What’s that smell? It reminds me of…
Said everyone, ever.
Whether it’s the smell of freshly baked bread, the sweet scent of a particular perfume, or the musky odour of your grandparent’s place, smells evoke emotions and trigger memories.
Admittedly, that in itself isn’t groundbreaking. But the science behind why, truly is. Let’s scratch (and sniff) away at the surface to reveal why smell can be so powerful.
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What’s going on with our schnoz?
First, the science. A scent is a chemical particle that floats in through the nose and into the olfactory bulbs, which start inside the top of the nose and run along the bottom of the brain. It’s here that the sensation is first processed into a form that’s readable by the brain.
The olfactory bulbs have a direct connection to the famous amygdala – where emotions are processed. As well as to the adjoining, and equally well-known, hippocampus – where learning and memory formation take place.
This unique pathway means that scent is the only sensation to travel directly to the limbic system first, the emotional centres of the brain. All other senses (sight, hearing, taste and touch) go through the thalamus, a “switchboard” if you will, that relays information to the rest of the brain.
This means whatever we see, hear, taste or touch, we process as a thought and then a feeling. For smell, we take a direct hit to the feels before any of that processing occurs. Ever lusted over the smell of something (or someone) without understanding why? Bingo.
It’s no surprise that a study on the neuroanatomy of odour produced by neuroscientist, Artin Arshamian suggests that memories triggered by an odour (like the scent of a rose) were much stronger than memories triggered by the verbal label of that odour (like the word “rose”).
This direct connection creates an intimate connection between emotions, memories and scents. Turns out it’s not simply the invention of perfumers marketing teams…
“I Smell Trouble (and Happiness?)”
And you’d be correct!
Happiness is usually easy to register, be it a beaming smile or giddy laugh. Now, a team of scientists at Utrecht University found that happiness does indeed have a smell.
Happiness generates chemicals that get secreted in sweat, and that sweat signal gets sniffed by those around us. Not only that, the scent of someone who is in a happy mood genuinely makes us smile – without even looking directly at the person! It’s known as “chemosignalling”.
A hefty pile of evidence suggests that more types of emotions have a scent too:
- The scent of someone who’s scared or startled will make you feel apprehensive
- The body odour of stressed-out people ups our vigilance
- The smell of a person who just watched something disgusting makes our faces twist in disgust
This strange entanglement of emotions and scents may actually have a simple evolutionary explanation. The amygdala evolved from an area of the brain that was originally dedicated to detecting chemicals.
Rachel Herz, an adjunct assistant professor of psychiatry and human behaviour at Brown University and author of the book “The Scent of Desire”, explains that “emotions tell us about approaching things and avoiding things. That’s exactly what the sense of smell does too. They’re both very intimately connected to our survival.”
This is backed up by an experiment published in 2014 in the journal Psychological Science. The experiment showed that people could identify signs of sickness and disease through body odour. For the evolution of a species, that certainly has its advantages.
Smell & Mood
When it comes to smell and mood, the waters become a touch murkier.
One, because people’s own peculiarities mean identifying “happy” smells is nigh impossible. I mean, it can’t just be me who loves the smell of burnt hair? It is? Okay…
Two, pleasant fragrances, like pine and citrus, can improve our mood. But it’s often our expectations of a scent, as opposed to the direct effects of exposure to it, that are responsible for the ‘benefits’.
In 2001, Herz and von Clef found that participants of a study rated an identical odour as more pleasant when it was presented with a positive label (“parmesan cheese”) rather than a negative label (“vomit”).
Another experiment by the Social Issues Research Centre found that just telling participants that a pleasant or unpleasant odour was being administered altered their self-reports of mood and well-being. Even when they might not be able to smell anything!
Despite these oddities of the human mind, we can make some significant generalisations about smell preference.
How so? Well, we do tend to ‘like what we know’. For instance, people give higher pleasantness ratings to smells which they are able to identify correctly. Now I feel no guilt in loving the smell of McDonald’s, just turns out I’ve got a nose for nuggets.
And there are also fragrances which appear to be universally perceived as ‘pleasant’.
Take vanilla. Not only does its scent have the medicinal power to reduce stress and anxiety, vanilla is powerful because it’s the one universal trigger for childhood memories of comforting, milky warmth. As well as sweet treats and rewards, ice-cream holidays, innocent pleasures and so on. We even describe plain, innocent people as “pure vanilla”. Harsh, but fair.
Remember that aroma?
It’s through memory that we learn to remember smells. So it’s no wonder that diseases that take away our memory, such as Alzheimer’s, also take away the ability to distinguish scents.
Like with vanilla, the scent of seaweed for some could conjure up memories of childhood trips to the beach. This can often happen spontaneously, with a smell acting as a trigger in recalling a long-forgotten event or experience.
It’s no surprise that childhood memories are most evocative when smell is concerned. Smell is the sense that’s most developed in a child through to the age of around 10 when sight takes over.
Because “smell and emotion are stored as one memory,” childhood tends to be the period in which you create “the basis for smells you will like and hate for the rest of your life”, says Dawn Goldworm, co-founder and Scent Director of olfactive branding company, 12:29. This also accounts for taste too, because taste and smell are intertwined.
Maria Larsson, Professor in Perception and Psychophysics at the Stockholm University, discovered similar patterns in a study from 2006. For visual and verbal cues, people’s memories came from their teens and 20s, as expected.
But for smells, people recalled things from their memory from as young as 5. “It was really, totally clear that when they recollected a specific memory, that memory was localized to the childhood period,” she says. Memories are also more emotional and more vivid than memories brought up by visual or verbal cues.
There you have it. Smell is arguably our most important sense – who’d have smelled that coming! It’s not surprising we look down on our noses (literally and figuratively). The human sense of smell receives a lot of stick. Not least for the falsehood that our sense of smell is awful compared with our furry friends. But we should be celebrating our schnoz! Turns out, it’s an incredibly powerful little sniffer.