The nose knows best? Not really, researchers say

The nose isn’t the only organ associated with smell, according to researchers. Apparently vision also plays a role in how we perceive smell.

Simona Manescu and Johannes Frasnelli from the Université de Montréal’s Department of Psychology found that a positive or negative description of an odour can affect the way it is perceived. When associated with a positive label or description, we enjoy the odour more than when it is accompanied by a negative label.

To demonstrate this phenomenon, the researchers asked 50 participants to smell four odorants: pine essential oil, geraniol, cumin and parmesan cheese. The odours were delivered through a mask and randomly presented with a positive or negative label displayed on a computer screen:

• Pine oil was labelled “pine needles” or “old solvent”
• Geraniol was labelled “fresh flowers” or “cheap perfume”
• Cumin was labelled “Indian food” or “dirty clothes”
• Parmesan cheese was labelled “parmesan cheese” or “dried vomit”

All participants rated the four odours most positively when they were presented with positive labels than negative labels. In particular, participants described the odours as pleasant and edible - even if they were non-food items - when they were associated with positive labels.

In contrast, the same odours were considered unpleasant and inedible when associated with positive labels - even for food items.

“It shows that odour perception is not objective: it is affected by the cognitive interpretation that occurs when one looks at a label,” Manescu said.

“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,” added Frasnelli.

The researchers say this means that the perceived edibility of an odour can be manipulated by a description, and that olfactory perception may be driven by a top-down cognitive process.