Once in awhile I'll smell something that transports me back in time. Memories I haven't thought about for years come flooding back, along with emotions that feel as vivid as they were then. The smell of pine trees brings me back to summer camp, certain old buildings conjure up my elementary school days, and if anyone is ever wearing Peach Bath & Body Works lotion I'm back in seventh grade. This winter as I was cleaning out boxes from my childhood closet I discovered some old chapsticks and perfumes - gross and dusty as they were, I hesitated to throw them away, since they contained so many memories.
But of course, as David Owens describes in his moving New Yorker essay, The dime store floor: What did childhood smell like? after repeated exposure, these time-travel-inducing smells lose their ability to transport us. Owens describes the discovery of his late father's deoderant brand (Old Spice), and his dilemma over whether to wear the same brand himself or save it for special occasions in order to preserve the memory it holds. This story made me think that maybe we should all keep time capsules of the smells that are important to us. The problem is, we don't always know what they are. It's usually the incidental smells we don't think much about - the hand soaps, the foliage, the mildew - that later evoke the most powerful emotions.
Why is smell so intimately linked with memory? One reason is that the olfactory bulb, the part of the brain that processes smell, interacts with regions of the brain that are responsible for storing emotional memories. Through the process of conditioned learning, a smell becomes associated with the particular experience, person, or time period with which it is repeatedly paired. In some cases, we may not be aware of a specific memory, we just have a positive or negative association with a smell and don't know why. Research suggests that some smell preferences, like an affinity for alcohol, junk food, and garlic, may even develop in the womb.
Because of our unique associations with smell, we have different preferences, some bizarre. When I was little, I loved the smell of permanent markers - knowing now how toxic they are, this seems like a strange preference. I must have liked them because using them made me feel more grown up - or maybe I was sniffing them a bit too much! Cultures also differ in the smells they prefer - according to the book Aroma: The Cultural History of Smell, the Dassanetch of Ethiophia smear cow manure on their bodies because the smell of cattle signals fertility and high status. Other cultures consider onions an aphrodisiac. In America, vanilla and cinnamon are supposed to be good for attracting men, maybe because they make you smell like cake.
Some smells, vanilla in particular, are almost universally liked (research suggests that vanilla has calming properties). These pleasant smells improve our mood but also sometimes impair our judgment. In one study, the presence of a pleasant smell increased the amount of money people gambled at slot machines. Certain good smells, however, like peppermint and lemon, seem to sharpen reasoning and improve work performance. Other smells, such as the familiar scents of home, can be comforting - taking your own pillowcase when you travel to a new place might help you sleep better. Odor can also be used as a memory aid.
Bad smells seem to have the opposite effect. In one series of studies, a disgust-inducing smell led people to make harsher moral judgments. Apparently guided by this research, in his campaign for New York Governor, Carl Paladino infamously mailed out thousands of garbage-scented ads with photos of Democrats involved in scandals (e.g., Eliot Spitzer) and the words "Something stinks in Albany." Although this was a clever tactic, in the end Paladino was the one who came to be associated with the bad smell, perhaps also because of the other tasteless emails he circulated.
Smell is also an essential element of attraction, especially when it comes to the hard-to-pin-down feeling of chemistry that two people share. Research suggests that humans subconsciously pick up on potential mates' pheromones, hormones that can travel outside of the body and are detected through smell (pheromones are what dogs are smelling when they sniff each other's butts; it's still unclear to what extent humans rely on pheromones). Some studies suggest that pheromones contain information about fertility and genetic compatibility. In one much publicized but controversial study, female participants sniffed sweaty T-shirts worn by men they had never met, and their preference ratings indicated that they preferred the scent of men whose MHC (major histocompatibility complex) genes were different from their own, a combination that can give offspring a stronger immune system. These findings suggest that people might literally be able to sniff out their ideal mate, but the evidence for this effect has been mixed. Patterns of attraction are also dependent on where women are in their menstrual cycle and whether or not they are on the Pill. Nevertheless, one dating company promises to match women and men based on their DNA, and pheromone-based colognes and perfumes are currently being marketed.
As Rachel Herz argues in The Scent of Desire: Discovering our enigmatic sense of smell, scent often goes unappreciated. It operates subtly, and its importance may only become clear to those who lose it. Anosmia, the loss of the sense of smell, has unfortunately not been taken as seriously as other sense losses, but it can have serious consequences, especially for people who are not born with the condition, including depression, loss of appetite and libido, and an inability to detect dangerous smells like gas leaks or spoiled food.
The lesson: don't discount your sense of smell. It has the power to bring you back to childhood and closer to far-away loved ones, to make you feel happy, alert, and comforted, to keep you safe from danger, and possibly even to help you find love.