How do scents, emotions, and memories intertwine?

1. How do scents, emotions, and memories intertwine?

What effect do scents have on psychology? In the opening of the famous 1919 novel Swann's Way, author Marcel Proust describes the taste of a Madeleine cake dipped in tea, which triggered a vivid memory of his aunt preparing this sweet treat on Sunday mornings during his childhood.

Since its publication, researchers have used this literary anecdote to explain how scents can vividly trigger our experiences, a phenomenon often referred to as the "Proust effect."

Various psychological studies have investigated the Proust phenomenon in humans, confirming that memories evoked by scents elicit stronger emotional responses compared to memories triggered by visual or verbal cues. This demonstrates the powerful impact that scents have on our psychology.

What effect do scents have on psychology? Scents can influence our mood, making us feel agitated or calm, and can evoke feelings of either positivity or negativity by recalling sad or joyful memories, or even sweet dreams...

In addition to triggering more dramatic emotional responses than other senses, scent-based memories are also described using much more vivid language compared to memories recalled through auditory or verbal cues. Interestingly, autobiographical memories evoked by scents can also originate from much earlier in life, even from the first decades, compared to memories tied to verbal and visual cues (which are typically limited to early adulthood, around ages 11-20).

As the most ancient and evolved sense, the human sense of smell is uniquely capable of quickly summoning emotional and extremely vivid memories, often formed very early in life.

2. The premise of aromatherapy as psychological treatment

While the ability to connect certain scents with old memories may seem insignificant, the link between scents, emotions, and memories is incredibly important. In fact, much of an animal’s olfactory learning takes place during crucial life events, playing a significant role in their ability to defend themselves from predators, find food, and mate with others.

The Proust phenomenon may surprise some, but a closer look at brain anatomy reveals how closely connected the sense of smell and memory are. Olfactory sensory neurons are specialized cells equipped to detect chemical stimuli from the environment, present in the olfactory epithelium covering the back of the nasal cavity.

Once detected by these neurons, scent stimuli are converted into electrical signals that allow them to travel to the olfactory bulb, which is the first relay station for olfactory information. Unlike other mammalian sensory systems, which first pass through the thalamus before reaching cortical regions, olfactory information can be sent directly to the limbic system—including the amygdala and hippocampus—via the olfactory nerve without any intermediary stops.

This direct access that olfactory information has to the amygdala explains why a specific scent can instantly trigger detailed memories and/or strong emotions. Several studies on both humans and animals have identified the amygdala as playing a crucial role in processing emotions. Additional research has confirmed this function by electrically stimulating the human amygdala, resulting in the elicitation of fear or other intense emotional reactions.

Together, the anatomical connection between the olfactory system and the amygdala helps explain the mechanism behind certain scents triggering emotionally charged, scent-related memories. This mechanism laid the foundation for the development of aromatherapy.