During the third snow day last winter, after putting the finishing touches on my Carnegie paper, I got a hankering to clean up the bulging piles of stuff incapacitating my bookshelves. Spelunking hat on, I dove into the depths, gathering large bundles of old French assignments and empty hair products and dumping them into voluminous trash bags. I felt energized and ready to complete my mission when, in an au bon pain takeout bag, I stumbled upon the contents of my 2016 sailing camp backpack. And lingering in the bottom of the bag was a goodbye letter from the boyfriend I’d had that summer—a letter I have no recollection of ever receiving.
I was struck with a wave of sentiment. I couldn’t place whether I was sad, or happy, or even neutrally pensive. I just felt. I read and reread the letter, moved my fingers over the dog-eared corners and traced the messy blue handwriting. I brought the letter closer to my face—it smelled of Neutrogena sunscreen, fruit-flavored chewing gum, and sweat. I looked one more time at the last line; my summer-camp boyfriend had closed the letter with “Love you! :D.”
Oh, my god. I hadn’t spoken to the boy in question, or really thought about him since we’d parted, but I was suddenly overcome by an intense longing for simpler, happier, sunscreen-scented times.
The English lexicon has a word for this exact sentiment: nostalgia. Nostalgia, according to the Oxford English Dictionary, is a “sentimental longing or wistful affection for the past,” and the word itself comes from Greek roots nostos and algos. Nostos means “returning home,” and algos means “pain,” so nostalgia etymologically means “the pain of returning home.” Sounds about right. Nostalgia is something everyone feels, and it’s ingrained in almost all cultures. Just think about the feelings that the smell of fresh-baked cookies, the ice-cream-truck jingle, and playgrounds evoke.
But what does nostalgia mean on a neuroscientific level? Where does it come from? To answer these questions, we need to look at the work of Sigmund Freud. Freud studied loss and nostalgia back when he was creating psychoanalysis in the early 1900s and wrote the book “Mourning and Melancholia,” which, among other pursuits, searched for the root of nostalgia. Critically, in 1908, Freud identified a strong link between smells, emotion, and nostalgia, which was pretty radical for the time.
Today, scientists have found evidence to verify the odor-emotion claim (10 points to Sigmund!). When you smell something, chemical particles travel up your nose and through the olfactory bulb located at the front of your brain. Scientists think the olfactory bulb works as a filter; it receives input signals that a smell triggers, and it decides where to direct them. The signals will most likely be sent to the hippocampus (which consolidates memories), the orbitofrontal cortex (which makes decisions), or the amygdala––the emotion-processing center of your brain.
More specifically, the amygdala is one of two almond-shaped clusters of neurons in the middle of your brain. Along with its partner in crime, the hippocampus, it uses input signals such as smells to create and store emotional memories. Researchers are working to figure out exactly how the amygdala stores emotional memories, but so far they think they know where: in the connections (a.k.a. the synapses) between its outer and inner neurons. From there, the amygdala works with the hormone system to evoke responses in your body, like the fight-or-flight response or the reward system.
But what does any of that have to do with nostalgia? Well, as far as scientists know, when you smell, see, or hear something that forms part of an emotional memory you already have, somewhere in your brain your memories are triggered, causing a sense of wistfulness or longing. That’s why smelling hot chocolate makes you remember snowy winter evenings with your family, watching kids on swings elicits a small smile, and hearing “Call Me Maybe” instantly transports you to the 2013 bat-mitzvah circuit.
Now that I’m about to wrap up my junior year, I find that nostalgia is popping up even more. College applications are on the horizon, accompanied by an ever-looming sense of adult responsibility; simply put, for many of us it’s a time of change. We’re far from being middle schoolers with bright pink braces, toiling over two-page essays with teachers guiding us at every step. Now we’ve written a history paper, and a profile, and maybe started calculus. We’ve learned how to grit our teeth and get through the work, even when we’re tired and would rather do anything else than study the respiratory system or write three pages of character description. So no wonder nostalgia’s hitting us particularly hard. We’re no longer the kids we used to be; we’re a changing amalgamation of everyday experiences, quiet passions, and nuanced opinions, with the occasional nostalgic memory thrown in for good measure.