Your brain hides memories of the things you hear while you’re asleep
Research suggests part of test subjects' minds responded to and remembered words heard while sleeping, even if their conscious minds couldn't call up the memories
If monsters whisper in your ear while you sleep, you’ll likely have no idea in the morning.
But your brain will, turning their words over somewhere deep in your mind, far beneath the surface of what your conscious thoughts can access.
That’s the lesson of a paper out of PSL Research University in Paris.
A pair of researchers had 22 French speakers, aged 20 to 28, perform a series of tasks to test their sleep memories while hooked up to an EEG, which measures electrical activity in the brain (also known as brain waves).
First, while the participants (mostly women) were awake, the researchers played a mix of real French words and fake French-sounding words and instructed the subjects to press a button in one hand if the word was real and in the other if it was fake. (That was to see if they were actually paying attention and to make it harder to memorise what they were hearing.)
Later, they had the subjects perform the same task while drifting off to sleep in comfortable chairs in a dark room — a task many people can still do reasonably well in early stages of sleep. (If you’re wondering if you’re the only person who would find this procedure a little unsettling, you’re not alone.)
The researchers measured the subjects’ level of wakefulness as they performed the task. Then, after they woke up, the researchers had them complete a memory test, going through a list of words (both real and fake) they’d heard while awake and while asleep.