Source: scopeblog.stanford.edu

We all have our favorite smells: freshly-cut grass, warm chocolate cookies straight from the oven, or crisp, clean sheets straight out of the dryer. But what gives these smells the power to evoke feelings of nostalgia or forgotten memories?

Research shows very early evidence of olfactory memory. Biopsychologist Julie Mennella created a study which tested the early development of a relationship between smell and memory. This study involved women during their last trimester of pregnancy as well as during the early stages of breastfeeding. Some of these women were given carrot juice, while another group of women was given water. When their babies grew old enough to eat cereal, some of the babies were given cereal made with carrot juice, while another group was given cereal made with water. According to the Association for Psychological Science (APS), “The babies who’d had prenatal exposure to carrot juice made fewer nasty faces while eating the carroty cereal and seemed to eat more, too.”

This study demonstrates that a clear connection between smell and memory begins to develop before we even enter the world. Several studies show that the most powerful links between smells and memories are developed before the age of five. This is because during this time period, we encounter countless new smells for the first time. For example, the smell of chlorine may lead one to remember days spent at the pool or childhood memories of summer.

How exactly does this happen? According to HowStuffWorks, the ability of smells to evoke memories and emotions is largely due to the olfactory bulb and its relationship to certain areas of the brain. The olfactory bulb has access to the amygdala, a structure in the brain responsible for the processing of emotions. The bulb is also closely linked to the hippocampus, the brain structure responsible for organizing memories through association.

The link between smells and memories is also due to the development of a conditioned response as the result of encountering a new smell. When we first encounter a new smell, our brain associates it with a specific experience or moment in time. Later on, when we encounter the same smell over again, there is already an existing link between the smell and the memory that we previously associated with it.

Smells have the remarkable power to bring back vivid memories of life experiences; through the rediscovery of these memories, smells also have the capability of influencing our mood and emotions. I was amazed to discover that something as simple as a smell has the ability to reopen an entire world of memories. As one New York Times article describes it, the nose truly is “an emotional time machine.”