Enhancing Our Power of Smell Improves Our Cognition
The alchemy of olfaction: Molecules into perfumes.
Posted May 6, 2026 | Reviewed by Lybi Ma
Our olfactory system, which originated millions of years ago, evolved to detect small changes in the chemical composition of the environment and thereby serve as a protective mechanism. Such a use remains operative today by enabling us to smell telltale odorants that may precede such things as an explosion secondary to a gas leakage.
But the olfactory system comes with good things too: Responding to such pleasurable odorants as flowers or the aromas of newly cut grass. Chemicals are the key. But a smell can’t always be predicted from its chemical composition or the order of its molecules. D-Carvone smells like caraway seeds, whereas its mirror image, L-Carvone, smells like spearmint. One scent stimulates a specific firing pattern in one part of the olfactory bulb; other molecules stimulate other firing patterns, with most molecules failing to stimulate any pattern at all.
But when a scent—a specific brew of chemicals—arouses our attention , our response differs according to the molecules involved. Smelling bergamot in our Earl Grey tea stimulates one activation pattern in the olfactory bulb; smelling Lattafa Asad perfume stimulates another. Scents are composed of chemicals with unique chemical signatures corresponding to the medley of chemicals in a particular odorant.
Unique among the five senses, olfaction is the only sensory receptor that links directly to the limbic system, which processes emotion . As a result of this direct connection, smell surpasses any of the other senses in evoking emotions. Further, these emotions are more intense, vivid, emotionally charged, and “experiential”—the odorant mentally transports a person back to a scene associated with their initial exposure to the scent. Think of Marcel Proust and the little cookie, the madeleine, which mentally transported him back to his childhood in Combray.
Now, if you are thinking that the madleine is eaten rather than smelled, you’re correct. But 70 to 80 percent of perceived flavor depends on olfaction, with the loss of smell (anosmia) greatly reducing flavor perception.
If you need further proof about the effect of olfaction on the taste of food, think back to the last time you suffered from heavy nasal congestion secondary to a cold or intense allergy. Your ability to taste your food was significantly compromised—a clue that a major portion of taste is dependent on smell. Both taste and smell are integrated within the brain in the orbitofrontal cortex, and from this integration emerges the sense of flavor.
Historically— dating at least from the Middle Ages—certain scents have been identified as evoking specific emotional responses. The art of perfumery involves an alchemy-like blending of various chemicals to create a particular scent and thereby provoke a specific emotion, such as passion, a sense of reverie, or tristesse .
After the reception of a scent from the olfactory bulb, which is a first step in processing and refining that particular odorant after smelling it, the scent is transferred to the limbic system, with one area especially important: The hippocampus, which also happens to be the initial step in the formation of a memory .
Thanks to this close approximation of the limbic-emotional area and the hippocampal-memory area, neuroscientists have long speculated that odor identification might serve as a powerful memory retrieval aide—that odorants might serve as facilitators for the formation, preservation, and retrieval of specific memories. Again, this insight was suggested by the linkage of the smell-emotion experiences of Marcel Proust.
In one memory experiment carried out in the emerging field of olfactory training , volunteers learned a series of words while being exposed to the scent of rosemary; another group learned the words while in a room gently suffused with the scent of peppermint. After only a few trials, it was clear that exposure to either scent while learning the words served to facilitate recall of the words when later exposed to the same scent. But if a switch was made (peppermint) while learning, (rosemary) while retrieving, no word improvement occurred. And it didn’t matter incidentally whether the subjects were exposed to peppermint or rosemary. In addition, in both instances, they did better than another group of students not exposed to any background scents at all.
In another experiment by Björn Rasch and associates, volunteers were exposed while sleeping to the same odor (rosemary or peppermint) as was used during the learning phase. Subsequently, participants recalled the words better the next day after the specific odor had been reintroduced to them the night before during sleep. The most economical explanation for this effect? During sleep, especially during slow wave sleep, the smell area consolidated the odorant with the words practiced before sleep to form a word-odorant combination. Later, upon awakening, both the word and the background scent were remembered together as a combo.
But lest we conclude too much too early, a few caveats are necessary to keep in mind.
What makes all of this appealing is the use of a formerly neglected sensory avenue to contribute towards the enhancement of both scent sensitivity, recognizing and naming the different odorants, and memory recall, especially with older people .
Not only did people, when trained with odors, demonstrate a gain in their ability to remember the words, but they also did better on tasks measuring visual memory and general memory. Such findings suggest the usefulness of smell training as a means of strengthening memory networks in general. The questions are: How long must the training be continued for it to be successful? And will people be willing to put in the necessary time and effort to reach these goals ?
Richard M. Restak, M.D.
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Richard Restak, MD , is Clinical Professor of Neurology at George Washington University School of Medicine and Health Sciences, and the author of The 21st Century Brain.
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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.