Humans share sensory systems with a common anatomical blueprint, but individual sensory experience nevertheless varies. In olfaction, it is not known to what degree sensory perception, particularly the perception of odor pleasantness, is founded on universal principles, dictated by culture or merely a matter of personal taste. To address this, a research team led by Karolinska Institutet and University of Oxford scientists asked individuals from nine diverse non-Western cultures — hunter-gatherer to urban dwelling — to rank odorants from most to least pleasant.
Odor preference rankings were collected from nine culturally and geographically diverse populations. These included the three hunter-gatherer groups, Seri from a coastal desert and Maniq and Semaq Beri from tropical rainforest, one shoreline forager, Mah Meri, from a tropical coast; one swidden-horticulturalist, Semelai, from tropical rainforest; one farmer-foraging community, Chachi, from tropical rainforest; one subsistence agriculturalist community, Imbabura Quichua, from temperate highlands; and two urban dwellers from industrial and postindustrial communities of bustling urban settings, Mexican and Thai. The data from these nine communities were then related to available data from a large dataset on odor preference collected from urban dwellers from New York City, the United States. Image credit: Arshamian et al., doi: 10.1016/j.cub.2022.02.062.
In 1878, the famous Irish romance novelist Margaret Wolfe Hungerford wrote, ‘Beauty is in the eye of the beholder,’ suggesting what one person finds beautiful, another may not.
Consistent with this, we now know that facial preferences vary across individuals. Importantly, however, they are also strongly shaped by culture and may even have components that are universal.
Similar to beauty, the perception of odor pleasantness or valence — the principal dimension by which odors are categorized — is said to vary across cultures.
For example, fermented herring is a greatly appreciated delicacy in Sweden, but it also emits a smell described as the ‘most repulsive in the world.’ In addition, people also display individual variability in food preference, even within families.
At the same time, more recent studies of urban western participants demonstrate that valence can be objectively predicted from an odorant’s chemical structure, despite the fact that universal odor preferences have been disputed historically.
It is unclear how to reconcile these perspectives: is odor preference culturally relative, driven by individual preferences, or universally constrained by molecular structure?
“We wanted to examine if people around the world have the same smell perception and like the same types of odor, or whether this is something that is culturally learned,” said Dr. Artin Arshamian, a researcher in the Department of Clinical Neuroscience at Karolinska Institutet.
“Traditionally it has been seen as cultural, but we can show that culture has very little to do with it.”
For the study, Dr. Arshamian and colleagues selected nine communities representing different lifestyles: four hunter-gatherer groups and five groups with different forms of farming and fishing. Some of these groups have very little contact with Western foodstuffs or household articles.
“Since these groups live in such disparate odiferous environments, like rainforest, coast, mountain and city, we capture many different types of ‘odor experiences’,” Dr. Arshamian said.
The study involved 235 individuals who were asked to rank smells on a scale of pleasant to unpleasant.
Contrary to expectations, culture explained only 6% of the variance in pleasantness rankings, whereas individual variability or personal taste explained 54%.
Importantly, there was substantial global consistency, with molecular identity explaining 41% of the variance in odor pleasantness rankings.
“Personal preference can be due to learning but could also be a result of our genetic makeup,” Dr. Arshamian said.
The odors the participants were asked to rank included vanilla, which smelled best then followed by ethyl butyrate, which smells like peaches.
The smell that most participants considered the least pleasant was isovaleric acid, which can be found in many foods, such as cheese, soy milk and apple juice, but also in foot sweat.
“A possible reason why people consider some smells more pleasant than others regardless of culture is that such odors increased the chances of survival during human evolution,” Dr. Arshamian said.
“Now we know that there’s universal odor perception that is driven by molecular structure and that explains why we like or dislike a certain smell.”
“The next step is to study why this is so by linking this knowledge to what happens in the brain when we smell a particular odor.”
A paper on the findings was published in the journal Current Biology.
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Artin Arshamian et al. The perception of odor pleasantness is shared across cultures. Current Biology, published online April 4, 2022; doi: 10.1016/j.cub.2022.02.062
Source link: https://www.sci.news/biology/odor-pleasantness-10684.html
