Summary: The structure of the odor molecule determines whether a smell is considered pleasant or not. Additionally, people tend to prefer the same smells over others, regardless of their cultural background.
Source: Karolinska Institute
What smells we like or dislike is primarily determined by the structure of the particular odor molecule. A collaborative study involving researchers from Karolinska Institutet, Sweden, and the University of Oxford, UK, shows that people share odor preferences regardless of cultural background.
The study is published in the journal Current Biology.
“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,” says Artin Arshamian, researcher at the Department of Clinical Neuroscience, Karolinska Institutet. “Traditionally it has been seen as cultural, but we can show that culture has very little to do with it.”
The present study shows that the structure of the odor molecule determines whether a smell is considered pleasant or not. The researchers found that certain smells were liked more than others regardless of the cultural affiliation of participants.
“Cultures around the world rank different odors in a similar way no matter where they come from, but odor preferences have a personal – although not cultural – component,” says Dr Arshamian.
Studied indigenous populations
The study was made possible through an international network of researchers that collaborated in a unique combination of experimental methods and field studies.
The network comprised researchers from Karolinska Institutet, Lund University and Stockholm University (Sweden), University of Oxford and University College London (UK), Arizona State University, Monell Chemical Senses Center and the University of Pennsylvania (USA), Universidad San Francisco de Quito (Ecuador), University of Melbourne (Australia) and National Autonomous University of Mexico.
Many of the researchers are field workers working with indigenous populations. For this present study, the researchers 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.
Disparate odiferous environments
“Since these groups live in such disparate odiferous environments, like rainforest, coast, mountain and city, we capture many different types of ‘odor experiences’,” says Dr Arshamian.
The study included a total of 235 individuals, who were asked to rank smells on a scale of pleasant to unpleasant. The results show variation between individuals within each group, but global correspondence on which odors are pleasant and unpleasant. The researchers show that the variation is largely explained by molecular structure (41 percent) and by personal preference (54 percent).
“Personal preference can be due to learning but could also be a result of our genetic makeup,” says Dr Arshamian.
Vanilla was considered most pleasant
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.
According to Dr Arshamian, 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.
“Now we know that there’s universal odour perception that is driven by molecular structure and that explains why we like or dislike a certain smell,” Dr Arshamian continues.
“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.”
The field work behind the study was financed by the Netherlands Organization for Scientific Research (NWO), the general study by the Swedish Research Council and the USA’s National Institutes of Health (NIH). The researchers have reported that there are no conflicts of interest.
The perception of odor pleasantness is shared across cultures
Culture plays a minimal role in the perception of odor pleasantness
Individuals within cultures vary as to which odors they find pleasant
Odor pleasantness can be predicted by the physicochemical properties of molecules
Human olfactory perception is strongly constrained by universal principles
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, we asked 225 individuals from 9 diverse nonwestern cultures—hunter-gatherer to urban dwelling—to rank the monomolecular odorants from most to least pleasant.
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.
Critically, these universal rankings were predicted by the physicochemical properties of out-of-sample molecules and out-of-sample pleasantness ratings given by a tenth group of western urban participants.
Taken together, this shows human olfactory perception is strongly constrained by universal principles.