Use of smells to boost learning while you sleep

A recent study explores the role of the odor in memory and learning. The authors confirm that the strategic use of aromas during learning and during sleep may improve the performance of examinations— even outside the laboratory.

Student studying for her exam
A recent study makes use of rose fragrance to improve student memory performance.

In a nutshell, the recent study concludes that we will find it easier to recall the information at a later date if we smell an aroma while we take on new knowledge and then sleep next to a source of that same odour.

Previous studies have described this type of effect before, but the recent paper is one of the few to explain it in a real-life situation. In the journal Scientific Reports the researchers published their findings.

As Dr. Jürgen Kornmeier, the lead author, states, “We have shown that the supporting effect of fragrances works very efficiently in everyday life and can be used in a targeted way.”

Taming memory

Every second of our waking day, details rushes through every one of our senses— sight, hearing, touch, taste, and smell — often at one. The brain extracts the pertinent information from this dizzying cacophony, and generates a clear picture of what is happening around us.

A small selection of this sensory information moves into our short-term memory, and an even smaller proportion of that moves into our long-term storage, enabling us to remember the details later.

Understanding something new depends on transferring the information from the short-term memory into the long-term memory, which happens through a consolidation process. Earlier studies have shown that consolidation during sleep is vital to memory building.

Scientists are keen to understand how consolidation can be influenced and increased. Some of them have looked to odour for this reason.

Smell and memory

Evolutionarily speaking, one of the oldest senses is the olfaction. It closely links with parts of the brain that deal with emotion and memory, which is why certain aromas can transport us back to a particular point in time with great and vivid ease.

Over the years, scientists have been wondering whether the links between olfaction and memory might be useful in the search to develop learning skills.

For example, in a 2017 study, some of the participants were provided by scientists with a specific odor while conducting a learning task. Instead, all of the participants showed the same odor. Those who smelled the smell during slow wave sleep performed better on memory tests than those who smelled the smell during rapid eye movement (REM) sleep. We have achieved better results than those originally not presented by scientists with the odour.

The idea of using an scent to support memory is clear and comforting. Nonetheless, earlier studies indicated researchers need to present the odor during slow wave sleep for it to function. For this to happen, we need to monitor the person as they sleep using hi-tech equipment. This technique, therefore, is effectively useless for the general public.

The researchers have set out in the new study to understand whether this type of technique could be successful outside the laboratory.

The smell of a rose

The scientists had recruited 54 students from sixth grade classes in Germany to investigate. These participants were asked to keep rose-scented sticks next to them as they learned English vocabulary at home. They sat an exam a week after the students first encountered the vocabulary during a class at school.

The scientists divided half the students into 4 experimental groups:

Group 1: No exposure to any odor cues.

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

Group 3: Exposure to rose scent while learning at home and during each night before the test but not during the test.

Group 4: Exposure to rose scent while learning at home, every night before the test, and during the test.

The remaining students, who did not receive any odor cues at any point, acted as controls.

The remaining students, who at any point did not receive any signs of odour, acted as controls.

In the test the participants in groups 3 and 4 performed considerably better than those in groups 1 and 2. It did not benefit those in group 2, who experienced the aroma during learning and testing. This finding proves the importance of exposure to the aroma during sleep.

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

– First author Franziska Neumann

Although group 4 individuals did perform slightly better than group 3 individuals, the difference was not statistically significant. Thus it seems that the pivotal factor is exposure to the aroma during sleep.

Real-world applications

One of the most important findings of this study is that the aroma boosted memory performance even though it was present for the entire night, meaning that during slow wave sleep there was no need to specifically present the smell.

As Dr. Kornmeier says, “This makes findings suitable for daily use.”

Naturally, a study that uses only 54 participants is not large enough to be definitive. This effect is now well researched, however, and there is little doubt that some people might find it useful to pair odors with memory tasks.

Such results demonstrate, for the first time, that this approach could be effective in real-life situations for people. As the protocol is relatively easy to follow, we hope to see more research coming soon.

Because of the real-life setting of the experiment some limitations are inherent. For example, the scientists had to rely on the participants to make proper use of the rose scent while at home.

The researchers also had no control over the proximity of the scented rose sticks during home or sleep learning, meaning that each student may have experienced varying aroma intensities.

All in all, the results of this study contribute to the existing evidence that combining learning and sleep with a specific scent can improve the output of memories.

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