OLFACTORY MEMORY: HOW SMELLS AWAKEN MEMORIES - NEUROPSYCHOLOGY - 2024

The olfactory memory refers to the memory of odors. Smells can bring us a lot of memories. This is because the olfactory bulb, which is a region of the central nervous system that processes sensory information from the nose, is part of the limbic system.

Since the limbic system is an area closely associated with memory and emotions, smells can evoke memories and trigger strong responses almost immediately.

How is the association between smells and memories formed?

The olfactory bulb has access to the amygdala, which processes emotions, and the hippocampus, the structure responsible for associative learning. Despite the connections between the structures, the smells would not evoke memories were it not for the conditioned responses that have formed over time.

When you first smell something, you unconsciously link it to an event, a person, an object, a time, or a place. Your brain forges a link between the smell and a memory, associating, for example, the smell of chlorine with summer or the smell of lilies with funerals.

Olfactory bulb

When you meet the scent again, the bond is already formed and ready to elicit a memory or even a mood. The smell of chlorine can make you feel happy because they remind you of summer moments in the pool with your friends.

Lilies, however, could make you inexplicably melancholic. This is, in part, why not everyone prefers the same smells: by pure association.

Since we encounter most new smells during our childhood and youth, smells often evoke childhood memories. However, we actually begin to make associations between smells, emotions, and memories even before we are born.

Children who have been exposed to alcohol, tobacco smoke, or garlic in their mothers' wombs often show a preference for these smells. To them, smells that may bother other babies seem normal or even pleasant.

The role of the amygdala

The amygdala is an almond-shaped structure of the brain that processes everything related to our emotional reactions. It is one of the most primitive areas of the human brain.

It is also associated with memories and memory in general, since many of our memories are related to some emotional experience.

A decade ago, Rachel Herz, an expert in the psychology of smell, and her colleagues at Brown University tested whether there was a correlation between the emotional intensity of a memory triggered by a smell and activation of the amygdala.

The participants first described a positive memory triggered by a particular perfume. Afterward, they went to the laboratory to participate in a functional magnetic resonance imaging experiment.

The participants were exposed to various sequences of visual and olfactory stimuli. The visual cues included an image of the perfume the participant had chosen and an image of an unbranded perfume. The olfactory stimulus included the participant's chosen perfume and the unbranded perfume.

If the stimulus elicited any memory or emotion, the participants were instructed to keep it in mind until the next stimulus was presented.

When the participants smelled the perfume they had chosen, it was when they showed greater activation in the amygdala and the parahippocampal gyrus (a region that surrounds the hippocampus).

These data suggest that smells that elicit strong emotional memories also cause heightened activity in areas of the brain strongly related to emotions and memory.

However, it is important to know that only five people participated in this study, and they were all women. Studies with a larger sample of participants, involving both men and women, are needed to confirm these findings.

Several behavioral studies have shown that smells trigger more vivid emotional memories and are better at inducing that feeling of "being transported to the past" than images.

However, there have been few studies, since that of Herz and his colleagues, that have explored the relationship between smell and autobiographical memory at a neural level.

Smell and emotions

The perception of smells is not only about feeling them, but about the experiences and emotions associated with those sensations. Smells can provoke very strong emotional reactions.

In surveys of reactions to some odors, responses show that many of our olfactory tastes are purely based on emotional associations.

Although there is compelling evidence that pleasant fragrances can improve our moods and feelings of well-being, some of these findings should be considered with caution.

Some recent studies have shown that our expectations of an odor, rather than the direct effects of exposure to it, may be responsible for the improvements in mood and health benefits that have been reported.

The effect of suggestion and placebo

In one experiment, researchers found that simply informing subjects that a pleasant or unpleasant odor was being administered (which they may not even be able to perceive) altered their self-reports regarding their moods and well-being.

Just mentioning a pleasant smell reduced reports of poor health and increased reports of positive mood. These findings suggest that these improvements may be due to a placebo effect.

However, more reliable results have been found in experiments using placebos in the form of sprays without any odor. These studies have shown that, although subjects respond somewhat to odorless placebos than what they think are fragrances, the effect of actual perfume is significantly greater.

Thinking about pleasant perfumes might be enough to make you feel a little more cheerful, but the actual smell can have dramatic effects in enhancing your mood and sense of well-being.

Although olfactory sensitivity diminishes as we age, pleasant smells have been found to have positive effects on mood at any age.

The effects of smells on our perception

The positive emotional effects that smells have also affect our perceptions of other people.

In one experiment, subjects who were exposed to fragrances they found pleasant tended to give higher “attractiveness scores” on people who appeared in photos that were shown to them.

However, some more recent studies show that these effects are only significant when there is some ambiguity in the photos. If the person in the photo is clearly very attractive or, on the contrary, extremely ugly, the fragrance does not usually affect our judgment.

However, if the person has only a “medium level of attractiveness,” a pleasant fragrance will tip the balance of our evaluation in their favor. In this way, the attractive models that are used to advertise perfumes probably have no need for it, but the rest of us can benefit from a spray that smells good.

Unpleasant odors can also influence our perceptions and evaluations. In one study, the presence of an unpleasant odor caused subjects not only to give individuals in photos worse scores, but also to judge some drawings that were shown to them as less professional.

Positive smells can also have negative effects

However, the mood-enhancing effects of positive smells sometimes work against us: increasing our positive perceptions and emotions, pleasant smells can cloud our judgment.

In an experiment in a Las Vegas casino, the amount of money made on a slot machine increased by 45% when the place was perfumed with a pleasant aroma.

In another study, a shampoo that participants had ranked last in overall results in an initial test was ranked first in a second test after altering its odor.

In another test, participants reported that the shampoo was easier to rinse, applied better, and left hair shinier. Only the fragrance of the shampoo had been changed.

Scent preferences

Smell preferences are often a personal matter, having to do with specific memories and associations.

For example, in a survey the answers to the question "what are your favorite smells?" included many odors that are generally seen as unpleasant (such as the smell of gasoline or body perspiration). However, some smells normally perceived as pleasant (such as the smell of flowers) got very negative responses from some participants.

These preferences were explained by the experiences (good or bad) that people had had and associated with particular smells. Despite the peculiarities of these individuals, it is possible to make some significant generalizations about olfactory preferences.

For example, experiments to date have shown that we have a tendency to like what we know: people give higher scores on how pleasant they find an odor that they are able to correctly identify.

There are also some fragrances that seem to be universally perceived as pleasant, such as vanilla, an increasingly popular ingredient in perfumes that has long been a "standard pleasant scent" in psychology experiments.

A note for perfume merchants: one of the studies showing our tendency to prefer fragrances that we can correctly identify also showed that using an appropriate color can help us make a correct identification, increasing our taste for perfume.

The smell of cherries, for example, was more frequently identified accurately when it was presented with the color red, and the ability of the subjects to identify the smell significantly enriched their scores.

Smells and increased productivity

Have you ever considered perfuming your workspace, your school or university? A priori it may seem silly. However, odors can also affect labor productivity, in addition to influencing moods, Rachel Herz notes that a growing number of studies show that positive mood is linked to increased productivity, execution, and a tendency to help other people, while negative mood reduces prosocial behaviors.

Notably, prosocial behavior and productivity are also enriched in the presence of pleasant environmental odors. For example, in one experiment, people who were exposed to the smell of cookies in the oven or coffee being made were more likely to help a stranger than people who had not been exposed to olfactory manipulation.

Likewise, people who worked in the presence of an air freshener that smelled nice also reported higher self-efficacy at work. Additionally, they set higher goals and tended to employ more efficient work strategies than participants who worked in an odor-free condition.

Pleasant ambient smells have also been found to increase alertness during a tedious task and improve performance on word completion tests.

On the contrary, the presence of odors considered negative reduced the subjective judgments of the participants and lowered their levels of tolerance to frustration. The participants in these studies also reported that they had concordant mood swings.

Therefore, it can be concluded more or less safely that the observed behavioral responses are due to the effect of air fresheners on people's moods.

Some of the fragrances that seem to increase productivity at work are the scent of lemon, lavender, jasmine, rosemary, and cinnamon.

So now you know: smells influence mood, job performance, and other forms of behavior through learned associations, especially emotionally.