My living room fills with the scent of the bright orange fall candle glowing in the corner. The label calls it an “invigorating blend of aromatic eucalyptus, juniper berry, and fresh sage … as crisp as fall air.” But my nose detects another note—something waxy and warm and familiar.

It smells a little like crayons.

Suddenly, I see the torn cardboard box, the rainbow lines of nubby and worn supplies, and the textured newsprint of my Jem and the Holograms coloring book. These flashbacks prove for me what scientists have long told us, that scent is tied to memory.

Mothballs can remind us of Grandma’s wood-paneled den, cinnamon of our favorite cookies, and Vicks VapoRub of being curled up in a childhood comforter.

The portion of the brain that detects smell, the olfactory bulb, has special connections to processing memory and emotions. Unlike when we discern images of sounds, we basically detect smell by forming a memory of that smell.

We have about 400 odor sensors in our brains, called olfactory receptor proteins. Each whiff of something new—pumpkin pie, peppermint, burning leaves—activates a custom pattern of these sensors depending on the type and intensity of the smell. Since many of them will go off with each scent, scientists have struggled to identify which receptor responds to each chemical compound in a particular smell. Even with just 400 functioning sensors in the human brain (compared to over a thousand in animals like mice and dogs), the possible combinations top 1 trillion.

We have no set pathways or patterns to process a smell until we smell it for the first time, and the sensors go on and off accordingly. Every time after that, when we breathe in a scent, we return to the memory of experiencing it. That’s why so many of our scent flashbacks come from childhood, when we created these scent patterns for the first time.

When psychologist Maria Larsson interviewed adults about their autobiographical memories, she found that verbal and visual cues prompted stories from their teens and 20s. But with smell cues, they talked about early childhood, typically around age 5, with more emotional and vivid recall—like me and my crayons. (Crayons are actually a popular childhood memory trigger: they ranked among America’s top 20 most recognizable smells in a Yale University study.)

While specific and unusual smells make us nostalgic, the process for more common smells gets so well-worn that we just associate them with a particular emotion or mood. The smell of fresh clothes from the dryer or cookies baking in the oven lifts our spirits—enough that real estate agents and retailers incorporate “olfactive branding” using positive-associated scents as a way to lure in customers to spend more.

On the opposite end, unpleasant smells stress us out. Alan Hirsch of the Smell and Taste Treatment and Research Foundation described in The New York Times how people tend to become more aggressive when surrounded by bad odors. Smellier kinds of pollution correlate with higher numbers of car accidents. But even negative associations with smell are a positive: its connection to emotion and early memory may mean that its most important function is to protect children, allowing them to detect and remember smells that indicate something dangerous.

Smells not only have an emotional dimension, but a relational one: they drift between source and subject. Even the language we use to talk about smell implies that each smell must come from something. As science writer Ed Yong recently observed, we have “a vast palette of dedicated descriptive words for colors, sounds, tastes, and textures,” but when it comes to smells, we simply name the source. “We say that things smell like cinnamon, or roses, or teen spirit, or napalm in the morning.”

These derivative descriptions of smells prove subjective in experience; not only can the same smells cue slightly different sensors in different people’s olfactory systems (the reason why cilantro, for example, is such a divisive flavor), they also become associated with particular and personal memories.

“I’ve always thought of the sense of smell as a more intimate sense than most other senses,” wrote Aaron Sathyanesan, a Christian and neuroscientist whose doctoral research looked at proteins involved in processing smell. “In smelling, the thing that we smell becomes almost a part of us. In detecting a smell, we essentially absorb the essence of the thing emanating it.”

When we smell, we allow a scent to enter our bodies, our brains, and our memories. And our spirits. Smell is there at our earliest moments—not just in utero (it’s the second sense to develop, after touch) but at Creation. The first man meets God through smell, a big whiff of life and energy and Spirit. “Then the LORD God formed a man from the dust of the ground and breathed into his nostrils the breath of life, and the man became a living being” (Gen. 2:7).

We try to return the favor, letting our Creator smell us. God is pleased at the aroma of man's offerings (Gen. 8:21), including the “living sacrifice” of his people, described in 2 Corinthians 2 as a pleasing smell:

But thanks be to God, who in Christ always leads us in triumphal procession, and through us spreads the fragrance of the knowledge of him everywhere. For we are the aroma of Christ to God among those who are being saved and among those who are perishing, to one a fragrance from death to death, to the other a fragrance from life to life. Who is sufficient for these things? (vv. 14–16, ESV)

The incense used in certain liturgical traditions symbolizes our prayers wafting to heaven, another instance of “fragrant offering” to our all-sensing God. The Bible seems to indicate that the God of the universe smelling us is not a mere metaphor. The aroma of our sacrifice is one way he knows and remembers his creation.

Leaders of the early church also saw the intricate and relational sense of smell as an illustration of God’s own nature. Cyril of Alexandria, for example, used smell to describe how the Holy Spirit (whose Hebrew word, translated like breath, shares a root with the term for smell) is from the Father and in the Father:

The perfume which reaches our sense of smell by coming from aromatic herbs is different, so to speak, from them—on condition we admit it in thought and conceive that smell does not come from some other source than by receiving, in order to be perceived, the virtue of these herbs. Nevertheless, this perfume is not different, since it naturally comes from them and is in them. There you have an idea of how to imagine God and the Holy Spirit.

Others used a similar example—a flower and its scent—to describe the distinct but united nature of Christ, as human and God, flesh and divine.

There’s so much we still don’t know about our sense of smell, with its trillion combinations, mysterious sensors, and deeply emotional pull. As Sathyanesan notes, science and society have privileged our “eyes to see” and “ears to hear” (Prov. 20:12) over our nose to smell.

Perhaps that’s why I used to think of my scent memories as a sort of superpower. I knew I didn’t have X-ray vision or superhearing. But I’d smell something nostalgic and familiar, then push my brain to recall the scent, like trying to remember a name that’s just out of reach. It was a little victory to discover the smell: It’s the flavor of Juicy Juice I drank as I kid. It’s the laundry detergent my mother-in-law uses. It’s the perfume my best friend bought in France. I felt like I had developed some hyper-specific scent perception. But really this was what our noses and minds have been designed to do all along.

Kate Shellnutt is editor of Her.meneutics. She tweets as @kateshellnutt.

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