Seeing is smelling: A study on odor perception

According to a study by the University of Montreal, a person's perception of an odor is dependent on and associated with a positive or negative label and description.

Researchers Simona Manescu and Johannes Frasnelli asked 50 participants to smell four odors - essential oil of pine, geraniol, cumin, and parmesan cheese. Each odor, smelled through a mask, was randomly associated with either a positive or negative label: pine oil was paired with the label "Pine Needles" or "Old Solvent"; geraniol was presented with the label "Fresh Flowers" or "Cheap Perfume"; cumin was accompanied with the label "Indian Food" or "Dirty Clothes"; and parmesan cheese corresponded with the cheese label or a label of dried vomit.

All partakers in the study rated the four odors more positively when associated with a positive label compared to a negative label. More specifically, they used words like "pleasant" and "edible" to describe the odors when paired with a positive label. However, the opposite descriptors "unpleasant" and "inedible" were used when the same four odors were presented with a negative label.

The results clearly show that a person's perception of a food's edibility can easily be manipulated, depending on whether it's presented in a positive or negative light, the researchers said.

"It shows that [odor] perception is not objective: it is affected by the cognitive interpretation that occurs when one looks at a label," Manescu said in a statement.

"Moreover, this is the first time we have been able to influence the edibility perception of an odour, even though the positive and negative labels accompanying the odours showed non-food words," Frasnelli added.

The Montreal researchers collaborated with a team from McGill University to measure participants' reaction times to these odors. Though past studies have shown that unpleasant odors cause rapid reactions and pleasant odors cause slower reactions, in their study, only the parmesan cheese odor coincided with this idea. It prompted a different reaction time, which was slower when the label was positive.

The results were published in the journal Chemical Senses.