Smells influence the human ability to visually perceive and correctly judge other people’s emotions – even if the person affected by the odor is unaware of its presence.
The findings, which include detailed measurements of this effect, were published in Plos One scientific journal. The research is part of the master’s degree by Matheus Henrique Ferreira, currently a doctoral student at the Institute of Psychology at the University of São Paulo (USP).
“If I am subjected to a pleasant smell, my perception of pleasant emotion improves”, says Mirella Gualtieri, PhD in Neuroscience and Behavior and professor of Experimental Psychology at USP. “The same happens with unpleasant odors, which improve the discernment of fear and disgust”, explains the scientist, Ferreira’s advisor.
The research team started from the premise that the smell stimulus has the peculiar characteristic of almost always being connected to a pleasantness judgment.
“We can be faced with many visual scenes and we won’t necessarily classify them as something we like or don’t like to see, but often the only thing an individual can describe about a certain smell is whether it’s good or bad”, says Mirella, who develops applied research in sensory psychology.
Using this premise, the group detailed their experimental design with the aim of evaluating how being subjected to an environment where there is a pleasant or unpleasant smell can affect the way a person evaluates the emotions they see in others. Mirella points out that this is not an unprecedented experiment.
“Assessing emotional expressions on people’s faces is a very old thing; What is interesting about us, and few studies have this, is that we do not use expressions of very strong emotions. People in this area usually work with features that are not very common on a daily basis. Joy, sadness, anger are portrayed in an almost stereotyped or caricatured way and this is not how we convey emotions in everyday life”.
In the experiment, images were used that portrayed a gradual of emotions. Cartoon faces, which expressed, for example, extreme joy or sadness (rated as 100% gradient), were blended with a neutral face.
Thus, gradations of 10% were created in 10% of a given emotional content (see the picture ). The group then tracked how people rated or judged that emotion. Volunteers looked at the face in the drawing and said whether it expressed joy, sadness, anger, disgust or fear.
“We observed how much intensity of this expression would be the minimum for the person to begin to correct the emotion that was present there – we know that it does not need 100%, but we wanted to know what the minimum value was – and we saw that it was usually around 20% to 30% of the total content of that emotion”, says Mirella.
Having determined the threshold of intensity of an emotion that people needed to discriminate against it, the speed, or reaction time, with which they made that judgment was evaluated. Finally, it was observed how all this could be modified with the presence of bad or good smells.
“Our contribution is to show how this effect between sensory modalities happens. We have our five senses, but for us to adapt to the environment, communicate and be able to live, these senses must be interacting. What we show in this article is an example of how this can happen”, says Mirella.
“The presence of a smell — and I don’t even necessarily need to be aware that it’s there — is going to affect my visual processing and the way I attribute emotions to the visual stimulus.”
Differentials
Another differential of the experiment is that the qualification of a smell as good or bad was determined by each participant, instead of adopting predefined conventions.
“Many works use a categorical classification, that is, people will necessarily think that the smell of strawberry it’s delicious and smelly is bad. There are these ready-made labels, but we know from experience that, especially with odor, this is very complicated, it doesn’t always work,” she says.
The participants – 35 people, 20 women and 15 men – were unaware that the experiment was about smell. They were only informed that their speed would be measured in detecting which emotions certain facial expressions indicated.
“They didn’t know it had a smell. They sat in front of the screen and, in the foam of the headset they used, we put a very minimal amount of some substance. The participant did the entire experimental session, identified the emotions, we saw the hit rate and reaction times”, he explains.
Butyric acid, with an odor of rancid butter, isoamyl acetate, a strong odor similar to banana and lemongrass, were used.
Only when that part was complete did the team explain that the goal was to see if having smells reaching the nose simultaneously with the emotion judgment affected discernment. Then the participants pointed on a scale, using a dial, to show how much they liked or disliked the smell.
Source: CNN Brasil
