Does Knowing a Smell Change How You Feel? A 772-Person Study

Some people find the smell of coffee nostalgic, while others simply perceive something that seems bitter. Might these differences relate to familiarity with the odor or knowing what it is?

A study of 772 people in Geneva, Liverpool, and Singapore found that the association between odor familiarity and pleasantness was especially strong among pleasant odors. For some odors, people who correctly identified them reported more nostalgia; for others, they reported less disgust. The study explored odor-specific emotional differences that are not captured by simply asking whether someone likes a smell.

Comparing not only pleasantness but the feelings an odor evokes

Ferdenzi and colleagues’ 2013 paper had two aims: to examine how odor-evoked feelings vary between regions and between men and women, and to investigate how those differences relate to knowledge of odors.

“Knowledge” here included both familiarity, the feeling of having smelled something before, and identification, the ability to name the odor. This was not a test of expert perfumery knowledge, but a measure closer to everyday experience.

Feelings were measured using Emotion and Odor Scales (EOS) previously developed in each region. These scales grouped 36–37 terms into six or seven categories. Four were shared across all three regions: happiness/well-being, energy, sensuality/desire, and disgust. Other categories included nostalgia and hunger/thirst in Liverpool, and intellectual stimulation and spirituality in Singapore. Even categories with the same name did not contain exactly the same words in every region.

772 people each rated seven or eight odors

There were 210 participants in Geneva, 351 in Liverpool, and 211 in Singapore. Recruited at science events, museums, and similar venues, they had mostly lived in the respective country or a neighboring country sharing its language.

The researchers prepared 56 odors for the two European sites and 59 for Singapore. The selection covered fruits, drinks, flowers, wood, cleaning products, body odors, and other everyday sources, with additions such as pandan and soy in Singapore. The odorants were adjusted to have similar perceived intensities and presented in numbered pen-like devices.

Rather than smelling every odor, each person rated an assigned set of seven or eight in random order. For each odor, they first rated how well emotional terms applied, then rated familiarity, pleasantness, and intensity. A free-naming identification task was administered only in Liverpool and Singapore. Analyses distinguished comparisons between regions and sexes using individual responses from relationships between knowledge and feelings calculated from odor-level averages.

Regional differences emerged, but sex differences did not all point one way

For this set of odorants, Singapore participants rated familiarity, intensity, and pleasantness lower on average than participants at the two European sites. Regional differences nevertheless varied by odor. For example, disgust toward durian odor was lower in Singapore, while strawberry odor evoked weaker sensuality/desire, energy, and some other feelings in Switzerland than in the other regions.

Women tended to rate odors as more intense and perform better at identification than men. However, there were no overall sex differences in pleasantness or familiarity, nor did women uniformly report stronger emotional responses.

In fact, higher happiness/well-being, sensuality/desire, and energy ratings in men were found only in the Swiss sample. The authors noted that this sample contained few middle-aged and older men, making age composition a possible contributor. Sex differences in disgust also changed direction across odors: women gave higher ratings for some body-odor-like and dairy-like smells, while men gave higher ratings for some plant and floral odors.

The link between familiarity and pleasantness was stronger for pleasant odors

Within each region, the researchers split odors into two groups at the median of their mean pleasantness ratings. Among the more pleasant odors, greater familiarity was associated with greater pleasantness, with correlation coefficients of 0.71 in Geneva, 0.79 in Liverpool, and 0.80 in Singapore. Among the less pleasant odors, the familiarity–pleasantness correlation was not statistically clear in any region.

Thus, the association between knowing an odor and finding it pleasant was asymmetric across pleasant and unpleasant odors. The findings do not fit a simple account in which getting used to unpleasant odors makes people like them in the same way.

The relationship between being able to name an odor and pleasantness showed a similar tendency, but the difference in correlations between pleasant and unpleasant groups was clear only in Liverpool. Nor did every EOS emotional category show the same asymmetry. The consistent familiarity–pleasantness result needs to be distinguished from the more varied findings for individual feelings.

Coffee was associated with nostalgia, lavender with well-being

The researchers compared people whose identifications were approximately correct, incorrect, or absent. Compared with people who could not provide an identification, those who identified odors correctly reported less disgust and higher happiness/well-being, energy, nostalgia, and intellectual stimulation. This comparison was restricted to odors with sufficient numbers of responses in the relevant groups.

Looking at patterns for individual odors, differences in nostalgia were particularly prominent for beer, coffee, shampoo, and some strawberry odors. Lavender and grapefruit showed large differences in nostalgia and energy as well as happiness/well-being. A group including clove and fried shallot mainly showed a pattern of reduced disgust.

By contrast, a group including laundry soap, eucalyptus, and cheese showed no marked emotional-rating differences between people who identified the odors correctly and those who could not identify them. The relationship with odor knowledge was not the same for every smell; it depended on the combination of odor and feeling.

How names and experience contribute remains an open question

The authors considered past experience, categorization as food or nonfood, and expectations about odors as possible influences on feeling. For example, recognizing coffee and linking it with personal memories might help explain differences in nostalgia.

However, this was not an experiment comparing responses before and after teaching an odor’s name. It compared people who already knew the odor with those who did not. A causal claim about how learning a name changes emotions requires a separate experiment.

Regional comparisons also combine differences in language, response style, and participants’ ages with differences in everyday experience. The odorants were manufactured by a European company and selected by European researchers, and that selection could have influenced the results. Findings from three sites should not be treated as fixed characteristics of entire countries.

Summary

In this survey of 772 people across three regions, the association between odor familiarity and pleasantness was especially strong for pleasant odors. People who could identify an odor tended to report more nostalgia for smells such as coffee and more well-being for smells such as lavender than people who could not identify them, but the pattern varied by odor.

Women scored higher on odor identification and rated intensity higher, while emotional intensity varied with region and odor. Understanding how smells are experienced requires looking beyond pleasantness and unpleasantness to what people know and which feelings that knowledge is associated with.

The study received funding from Firmenich and the NCCR Affective Sciences, supported by the Swiss National Science Foundation. The paper lists two authors as affiliated with Firmenich.

Reference

Ferdenzi C, et al. Variability of Affective Responses to Odors: Culture, Gender, and Olfactory Knowledge. Chemical Senses. 2013;38(2):175–186. doi:10.1093/chemse/bjs083. Full paper at the University of Geneva.