According to a survey conducted by Top Ten, the top 10 smells of all time are fresh air, vanilla, fresh petrol, coffee, rain, grass, barbecue, popcorn, bacon, and new books. Without a human brain, these smells are just floating particles of things that have detached and separated from their original compound. What makes these smells important is the brain, specifically the memories within the brain. Smell is the sense by which odors are perceived. It occurs when an odor binds to a chemoreceptors, which are sensory cells, within the nasal cavity transmitting a signal through the olfactory system to the brain. The brain interprets the patterns of electrical pulses sent from the olfactory system as specific odors and this olfactory sensation becomes something that humans can recognize as smell. Smell is linked to parts of the brain that process emotion and associative learning causing it to be influenced easily by personal experiences.

The sense of smell is intertwined with memory, probably more so than any of the other human senses.  Those with full olfactory function may be able to think of smells that evoke particular memories; the scent of a pumpkin conjuring up recollections of a childhood holiday tradition, for example.  Smells often simultaneously act as a trigger in recalling a long-forgotten event or experience.  Marcel Proust, in his Remembrance of all Things Past, wrote that a bite of a madeleine vividly recalled childhood memories of his aunt giving him the very same cake before going to mass on a Sunday.

In addition to being the sense most closely linked to memory, smell is also highly emotive.  The perfume industry is built around this connection, with perfumers developing fragrances that seek to convey a vast array of emotions and feelings; from desire to power, vitality to relaxation. It is likely that much of our emotional response to smell is governed by association, something which is borne out by the fact that different people can have completely different perceptions of the same smell. Back to the perfume example; one person may find a particular brand ‘powerful’, ‘aromatic’ and ‘heady’, with another describing it as ‘overpowering’, ‘sickly’ and ‘nauseating’. Despite this, however, there are certain smells that all humans find repugnant, largely because they warn us of danger; the smell of smoke, for example, or of rotten food.  

It is not the nose that makes us smell, it is the memories and experiences of each individual that allow for these simple molecules morphed into electrical pulses to make us feel something and be further able to perceive our world.