Science Behind Smell

In A Natural History of the Senses, Diane Ackerman mentions that smell is a unique sense, different from senses such as sound or sight. In sight or sound, whatever we hear or see first goes into a relay center in the cerebral hemisphere of our brain, and then it travels to other regions of our brain. However with smell, it travels directly to different regions of the brain. This is due to the fact that our sense of smell evolved before our other senses.

When we inhale, chemicals we inhale land in a mucus membrane covering our olfactory neurons. The chemicals dissolve and then bind to our neurons, which triggers a signal, and follows a pathway to different parts of the brain. 

There is a chemical known as androstenone. This chemical is found in boar’s saliva. It is the first mammalian pheromone to be identified. Androstenone can smell like vanilla to some people, while for others it smells like sweat and gives off an unpleasant odor. 

For example, fresh cut grass for me reminds me of childhood as my dad mowed the lawn and I played outside with friends. While for others, they may not have linked any specific memorable experience with that specific smell, therefore when they smell fresh cut grass it won’t trigger any memories. 

Another scent that triggers memories for me are crisp, freshly printed pages and books. I’ve been playing piano since I was a kid, and everytime a new piece was assigned by my teacher, my mom would help me print out the notes for the music and we would sit down at night and learn the piece.

It’s fascinating how smell was our first evolved sense. Possibly it could be due to the fact that when our ancestors were foraging, they would smell and then taste what they found, and based off whether or not the sense was pleasant, they would pick what they found.