Exploring the Link Between Smells and Memory

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Have you ever caught a whiff of meat grilling or cookies baking and been brought back to a moment in your childhood? Maybe the smell of fresh flowers, newly cut grass, or salty ocean air does it for you. Wherever you are and whatever the smell may be, you’re sent back into a whirlwind of memory with a pang of yearning for a time gone by.

Our sense of smell has a strong connection to our memory and how we view the past. Perhaps no one knows this better than Dr. Alan R. Hirsch, founder of the Smell & Taste Treatment and Research Foundation, who in 1992 conducted a study to better understand nostalgia and what role our senses play in bringing it on.

BTRtoday spoke with Dr. Hirsch about his study from 1992 — the connection between our olfactory system and our sense of smell, and why we tend to view the past in a more positive light.

BTRtoday (BTR): What were the parameters of the 1992 study “Nostalgia: a Neuropsychiatric Understanding” and what did the findings show?

Dr. Alan Hirsch (AH): We looked at the phenomena of what’s called olfactory-evoked nostalgia. You smell a smell and receive a vivid image of your childhood. We looked at 989 people from 45 states and 39 countries, and about 85 percent said that odors made them nostalgic of their childhood. The number one odor was baked goods, across the board.

The second was dependent on where you were born and when you were born. If you were born on the East Coast, the smell of flowers made people nostalgic for their childhood. In the South, it was the smell of fresh air, in the Midwest it was the smell of farm animals, and on the West Coast it was the smell of meat cooking or barbecuing. It also depends on what country you’re in—people form Africa describe the smell of maize, Scandinavians described the smell of herring.

The older you were, the more likely it was that natural smells made you more nostalgic of your childhood—corn, hay, horses, meadows, those sorts of things. The younger you were, the more likely it was for artificial smells to make you nostalgic for your childhood—Play Doh, Pez, Sweet Tarts.

One of the other things that we found had to do with whether or not you had a happy or sad childhood. We found that one in 14 people had unhappy childhoods. And we predicted that if you had an unhappy childhood that nothing would make you nostalgic for your childhood, because you would suppress those memories. But that’s not what we found—we found that if you had an unhappy childhood, other smells brought about nostalgia such as blood, feces, smells that were otherwise negative.

It suggests that odors have such a strong way of inducing recall from the past because they can overcome that suppression.

BTR: What does this reveal about us?

AH: This says a lot about how we deal with these in day to day life, because often times we’ll smell something and we’ll get happy. It’s not because the smell is what arouses us at the time, but because the odors and the smells that make you nostalgic for your childhood have the same affect or emotion associated with it. So if a person smells good, you might like them more not because of who they actually are, but because of what their smell reminds you of.

BTR: Is smell more correlated with positive than negative emotion?

AH: Nostalgia is not actually memory of the past, it’s a scrubbed, sanitized recall of the past. It’s not actually the way the past was, it’s the way your brain decides to recall it. So you don’t recall the bad things, you tend to recall the more positive things. As a result, when you recall something based off of a smell you’re more likely to recall a positive event.
The reality is you can induce people to have emotions that are positive and negative based on odor, and you can have well conditioned responses. For instance, if you happened to go to Catholic school and a nun would keep hitting you with a ruler when you were little, and there was a certain smell of mold in the classroom, that moldy smell will make you recall the negative experience you had in the past. However, most odors that we come across in everyday life tend to induce more of a positive response.

Not all smells do that, because smells are a combination of the olfactory nerve and the trigeminal nerve, which is the largest cranial nerve, the one that makes you cry when you cut onions. When you smell those odors, you tend to then be in a more negative mood. Things like ammonia, tear gas, or very high levels of citrus will do it. So this trigeminal signal often causes people to be in a more aggressive or negative mood—but that aggressive mood could be something that’s positive. For example, some weightlifters before they lift will take a whiff of ammonia to give themselves an extra boost of energy. So even though it’s generally viewed as negative, in the right context it can be positive.

BTR: Is that part of the reason why people always view the past more positively?

AH: Absolutely. We see the past through rose-colored glasses. Our brains sanitize the past and we views things that are affectively charged negatively become more emotionally neutral or positive. That’s why we look back at events in the past and our views change from negative to positive, even though their nature is generally the same. A good example is the American view of the Japanese during World War II. During the war it was so negative, and now it’s positive as an ally.

What happens is our perception changes over time and our affect becomes limited based on space and time. That explains why people can’t be angry at things for very long or hold onto definitively positive or negative emotions for a very long time. Our brains are used to adapting to change.

BTR: Do people with better senses of smell have stronger or more vivid memories?

AH: No, but I’ll give you caveat. While they don’t have stronger memories, when you lose your sense of smell, you have trouble accessing those olfactory-evoked memories. For instance, if you’re at Thanksgiving dinner and smell the turkey or the cranberries or whatever, because of that smell it’s easier to recall your experience and the emotions of Thanksgiving dinner. When you lose your sense of smell, everything smells like plastic or cardboard, so you can’t access those memories as well. So you lose both your memories and many of the emotions associated with them.