This Is Why We Associate Memories So Strongly With Specific Smells

It probably comes as no surprise that the sense of smell is closely linked with memory. “People often do say that the sense of smell conjures up memories so well that they feel as if they were experiencing the event again,” says Theresa L. White, PhD, professor and chair in the department of psychology at Le Moyne College in Syracuse, New York. “Smelling Gramma’s pasta sauce makes them feel as if they were back in her home, enjoying a good meal.”

This year, several studies have looked closely at the connection between odors and powerful memories. One Northwestern Medicine study, published in Progress in Neurobiology, identified a neural basis for how the brain enables odors to trigger powerful memories.

And researchers from the University of California, Irvine, discovered specific types of neurons within the memory center of the brain that are responsible for acquiring new associative memories, i.e., memories triggered by unrelated items, such as an odor.

The Olfactory System and the Brain

“Our experience with odors is typically where odor is the backdrop or context for a person, place, or emotional state,” says Pamela Dalton, PhD, MPH, an experimental psychologist and faculty member at Monell Chemical Senses Center. When those are important or salient events, the odor can be strongly associated with the memory—to the extent that re-experiencing the odor often revives the emotions or feelings that were initially experienced, Dalton explains.

The stronger emotional memory connection with odor than other sensory experiences appears to be due to the privileged access of the central brain structures of the olfactory system to the limbic system structures—such as the amygdala and hippocampus, which are involved in regulating emotion and emotional memories.

A Particular Type of Memory

A 2010 study published in The American Journal of Psychology found that memories associated with smells were not necessarily more accurate, but tended to be more emotionally evocative.

Typically the most salient odors are ones that are infrequently experienced, so when they are smelled they have a specific association. “They often are ones that were initially experienced at a younger age,” Dalton says. However, she points out that because everyone’s experience with odor is so idiosyncratic and personal, the actual olfactory trigger can vary enormously from person to person.

“It’s worth saying that episodic memories, or memories of specific events from a first-person point of view, are where the sense of smell is best connected to memories,” says White. “Odors are not very good in terms of other types of memory. For example, if I gave you seven words to remember and seven smells to remember, there is no question that you’d do better with the list of words.”

White explains that associative memory can work for any sense, and smell is no exception. “Imagine that you always relax in a hot lavender–scented bubble bath at the end of the day,” she says. “You’ll come to associate the smell of lavender with the feeling of relaxation. This means that over time, when you smell lavender and you’re not in the bath, you’ll still have the feeling of relaxation.”

Harnessing the Power of Scent 

Researchers have found that odors can serve as a memory trigger, augmenting our ability to recall or recognize information.

In Dalton’s graduate work, she had people study the faces of strangers in the presence of different odors. “The best recognition performance occurred when they were tested with the same odor that had been present when they first saw those faces,” she reveals. “A number of other studies have confirmed similar findings, i.e., that studying in the presence of an odor can help one’s recall of that information.”

During these pandemic times, it’s natural to wonder whether the disabled sense of smell of some COVID-19 survivors could hypothetically lead to memory issues.

But to date, nobody has specifically studied memory among individuals who have lost their ability to smell (pre-COVID-19). “Olfactory decline is associated with cognitive impairments, but that’s because the central structures involved in olfaction can be impacted in neurodegenerative diseases,” Dalton says. “Loss of smell may mean that any olfactory memories will no longer be revived and that no new ones can be formed.”

Hopefully, in time we’ll have an understanding of all the ramifications of the loss of smell among so many individuals on all aspects of cognitive and emotional function, including memory.