Using smells to improve learning during sleep

A recently available study investigates the role of odor in learning and memory. The authors confirm that the strategic use of aromas while learning and during sleep might improve test performance - even beyond the laboratory.

In a nutshell, the recent study concludes that if we smell an aroma while we undertake new knowledge and sleep next to a way to obtain that same odor, we will find it easier to recall the information at a later date.

Earlier studies have previously determined this sort of effect, but the recent paper is among the few to spell it out it in a real-life situation. The researchers published their findings in the journal Scientific Reports.

As the lead author, Dr. Jürgen Kornmeier, explains, “We showed that the supportive aftereffect of fragrances works very reliably in everyday life and works extremely well in a targeted way.”

Every second of our waking day, information rushes in through your senses - sight, hearing, touch, taste, and smell - often together. From this dizzying cacophony, the brain picks out the salient information and builds a coherent picture of what's happening around us.

A small collection of this sensory information moves into our short-term memory, and a straight smaller proportion of this moves into our long-term storage, allowing us to recall the facts at a later time.

Learning anything new relies on the conversion of details from the short-term memory into the long-term memory, which occurs through an activity called consolidation. Earlier studies have demonstrated that consolidation while asleep is vital for building memories.

Scientists are keen to comprehend how exactly to influence and enhance consolidation. To this end, many of them have looked to odor.

Evolutionarily speaking, olfaction is among the oldest senses. It links closely to elements of the brain that manage emotion and memory, which explains why certain aromas can, with great and vivid ease, transport us back to a specific time.

Through the years, scientists have wondered if the ties between olfaction and memory could be useful in the quest to enhance learning abilities.

For instance, in a 2017 study, scientists presented a few of the participants with a particular odor while they carried out a learning task. Then, they presented the same odor to all of the participants. Those that smelt the odor during slow wave sleep performed better on memory tests than those who smelt the odor during rapid eye movement (REM) sleep. In addition they achieved greater results than those whom scientists hadn't offered the odor initially.

The idea of using an aroma to aid memory is reassuringly simple. However, earlier studies suggested that researchers must present the odor during slow wave sleep for it to work. To do this, they need to track the individual because they sleep, using hi-tech equipment. This system, therefore, is effectively useless for everyone.

In the brand new study, the researchers set out to understand whether this sort of technique could be successful beyond the lab.

To research, the scientists recruited 54 students from sixth grade classes in Germany. They asked these participants to keep rose scented sticks next to them while they learned English vocabulary in the home. A week following the students first encountered the vocabulary during a school class, they sat an exam.

The scientists split half of the students into four experimental groups:

Group 1: No contact with any odor cues.

Group 2: Exposure to rose scent while learning in the home and during the vocabulary test.

Group 3: Contact with rose scent while learning in the home and during every night before the test however, not during the test.

Group 4: Contact with rose scent while learning in the home, every night prior to the test, and through the test.

The remaining students, who didn't receive any odor cues at any point, acted as controls.

The participants in groups 3 and 4 performed considerably better in the test than those in groups 1 and 2. Those in group 2, who experienced the aroma during learning and testing, didn't benefit. This finding demonstrates the value of aroma exposure while asleep.

“The students showed a significant upsurge in learning success by about 30% if the incense sticks were used during both learning and sleeping phases.”

- First author Franziska Neumann

Although individuals in group 4 did perform slightly much better than those in group 3, the difference was not statistically significant. It appears, therefore, that contact with the aroma while asleep may be the pivotal factor.