Other people’s emotional reactions appear to influence how positive or negative we perceive an odor, according to a new study conducted by neuropsychologists at the Ruhr-Universität Bochum in Germany.
The researchers say this may be due to the activity in a certain brain region associated with our sense of smell which becomes activated even before we perceive an odor.
“When we see someone that makes a face, because a bad smell stings his nose, the same odor appears to be unpleasant for us as well,” said Dr. Patrick Schulze, one of the authors.
The research team, led by Schulze, Dr. Anne-Kathrin Bestgen and Professor Boris Suchan, used functional magnetic resonance imaging (fMRI) to investigate how the brain processes the combination of emotional information and odors. Participants were asked to look at a picture of a person with a happy, neutral, or disgusted facial expression. Then they had them rate one of 12 scents.
The photos of the different facial expressions influenced how the participants perceived the odors. For example, the volunteers rated the valence of a scent higher when they saw a happy face first and they rated the valence as poorer when they saw a disgusted face before.
These results applied to a wide range of aromas, including caramel and lemon, as well as the more pungent smells of sweat or garlic. Only the smell of feces could not be valued higher by a positive facial expression.
Responsible for the variety of perceptions is a particular part of the olfactory brain known as the piriform cortex, which processes what we see and creates an expectation about how something is going to smell — and thus is activated even before someone senses an odor. This expectation influences how we actually experience the smell.
According to the fMRI data, the researchers found that the cells of the piriform cortex became active before a scent was in the air. In earlier studies, researchers had always presented the pictures and the odors at the same time.
“Only now that we analyzed the interaction of olfactory and visual information in a timely separated manner, we were able to see that the piriform cortex is activated before we smell something,” said Suchan.
The findings are published in the journal Scientific Reports.
Source: Ruhr-Universität Bochum