Why Are We Scent-Imental?

You may have noticed that certain smells flood your brain with childhood memories—the scent of freshly baked cookies that reminds you of home or that of newly cut grass that brings you back to summertime. Smells can be associated with memories that may trigger emotions and impact our actions. 

The brain’s emotional center is the limbic system, which is connected to our sense of smell. There are several structures that make up the limbic system, whose main function is to process emotion and memory. Our sense of smell, behavior, motivation, and long-term memory are all impacted by the limbic system. In particular, the amygdala is crucial for managing a range of emotional behaviors, including anger, fear, and anxiety. Our sense of smell has a stronger influence on invoking memory and emotion than any of the other senses that we have. There is a higher chance of us remembering something we smell rather than something we see. In a 2004 study conducted at Brown University, Dr. Rachel Herz and her colleagues discovered that five women’s brain activity increased when they smelt a perfume that brought back pleasant memories as opposed to a control scent they had never experienced before. 

Additionally, there was more brain activity linked to the scent that was associated with a positive memory than brain activity produced by the visual stimulus of observing the perfume bottle. In a more recent 2013 study, researchers observed that there was an increase in brain activity when subjects were exposed to a scent, like that of a rose, compared to the response triggered by a visual cue, such as seeing the rose. Around 75 percent of the emotions that we experience daily are influenced by what we smell which is made possible by the olfactory system. This system is made up of the nose and nasal cavities, which play a crucial role in the sense of smell. The upper section contains the olfactory mucous membrane responsible for smell perception, while the lower section functions as a respiratory passage. When the olfactory system—the bodily system that detects and identifies smells—identifies a scent, it transmits signals to the limbic system which then triggers an emotional reaction influenced by our past experiences and associations with that specific smell. 

When you experience sensations like hearing, touching, or tasting, the sensory information first reaches the thalamus, which acts as the brain’s relay station and is commonly known as the sensory checkpoint. The thalamus then passes on this information to specific brain regions, including the hippocampus, responsible for memory, and the amygdala, for processing emotions. However, the pathway for smells bypasses the thalamus. Rather, odors take a direct route to the olfactory bulb, the brain’s smell processing center. This bulb maintains a direct connection to both the amygdala, associated with emotions, and the hippocampus, linked to memory. This intense connection happens because the olfactory bulb is directly linked to the amygdala through the piriform cortex of the primary olfactory cortex. Information is sent directly from the main olfactory bulb to specific areas in the amygdala. The amygdala then transfers olfactory information to the hippocampus. The olfactory bulb’s close proximity to the brain’s emotion and memory centers provides insight into why scents can promptly evoke vivid memories or powerful emotions. In a Northwestern Medicine study, scientists discovered that our hippocampus has a stronger connection to the olfactory bulb than any other sensory system. This means that since the hippocampus is important for creating and remembering memories, the direct link between the olfactory bulb and the hippocampus enables powerful and immediate connections with past experiences and feelings when we encounter scents. This direct connection explains the emotional effect of scents on our mood. Rapid recollection of positive or negative experiences associated with a specific smell can then influence our present emotional state.

Neurotransmitters are chemical messengers in the brain that serve many purposes such as regulating mood and memories. Certain scents have the ability to prompt the release of neurotransmitters such as serotonin, dopamine, and endorphins, contributing to sensations of happiness or relaxation. Understanding this connection allows scientists to strategically utilize fragrances to influence our emotional state. For example, aromatherapy is a natural way of healing that uses the scents of plant extracts and essential oils to help one achieve a desired emotional state. At home or in the workplace, spreading essential oils can easily cause mood-boosting benefits that improve our well-being. Previous research has proven that essential oils have therapeutic benefits. For instance, inhaling essential oils like lavender and chamomile has shown a reduction in levels of depression, anxiety, and stress in older adults. Scientists suggested that the anxiolytic and antidepressant effects are associated with the suppression of the sympathetic nervous system, a network of nerves that typically triggers the body’s "fight-or-flight" response during stress, danger, or physical activity. Many scents demonstrate beneficial effects on our moods in our everyday lives. Additionally, patients undergoing an MRI procedure experienced decreased anxiety in 63 percent of cases when exposed to the scent of vanilla beforehand, contrasting with only four percent in those without the olfactory stimulus. Psychologist Julie Walsh-Messinger, specializing in the study of smell, emotions, and social behavior, suggests that changing your perfume could potentially aid in distancing yourself from negative memories associated with it and fostering the creation of new ones.

The Sensory Marketing Laboratory at the University of Michigan discovered that combining sensory elements can be effective in marketing. In one study, led by neurologist Alan Hirsch, researchers put two identical pairs of Nike running shoes in almost identical rooms with one difference—one room had the subtle fragrance of flowers, while the other had no scent. Following the investigation, Hirsch and his colleagues concluded that in the perfumed area, customers were 84 percent more likely to purchase Nike running shoes. Shoppers may not even be aware of the scents that retailers utilize, but studies have shown that scents make them remain in stores longer and purchase more. For example, Bloomingdale uses a coconut smell on their swimsuits to bring back memories of the beach. Old Navy is known to use seasonal scents such as nutmeg and evergreen to spark warm emotions from their customers. Stores sprayed with a welcoming scent like fresh blueberries or warm vanilla have found that guests tend to have a better experience and remember the brand better. Certain smells cause certain emotions in potential buyers which makes them want to purchase the products more. 

In South Korea, Dunkin’ Donuts launched a scent marketing campaign by releasing coffee aromas from perfume atomizers whenever the company jingle played on public buses. This strategy resulted in a 16 percent increase in visits to Dunkin’ Donuts stores near bus stops and a 29 percent boost in sales for those particular stores.

Ongoing research on the beneficial effects of connecting smells to contextual memory presents potential advantages for students today who are looking to retrieve information from their memories such as a term for a test or an answer to their homework assignment. Researchers are investigating the potential of scent in aiding Alzheimer’s patients, as specific odors align with memories, thus helping with the recollection process and ultimately enhancing their overall quality of life. While this field of research is still evolving, its future implications are promising if the link between smells and contextual memory can be fully understood and harnessed.