We make use of all 5 of our senses to relate to the world around us and our place in it. One of the most powerful of these senses is, perhaps surprisingly, our sense of smell. Our brain has become what is essentially a highly complex molecule reader, able to detect just a small handful of molecules and draw powerful associations from them. Understanding how our sense of smell works and how we relate to it can inform us about why we like what we like and how we might come to enjoy new things.
The Power of Smell
Compared to other mammals, it's an understatement to say that we don't have the best sense of smell. Perhaps because of this, we tend to think of other senses like vision and hearing as being more essential to our survival and experience in life. This way of thinking, however, underplays just how powerful our sense of smell really is. Think of peppermint, the beach, or something sweet cooking in the oven. All it takes is one small whiff to not only instantly recognize what we're smelling, but to also be transported to another place or time.
In fact, our sense of smell is so powerful that we can know exactly what we’re dealing with just by smelling something—even if that something is so far away that we can barely detect a few molecules of it. Smell allows us to detect a substance even when it is less than a 50th of 1 percent of the amount of the makeup of the air. We can be alerted to something dangerous in the distance, or we can track down something pleasant close up. We even use our sense of smell purely to bring us joy, not just to avoid danger for survival.
How Smell Works
When it comes to smell itself, the brain detects a scent by first noticing a particle entering through the nose. That molecule is then picked up by an olfactory receptor—receptors like any found in the brain, only activated mainly through exogenous means rather than endogenous (internal). The olfactory receptors transmit information to olfactory bulbs, which in turn send the information to two places.
First, the information is sent to the limbic system, which includes the reward system of the brain and powers our basic emotions and urges. Then it gets sent to the neocortex, where it influences our higher conscious thought. Basically, the limbic system is what makes you feel good when you smell something relaxing, and the neocortex is what makes you associate that smell with distant places and past memories.
Smell & Memory
On the topic of smell and memories, we actually have strong evidence that the memories we associate with smells exhibit some unique qualities. One study divided people into three groups, and each group was given a positive, negative, or neutral experience while being exposed to certain smells. Each group was given either a control odor or an experimental odor that they found enjoyable. When shown images while smelling the odor that they enjoyed, the same signals lit up as if they were smelling that odor currently. As well, when they were exposed to the positive odor, their CAT scans lit up as if the participants were also receiving the positive stimuli alongside the odor.
After some more field tests were done, two conclusions were drawn. The first was that memories are indeed linked by the senses, as positive smells bring you back to positive mindsets and strong memories. Perhaps more surprisingly, they also concluded that the specific smells themselves could have the same impact as receiving other stimuli related to that smell. Basically, if you smell grandma’s cooking, it’s the same mental response as if you were actually hanging out with your grandma or receiving a hug. And the same can go for simply seeing a loved one—it can make you think of certain smells you associate with them. Memory is funny and unique like that.