Picture this: You’re walking down a busy street in a city filled with loud noises and stimulating sights. You pass a small bakery and catch a whiff of the most recent batch of cookies. A chill runs down your spine. You wince. Your mind flashes back to that time when you were six, learning to bake cookies with your grandma and accidentally burned your hand. Your hand became vibrantly red, blistered and it was painful for a week. Your mood converts from bliss to melancholy. Until this moment, you hadn’t thought about that in years, decades even. And all this came from a smell? “How weird!” you think. But no, it’s not weird: It’s neuroscience.
Okay, so maybe this didn’t happen to you. Maybe you didn’t ever burn your hand or even learn to bake cookies — a true crime — but the idea that a smell can trigger memories, both good and bad, is true. It’s called the Proustian Effect named after Marcel Proust, a French writer who was the first to write about the effect, albeit not scientifically, but as an observation in his novel “In Search of Lost Time.”
Unlike the other senses which pass through the thalamus — a relay station for movement and sensory information in the brain — before moving to the cerebral cortex for processing, smells transmit directly to the olfactory bulb, without interruption. In fact, a smell has been proven more likely to trigger emotional memories than a sight or a sound because of its direct entrance to the brain.
The olfactory bulb is located close to both the amygdala — the area of the brain where emotion and emotional memory is processed — and the hippocampus — the area of the brain connected with more general memory. The close proximity of these regions with the site of processing the smell stimulus provides the link of smells with memory. Likewise, it explains why the memories associated with smell are of the emotional type rather than the episodic type, which involve particular details.
This goes into a more complicated idea associated with the smell memories: They are completely involuntary. When one actively tries to remember things, they focus on details, on the elements they want to remember — they’re selective. You wouldn’t actively try to remember that time your dog died or when you saw a car accident. However, when one focuses on details, they don’t focus on the feelings they’re feeling. For example, you’re trying to remember what your professor is saying in class. When you recall that moment, you remember the words, but you don’t remember that you were depressed from getting a less than satisfactory grade on that paper you just were handed back. Details and emotions are stored in two different areas of the brain. Thus the memories associated with emotions and smells are likely to be unexpected and less focused, more nostalgic. The things you didn’t want to remember but are encoded in your brain anyway.
This is why when you smell a man walking by wearing the same cologne as your ex you may be filled with sadness, or when you smell a flower, it could trigger your happy memories of Hawaii.