The Neuroscience of Taste: A Q&A With Psychologist Charles Spence

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Dr. Charles Spence is a professor of experimental psychology at the University of Oxford and author of “Gastrophysics: The New Science of Eating.” Among numerous other awards, he won the Ig Nobel Prize for his breakthrough “sonic chip” experiment, which showed that altering sound alone changed whether people perceived one Pringles potato chip to be fresher than another (identical) chip.

Brain World spoke to him about multisensory integration, how expectation shapes perception, and the arrival of technology at the dining table.

Brain World: How did you become interested in multisensory integration and its influence on flavor perception?

Charles Spence: I have always been interested in how the senses affect each other, since I was an undergraduate — about 30 years ago. At the lab here at Oxford we do applied research, not just how one sense influences another, but how we perceive the world through all our senses, and how to apply that in the real world. Most of the funding has come from industry, like Unilever. Previously, we’ve worked on designing multisensory warning signals to make them more effective for drivers. Now our research is more about eating and drinking, probably the most multisensory of our experiences. Taste and smell are especially interesting because of how they’re combined by the brain.

BW: Could you please tell us about your “sonic chip” experiment?

CS: We were thinking about the sound of food — crunchy, crackly, crispy foods — and its impact on taste. We began changing the sound of the crunch of potato chips, building on the rules of multisensory integration applied to taste. That became the “sonic chip” experiment. When we won the Ig Nobel award, it generated a huge amount of interest and continues to do so to this day. Initially it seemed like kind of silly research that makes people laugh. Why would anybody change the sound of the crunch? But over 15 years later it turned out to be far more important than we realized, and it has forced us to raise some philosophical questions about flavor and perception.

BW: How do our senses combine in the perception of taste or flavor?

CS: All perception is influenced by multiple senses. Even though it feels like we’re seeing or hearing or feeling or tasting — like we can break down our experience into different senses — in fact much more goes into our judgment and perception than we realize. One demonstration I use is to ask people to hold their nose and bite into a jelly bean and then chew it. With their nose closed, they only get the sweetness, which is a very thin sensory experience. But when they release it, suddenly they get the flavor or taste; all of the volatile, rich smells flow through the back of the nose. The addition of smell is really what we’re tasting.

BW: In your book you discuss the food industry. How does the food and beverage industry alter our perception of taste?

CS: There are many ways. We’ve actually been altering the perception of taste for thousands of years. Nearly every food has a color and that color affects us. Changing the color of wine can change people’s perception of its smell. Brightly colored foods seem to taste stronger and pink food tastes sweeter. A third of the time we eat food or drink directly from the package, so the shape and weight of the can or bottle also influences taste. Why do potato chips come in noisy packaging? Research shows that serving chips in louder packaging enhances their crunch. Smell or aroma is also very important. It might be used to make us hungry or to bias us toward one food choice or another — like the smell of coffee in a bookstore. Design is also not optimal. If you look at how people consume coffee — across cultures one of the world’s best-smelling products — with a plastic lid that doesn’t allow you to smell the coffee. So things can be done to use the science of multisensory integration to have a better tasting experience — that’s the aim of gastrophysics.

BW: Can we learn to experience food differently?

CS: Yes. Some would say all of our responses are learned, that we’re born into this world only liking the taste of sweetness and umami and disliking bitterness. All of our responses — to creamy, meaty, citrus, herbal, floral or coffee — are actually learned by conditioning through exposure. A vanilla pod tastes bitter if you bite into it. We aren’t born thinking vanilla or caramel smells sweet, but we learn that — that smell normally comes together with sweetness, like vanilla ice cream. And we internalize that connection. By adding sweet smells to food we can lower the actual sugar level. There’s a lot of work in that space right now: How can we enhance sweetness while reducing actual sugar, simply by using smells more intelligently? Companies must try to figure out ways to reduce unhealthier ingredients while keeping the taste experience.

BW: You have also explored aspects such as menu design. Could you please tell us about that?

CS: Naming and branding also set our expectations. Wine can seem fruitier, fresher, sweeter, more expensive, higher quality or older by manipulating other cues, be they sensory or informational. They all draw our attention to something and/or set our expectations about what we’re going to taste. A dominant view in the literature states that our brain is really a prediction engine, generating internal models of the world. In food science, flavor is technically a mixture of smell and taste on the tongue. But far more important to our flavor experience is the sizzle of the hot plate as it’s being brought to the table because that sets our expectations and updates our predictions. Before that meal comes to the table, or we open that package, or uncork that wine we already have in mind what it’s going to taste like.

BW: Has anything surprised you?

CS: When we started looking at how music — “sonic seasoning” — can change the taste of the food, that was really surprising and it is still surprises people today. Can you really change the taste of food, coffee, or wine by playing some music? But when people are exposed to it that’s when suddenly they start changing their behavior, so that’s what led me to do more of these experiential events.

BW: How is technology transforming our eating experiences?

CS: We’ve had three decades or more of modernist cuisine and molecular gastronomy. We’ve seen science being brought into the kitchen with new scientific devices, equipment, and approaches to cooking. But now we’re bringing science or psychology to the dining room, with the world’s leading restaurants like the Fat Duck bringing iPods to the tables, playing sounds of gulls along with their signature dish, “Sound of the Sea.” Also sensory apps on mobile devices that most people carry in their pocket all the time. The technology’s amazing and if it can be repositioned to add “sonic seasoning” to your food, great!

BW: You’re also involved in several projects to help the elderly or ill. What are you currently working on?

CS: We have one line of research, with Jozef Youssef from Kitchen Theory, making ice cream for the elderly because people with Alzheimer’s or dementia are often chronically underweight from not eating enough. Together we’ve worked to make nutritious ice creams, containing less cream and fat, and to come up flavors like tomato soup ice cream — things people have never seen before, so they generate a surprise. We’ve also been working for five years with a children’s cancer hospital outside Barcelona, changing the packaging and presentation of hospital food in order to make mealtimes more fun and improve the kids’ well-being and recovery.

BW: What are the future directions for your research?

CS: One area is using sensory technology to deliver an extraordinary experience. There are examples where diners are brought to tears by the sound of the sea. What is it about the multisensory techno-delivered experience that makes people cry, and can we deliver that kind of extraordinary experience? We’re also working with a magician and a chef. Sometimes food and magic go side-by-side, but can you ever eat magic? A theoretical, neuroscientific, magical, multisensory project. Creating a magical food experience — is that an impossible goal?

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