The Unexamined Life

Smells Exposed To During Learning And Sleeping Improve Memory

Retaining information can literally happen overnight in your sleep, provided you were exposed to similar fragrances while studying and sleeping. A new study by the biology department at University of Freiburg, Germany, drew the link between odor cues during sleep and improved memory. 

Unlike previous studies, participants were not monitored during different stages of sleep cycles to test this theory. Participants of this study published recently in the Scientific Reports were exposed to rose scented incense sticks the whole night. 

Two classes in the sixth grade were recruited with their parents' consent, one class with 32 students and another with 22 students, respectively.  All of the participants were between 11 and 12 years old. Students were observed in their natural home and school environments without any external measurement. 

What The Study Found

Prior to the study, German students had undergone one year of English classes and were given a test based on a lesson they were imparted a week before. No odor cues were present at this point during the class on vocabulary translations from German to English. 

While the control group had 15 girls and 12 boys, the test group also contained 15 girls and 12 boys too. As part of the experiment, students in the test group were first asked to keep rose scented incense sticks next to them at home while they were studying. 

Next, the test participants were exposed to the fragrances at home and during the test at school one week after the teacher's lesson. Afterwards, the participants were made to inhale the fragrance while studying at home and every night of the week leading to the test while sleeping, for the whole night. Lastly, students not only received odor cues at home, incense sticks were kept in their immediate environment every night and during the vocabulary test. 

“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,” Franziska Neumann, senior author, said. Previous studies were tested in lab settings, however, this study proved that odor cues could be applied to everyday life. 

“Second, continuous cueing at night produces similar effect sizes as a study with selective cueing in specific sleep stages. Whether odor cueing during memory recall further increases memory performance has to be shown in future studies,” the researchers wrote in their paper. 


“The vocabulary learning units as well as the vocabulary tests in school had been conducted by two different teachers in two different school classes and with slightly different vocabulary tests. Therefore, there might be small differences in the instructions given to the students and other realization details,” the researchers said, explaining one of the many shortcomings of the study. 

“We had no control over how often the students repeated the learning material at home within the seven days before the final test,” the researchers added further. 

Incense Rose scented incense sticks can be used as effective odor cues during the whole night, while studying and writing the test, according to a new study conducted by University of Freiburg. Shutterstock