A Natural History of the Senses . “Hit a tripwire of smell, and memories explode all at once. A complex vision leaps out of the undergrowth.” Complex, indeed.
So smell is tied to emotion through the broad hand of brain wiring. But what does that mean about specific memories? How does this surprising little sense tie itself to a place, a person, a day? It’s through something much less romantic than Proust and his madeleine: learning.
Memories are tied to scents the same way that reading Proust over and over taught my mother about the symbolic value of dreams, the same way that I could eventually recall the definitions to Italian grammar words on my flash cards without having to turn them over to look. Smells are associated with specific events, people, and places because we learn them that way.
Trygg Engen, a professor of psychology at Brown University who passed away in 2009, was one of the first to theorize on odor memory and learning. It begins in childhood, he said, upon emerging from the womb. (Or even earlier. Studies have suggested babies are born with preferences for flavors similar to those ingested by their mothers while pregnant—even choosing chew toys scented with the aroma of alcohol over those with vanilla.) But babies, who have a fully developed sense of smell after only twelve weeks of gestation, are born without any preexisting knowledge of or opinions on scent, Engen believed. Emerging from the womb a blank slate, nothing is positive or negative until they learn it to be that way. The scent of a dirty diaper bears as much pleasure as a rose. Engen found that newborns responded the same way to the scents of foul onions and licorice, and that four-year-olds reacted similarly to the scents of rancid cheese and bananas. We learn smells through experience, often programmed into our brains while young, when we encounter most for the first time, when everything in the world seems large and intense. It’s these memories that stick.
This slate is soon filled, however. It’s filled with a love for anchovies like mine, a love that I learned while mimicking my father, who learned in turn from his father, who ate the strong salted fish piled on slices of pizza with cheese. It’s filled with a hatred for ripe bananas like my mother’s, which is so virulent she cannot stand in the same room as a peel that is soft and fragrant and dotted in brown. I once met a chef in New York City who fell in love with her partner after learning that she, too, was fond of the taste of durian, the famously stinking fruit from Southeast Asia. “She just had to learn to appreciate its smell,” she told me with a smile.
This is in part a mechanism of biology: if you eat something and become sick, the brain is programmed to remember the warning signals. I will never forget the slice of New York–style cheesecake, which I ate while on vacation with my family, only to spend the entire night helplessly huddled on the cold tile floor of the hotel bathroom, leaning over the toilet. It took years for me to bring myself to taste cheesecake again. Its creamy aroma, no matter how far away, nauseated me.
But how long do these scent memories last? Could Proust’s protagonist really remember that specific cookie from that specific visit to his aunt’s house in Combray all those years before? Engen was one of the first scientists to study long-term odor memory. In 1973, he asked a group of people to memorize a certain number of novel odors in his lab. Over the following days and weeks, he tested them periodically and found that their retrieval rate didn’t lessen over a period of many months. They could remember far fewer of the smells than they could a list of novel words in the same time span, true. But, nonetheless, Engen believed that scent memory was long lasting. “The Proustian insight is validated!” he wrote.
Though it has since been found that if another new scent is smelled soon after the one to be remembered, the memory
So smell is tied to emotion through the broad hand of brain wiring. But what does that mean about specific memories? How does this surprising little sense tie itself to a place, a person, a day? It’s through something much less romantic than Proust and his madeleine: learning.
Memories are tied to scents the same way that reading Proust over and over taught my mother about the symbolic value of dreams, the same way that I could eventually recall the definitions to Italian grammar words on my flash cards without having to turn them over to look. Smells are associated with specific events, people, and places because we learn them that way.
Trygg Engen, a professor of psychology at Brown University who passed away in 2009, was one of the first to theorize on odor memory and learning. It begins in childhood, he said, upon emerging from the womb. (Or even earlier. Studies have suggested babies are born with preferences for flavors similar to those ingested by their mothers while pregnant—even choosing chew toys scented with the aroma of alcohol over those with vanilla.) But babies, who have a fully developed sense of smell after only twelve weeks of gestation, are born without any preexisting knowledge of or opinions on scent, Engen believed. Emerging from the womb a blank slate, nothing is positive or negative until they learn it to be that way. The scent of a dirty diaper bears as much pleasure as a rose. Engen found that newborns responded the same way to the scents of foul onions and licorice, and that four-year-olds reacted similarly to the scents of rancid cheese and bananas. We learn smells through experience, often programmed into our brains while young, when we encounter most for the first time, when everything in the world seems large and intense. It’s these memories that stick.
This slate is soon filled, however. It’s filled with a love for anchovies like mine, a love that I learned while mimicking my father, who learned in turn from his father, who ate the strong salted fish piled on slices of pizza with cheese. It’s filled with a hatred for ripe bananas like my mother’s, which is so virulent she cannot stand in the same room as a peel that is soft and fragrant and dotted in brown. I once met a chef in New York City who fell in love with her partner after learning that she, too, was fond of the taste of durian, the famously stinking fruit from Southeast Asia. “She just had to learn to appreciate its smell,” she told me with a smile.
This is in part a mechanism of biology: if you eat something and become sick, the brain is programmed to remember the warning signals. I will never forget the slice of New York–style cheesecake, which I ate while on vacation with my family, only to spend the entire night helplessly huddled on the cold tile floor of the hotel bathroom, leaning over the toilet. It took years for me to bring myself to taste cheesecake again. Its creamy aroma, no matter how far away, nauseated me.
But how long do these scent memories last? Could Proust’s protagonist really remember that specific cookie from that specific visit to his aunt’s house in Combray all those years before? Engen was one of the first scientists to study long-term odor memory. In 1973, he asked a group of people to memorize a certain number of novel odors in his lab. Over the following days and weeks, he tested them periodically and found that their retrieval rate didn’t lessen over a period of many months. They could remember far fewer of the smells than they could a list of novel words in the same time span, true. But, nonetheless, Engen believed that scent memory was long lasting. “The Proustian insight is validated!” he wrote.
Though it has since been found that if another new scent is smelled soon after the one to be remembered, the memory
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