I’m sure this has happened to you before – you’re walking down the street and you smell something that takes you back to a holiday, or a time when you were younger. It could be the smell of a sweet shop or someone’s perfume, and you are taken straight back to a moment from years ago. But why are smells so linked to memories?
A simple answer is that this link is due to how the brain is organised. Our sense of smell is triggered by a molecule that enters our nose and binds to the hair-like projections (cilia) on neurons at the top of your nasal passage. These neurons project to a part of the brain called the olfactory bulb, which run along the front of the brain, at the bottom. This structure is thought to be involved in interpreting these signals and processing information about smells.
What’s interesting about the olfactory bulb is that it’s the one part of the brain responsible for our senses that has projections to and from the areas of our brain responsible for memory and emotion – the hippocampus and amygdala. You can see this from the image below:
This explains why smells can trigger memories and emotions. The hippocampus is responsible for our episodic memories in particular – personal memories about our lives, which is why it is this type of memory activated by smell. One theory about why these connections exist between the hippocampus and the olfactory bulb is that they enable us to recognise smells from previous experience.
Studies have shown that using smells to trigger memories can be more effective than cuing them with words. For example, Maylor et al (2002) asked young and old adults to recall autobiographical memories associated with 6 cue words. They were then shown the same words and were asked to recall new memories, and for half of these words the appropriate smell was presented too. The researchers found that for both age groups, the participants recalled twice as many memories when the smell was presented too, showing the large impact of smell and memory recall.