Smell.
In the end, it all comes down to remembering a scent. It’s common to say that we are the culmination of past experiences and our link to these, the good and the horrible, is by memory. Undoubtedly, few senses are better at instantly transporting us to our long-forgotten past, than the unexpected whiff of a mundane orange or a trace of shoe polish. The way the recollection manifests even feels different to hearing, seeing, tasting (which is mostly smelling anyway) and touching a reminder.
The memory triggered by the smell of, say, freshly cut grass or rain on barren earth, is so powerful and prominent that it warrants a label: a Proustian moment (although in his 1913 novel, “À la recherche du temps perdu,” Marcel Proust referred to a sensory experience, which included tasting and smelling, of a madeleine he nibbled on after ceremoniously dipping it in tea).
Merriam-Webster explains “scent”, a transitive verb, as perceiving odour by means of stimuli that influence the olfactory nerves. To understand how freshly ground coffee instantly kindles a vision of your grandma’s farm kitchen, a little dip into the world of olfaction is prudent.
Lining the higher portion of the nasal cavity is the mucous membrane, which is imbued with millions of tiny, thin nerve cells called olfactory receptors. Importantly, amongst the horde of receptors, they probably differ in their sensitivity to a multitude of chemical substances, and therefore scents. As soon as the chemical airborne matter of, for example, freshly baked bread breaks down in the mucous membrane, thin hairs on the olfactory receptors become aware of it. The receptors transmit their findings to the olfactory bulb in the forebrain by way of nerve fibres that reach through the nasal cavity’s roof.
So, now we’ve worked out that we are smelling a fresh baguette, but what’s the reason for suddenly remembering one’s earliest childhood interaction with the comforting aroma of a loaf and some piquant Emmental?
The olfactory bulb transmits information to our bodies’ central command structure for more analysis. Scents route directly (and quickly) to our limbic system, which includes the amygdala and hippocampus: the brain’s emotion and memory regions. Although Proust mentioned taste, the key is in our ability to smell. While eating, food molecules enter our nasal cavity and in essence, the pepper-infused aged salami flavour reminding you of your childhood visits to the family butcher shop is in fact due to the sausage’s aroma. One can test this fact by pinching one’s nose while eating chocolate: the sweet taste is present but not the chocolate flavour. An additional strong link between childhood memories and smell is due to how we develop and learn.
As a survival mechanism, the olfactory bulb and the amygdala appear to encourage the use of the olfactory cortical regions during most learning stages. (For example, an infant knowing the smell of its mother triggers an emotional scent recollection.) Compared to our other sensory systems, our olfactory structure uses relatively simple neural circuitry, but importantly, it accesses the emotional part of the brain directly. Hence, scent affects our emotions and determines our behavioural response from an early age when it comes to social situations and even survival. Throughout our lives, smell continues to play a vital part in our emotional and social well-being.
When the nostalgia floods back when you smell the jasmine in the morning or honeysuckle in the late afternoon, making you feel as if you are back in your childhood, think about Proust’s writing:
“But when from a long-distant past nothing subsists, after the people are dead, after the things are broken and scattered, taste and smell alone, more fragile but more enduring, more immaterial, more persistent, more faithful, remain poised a long time, like souls, remembering, waiting, hoping, amid the ruins of all the rest; and bear unflinchingly in the tiny and almost impalpable drop of their essence, the vast structure of recollection.”