LIFE

Why Can We Do Things In Our Sleep And Not Remember Them?

The transition from sleep to wakefulness is far from instantaneous.

10/08/2017 9:31 PM AEST | Updated 10/08/2017 9:35 PM AEST

Have you ever turned your alarm off, eaten something naughty, laughed, talked or spoken in your sleep and not remembered any of it?

Well, there's actually a scientific explanation for these mysterious midnight escapades and it all has to do with how we turn our actions into memories.

Drew Dawson is the director of the Appleton Institute and Associate Vice Chancellor (South Australia) at CQ University. He explained that not having time to process our sleepy actions into memories is the reason why we can't remember doing some things while we sleep.

"So what happens is, you can be awake, and you can respond to stuff, but you are not awake enough to be encoding it into memory," Dawson told HuffPost Australia.

"If people do wake up quite quickly, and their brain is still catching up, there are lots of reports of people not being aware. The thing is, they are awake enough to function but they are not putting stuff into memory yet."

If your body hasn't had the time to wake up you feel terrible. Your eyes feel ... gritty, you're grumpy, you don't want to talk to anybody.

Waking up is one thing, but the way we wake is quite a lengthy process and can be different from person to person.

"Everybody assumes that there is a relatively instant transition [from sleep to wakefulness], like you open your eyes, you wake up, you're awake," Dawson said.

But it's far more complex than that.

"For many people, on most occasions, particularly if you are sleeping at night and getting up during the day after having enough [sleep], the sleep-to-wake transition is quite rapid and biologically appropriate. But if you are sleep deprived, if you wake up in the middle of the night, your brain can take a lot longer to become awake."

Justin Horrocks
The process of waking up can be different from person to person.

'Sleep dunkenness' occurs in the cases where your body hasn't had the time to wake up properly. This usually happens when the time spent asleep is shorter than what it should be.

"Let's say you wake up at four o'clock in the morning after only having three hours sleep," Dawson said.

"If your body hasn't had the time to wake up you feel terrible. Your eyes feel ... gritty, you're grumpy, you don't want to talk to anybody. Now, the process of waking up under those circumstances can take as long as 20 or 30 minutes."

"On the other hand, if it's eight o'clock in the morning and you went to bed at nine o'clock the night before, you had a great sleep and you woke spontaneously, without an alarm clock, then you'd go off, bright-eyed and bushy-tailed -- you can wake up in a matter of minutes," Dawson told HuffPost Australia.

stevanovicigor via Getty Images
Sleep drunkenness feels terrible.

What's interesting is that we base our perception of how good a previous night's sleep was, not on the time that we spent asleep, but the amount of time we stayed awake for.

"If we put people to bed at nine o'clock and make them stay in bed for nine o'clock in the morning, for 12 hours... they say 'I had a bad sleep, I was awake for five hours', but they got seven hours of sleep," Dawson explained.

"But if we put them to bed at 11 o'clock at night and get them up at seven o'clock they'll say, 'I had a really good night's sleep, I was only awake an hour', but they still had exactly the same amount of sleep."

So essentially, by reducing someone's wakeful hours, their perception of their sleep improves and this is exactly how sleeping pills work.

"For example, if we are talking about people with insomnia and we give them sleeping tablets. On average, sleeping tablets increase the amount of sleep people get by about 20 mins, so it's not much, but one of the effects of sleeping tablets is you forget waking up. So people don't recall waking up and so they go, 'oh well, I slept well,'" Dawson said.

Essentially, the less of those bizarre night time food binges and sleep walks you remember the better, because you'll actually believe you have had a better rest. So maybe in this case, not remembering could actually be a good thing.

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