Have you ever noticed how smelling something- whether it is a flower, perfume, or something cooking or baking, perhaps- often results in your sudden recall of a prior experience? Odors are processed by the olfactory bulb inside the nose, which runs to the brain and is connected to the limbic system. The limbic system is comprised of the amygdala, which processes emotions, and the hippocampus, which stores memory.
Information from our other senses, such as vision, hearing, and touch, does not pass through the amygdala and hippocampus. This explains why our sense of smell, or olfaction, is often more likely to elicit memories and emotions. Studies have shown that odors are more successful at eliciting the feeling of “being brought back in time” than are images. This is referred to as “odor-evoked autobiographical memory” or the Proust phenomenon, after French writer Marcel Proust. In his famous novel In Search of Lost Time, the narrator dips a madeleine cookie into a cup of tea and is transported back into time as long-forgotten memories of his childhood come flooding back. The Proust phenomenon is the term used to describe what happens when an odor triggers the recollection of a meaningful past personal episode.
In some cases researchers have found that memories triggered by an odor resulted in greater activity in the limbic system than memories triggered by the words associated with the odor. So, being presented with the scent of a rose would result in more activation of the amygdala and hippocampus than would seeing or hearing the word “rose.”
An interesting aspect of this is that the first association to be linked to an odor usually remains tied to that odor, even if that odor is later experienced in different contexts. Pleasant odors can evoke positive emotions and memories of pleasant experiences. However, negative odor-evoked memories, such as in PTSD, are very difficult to extinguish. Women tend to be more sensitive to odors than are men, which may influence the extent to which odor-evoked memories elicit physiological and emotional responses.
In other studies it was discovered that both young and old adults were able to recall more than twice as many memories when they were associated with an odor, indicating that the ability of odors to trigger memories continues to function well in older adults.