Smell is the trickiest of the senses.
Touch is easy— it’s categorized as heat and cold, pressure and pain. Sight and sound are even more obvious; they’re both measurable physical phenomena, described through our perceptions of light and sound waves. Even taste is straightforward; there are countless variations but just five basic categories—sweet, salty, sour, bitter, and umami. Only smell combines extraordinary precision—think of how many things you can identify by smell alone—while at the same time it’s the most subjective of the senses. A smell is impossible to describe to someone who’s never smelled it, and everyone’s perceptions are different, rooted in their own unique memories and associations.
We take more than 23,000 breaths each day, and each one is an opportunity to smell.
The world is awash in olfactory information. There are more than 100,000 smells floating around the globe, and it takes just eight microscopic particles to trigger a reaction in one of the five million receptor cells in our noses. The sensation is processed in the limbic region, the emotional center of the brain, where the sensory data get all tangled up in memories. That’s why a whiff of roasting turkey can flood you with warm and fuzzy memories of family Thanksgivings, or a fragrant bouquet of flowers will have you thinking of your beloved grandmother, even if you never knew that her hand cream was lily-scented.
Even though a smell can be sensed by just a handful of molecules reaching your nose, objects can have hundreds or even thousands of different volatile compounds all throwing off their own molecules. Each compound contributes a single core odor, and just 230 of them are food-related. A simple food like butter contains just three different odor compounds, strawberries have 12, and a complex wine can hit the upper limit with its aroma encoded by a combination of 40 different molecules.
Smell and taste are the sister senses, playing off of the same molecules.
About 80% of what we taste is due to our sense of smell. Without it we are perceiving only the building blocks of flavor– the sweet, salty, sour, bitter, and umami. With it we have the nuance of an infinite universe of sensory combinations.
Fun olfactory facts:
- Most of what you smell is coming through the left nostril. The reason you never noticed this is because 80% of noses are not in the middle of the face but pitched slightly to the right, so it seems like the smell is coming right up the middle.
- Marijuana-induced munchies are not a gustatory phenomena so much as an olfactory one; cannabis enhances the sense of smell which leads to increased appetite.
- Lose your sense of smell and you’ll lose your libido.
- Your nose grows all-new scent receptors every 30 days.
- The fatter you are the better the chocolate smells; scientists don’t know if this is cause or effect.