This essay is part of Scent Access Memory, our editorial series with Dirt.

Every so often my phone will surface a picture of myself sitting before a light green wall, electrodes and wires protruding from my scalp like the spines of a sea urchin at a science museum. I’m wearing a black surgical mask. I can tell that I’m smiling by the crinkled edges of my eyes, one slightly smaller than the other, as pointed out earlier by my blunt German neurologist. 

The EEG was being administered by his much warmer son, who after applying the small metal discs to my head with an odorless gel, offered to take my picture with my phone. It’s now buried under a year’s worth of images in my camera roll; only when it surfaces via a widget on my home screen do I remember it at all — the antiseptic smell of the sterile little room, the cold clip of the wires, the mercurial patterns produced by strobe lights that played out behind my lids. 

Where does that memory live otherwise, when I’m not thinking about it? In my phone, on the cloud, or waiting in the misty backdrop of the mind, that vast exosystem existing outside of consciousness. Are our memories sealed behind skin, encased in skull? Or do they also exist in our environments and devices, as suggested by philosophers Andy Clark and David Chalmers. In 1998, when Clark and Chalmers published a paper which theorized that elements of the outside world, such as computers, act as extensions of the mind, it was met with some intrigue but mostly dismissal. Not even a decade later, when humans acquired the iPhone, that attitude started to shift. It’s now one of the most-cited philosophy papers in recent decades. “This phone is becoming part of your memory,” Chalmers explains in a 2018 video, gesturing smartphone in hand, the pad of his palm armored in silicon. “If we say that memory is part of the mind, then my phone is likewise storing my memories.”

Note his use of the word “storing” — a phone stores memories, just like the mind stores memories. Both retrieve them, process them. While Clark and Chalmers’ theory invites our computers and devices to be considered as an extension of our minds — of our consciousness — neuroscientists have for half a century been describing the mind as itself a computer. Parallel advances in computer technology and cognitive research have led to a cross-disciplinary effort to understand human intelligence as essentially information processing. The brain is a computer, the metaphor goes, a programmable machine. The mind is the software it runs on. The brain-computer metaphor has become so pervasive, among both scientists and everyone else, we hardly recognize when we’re using it. 

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My mom loved magnolia trees and the scent of their flowers: sweet, floral, lush and creamy, edged with citrus. There was a magnolia tree outside of her bedroom window in her childhood home in Southern Virginia. There were also magnolias all over the neighborhood I grew up in, just a couple hours west. With their waxy, deep green leaves and sculptural white flowers, magnolia blooms announce the beginning of summer in Virginia. Later in the season, the flowers drop to the ground –– their fragrance only heightened by the petals crushed underfoot. Thick as summer humidity, their scent can carry half a block. It’s the smell of magnolias that brings my mom to me, more so than the perfume she wore or the scent of her soap. 

“Unlike the other senses, smell needs no interpreter,” writes Diane Ackerman in A Natural History of the Senses. “The effect is immediate and undiluted by language, thought, or translation.” Smell is the sense of nostalgia, both phenomena felt but fleeting, more defined by a lingering absence than an actual presence. Neurologically speaking, the connection between smell and emotional processes is much stronger than that between smell and language. Odors are difficult to name, even when we recognize them, to say nothing of describing them with our scant scent vocabulary. Smell-sensing neurons extend directly to the olfactory bulb in the brain, rather than taking the more circuitous routes of other senses, which is one theory for why scent can conjure a memory, emotion, or desire so immediately. Smells disappear quickly, but their imprint lasts. “There  is  almost  no  short-term  memory  with  odors,” Edwin  T.  Morris writes  in Fragrance. Just long-term ones.

The loss of smell can be an early symptom of Alzheimer’s disease. I don’t remember my mom losing hers. I do remember her short-term memory going first, before the long-term. “[It] begins, a trickle, this thin slow falling of the mind,” writes Anne Carson, who lost her father to Alzheimer’s. After my mom was diagnosed, we got her an iPhone in hopes that it would help her keep track of things, but it was a bit too late to form the habit. Instead, she wrote notes to herself, always a writer — in notebooks, on the corners of envelopes, and the back of receipt paper, a long, thin list of reminders. I still find these notes tucked into purses and in the back of drawers. The slanted letters with their long, looping tails, which I tried tirelessly to copy as a kid, feel as familiar to me as hearing her voice. As Christina Sharpe writes in Ordinary Notes, “note” can be a noun, a record of facts or thoughts written down to aid memory. It can also be a verb, “to notice or observe with care.” On a different page of the book, Sharpe has scanned in one of her mother’s notes, a list of books and their prices written on the back of a faded blue bookmark. 

For the philosophers Clark and Chalmers, this type of note-taking is also part of the extended mind. In their paper, they invent a character named Otto who has Alzheimer’s, lives in New York City and one day wants to visit MoMA. Otto looks in his notebook and finds the address is on 53rd Street. When Inga, who also lives in New York and doesn’t have Alzheimer’s, wants to go to MoMA, she thinks for a moment and recalls that it's on 53rd Street. Inga consults her memory like Otto consults his notebook. “For Otto,” the authors write, “his notebook plays the role usually played by a biological memory.” Both already held the “belief” that the museum was on 53rd street, it just needed to be accessed, which each did by different means. (If I wanted to get to MoMA, I would consult my phone and let it lead me via little blue dot all the way to 53rd street, despite the fact that my memory’s fine.)

Recently, I watched a video of Clark talking about the extended mind theory where he mentions a colleague who’s an occupational therapist and works with people with Alzheimer’s. Going by the results of her tests alone, Clark’s colleague couldn’t understand how her patients were getting around the city and living by themselves. But when she went to visit them in their homes, she found they were “beautifully structured” with post-it notes, recorded routines, and written reminders. An external mnemonic system that instructs and directs and reminds, not unlike how biological memory prompts recall, pulling information from the outskirts of consciousness temporarily back in. When these people were taken out of their structured environments and moved into a care home, Clark’s colleague found that their cognitive function decreased dramatically. “Sometimes interfering with what looks like our environment is doing something so profound to us we could think of it as interfering with ourselves,” he concludes.   

I find the idea that my mom’s notes are an extension of herself a comforting idea, poetic even. I’ve never thought of them that way before, at least not consciously, but I guess that’s why I keep them: a part of her internal self made concrete, accessible to me where she is not. 

**

There are also biological “devices” that are considered—scientifically speaking––something like external sensors to the brain. The brain can’t smell or taste or touch or hear. Our noses, tongues, fingers, and ears do those things. Then they transmit the information back to the brain, faithful messengers they are. But only the mind can make any sense of them, can stitch these sensations into the gauzy fabric of meaning. 

My mom’s hospice nurse, Deb, told me that hearing was usually the last sense to go. I sat by her bed in the care home and tried to speak in a tone that was soothing but still louder than the robotic puffs of the oxygen machine. I recounted my days, told stories of her friends, talked about my sisters. When the day’s details ran dry I told her over and over again that we loved her. Told her we were all fine, she could leave us. Played her Charlie Brown’s Christmas, a favorite, from the tinny speakers on my phone. When my dad and I were both there, we’d volley stories across the room, weaving easily through an inventory of memories long-since worn smooth from the telling. We told them for her, but what it did was make us feel better. Even my mundane monologues had the effect of settling my body, the vibrations of my vocal cords falling into an easy rhythm with breath. It was early June in Virginia, the magnolias were in full bloom. 

After my mom’s funeral I flew back to where I was living in Berlin, and started going on long walks in the morning. My mind was foggy and unfocused, the world felt removed; swaths of time would just fall away. Walking lessened the grief but also eased my mind, a clearing. When I mentioned this to a friend, she told me about a book she’d been reading by science writer Annie Murphy Paul called The Extended Mind. The book borrows its title from Clark and Chalmers’ paper, but Paul is less interested in computers as extensions of the mind as she is in the other entities of our environment—sensations, built spaces, even gesture—that take on that role. In a chapter called “Thinking with Movement,” a series of empirical studies show that we think better in motion than we do sitting down. Mild physical activity like walking has proven to sharpen attention and improve memory; our body and our environment helping us to think.

Paul is not a big fan of the brain-computer metaphor. “The brain, according to this analogy, is a self-contained information-processing system,” she writes. “From this inference emerges a second: the human brain has attributes, akin to gigabytes of RAM and megahertz of processing speed, that can be easily measured and compared.” This sentiment is echoed in the book God Human Animal Machine, when Meghan O’Gieblyn writes that the brain-computer metaphor is strongest in accounting for functional consciousness, but hits its limits when confronted with the question of subjective experience, our rich inner lives. 

Thanks to brain imaging technology like MRIs and EEGs, we have a pretty good understanding of how consciousness functions — what constitutes smell, for example, or the mechanisms by which the brain calls forth an image. But what we still can’t explain is why these processes give rise to interior experience — why the fragrance of magnolias elicit maternal love, or why a photo on my phone evokes the smell of a doctor’s office, the chill of metal on scalp. This is where the mechanical metaphors for the mind start to dilute and dissolve. 

So much of the mind is still a mystery to us. There’s the mystery of subjective experience, why brain processes are accompanied by interior experience at all, which Chalmers calls the “hard problem of consciousness,” a question that has plagued scientists and philosophers for centuries. There’s the fear of it all unraveling — memory, the stuff of self — which is why I was in that office with wires attached to my head in the first place.   

This sense of unknowing could be why the brain-computer metaphor is so dominant in our thinking about mental activity. Metaphors are stories we tell to make sense of something we don’t fully understand, as psychologist Robert Epstein writes in Aeon. When Epstein challenged a group of researchers from a prestigious research group to explain human intelligence without using any terms encompassed by the brain-computer metaphor, he found they couldn’t do it. “There is virtually no form of discourse about intelligent human behavior that proceeds without employing this metaphor.” 

The curious thing about the brain-computer metaphor is that it loops back on itself like a Möbius strip. In 1946, when the ENIAC, one of the first electronic computers, was unveiled, newspapers and magazine articles described it as a “giant electronic brain” and a “brain machine.” Today, our descriptions of AI are replete with human attributions: these systems “learn” and “see” and “understand.” When we describe computers, we describe them in our own image.

Metaphors are slippery, like memory. But then, putting things to words is always a translation, an approximation of the thing. There’s perhaps no better reminder of that than our inability to describe the sensation of scent, its transportability, what it feels like and means to us. As Epstein suggests, the mind and memory are equally inarticulable without leaning on metaphor. Logic liquifies, facts diffuse. Perhaps best to turn to literary metaphors, then. My favorite is one from Annie Ernaux, who also lost her mother to Alzheimer’s: “Our memory is outside us, in a rainy breath of time.”