An apple pie crisps to a golden brown in the oven, as the delicious aroma of sugary dough, soft apple slices, and spicy cinnamon waft through the air of the kitchen. You close your eyes, taking a moment to breathe in the warm smell. Suddenly, you are transported through time and space, as the scent envelops you in the childhood feeling of baking with your grandma as the leaves begin to change colors outside, welcoming fall. 

If you have ever had a similar experience, whether that be with the smell of chlorine reminding you of summer or the smell of books teleporting you to the public library, you have experienced the Proust Effect. This phenomenon explains why certain smells subconsciously trigger your brain to relive a certain memory or feeling. Compared to the other four senses, our olfactory sense is the one most linked to feelings of nostalgia. Looking at a picture of an event or wearing the same clothes from that experience is not enough on its own to fully transport you into the memory. 

The reason for this heightened connection between memories and smell versus the other senses can be explained scientifically through a deep dive into the structure of the brain. The olfactory bulb, which is responsible for our sense of smell, is triggered when scent molecules come into contact with the neurons in this area. Once the molecules are interpreted as specific scents, they can be directly transported to the amygdala and hippocampus, which are responsible for memory and emotional processing, respectively. Because of this close physical proximity between the olfactory bulb and the regions associated with memories and emotions, our brains form a nostalgic connection between scents and experiences. While smells have close access to the amygdala and hippocampus, the other senses need to first pass through the thalamus to get to these areas, which is why the acts of touching, seeing, hearing, and tasting do not usually elicit a sense of nostalgia. Scientists have also discovered that a region of the olfactory bulb itself—the piriform cortex—is able to store memories, which further links the sense of smell with our past experiences.

More generally, certain places or times of year can be associated with certain smells. For example, when you smell pine, you might be reminded of Christmas and feelings of joy. However, there are times when memories may only excite a specific emotion, but not a specific memory, causing an individual to feel a certain emotional connection to a scent, but not know why. The association between smell and emotions is not always positive or nostalgic, however, but can also be linked with Post Traumatic Stress Disorder (PTSD) and negative memories. Smelling rubbing alcohol or blood, for example, can remind you of the hospital or a serious injury you underwent. In these cases, smells can trigger a person unpleasantly by forming a connection to a traumatic memory. 

This association between the olfactory sense and memory can also be seen through conditions such as Alzheimer’s Disease. As individuals affected with Alzheimer’s lose their memory, their sense of smell also becomes destroyed because of the connection between the olfactory bulb and the hippocampus. An example of how the connection between smell and memory has been capitalized is through perfume or candle companies creating specific scents that tie to memories, such as going to the beach. In the 50s, many film companies also tried to incorporate smells into their movies using “Smell-O-Vision” technology in order to add another level of immersion for the audience. Scientists are continuing to research the ties between memory and smell and how this connection can be utilized to increase and enhance memory. Through this, it is seen that memories, emotions, and the sense of smell do not exist independently, but are tied together through the brain in order to create a sense of nostalgia when exposed to certain scents.


Photo Credit: Psychology Today