Smell, Memory, and Emotion: What Science Says About This Powerful Sense

Have you ever smelled something and been instantly transported to a specific memory? Perhaps your grandmother’s house, a memorable trip, or even the embrace of a loved one?

This experience is more common than it seems and has a scientific explanation: olfaction (the sense of smell) is one of the most powerful senses and is intimately linked to our memory and emotions.

Olfaction and Its Ancestral Connection to the World

Olfaction is a primitive and essential sense, present in humans and other mammals as a tool for survival and socialization. It is used, for example, to recognize safe foods, avoid toxic substances, and identify members of the same group.

In humans, although the immediate survival role is less evident, the importance of smell persists, especially in its ability to evoke memories and influence emotional states.

Research has already shown that the olfactory system is functional even during gestation: human fetuses can detect odor molecules present in the amniotic fluid.

After birth, babies show a preference for familiar odors, like that of their own mother—which is why the popular expression “mother’s scent” makes so much sense.

Memories and Emotions Through Smell: By the Numbers

Scientifically, it is known that the sense of smell is directly connected to the limbic system, the brain region responsible for emotions, memory, and motivation.

Unlike sight and hearing, whose stimuli are processed before reaching the brain’s emotional areas, olfactory signals take a direct route to the olfactory bulb, which connects with structures like the amygdala (associated with emotional content) and the hippocampus (essential for forming autobiographical memory).

This privileged connection helps explain the phenomenon known as the Proust effect: a term coined in reference to the author Marcel Proust, who described in his work how the smell of a cookie transported him back to his childhood.

Today, neuroscience recognizes this phenomenon as real: memories evoked by smells tend to be more emotional, vivid, and older than those triggered by visual or auditory stimuli.

Furthermore, olfactory memories are generally less verbal and more sensory, making them more resistant to being forgotten and less prone to rational reconstruction.

This occurs because the brain stores these experiences directly in emotional and sensory networks, without necessarily passing through areas associated with language or conscious judgment.

Moreover, numbers reinforce the power of smell: humans have about 400 different types of olfactory receptors, which, in combination, allow us to detect over 1 trillion different smells.

For comparison, we can identify about 10 million colors and distinguish approximately 500,000 sounds.

It’s no coincidence that consumer neuroscience expert Martin Lindstrom points out that up to 75% of the emotions we feel throughout the day are related, consciously or unconsciously, to smells.

Far Beyond the Nose: How We Process Smells

Smelling something involves much more than just capturing molecules in the air. After detection by receptors located in the nasal cavity, the information is processed in the olfactory bulb and quickly forwarded to brain regions such as:

• Amygdala: Interprets the emotional content of the odor.
• Orbitofrontal cortex: Encodes pleasure, disgust, and reward related to the smell.
• Hippocampus: Stores and retrieves memories associated with the odor.
• Prefrontal cortex: Participates in decision-making based on previous experiences.
• Anterior cingulate cortex: Integrates emotion and action, influencing behavior motivated by rewards.

Furthermore, the olfactory system is highly plastic—meaning it continuously adapts to sensory, emotional, and environmental experiences throughout life.

Repeated exposure to certain smells can make them more familiar and pleasant (or unpleasant), depending on the context in which they were experienced. This plasticity helps explain why the sense of smell is so personal, changeable, and sensitive to time.

This pathway explains why a simple smell can trigger an intense reaction—from euphoria to aversion—in a matter of seconds.

Anosmia: When the World Loses Its Scent

Unfortunately, not everyone can experience these olfactory sensations. Anosmia, which is the total or partial loss of the ability to smell, affects about 5% of the world’s population.

This condition can be congenital, acquired through viral infections (like COVID-19), trauma, or neurodegenerative disorders. During the pandemic, the increase in temporary or persistent cases of anosmia brought light to the neglected role of olfaction in well-being and quality of life.

The loss of smell goes far beyond the absence of pleasure in eating or appreciating a fragrance: it can affect safety (e.g., not noticing gas leaks or spoiled food), socialization, and even the recognition of oneself and others. Studies show that people with anosmia have a higher propensity for depression, anxiety, and social isolation.

In recognition of the topic’s importance, World Anosmia Awareness Day was established, celebrated on February 27, as a way to give visibility to the condition and promote advances in its understanding and treatment.

Smells, Identity, and Culture

It is worth remembering that the olfactory experience is unique to each individual and can be influenced by factors such as genetics, sensory repertoire, culture, gender, ethnicity, and even emotional state.

What is pleasant for one person may be neutral or even unpleasant for another. This reinforces the importance of understanding olfaction not only as a biological phenomenon but also as a sensitive and cultural construct.

Grupo Boticário Group Continues to Study Olfaction

At Grupo Boticário, the sense of smell is a subject of continuous study. The Olfactory Research Center (Centro de Pesquisa do Olfato) has the mission to deepen scientific knowledge about this sense and disseminate it accessibly to society, reinforcing its importance in our daily lives.

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