefore differs from a condition such as sleep walking which must occur during non-REM sleep.
"Sleep talking can occur in any phase of sleep -- whether that be non-REM or REM -- it’s pretty non-specific," Banerjee said.
"It is not regarded as a non-REM parasomnia. It’s something you can do at any time. It's not really regarded as abnormal behaviour."
Abnormal or not, it can still be pretty amusing. Check out this clip of a sleep-talking baby below.