It sounds almost too good to be true, like a sales pitch from a phony self-help guru, but a new study on sleeping brains suggests that listening to languages while you sleep can actually help you to learn them, reports Discover.
"What we found in our study is that the sleeping brain can actually encode new information and store it for long term. Even more, the sleeping brain is able to make new associations," said Marc Züst, co-first-author of the paper.
For the study, researchers played recordings of foreign words and their translations to snoozing subjects enjoying slow-wave sleep, a stage when a person has little consciousness of their environment. To ensure that the results were not compromised by foreign language words that subjects may have had some contact with at some point in their waking lives, researchers made up totally fake foreign words.
When the subjects woke up, they were presented with the fake words again without their translations. The subjects were then asked to imagine whether this gibberish denoted an object that was smaller or larger than a shoebox. This vague way of testing their understanding of the words is an approach that is supposed to tap into the unconscious memory.
"Implicit memory is hard to explicitly state. We had to access their unconscious, implicit knowledge through questions about semantic aspects of these new words," explained Züst.
Incredibly, the subjects were able to correctly classify the words in this way at an accuracy rate that was 10 percent higher than random chance. That's not a rate high enough to have them suddenly opining in a foreign tongue, but it is enough to suggest that the brain is still absorbing information on some level, even during sleep.
"If you present 'biktum' and 'bird' to sleeping humans, their brains can make a new connection between the known concept 'bird' and the completely new and unknown word, 'biktum,'" Züst suggested. "This sleep-formed memory trace endures into the following wakefulness and can influence how you react to 'biktum' even though you think you've never encountered that word before. It's an implicit, unconscious form of memory – like a gut feeling."
Researchers have long known that sleep is important for memory, but previously its role in memory was thought to pertain only to the retention and organization of memories acquired during wakefulness. This is the first time that memory formation has been shown to be active during sleep.
In other words, our brains are listening to the world, and learning about it, even when our conscious selves are not present.
"I find it amazing that humans are capable of such sophisticated information processing without consciousness," said Züst.
The next step for researchers will be to see if new information can be learned quicker during wakefulness if it was already presented during sleep. If so, it could forever change what how we train our brains to learn new things. Sleep learning might become a widespread practice.
Even if the benefits are only marginal, what have we got to lose? It's not like our conscious selves are doing anything else while we're sleeping.