Sleep is a state of being characterized by a lack of consciousness. But are we capable to perceiving sensory stimuli while we are asleep, or we totally oblivious to the world around us? It is known that humans can strengthen previously acquired memories during sleep, but it is not known if we can actually take in new information.
If a Skunk Passes By While We Sleep, Would Our Brain Know It?
Researchers at the University of Israel decided to test the assimilation and acquisition of new non-verbal information during sleep. It is known that we respond to unpleasant smells by producing shorter sniffs, and to pleasant smells by longer, deeper sniffs. The research team used this information to create a unique test. While participants were asleep, they paired odors with musical tones, i.e., an odor-tone pairing was created with the tone being separated by the odor by at least 1 second. To ensure that these were being detected by the participants, their sniffing behavior was studied, and it was ensured that their sniffs were shorter when unpleasant odors were being presented. They also ensured that participants did not wake up in response to these odors; participants who did wake up within 30 minutes of the experiment were excluded from the analysis.
Upon waking up, the same participants were presented to the tones alone, and it was found that the tones which were paired with unpleasant odors induced a shorter sniffing response in the participants. Moreover, they were unaware of the experiments that had been conducted while they were asleep. This shows that their brains could process at least two things—odor processing, and association of tones with odors while sleep. This shows that our senses are definitely at work while we sleep!
What, and How Much Can We Take In While Asleep?
These participants only learned a simple non-verbal response. More studies will have to be conducted to determine the extent to which we can learn during sleep. Head researcher Anat Ariz says, “There will be clear limits on what we can learn in sleep, but I speculate that they will be beyond what we have demonstrated.” Though it is unlikely that we can learn all our Algebra by listening to recordings while we are asleep, this research could have implications in treating addictive disorders, for example, by using conditioning that pairs addictive drugs with a negative connotation. As Arzi says, perhaps the best way to cure such disorders might be learning at a level of non-awareness.
You can read more about this research here.