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Scents Improve Learning During Sleep

©UKF / Britt Schilling

Scent can very easily help to better store newly learned information during sleep, as shown by researchers at the Medical Center - University of Freiburg / Online experiment describes how the learning effect is particularly high / Publication in Scientific Reports.

Effortless learning during sleep is the dream of every human being. It has been known for several years that odors can increase learning success if they are presented during learning and later again during sleep. Now, researchers at the Medical Center - University of Freiburg and the Freiburg Institute for Frontier Areas of Psychology and Mental Health (IGPP) have shown that memory performance increases especially when scent is used over at least three days and nights. However, it also showed that scent facilitates learning but does not prevent later forgetting. The study was published in Nature group's open-access journal Scientific Reports on February 9, 2023.

"We were able to identify conditions under which the supportive effect of scents works particularly reliably in everyday life and can be used in a targeted manner," says study leader PD Dr. Jürgen Kornmeier, director of the Freiburg IGPP and scientist at the Department of Psychiatry and Psychotherapy at the Medical Center - University of Freiburg.

The Scent of Roses During Learning, Sleeping and the Final Vocabulary Test

For the study, first author and biology master's student Jessica Knötzele conducted an online experiment with 183 adult subjects. The subjects were sent sealed envelopes containing either rose-scented granules or just paper shreds, along with detailed instructions on when and where to place the closed envelopes while learning Japanese vocabulary, sleeping, and respectively or during the final vocabulary test. The vocabulary test results of the groups with scent in all phases (learning, sleeping, and testing) were compared with test results in which only paper shreds were in the envelopes instead of scent during one or more phases. This study was conducted by Knötzele as part of her master's thesis. "Subjects showed significantly greater learning success when scent was used during both learning, sleep and vocabulary testing," Knötzele says. The difference in scent-assisted learning success even increased over the three days. "However, it has to be said in a limiting manner that although the scent helps with learning, it cannot prevent subsequent forgetting," Knötzele says.

Findings Suitable for Everyday Use

"What was particularly impressive was that the scent works even if it's there all night," Kornmeier says. "That makes the findings suitable for everyday use." This finding was already apparent in the first study and could now be confirmed once again. Previous studies had always assumed that the scent may only be present during a particularly sensitive sleep phase. However, since this sleep phase can only be determined by an elaborate measurement of brain activity using an electroencephalogram (EEG) in a sleep laboratory, the finding was previously not suitable for everyday use. "Our study shows that we can facilitate learning while we sleep. And it's remarkable that our nose can help with this," says Kornmeier.