If there is one thing we all have learned throughout our education, it is how to memorize a large amount of information in a very short amount of time. Many of us have tried mnemonics, storytelling, rereading, and rewriting, but how many of us have tried smelling a rose? This may seem strange to hear, but according to a recent study, presenting an odour cue while sleeping can increase memory consolidation and optimize learning.

How memory works is a fascinating and complex process, but you can break it down into three simple steps: encoding, consolidating, and retrieving. When you learn some new information, your brain encodes it into your short-term memory in the hippocampus (the region of the brain involved in learning and memory).

Encoding causes neurons (nerve cells) to fire in a specific pathway, which become more familiar the more you access the memory. This consolidates the memory, or shifts it from your short-term memory to your long-term memory. You can compare it to walking down a path through the forest. The first time, you have to think carefully about where you are going, but if you do it long enough, eventually you will be able to walk the path with barely any thought. The final step, retrieval, is the process of accurately recalling the now-consolidated memory.

What scientists have found is that sleeping can help strengthen the connections between neurons, therefore helping to integrate short-term memories into long-term memories. A study from the University of Lubeck in Germany found that presenting an odour while learning the locations of objects, and then presenting the same odour during the slow-wave sleep (SWS) part of the sleep cycle improved memory consolidation. They believed that the scent reactivated the part of the brain containing the short-term memory which increases its likelihood of being integrated into the long-term memory.

Another recent study tested this, and if presenting the odour cue all night rather than just during SWS still increased retention.

This study involved students from two classes who were randomly assigned to either a test or control group. The test group was taught and tested on German-English vocabulary under four different conditions: No odour cue (N), rose odour during the vocabulary learning period at home and the vocabulary test at school (LT), rose odour during the vocabulary learning period and every night the week before the test (LS), and rose odour cue while learning vocabulary at home, every night while asleep, during the test (LST).

Each condition lasted a week. They found that there was not much of a difference between the test and control groups when a rose scent was presented during just the learning and testing period, or when no scent was presented at all.

However, when the scent was presented during learning periods, and every night before the test, the test group did significantly better than the control group. This benefit increased when the scent was also presented during the testing period, suggesting that the odour helps with both memory consolidation and memory retrieval.

Now, you might be considering applying this knowledge to your own lives. However, if you’re not a fan of strong scents, then you can also try auditory cues. Some research has shown that playing a recording while sleeping can help with memory consolidation. You can also experiment with the intensity or use different scents for different subjects to reduce memory interference.

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