Vanilla ranked as the best odour, new study finds, with people liking the same smells wherever they're from in the world

Culturally diverse people around the world like and dislike the same kinds of smells, and vanilla is consistently rated the most pleasant, according to international scientists.

A collaborative study involving researchers from the Karolinska Institutet in Sweden and the UK's University of Oxford discovered that people like and dislike the same odours regardless of their cultural backgrounds. The peer-reviewed research was published in the journal Current Biology this week.

According to the research, the two best-smelling odours are vanilla and ethyl butyrate, a chemical compound used as a flavour enhancer in processed orange juices. The ester is often described as having a fruity odour, similar to pineapple or peach.

The research also found that the least pleasant smell is universally considered to be isovaleric acid - a short-chain fatty acid found in a number of foods including cheese, soy milk and apple juice, but also in foot sweat. 

To determine whether people like and dislike the same smells across the globe, the researchers tested the preferences of 235 people, including westerners, representatives of hunter-gatherer lifestyles, and farming and fishing communities. The individuals were asked to rank smells on a scale of pleasant to unpleasant. 

The results showed variation between individuals within each group, but consistency across the diverse range of participants on which odours were considered pleasant and unpleasant. The research identified that the smells humans like or dislike are partly determined by personal preference (54 percent), but also by the odour's molecular structure (41 percent). 

As a result, the study determined that finding smells to be pleasant or unpleasant has very little to do with cultural affiliation. However, a possible reason why people like some smells more than others is that such odours increased the chances of survival during human evolution.

"We wanted to examine if people around the world have the same smell perception and like the same types of odour, or whether this is something that is culturally learned," said Dr Artin Arshamian, a researcher at the Department of Clinical Neuroscience at the Karolinska Institutet. "Traditionally it has been seen as cultural, but we can show that culture has very little to do with it.

"Cultures around the world rank different odours in a similar way no matter where they come from, but odour preferences have a personal - although not cultural - component. 

"Personal preference can be due to learning but could also be a result of our genetic makeup."

To conduct the study, an international network of researchers - many of whom have been working with indigenous populations - collaborated on a unique combination of experimental methods and field studies. The researchers selected nine communities representing different lifestyles: four hunter-gatherer groups and five groups with different forms of farming and fishing. Some of the groups have very little contact with Western foodstuffs or household articles.

"Since these groups live in such disparate [smelling] environments, like rainforest, coast, mountain and city, we capture many different types of 'odour experiences'," Dr Arshamian said.

The research concluded that there is a universal, shared perception of odour among people, with the molecular structure of the odour primarily determining whether we like or dislike the 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 odour," Dr Arshamian said.