Smells affect a person’s ability to visually perceive and correctly judge the emotions of others – even if the person affected by the smell is unaware of their presence. As a result of a master’s research conducted by Matthews Henrique Ferreira, a doctoral student at the Institute of Psychology of the University of São Paulo (IP-USP), an article containing detailed measurements of this effect was published in magazine Plus One.
“If I’m exposed to a pleasant smell, my perception of pleasant emotion improves,” says Mirella Gualtieri, Ph.D. in Neuroscience and Behavior and Professor of Experimental Psychology at IP-USP. “The same thing happens with unpleasant odors, which improves the discrimination of fear and disgust,” explains the scientist, Ferreira’s consultant.
The research team started from the hypothesis that the scent stimulus has the peculiar property of being always associated with a judgment of pleasantness.
“We can encounter many visual scenes and won’t necessarily categorize it as something we like or don’t want to see, but often the only thing an individual can describe about a particular scent is whether it’s good or bad,” says Gualtieri, who develops applied research. In sensory psychology.
Using this hypothesis, the group elaborated their experimental design with the goal of evaluating how exposure to an environment where there is a pleasant or unpleasant odor might affect the way a person evaluates the feelings they see in others.
Gualtieri points out that this is not an unprecedented experience.
“Evaluating emotional expressions on people’s faces is a very old thing, and what’s interesting to us, and there are few studies that have this, is that we don’t use very strong emotional expressions. Usually people in this area work with features that are not very common in everyday life. Depicting joy, sadness and anger in a semi-stereotypical or caricatured manner, and that is not how we convey feelings in everyday life.”
In the experiment, pictures depicting gradual emotions were used. Cartoon faces, expressing, for example, intense joy or sadness (rated as grading 100%) were mixed with a neutral face. Thus, gradients from 10% to 10% of a given emotional content were generated (see Figure A). The group then tracked how people rated or judged these feelings. The volunteers looked at the face in the drawing and said whether it expressed joy, sadness, anger, disgust, or fear.
“We noticed how much intensity this expression would be the minimum for a person to start affecting the emotions that were there – we know it doesn’t need 100%, but we wanted to know the minimum value – and we saw that it’s usually about 20% to 30% of the The total content of those feelings,” says Gualtieri.
After determining the emotional intensity threshold that people need to discriminate against, the speed (reaction time) with which they made that judgment was assessed. Finally, it is noted how all this can be modified by the presence of bad or good smells.
“Our contribution is to show how this effect occurs between the sensory modalities. We have our five senses, but for us to adapt to the environment, to communicate and to be able to live, it is necessary that these senses interact. What we show in this article is an example of how this happens,” says Gualtieri. .
“The presence of the smell – and I don’t necessarily need to be aware of its presence – will affect my visual processing and the way I attribute feelings to visual stimulation.”
Another variation of the experiment is that the classification of smell as good or bad was determined by each participant, rather than adopting pre-determined conventions.
“Many works use a categorical categorization, meaning that people will necessarily think that strawberry smells good and feet smell bad. There are these off-the-shelf labels, but we know from experience that, especially with smell, this is very complicated, and it doesn’t always work. What has been guiding our work is What the person judged, whether it was pleasant or unpleasant for them, and that changed the analysis process a lot compared to when we used the label, assuming the smell was always bad. This choice changed our results in a very important way, so we chose that from now on we won’t We base ourselves only on the judgment of kindness that people have made themselves.”
The participants—35 people, 20 women, and 15 men—were not aware that the experiment was about smell. They were only informed that their speed at detecting the emotion indicated by certain facial expressions would be measured.
They didn’t know it had a smell. They sat in front of the screen and in the foam Earphone that they used, we put a very small amount of some materials [ácido butírico, com odor de manteiga rançosa; acetato de isoamila, odor forte similar ao de banana; ou capim-limão]. The participant ran the entire experimental session, quantified the emotion, and we saw the beat rate and reaction times.”
Only when this part was completed did the team explain that the goal was to see if scents reaching the nose simultaneously with emotional judgment affected discrimination. Then participants referred to a scale, by means of a communicateTo show how much they like or hate the scent.
“Although previous studies have highlighted the role of the pleasurable valence of smells in the emotional processing of visual stimuli, several other factors are likely to be involved. This study demonstrates that there is an important dual effect between olfactory and visual stimuli. It was It is possible to verify that smells affect the identification of facial expressions, just as they influence the emotional reaction to smell as well,” comments Patricia Renovato Topo, Scientific Director of Natura Inovação e Tecnologia de Produtos and co-author of the article.
The research was conducted under the Center for Applied Research (CPA) run by Fapesp and Natura at IP-USP between 2016 and 2021. Also involved in the work was Carla Barrichello, Natura’s Director of Social Welfare Sciences.
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