Are there certain scents that transport you to another place or time?  Maybe the smell of freshly baked cookies elicits memories of being a young kid, or your spouse’s cologne reminds you of pleasant memories you’ve shared. On the other hand, unpleasant odors such as cigarette smoke or alcohol also have the ability to take us back to places or situations that we would rather avoid. These types of odor-linked memories are experiences that all of us have undergone, and they evoke powerful emotional responses, shape our experiences, and influence our decisions. When we experience positive emotions due to odor-linked memories, our mental states respond in an uplifting way. However, when odor elicits negative emotions, our emotional state might take a dip.  Even though smell may often take a backseat to the more prominent senses of sight and hearing, the psychology of smell reveals an interesting world where emotions, memories, and behaviors intertwine. In this blog, we will explore how smell interacts with our memories, emotions, and overall psychological well-being.

The Evolution and Science Behind Smell

Throughout the history and development of human life, survival depended heavily on an individual’s ability to detect and interpret various environmental cues. The sense of smell served as an early warning system to potential dangers, such as predators or spoiled food. Until this day, remnants of this evolutionary instinct persist, and it shapes our preferences, behaviors, and even our social interactions.  In other words, odor has long served as a crucial aspect of human interaction and survival, and it makes sense that it can play such instrumental roles in not only our physiological health, but psychological health, too.

As for how smell is processed by the brain, the mechanism is quite unique.  After we inhale, airborne scent molecules immediately pass through the olfactory bulb in the nasal cavity.  The olfactory bulb is simply known as the brain area that receives information about smells.  Once the smell passes through the olfactory bulb, its information is sent to the amygdala and hippocampus, two brain areas that are closely associated with emotion and memory.  What makes olfaction unique is that it is the only sense that gets processed in this brain area! While other sensory inputs undergo extensive processing before reaching consciousness, olfactory signals take a more direct route into the brain.  By entering a region of the brain that deals so heavily with emotion and memory, smell is the sense that is most strongly related to learning, emotion, and memory.1   This network of neural pathways allows our brains to perceive and process a seemingly endless array of scents, each with its own significance and influence.

Proust Effect

Among the five senses, smell has the most unique ability in being able to unlock numerous and even random memories with clarity.  The connection between smell and memories has been commonly referred to as the Proust effect, named after an author Marcel Proust.  In his work titled “Remembrance of Things Past”, Proust wrote about how a fleeting experience of smelling a pastry dipped in tea brought him back to his childhood, eliciting long-forgotten moments and emotions that were joyful and vivid.1  This phenomenon encompasses how scent can influence memory enhancement, and it led researchers to new discoveries that scientifically explained the mechanism behind odor-related memories and how they can impact our lives and emotional well-being.

In a 2018 study, researchers asked 170 participants to smell different odors and record what kinds of memories surface.  The researchers followed up by asking more questions related to each memory, such as whether the memory stood out as fuzzy vs. clear or boring vs. emotional.  Results determined that olfactory cues were far more effective at triggering clear and emotionally related memories than visual cues, like photos or images.2  Further, elderly adults can remember older, much earlier memories with a smell rather than with pictures or words.

Odor memories affect human health

Beyond their ability to conjure up emotional memories, odor memory functions to maintain overall human health. Odor memory, identification, and recognition is a critical component to our physiology.  Data collected from a representative sample of over 3,000 US adults 57 years of age or older showed that people who failed to or were dysfunctional at odor identification were 4x more likely to die within a 5-year period compared to their same-aged peers who had normal-functioning olfactory abilities.3  In addition, an impairment of odor identification is known to be an early symptom predictor of numerous neurological disorders, like Alzheimer’s disease and Parkinson’s disease.3

Odor-linked memories show up on fMRI

Apart from the numerous participant-based studies that support the relationship between olfaction and memory retrieval, functional magnetic resonance imaging (fMRI) brain scans also prove the connection.  Researchers use brain scans known as fMRIs in order to measure what brain activity takes place when people perform various mental tasks.  fMRI measures and takes a snapshot of what the brain looks like when it functions, and it also aids researchers in seeing what parts of the brain are more in use depending on what people are doing.  In other words, it can help researchers determine which parts of the brain are ‘in use’ when people remember events or situations from their past while either looking at a visual cue or smelling an olfactory cue.  fMRI evidence actually shows that brain activity is different when odor-linked memories are triggered versus picture-linked memories.  This type of brain scan shows that the areas of the brain that are involved with memory and emotion are more active when odor-related memories are evoked rather than pictures or other visual stimuli.1  Not only is the brain more active when olfactory memories are induced, but studies also show that autobiographical memories that are triggered by odors actually feel more emotional, and individuals are more likely to remember the original place and time of their memories with so much more clarity compared to when these same memories are recalled through other senses.3

Scent affects your emotions and mood

Smell can have such a significant impact on our emotional states.  Certain fragrances, like vanilla or lavender, are associated with feelings of calmness, relaxation, and tranquility.  And on the other hand, pungent scents such as garbage or rotting food can evoke aversive and discomforting feelings.  The emotional power of scent cannot be understated, as it also has the ability to influence our moods and attitudes.  Beyond its influence in recollecting memories, odors can readily modulate emotion and mood (even without conscious awareness).4 

In one research study, participants were exposed to an unpleasant odor for five minutes and a pleasant odor for five minutes. Results concluded that those who smelled the unpleasant odor reported a negative mood and mild anxiety, while those who had exposure to a pleasant odor reported a positive mood and feeling calm.4  Another study tested out the effects of lavender and orange aromas on men and women’s emotional states when compared to music and no-odor conditions.  Results demonstrated that when participants were in rooms that smelled like orange and lavender, both groups of men and women reported having an improved mood and reduced anxiety compared to rooms with no odor or music.

Researchers can also assess the impact of odors on mood through tools such as the Profile of Mood States (POMS) and Total Mood Disturbance (TMD) measures.  The POMS assesses mood shifts across six factors, including: tension-anxiety, depression-dejection, anger-hostility, vigor-activity, fatigue-inertia, and confusion-bewilderment.4 Using these tools to assess the effects of cologne usage on mood, results concluded that the daily use of cologne as part of an everyday routine for male and female participants elevated their moods in midlife.  On the other hand, individuals who lived close to swine operations were constantly exposed to adverse odors, and they reported lower levels of mood ratings compared to controls.4

Benefits of Odor-Related Memories

Odor-linked memories are important because they not only act as a way to transport us back to a fond place or time we want to remember, but they can improve our psychological well-being. These emotional experiences we undergo as a result of smell can influence our future behavior and outlooks. The intricate relationship between scent, memories, and mood enable us to understand emotional regulation and well-being a little better. Since odor-linked memories are considered to be the strongest recollectors of past emotions, researchers have discovered that smell-related memories are more positive for humans than any of the other senses.  Pleasant memories uplift an individual’s mood, and being in a good mood reduces stress.1 Stress manifests itself in the body through redness and swelling, also known as inflammation. Therefore, when odor-evoked memories reduce stress, we are able to relax and also reduce our risk of inflammation.   

In addition, odor-linked memories can be a positive influence on our mental health.  Studies have shown that olfactory memories can boost self-esteem, improve our social interactions, and provide individuals with a sense of optimism.  Smell-related memories can even motivate individuals to quit adverse habits, such as smoking.  Research shows that when smokers evoked pleasant odor-related memories, they reported that their cigarette cravings decreased.1 All in all, unraveling the world of smell and odor allows us to gain deeper insights into how our memories and emotions are stored.  Through scent-related memories, we can enhance and uplift our psychological well-being.

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