One in a trillion. The vials of smells that volunteers sniffed in the new study were only a tiny sampling of all the possible smells that humans can distinguish.

One in a trillion. The vials of smells that volunteers sniffed in the new study were only a tiny sampling of all the possible smells that humans can distinguish.

Zach Veilleux/The Rockefeller University

Can You Name That Smell?

Ask a group of people to describe the color of a sheet of paper, a cloud, or a glass of milk, and chances are they’ll all say “white.” But ask the same group to describe the smell of cinnamon, and you’ll likely get a potpourri of answers, ranging from “spicy” to “smoky” to “sweet,” and sometimes all three. When it comes to naming smells, humans struggle to find concise, universal terms. Indeed, scientists have long thought the ability was out of our reach. But a new study indicates that the inhabitants of a remote peninsula in Southeast Asia can depict smells as easily as the rest of us pick colors.

The study concerns the Jahai, nomadic hunter-gatherers who live in the mountain rainforests along the border between Malaysia and Thailand. Smell is very important to this society. Odors are often evoked in illness, or medicine, for example, and it is one of the few cultures to have words devoted exclusively to smells. “For example, the term pʔus (pronounced ‘pa-oos’) describes the smell of old huts, day-old food, and cabbage,” says Asifa Majid, a psychologist at the Centre for Language Studies at Radboud University Nijmegen in the Netherlands. This suggests, she says, that the Jahai can isolate basic smell properties, much like we can isolate the color white from milk.

To find out if the Jahai are better at naming smells than the rest of us, Majid and colleagues asked native Jahai speakers and native English speakers to describe 12 different odors: cinnamon, turpentine, lemon, smoke, chocolate, rose, paint thinner, banana, pineapple, gasoline, soap, and onion. The Jahai easily and consistently named the odors, whereas English speakers struggled, the team reports in the February issue of Cognition.

For example, all Jahai speakers tested agreed that the smell of cinnamon should be described as əs, pronounced "cheng-us," the same word they use for the smells of garlic, onion, coffee, chocolate, or coconut. This suggests that Jahai are able to identify common odor properties in all of these foods, suggesting a special perception ability compared with other cultures.

In contrast, Majid says, “English descriptions for odors were five times longer and nearly every participant came up with a completely different name. There is little consensus on how to describe smells, and people often give many conflicting and contradictory descriptions.” What’s more, she notes, when English speakers described smells, they often used the source of the smell in their description; a lemon, for example, smelled “lemony.” The Jahai, meanwhile, had their own unique words for the smells.

The disparity may be due to importance of odors in the daily life of the Jahai, says Douglas Medin, a psychologist at Northwestern University in Evanston, Illinois, and an expert in cognition and learning in indigenous cultures. In a dense rainforest, trunks can look the same, for example, so it is not always possible to identify a tree just by its looks, says Medin, who was not involved in the work. In addition, after a heavy rain, smells become more evident and you can easily identify a pile of monkey scat, decomposing leaves, or flowers nearby, if you learn to identify the smells. Alternatively, having an agreed-upon way to describe a smell that could attract a tiger might save your life.

It’s also possible that the Jahai are built differently than the rest of us. The genes that code for the olfactory receptors in our noses exhibit a great deal of variation not only between different human populations but also between people. So it may be that the Jahai have evolved more of these receptors or a greater diversity of them than everyone else, much like the Tsimane tribe from the Bolivian rainforest were shown to be more sensitive to smells than were Germans.

“We won't be able to answer these questions until comparable studies are carried out on lots of other human cultures,” says Nicholas Evans, a psychologist and biologist specializing on the diversity of linguistic structures at Australian National University in Canberra. “But this study has broken open the seal on the perfume bottle.”