Our sense of smell is based on two delivery pathways, orthonasal and retronasal; that makes it the only “dual sense modality” we possess, one that provides information about things both external and internal to the body.

When it comes to evaluating as well as marketing wines, the duality of smell has important consequences for perception. Not surprisingly, there are differences in the odors resulting from orthonasal and retronasal olfaction, even though they are processed in the same way.

While both pathways deliver volatile aroma compounds to the same receptors, the quality of those odors and our thresholds for detecting them differ due largely to the airflow patterns that the molecules follow, the temperature differences of the air traveling through each pathway, and the different enzymes found in our saliva and the membranes of our mouth and throat.

Researchers at Ohio State University have determined that food odors elicit similar responses through orthonasal and retronasal olfaction—but that’s not the case with non-food odors such as floral aromas. Participants in the study were asked to match an identified scent, such as rose, with one of four unknown scents using two methods: by drinking a solution to activate the retronasal sense of smell through the internal nares, or nostrils, at the back of the throat and by sniffing from a vial to activate the orthonasal sense of smell through the nose.

Participants were presented with the reference aromas of honeysuckle, lavender, rose, and jasmine labeled in three different ways: with their common names, with their Latin or species name, and with a letter. When the routes of delivery differed, for example by smelling one sample and tasting another, participants made more mistakes, which were attributed to the differences in those delivery systems affecting their ability to match the scents.

Regardless of how the samples were labeled, the best results were achieved when aromas were introduced in the same way, either through sniffing them in a vial or drinking them in a solution.

However, researchers were surprised to find that the less participants knew about the reference aromas—that is, when they were labeled with their species name or a letter—the better their chances of correctly identifying a match when using different routes of delivery. The unexpected finding suggests that aroma detection (and thus perception) involves learning, memory, and cognitive strategy.

Researchers point to cues provided by familiar labels as the cause of cognitive
interference from the brain’s language centers, which has a negative impact on our ability to identify aromas: Even when the same aromas are activating the same receptors, albeit through different pathways, we still can’t make a match.

That discovery and its relation to the duality of-smell phenomenon is further illustrated by a small study conducted by Cornell University researchers in tasting rooms in New York’s Finger Lakes region, which showed that both the volume and value of wine sales were higher when tasting sheets omitted sensory descriptors like “dry and full-bodied, with decadent flavors of pink grapefruit, honeysuckle and lemon meringue” in favor of details on the climate in which the grapes were grown and the foods the wines in question paired with.

Their conclusion: Sensory descriptors are likely intimidating to inexperienced
consumers, who get frustrated when they can’t identify the aromas and flavors used to describe the wine. The consumers studied had a better tasting experience and purchased more wine when they had less information about the sensory attributes of the wines they were tasting.

In short, the challenges created by the duality-of-smell phenomenon in combination with cognitive dissonance are at least partly responsible for the confusion consumers experience when they have difficulty identifying non-food aromas ascribed to wines.