Human Flower Project
The Science of Scented Memories
A blast of rose fragrance improves human recall, bee recall, too.
Sleeping and sniffing to remember
from The Briar Rose series, by Edward Burne-Jones
Image: Pre-Raphaelites
How do you nudge a hippocampus? That’s the little buried part of the brain, somewhat resembling an unshelled purple-hull pea, that stores each day’s memories.
A team of German neuroscientists reports that by spritzing research subjects with rose scent as they perform a memory exercise, then spritzing them again when they’re sound asleep, the researchers could improve their subjects’ recall by 13%.
The findings were published in the latest issue of Science. And Benedict Carey, who writes for the New York Times and therefore can afford a subscription to Science, spread the word.
(Here’s another story on the research and still another, in case you have trouble accessing the NYT and Science, too).
With the whiff of rose administered to sleepers, “what is most likely happening,” Carey writes, “is that the cortex is telling the hippocampus to reactivate the same neurons that fired when a particular fact was noticed or learned. The hippocampus does so, encoding the firing sequence in the cortex and thereby consolidating the memory.”
Hippocampus (in blue)
Image: Brain Connection
As when Star Trek’s Jean Luc Picard marches over to the dumb-waiter and says, “tea, Earl Grey, hot,” and a steamy cup and saucer materialize. Well, kind of like that. Here, fragrance plays the part of the ship’s captain’s voice.
Deep sleep helps us all remember – perhaps one of the reasons why older people (i.e. women with hot flashes), whose sleep gets interrupted, also suffer memory lapses.
Dr. Jan Born, one neuroscientist on the research team, explained, “We would expect spontaneous reactivation driven by the slow-wave sleep, but by presenting the rose odor cues we intensified this activation and enhanced the transfer of these memories.” The sense of smell is more directly tied to the hippocampus, the memory bank, than the other four senses are.
We were intensely curious to know why the research team used rose, rather than some other floral scent. Would carnation have shown the same result?
According to Dr. Alan Hirsch, a taste and smell specialist, different flower fragrances affect us in a variety of ways.
Lavender, he’s found, causes relaxation. Jasmine has ”been proven to enhance athletic performance, and the smell of violets “enhance(d) learning speed by 17%.” (Lilies, by the way, “increase wakefulness” so should probably be nixed for sleep studies.)
And roses? Their fragrance, according to Hirsch, “increase(s) olfactory evoked nostalgia that will bring happy moments back to memory.”
We contacted the neuroscience team in Germany pointing out this psychological association of roses with memory and asking if this were why roses, rather than some other scented flower, has been chosen for the experiment. Dr. Björn Rasch from Universität zu Lübeck kindly wrote back.
He explained that the researchers used rose for several reasons; its fragrance “stimulates only the olfactory nerve in the nose, and not also the trigeminal nerve, like most scents do,” so the scientists could isolate olfactory response in the brain. He added that the rose scent they used “is only one substance (Phenethylalcohol), and no mixture. The substance is easy to handle, and the smell does not stick to the mask or the tubes we used, and vanishes relatively quick from the room air. Because of these properties, phenetylalcohol is often used in experiments about human olfaction.”
But what about the social psychology (as well as centuries of art and literature) that link rose fragrance with remembrance?
Le Bouquet de Violettes
By Edouard Manet
“We did not explicitly choose the odor because of its particular association with memory,” Dr. Rasch wrote. Nor did the team try other floral scents, “but I suppose.” Rasch added, “that other fragrances should have the same effect on memory formation during sleep. Other scientists investigating the potential of odors as context cues for memory during wakefulness have successfully used jasmine, geraniol or other, more exotic floral fragrances (e.g. Rachel S. Herz at the Brown University, Providence).”
Several years ago, another research group demonstrated how fragrance reinforced the memory of bees. You can read all about their study here.
At the time they published their findings, the entomologists stressed, “Honeybees are a great model to study learning and memory….With the honeybee genome near completion,” wrote Dr Judith Reinhard, “we now have a chance to discover the molecules involved in memory. We hope this could then help us better understand associative recall and memory in humans.”
Back in 2004, Professor Mandyam Srinivasan said the bee study might have practical application, for example “students burning incense whilst studying for an exam, then dabbing on the same incense whilst writing it, to facilitate recall of important facts.”
Based on Dr. Hirsch’s work, the bee study, and the German neuroscience report, we’d recommend neither roses nor incense. All you leg-jiggling type-A kids out there, cramming and high on Adderall, might try some violet water and a good night’s sleep.
Comments
My Chemistry professor used to discuss to us the connection between floral scents and a person’s feelings. I’m not clear about things but she mentioned that each floral scent triggers the production of a certain chemical in our body system that can make us feel in love, blush, or hug the person we love.
This is a really fascinating study for a number of reasons. First, I like the fact that it took things we already basically understood and tried combining them in a new way. We’ve known for some time that scent is very tied to memories, though typically the connection has never been suggested in such a specific way. Rather, we’ve known that a smell could evoke a specific time or place for an individual in very powerful ways. At the same time, there’s also been a general understanding that sleep is connected to memory, something that is essential to a lot of hypnotherapy. The notion of combining the two in a very specific way is quite clever. This experiment does raise a number of interesting questions, though. First, you list a number of smells that are tied to specific reactions in humans. Is that based on neurology, do you think, or on our culture’s association with these particular smells? Second, I notice that all the smells were flower-based. Would there be any difference if, say, the smell of cookies were used instead? And what would be the effect of a very negative smell?