Watching a perfumer calmly describe an odor that you find unpleasant may make you wonder whether becoming a professional changes even what a person likes and dislikes. In a 2014 study, the most striking difference was not a weakening of pleasantness and unpleasantness ratings, but the language people used to describe odors.
Perfumers and flavorists, who design flavors for food, used more chemical names and odor-quality terms. Meanwhile, pleasantness ratings did not support the prediction that experts would make a smaller distinction between pleasant and unpleasant odors. The researchers compared two things: how people experience odors and how they put them into words.
Four groups evaluated the same 20 odors
There were 64 participants in total: 16 each of people without specialist olfactory training, trainee cooks, flavorists, and perfumers. The trainee cooks were in their second year and regularly encountered food odors, but had not received specific instruction in olfaction itself. The two expert groups had approximately 9–10 years of experience on average.
The samples were 20 individual compounds, including linalool, benzaldehyde, and butyric acid. A preliminary evaluation by a separate group of 19 people confirmed that the samples covered a range of pleasantness. Each compound was diluted in mineral oil to approximately equalize its partial pressure in the vapor phase. This does not mean that all the samples were equally intense perceptually.
In the main experiment, an experimenter held a vial approximately 1 cm below the participant’s nose. After smelling it, participants rated intensity first and pleasantness second, each on a nine-point scale. They then described the same odor in as much detail as possible. Samples were presented at 45-second intervals.
For the analysis, the 20 compounds were divided into 10 relatively pleasant and 10 relatively unpleasant odors based on pleasantness ratings across all participants. The classification was therefore a relative division under the concentrations and presentation conditions used. It did not establish predetermined “good smells” and “bad smells” as a correct answer shared by everyone.
Does expertise flatten pleasantness ratings?
The authors predicted that experts, because they regard odors as materials, might rate pleasant odors as less pleasant and unpleasant odors as less unpleasant. No consistent pattern of this kind emerged.
For example, the untrained participants’ mean ratings were 3.63 for the relatively unpleasant samples and 5.58 for the pleasant samples. The corresponding ratings for perfumers were 3.62 and 5.45. When asked about pleasantness, perfumers still distinguished between the pleasant and unpleasant sets.
The overall main effect of group was statistically significant when the four groups were analyzed together. However, subsequent pairwise comparisons accounting for multiple testing did not identify any significant pair of groups. The conclusion is that the expected flattening of experts’ pleasantness ratings was not supported. The findings do not establish that experts and untrained people experience odors in exactly the same way.
From “unpleasant” to words for sources, odor qualities, and compounds
Differences in language were clearer. The researchers counted freely supplied descriptions in categories covering pleasantness or unpleasantness, odor sources, odor qualities, and chemical names.
For example, “flower” and “candy” refer to sources, “woody” to an odor quality, and “beta-ionone” to a chemical name. “Unpleasant” is different: it directly expresses the evaluator’s hedonic response.
Perfumers and flavorists used more chemical names and odor-quality terms than untrained participants and trainee cooks. The two expert groups also used more source terms than trainee cooks, who in turn used more than untrained participants. The way odors were described thus differed in stages between experience with cooking and systematic experience learning fragrance materials.
Untrained participants used more negative emotional words than trainee cooks or perfumers. The difference between untrained participants and flavorists was not significant after correction for multiple comparisons. Rather than saying that “no expert ever uses pleasantness language,” it is more appropriate to say that the focus of descriptions shifted toward words identifying an odor’s characteristics or materials.
More odor-quality and source terms were also used for the pleasant samples than for the unpleasant ones. The richness of a description depended not only on occupation but also on the kind of odor being described.
Perfumers rated odors as stronger, but that does not yet mean a more sensitive nose
For intensity ratings, perfumers rated the odors as stronger overall than untrained participants did. In every group, the unpleasant samples were rated as stronger than the pleasant ones.
The authors considered two possibilities: perfumers might be able to detect lower concentrations, or recognizing an odor might make it seem stronger. However, the experiment measured the intensity of the samples presented, not detection thresholds, the lowest concentrations a person can detect. Why perfumers reported greater intensity remains a question for future work.
Similarly, the comparison of four groups did not follow the same people before and after training. The experts were also older on average, and experience, pre-existing interests, and the kinds of descriptions required at work overlap. Supplementary analyses examined associations between pleasantness and age or sex, but the design does not establish that training alone caused the differences in language.
Summary
Perfumers and flavorists used more chemical names and odor-quality terms than untrained participants, and described odor sources more richly. In contrast, the prediction that experts would give flatter pleasantness ratings was not supported. Perfumers also rated odor intensity higher than untrained participants.
Being able to describe an odor without relying on pleasantness words is not the same as lacking a personal sense of pleasure or displeasure. By separating odor evaluations from the expressions used to communicate them, this study captured a feature of expertise. It shows clearly that alongside “Do I like it?” there is another layer of language: “What does it remind me of?” and “What kind of odor quality does it have?”
The research was supported by a grant from the French National Research Agency (ANR) and a research program in the Rhône-Alpes region. The authors declared that there were no commercial or financial relationships that could represent a potential conflict of interest.
Reference
Sezille, C., Fournel, A., Rouby, C., Rinck, F., & Bensafi, M. (2014). Hedonic appreciation and verbal description of pleasant and unpleasant odors in untrained, trainee cooks, flavorists, and perfumers. Frontiers in Psychology, 5, 12. Original research
