Vanilla, Peaches, and All the Other Lesser Smells

The scientific search for fundamental human taste preferences is commendable but our "evolutionary instincts" can't explain the full complexity of our social behavior

Back in May, a group of British and Swedish researchers published a paper in Current Biology called “The perception of odor pleasantness is shared across cultures,” in which they demonstrate that most people around the planet preferred the smell of vanilla (vanillin, 4-Hydroxy-3-methoxybenzaldehyde) and the smell of fresh fruit/peaches (ethyl butyrate) over other scents. The research subjects also agreed that the smell of isovaleric acid (described as “sour stinky feet”) was unpleasant. (NPR summary of the paper)

These findings make sense. I, too, like the smell of vanilla and peaches and dislike the smell of sour stinky feet. The evolutionary logic is also clear: We have succeeded as a species because our olfactory systems nudged us towards the ethyl butyrate in fresh fruit and away from the isovaleric acid in rotting plants.

But I have a lot of quibbles with this research otherwise (including but not limited to the supposed evolutionary advantages of humans eating vanilla beans.) I mostly object to the paper's broad conclusion that "culture plays a minimal role in the perception of odor pleasantness.” Their evidence is not only weak, but the findings may actually prove the opposite point. If there is an inherent human preference for the smell of vanilla and peaches, then clearly chemistry and biology offer few clues into how our current society values some scents over others.

To understand these points, we first have to unpack the term "perception." The research paper is using perception to mean something like "direct bodily sensation." The experiment asked subjects to rate the smell of Sniffin’ Sticks permeated with the odor of pure chemical compounds, and then the researchers equated a "good" rating for the smell as a positive perception. Surely our brains sense vanillin in a positive way, but the perception process also includes recognition, categorization, association, and interpretation. In other words, our noses sense vanillin, and then we perceive that stimulus as the concept "vanilla." But we can only sense "vanilla" if we have prior knowledge this smell is called "vanilla." And since specific experiences and social contexts shape our interpretation of stimuli, culture plays an obvious role in our perception of smell. Jasmine may automatically register "good smell" in our brains, but as scholar Sianne Ngai recently told The Paris Review, “When we smell jasmine, we also smell civilization, well-ordered beauty, luxury. I have to say, when I smell jasmine, I smell gender.” (Artificial vanilla makes me immediately think about C-3POs Cereal.) Even the research paper writers understand the cultural differences around smell; they note that Swedes love fermented herring but others find it the "most repulsive [smell] in the world.” In a research setting, most subjects would likely rate the chemical compound behind the aroma of pickled fish as "bad"; when Swedes sense this smell in real life as an opportunity to eat their favorite comfort food, it would surely be perceived as "good."

But let's just assume the findings are 100% true as this helps us see the larger issues with the paper's conclusion about biology and culture. If humans are condemned to love the smell of vanilla over all other smells, does this preference manifest in our social behavior? Yes, vanilla is the "basic" flavor of ice cream, but otherwise, is vanilla widely treated as the "best" possible smell?

The best way to test this is to look at the perfume industry — a $30 billion marketplace where consumers spend lots of money to intentionally smell a certain way. In theory the human propensity towards vanilla and peach-scent would predict that these are the core scents behind most beloved perfumes. The world's most popular perfume is Chanel No. 5, which is said to have notes of vanilla and peach but the ylang-ylang, neroli, and citrus are much stronger. There are, of course, many vanilla-based perfumes, but perfumers must balance the vanillin with more oblique fragrances or otherwise the overall effect is "basic" and "cloying." This practice suggests that elegance requires avoiding human's inherent smell preferences rather than mapping to them. Additionally, evolutionary logic should make us dislike the scent of human waste; yet the much-used jasmine has a “fecal decay note."

These only seem like contradictions, however, if we try to explain everything through biology and deny that commercial fragrances have a specific social function to make individuals smell uncommon. Vanilla was once rare, but now that it's everywhere, pure vanilla would just make a person smell like Facebook-ad candles and supermarket bakery cakes. A good perfume offers an unrecognizable smell that marks off a person's existence from others. This social function requires perfumers to use a melange of rare floral compounds, and most intriguingly, plenty of acrid smells as well. Comme des Garçons Series 6 Synthetic: Garage, for example, uses fragrance notes of “Laurel aldehyde, traces of kerosene, leather notes, plastic floral notes, vetiver acetate, Chinese cedarwood" to allow its wearers to smell uniquely like burnt tires.

So we can commend biologists for trying to understand the universals of human sensory systems, but hard scientists (and the non-fiction authors who popularize their findings) go too far when they claim the "hidden" brain mechanisms formed in the evolutionary process somehow explain everything about contemporary human behavior. As we see in the case of smells, our biologically predetermined tastes don't predict how smells manifest in society, which means their influence on our choices is too weak to have explanatory or predictive power in the real world. And most critically, they don't explain at all why tastes differ by group and change over time. At best, these research findings help us map out the permissible range in which human preferences form, but the incredible diversity of beloved smells suggests this range is so wide as to be nearly meaningless. Knowing that all humans prefer the smell of vanilla and peaches doesn't provide any insight into why humans employ a bewildering number of complex smells in their daily lives, most of which try to avoid directly smelling like vanilla and peaches. To understand that phenomenon, you have to look to the incredibly strong influences of history, society, and culture in shaping our tastes.