It’s obvious that we human beings are all pretty different from one another—in appearance, experience, attitude, gender, and countless other attributes. Each of us has things that come effortlessly and others at which we struggle. It goes without saying that these differences affect our abilities as tasters. But how, exactly?
I want to preface this topic by saying that few of us are good at self-assessing our abilities in this area. There is a lot of insecurity out there, and people often tell me, “I guess I’m just not very good”—and without some training and experience, it is difficult to know where one stands. There is a difference, though, between inherent limitations and those based on lack of experience, interest, and training. No one is born learning to read, but most of us eventually figure it out.
It’s helpful to know that the chemical senses are so important that they have a lot of redundancy built into the systems. General weaknesses are quite rare, most commonly the result of disease rather than genetics. Even more rare are general hypersensitivities—there really aren’t true “super-smellers,” though an experienced professional “nose” can seem that way to novices.
When we talk about being good tasters, what do we really mean? It’s helpful to define some terms and talk about the different aspects of perception involved in tasting. One of the more basic things that can be measured is threshold. This is the minimum amount of a substance that can be detected in a particular context such as air, water, beer, etc. It is usually tested by one’s ability to identify the one sample out of three that is different from the others.
Threshold is purely based on olfactory sensitivity, and it does not require identification or even recognition of the specific difference. Those are different functions that involve other parts of the brain as well as higher concentrations of the stimulus.
We’re Born Different
Each of us has our own, highly specific genome. This sets our basic capabilities and limitations. We have fewer than three dozen receptors for taste, with more than two-thirds of those used for sensing bitterness. Another dozen or so are for mouthfeel.
Most genetic variations in taste sensitivity involve bitterness. You’ve probably heard the term “super-taster,” or possibly even been tested for it in high school biology class. This primarily involves a bitter receptor called TAS2R38, which is sensitive to a wide range of bitter chemicals including those found in the broccoli family. PROP bitterness sensitivity, named for the chemical used to test for it, varies significantly among individuals. We have two copies of TAS2R38 in our genome, and to simplify things a bit, each comes in both sensitive and insensitive forms. So, by simple combinatorial math, about a quarter of us have two sensitive copies while another quarter has two insensitive ones; the remaining half of us has one of each and so have medium sensitivity. Yet genetics are almost always more complex than that; there are known genetic variations in about half of human bitter receptors.
On the other hand, sweet taste relies on just two receptor types, and variations in those are uncommon. Genetic variations in sweet “liking” are a bit mysterious, involving genetic variations far removed from taste itself. Because of their importance to the organism, sour and salty taste also have only infrequent variations—and this is even more true for trigeminal sensations, such as mouthfeel. (The trigeminal sense, named for the cranial nerve that delivers its signals to the brain, is actually a complex suite of sensory systems that can respond to heat, cold, irritants, and various types of mouthfeel textures, from creamy to grainy to astringent.)
Besides variations in the genes that code for the receptors themselves, there is information in our genome that codes for the number of copies produced—another mechanism for variations in sensitivity or functionality. Often, genetic variations of one thing are coupled to another in “genomic blocks,” and these linked variations may have little to nothing to do with each other. With some tastes, there are other molecules that assist the process in various ways, and these also are subject to genetic variations.
Our sense of smell, meanwhile, is genetically vast; it occupies more of our DNA than anything else. With close to 400 different receptors, it offers huge opportunities for genetic variation. If you’ve spent any time around the tasting table, you’ve probably noticed that you and your fellow travelers respond differently to the same aromas. As with taste, variations depend on receptor coding errors as well as variations in copy numbers and associated “helper” molecules.
Naturally, how all this works is complex. Rather than responding to a single receptor (or linked pair of them) as with taste, smell depends on patterns of response to specific chemicals in a receptor—or, more commonly, multiple receptors. Generally, a receptor type will respond to multiple chemicals, and a single chemical may create positive or negative responses in multiple receptors. Your nose sends this pattern to your brain, and it constitutes the identity document of the odor. However, once signals from the nose are processed through the olfactory bulb, all information regarding the odor’s chemistry is irretrievably tossed out, replaced by things like meaning, identity, and context.
In terms of variation, the fewer receptors engaged in a particular odor, the greater the chance that a genetic variation may reduce our sensitivity. Some of these are well-known in wine and beer tasting—about one in 10 people have a reduced sensitivity to buttery-smelling diacetyl, for example. Because most odor chemicals stimulate multiple receptors, there’s less chance that any one variation would seriously affect our ability to smell them.
Also, real-world smells are almost always composed of dozens of different chemicals. The fact that the brain discards the chemistry but replaces it with a pattern of meaning further facilitates our ability to relate to one another. Whatever pattern the nose creates from a mix of chemicals, it’s the pattern of meaning that we build, maintain, update—and ultimately share with one another.
Excepting those with extreme genetic defects, injuries, or respiratory issues, people generally follow a bell curve in terms of their sensitivities. As there are few mechanisms for an extreme and general enhancement of smell sensitivity, there really aren’t “super-smellers.” There are super-noticers, and these may develop with training and experience in smell-related pursuits, or as extreme responses to perceived threats from environmental odors unconnected to specific physiological conditions.
Among a panel of 20 trained and tested panelists, a handful will have smell deficits for one or more chemicals, and a few will show higher sensitivity to at least one. A few chemicals such as beta-damascenone—a cooked/dried fruit odor common in wine and present as a staling flavor in hoppy beer—have blindness rates of about 50 percent of the population. Understanding your own strengths and weaknesses is a crucial part of becoming an accomplished taster. While threshold testing can be done, it’s cumbersome and difficult outside of a laboratory situation. Simple experience in an activity such as beer judging will, over time, make you aware of both your weak spots and useful sensitivities.
Psychological factors are also at play. There are relatively minor differences between the sexes, and females generally have a very slight edge with most chemicals—but they are generally better noticers and may also be better at verbal labeling than males. Curiosity, novelty-seeking, introversion, and just plain interest all affect our abilities here, as smell is particularly responsive to attention.
Photo: Matt Graves
Experience Matters
While perception involves the hardwired boundaries of threshold responses, other things are equally or even more important in tasting. Recognition means you’ve been able to retrieve a memory of a smell, even if you haven’t yet been able to put a finger on what it is. This involves the activation of the hippocampus, the brain’s main memory processor and index. These little messages from the limbic system can often offer valuable clues to what the smell is, so linger in them if you can. Identification is a semantic process, meaning it involves higher cognitive processes that include context and language.
You can slightly improve thresholds with training, but one remarkable fact is that our bodies are constantly replacing olfactory receptor neurons and parts of the olfactory bulb—so in just a few weeks, you’ll have a whole new set. Even more amazingly, the mix of these receptors is tailored to the smell of your environment. Move from the city to the country, and soon you’ll be more sensitive to country smells. Want to smell beer better? Smell more beer.
Studies consistently show that recognition, and especially identification, abilities can be improved dramatically by even a few hours of practice. These are what really set professional “noses,” such as perfumers, flavorists, sommeliers, and great brewmasters apart from the rest of us. Those first two careers involve seven to 10 years of apprenticeship and knowledge of well over 1,000 individual chemicals. Experts also adopt the vocabulary of their specific pursuit. In wine, it’s mainly related to grape varietal, terroir, and aging. In beer, it tends to be more single-chemical fault-oriented. Flavorists and perfumers learn their raw materials, which are mostly individual molecules. The ability to summon olfactory sensations purely from memory is another important skill acquired from long experience, especially revolving around recipe formulation.
Because much of the skill set is cognitive, it’s dependent on cultural context as well as your own personal frame of reference. Different languages not only use different words but may have larger or smaller odor vocabularies. Industrialized societies generally have the fewest, reflecting the relatively lower importance of odor compared to others.
As we age, we pick up skills, experiences, and abilities, but our senses inevitably decline as well. The good news is that with constant practice and learning—and maybe simply paying attention to the aromatic world around us—we can compensate well into the eighth decade and beyond.
A recently published study suggests that smelling odors, even when sleeping, can enhance all kinds of cognitive connections. That’s the big takeaway here: Your sense of smell requires your active participation, and it will reward your attention with a fuller and richer sense of being in the here and now.