Effortless learning during sleep is a fantasy of many people. The supportive effect of smells on learning success when presented both during learning and sleep was first proven in an extensive sleep laboratory study.
Researchers at the University of Freiburg Medical Center, the Freiburg Institute for Frontier Areas of Psychology and Mental Health (IGPP) and the Faculty of Biology at the University of Freiburg have now shown that this effect can be also achieved very easily outside the lab.
“We showed that the supportive effect of fragrances works very reliably in everyday life and can be used in a targeted way,"
said study leader PD Dr. Jürgen Kornmeier, of the Department of Psychiatry and Psychotherapy at the University of Freiburg Medical Center.
Learning And Sleep
For the study, first author and student teacher Franziska Neumann conducted several experiments with 54 students from two 6th grade classes of a school in southern Germany. The young participants from the test group were asked to place rose-scented incense sticks on their desks at home while learning English vocabulary and on the bedside table next to the bed at night.
In another experiment, they also placed the incense sticks on the table next to them during a vocabulary test at school during an English test. The results were compared with test results in which no incense sticks were used during one or more phases.
“The students showed a significant increase in learning success by about 30 percent if the incense sticks were used during both the learning and sleeping phases,"
says Neumann. The results also suggest that the additional use of the incense sticks during the vocabulary test promotes memory.
Previous studies had assumed that the fragrance needs to be only present during slow wave sleep, a particularly sensitive sleeping phase. However, since this sleep phase needs to be determined by an effortful measurement of brain activity by means of an electroencephalogram (EEG) in the sleep laboratory, this finding was not suitable for everyday use.
“One particular finding beyond the seminal initial study was, that the fragrance also works when it is present all night. This makes the findings suitable for everyday use. Our study shows that we can make learning during sleep easier. And who would have thought that our nose could help considerably in this,"
says Kornmeier. Unfortunately, sleep does not replace learning effort. However, experiments working with cues during memory encoding and during consolidation show that we can at least optimize learning during sleep.
 Neumann, F., Oberhauser, V. & Kornmeier, J. How odor cues help to optimize learning during sleep in a real life-setting. Sci Rep 10, 1227 (2020).