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The Taste Of Wine Isn't All In Your Head, But Your Brain Sure Helps

Molecules in wine stimulate thousands of taste and odor receptors, sending a flavor signal to the brain that triggers massive cognitive computation involving pattern recognition, memory, value judgment, emotion and, of course, pleasure.
Alex Reynolds/NPR
Molecules in wine stimulate thousands of taste and odor receptors, sending a flavor signal to the brain that triggers massive cognitive computation involving pattern recognition, memory, value judgment, emotion and, of course, pleasure.

What do listening to music, hitting a baseball and solving a complex math problem have in common? They all activate less gray matter than drinking wine.

According to Yale neuroscientist Gordon Shepherd, the flavor of wine "engages more of our brain than any other human behavior." The apparently simple act of sipping Merlot involves a complex interplay of air and liquid controlled by coordinated movements of the the tongue, jaw, diaphragm and throat. Inside the mouth, molecules in wine stimulate thousands of taste and odor receptors, sending a flavor signal to the brain that triggers massive cognitive computation involving pattern recognition, memory, value judgment, emotion and of course, pleasure.

Whereas most wine writers tend to focus on the various elements that go into the wine itself — the grape, the oak, terroir, the winemaker — Shepherd's subject is the drinker. He explores biomechanics, physiology and neuroscience to describe a journey that begins as wine passes the lips and ends with a lingering "finish" that can last for minutes.

If you've ever wondered how many muscles there are in the tongue (eight), if a high-fat diet can affect the perception of wine (it can), or if it's possible to experience the full flavor of a wine that's been spat out (it is not), Shepherd has answers — extraordinarily detailed, scientifically rigorous answers. I spoke to Shepherd about his new book, Neuroenology: How the Brain Creates the Taste of Wine. Our interview has been condensed and edited.

The subtitle of your book is "How the Brain Creates the Taste of Wine." Can you explain what that means?

The analogy one can use is color. The objects we see don't have color themselves — light hits them and bounces off. It's when light strikes our eyes that it activates systems in the brain that create color from those different wavelengths. Similarly, the molecules in wine don't have taste or flavor, but when they stimulate our brains, the brain creates flavor the same way it creates color.

Chapter one is on fluid dynamics, a subject you almost never hear mentioned by wine connoisseurs. How does fluid dynamics inform our understanding of wine?

You don't just put wine in your mouth and leave it there. You move it about and then swallow it, which is a very complex motor act. If you search on YouTube for anyone doing serious wine tasting, they are working it with their mouths. It's a very active process. So to understand the physiology of tasting wine, it's necessary to give people a whole new context of how wine sensing and wine tasting takes place.

You talk about a "hidden force" in wine tasting. What is it?

When you sniff wine in the glass, you appreciate the bouquet. That's called "orthonasal" smell — the external smelling we're all familiar with. But what most people are unaware of is that when you take wine in your mouth and experience the flavor, most of that flavor is due to a kind of internal smelling. The air comes in from the throat, not your nostrils. That's called "retronasal" smell. The molecules are carried to the same receptor cells in the nose, but from the opposite direction. This is very important when it comes to wine flavor. An example is the famous jelly bean test. If you put a jelly bean in your mouth and plug your nose and sense it with your tongue, all you sense is sweet from the sugar. But if you then unplug your nose, suddenly you're flooded with the full flavor experience, and it's because you're smelling through the back of your nose.

One thing you write about that I've never read elsewhere is the effect saliva has on wine.

Our bodies produce saliva all the time, and saliva has stuff in it — stuff that both dilutes the wine and interacts with it. So as soon as the wine enters your mouth, it immediately begins to change. For example, saliva contains enzymes that break down the molecules in the wine to create compounds that effervesce into the air to stimulate the smell receptors in your nose. This produces new compounds that were not originally in the wine — they were created by this interaction.

The amount of saliva a person produces can affect their perception of wine. So can things like age, gender, or even the amount of acetone — a byproduct of energy metabolism — in a person's breath.

And the time of day. And whether or not they're depressed. If we're talking about smell, we have about 350 different kinds of olfactory receptors. They are not the same between individuals — yours will be different than mine. And they're not always the same over the course of months or years. As the cells turn over, they can change.

Given all these subjective variables, and the fact that the brain "creates" the taste of wine, is it possible for two people to experience the same wine in the same way?

There is still a commonality. We all know it's a liquid, after all. We all know it comes from fruit. We all know it contains alcohol. And we all have saliva that is more or less the same. So probably 90 percent is the same and 10 percent is different. That's part of the pleasure of wine —comparing your pleasure.

Does your research suggest wine drinkers are doing anything wrong?

Within a few sips or drinks, people are just downing the stuff. There needs to be more to it than that. If you take too large a sip, you've saturated your system.

Is expensive stemware worth it?

My wife and I have a sit-down meal every night. We used to use modest stemware, but we would occasionally knock it over and it would break, so now we use plain water glasses. But if we're having a proper sort of dinner, we use some kind of glass with a bowl so you can capture the aroma. Just fill the bottom few cubic centimeters, because if you fill up a glass you don't get much aroma. The reason for having a large bowl is that it amplifies the headspace for sniffing in the bouquet and you take small sips. But once you understand the flow dynamics that I describe, you can make your own choice as to how important the glass will be.

I will end with what may be the most enduring question in science. What's the best value in wine for under $20?

For table wine, we stick to around $10 or $12 per bottle, and it's a fun challenge to find a wine in that range. I don't want to mention any names, because that would give someone a commercial advantage. For more interesting wines, we like Sancerre because it seems to have an edge to it. [Editor's note: Sancerre is a designated wine district in the eastern Loire Valley known mostly for wines made from Sauvignon Blanc.] One of the reasons I prefer European wines is they have a slightly lower alcoholic content. There is research that shows people prefer wines with less alcohol. This is important, because global warming is driving alcohol content up, not down.

Mark Schatzker is the author of The Dorito Effect: The Surprising New Truth About Food and Flavor.

Copyright 2023 NPR. To see more, visit https://www.npr.org.

Mark Schatzker