It's the student dream: to listen to a recording of necessary information while sleeping and absorb it before a big exam. Surprisingly, new research indicates we really can process meaning in our sleep, but the authors sadly conclude it won't allow us to study and sleep simultaneously.
Sleep researchers have shown that even during sleep we can be responsive to sounds' relevance. Some people will wake upon hearing their names, when other words spoken equally loudly leave them sleeping, and parents have been shown to be more likely to be woken by their own baby's cries than those of others.
Dr Thomas Andrillon of Australia's Monash University has gone further. With collaborators in France, he has shown people can focus on meaningful sounds over gibberish, in the same way you can concentrate on the conversation you are listening to in a noisy place, while in light sleep mode. The researchers even found their subjects recalled some of what was played to them.
It is possible to have electroencephalograms (EEGs) monitor the brain and identify a signal responding so specifically to incoming information scientists can subsequently examine an EEG and work out what someone has been listening to, Andrillon told IFLScience. “It's the closest thing to mind reading we have,” he said.
In Nature Human Development, Andrillon and co-authors describe playing a loop made of news reporting and film excerpts in one ear of 24 subjects. In the other ear, participants heard what is is known as a Jabberwocky (after Lewis Carroll's famous poem), a recording of invented words with the same syntax and grammar as their native French.
The EEGs showed that both when awake and in light sleep, participants “[h]ave the tendency to prioritize stories that make sense over stories without meaning,” Andrillon said. During deep sleep, however, even the meaningful sounds had no impact.
There are many reasons why we can't use this to cram knowledge into our brain, Andrillon added. For one thing, the messages only lasted a minute, and people only seemed to absorb the first 30 seconds, based on quizzes after waking.
Moreover, Andrillon's subjects experienced sleep amnesia, not consciously remembering processing the information, just as people forget most of their dreams or even things they heard when woken in the night. This makes for a doubtful store of knowledge to rely on.
Most crucially, sleep amnesia happens for a reason. “Sleep is very important for the consolidation of past memories,” Andrillon told IFLScience. “The brain shuts down forming new memories so it can process past ones without contamination.” What little we might learn during sleep, would interfere with our memories of anything we picked up during the day.
Guess it's back to the old book under the pillow trick.