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[restaurant SFX]

You're listening to Twenty Thousand Hertz... The stories behind the world's most recognizable and interesting sounds. I'm Dallas Taylor. This is the story of how sound can impact our taste buds.

In 1984, a strange and remarkable thing happened across the restaurant industry, and it all had to do... with fajitas.

Up until the early 1980s, tex-mex restaurants primarily served chili, enchiladas and tacos as their signature dishes. But in 1984, the fajita became all the rage. When the popularity of this steak and pepper combo began to spread, national restaurant chains clamored to create the perfect recipe. Some would focus on a unique spice blend, or the addition of side ingredients to lure in curious customers.

...but, Chili’s - the young tex-mex chain out of Dallas - took a different approach. For them, a fajita order was treated like a performance. Once the steak and vegetables were finished cooking, the chef would plate the meal on a fiery-hot skillet [hot skillet SFX], causing them to immediately crackle and hiss. The server would then march the loud, sizzling skillet through the dining room for all the patrons to hear. [sizzling skillet traveling through dinning room SFX]

More than a unique spice blend or specialty ingredients, sound made all the difference. During each mealtime, once the first skillet sizzled down the aisles, restaurant workers quickly discovered that fajita sales would increase immediately. Chef’s all across Chili’s restaurants began referring to this phenomenon as “the fajita effect.”

In fact, once the first order of fajitas made its way to the kitchen, [bell SFX] the cooking staff would begin firing up the skillets and chopping ingredients [chopping SFX] for the massive influx of fajita orders that were sure to follow. Not only did their approach to serving fajitas prove to be a genius marketing tactic, but the sizzle of the dish also provided a sense of flavorful freshness for those enjoying the entree.

And just like that, the summer of 1984 quickly became known as ‘the summer of fajita madness’. Thanks to Chili’s, a huge percentage of restaurants across the country now serves their fajitas on mouth-watering sizzling skillets.

How does the sound of sizzling beef influence our dinner choices? What does the crunch of a potato chip have to do with our overall taste satisfaction? And, can the right music or sound make a dessert taste sweeter?

Charles: This is a really fun area to talk about, to explore, because it is something that is counterintuitive.

That’s Professor Charles Spence, head of the Crossmodal Research Laboratory at Oxford University. Crossmodal is a term used to describe when an experience in one of our main senses - touch, taste, hearing, vision, or smell - impacts or changes the perception of another sense. Charles is the leading authority on this phenomenon. He started his research in the 1990s, and has published over 500 articles in scientific journals on the subject. He’s also consulted for a number of multinational companies, advising on various aspects of crossmodal design, packaging, and branding.

Charles: For example, if I spray a certain perfume around and suddenly the people you're looking at look more attractive that would be a crossmodality effect of scent on sight. The more we look the more of these crossmodal connections are that what we see changes what we hear, what we hear can change what we feel, what we feel might change what we taste, and what we taste might change what we smell.

By changing what people hear, you can influence what they taste, and how they think about what they’re tasting. If you happen to have a piece of plain chocolate nearby, keep it handy. Later in the show, we’ll be doing our own crossmodal experiment featuring sound and taste, so you can experience these sensory connections for yourself. Connections that, in his early research, Charles investigated through the sensation of ‘crunch.’

Charles: We started out by having people in the lab here in oxford biting into potato chips [potato chip crunch SFX] and every time they bit into a potato chip we would change the sound of their crunch. Sometimes making it louder [loud crunch SFX] or quieter [quiet crunch SFX]. Sometimes boosting just certain frequencies of people's crunching sounds. In so doing we could add about 15% freshness or crunchiness to the potato chip simply as a function of sound.

Think about what things taste like, maybe what they smell like, what they look like but very few really think about sound. Yet, when you think about what it is you do like in foods and what you like to snack on then probably things like crunchy, crispy, crackly, creamy, carbonated, maybe even squeaky will come in there. All of those attributes that you might think that you feel in your mouth or between your teeth are really primarily driven by what you hear when you bite into and interact with those foods.

Crunch is certainly ONE aspect of taste, but the crossmodal effects of sound don’t stop there. Sound can also manipulate flavor. Now, for any skeptics out there, Charles was kind enough to supply us a few tracks he uses in his experiments. Still have that piece of chocolate? Go ahead and take a bite, then listen to the following two music tracks I’m about to play. While listening, think specifically about how the chocolate tastes. Here’s the first track.

[SWEET track]

Did any flavor stick out in your mind? Now, with the same piece of chocolate - or a new piece. Or three or four new pieces - take a listen to this second track.

[BITTER track]

Any change? According to Charles’ research, the first track - the higher-pitched music - should have brought out the sweetness of the chocolate. The second track - the low-pitched music - should have brought out the bitterness.

Charles: It's kind of bizarre at one level that playing music would change the taste of a food. If you are trying to bring out sweetness then you are looking for higher pitch [high pitch ding SFX] rather than looking for lower pitch [low pitch ding SFX].

Feel free to go back and test this with as many chocolates as you like - don’t worry, I won’t judge.

Charles: The whole world of taste and flavor is a complex one because one, people can't agree what the basic things are. I know that kind of on your tongue you get sweet, sour, salty, bitter, and umami, that mysterious fifth taste of tomatoes and Parmesan cheese. Beyond that what are the other basic categories that we could play with? Is it maybe citrus or meaty, floral, fruity, burnt, creamy?

The majority of us all seem to share these surprising connections between our senses, between sounds and tastes that no one really knew existed but the more we study them the more robust they seem to be and the more we can integrate them into experience design.

The practical uses of crossmodal research have expanded beyond Charles’ lab. Companies and celebrities alike are getting in on the experience.

Charles: I was lucky enough to go to New York to work with The Roots.

Charles teamed up with QuestLove and the rest of The Roots to bring sonic seasoning to the masses.

Charles: The Roots created a new song, together with Stella Artois, based on our research of the sounds of tastes that you find in that beer. As you move the dial across the screen on your computer then different instrumentation comes in or fades out to enhance the sweetness or the bitterness of the drink.

In this experiment, The Roots created two versions of the same track - Side A & B - one with higher pitched instrumentation, which is suppose to bring out the fruitier and sweeter notes and one with lower pitched instrumentation, which is suppose to bring out the bitter notes. Take a listen, and see if you can tell the difference as we switch back and forth.

Here’s side A...

[Bittersweet Side A]

And here’s side B...

[Bittersweet Side B]

Did you hear the difference? Again, the first track was designed to bring out the sweetness, while the second was to bring out the bitterness. Pretty cool, right?"

Charles: These findings have created a lot of interest now and there are a number of examples from out there in the real work of people who have taken up the findings and incorporated them into their offering.

After the break, find out how other companies are putting Charles’ research to good use, and why these crossmodal relationships might exist between our senses.

[music out]

MIDROLL

[music in]

We’ve already heard some fantastic examples of ways sound can influence the taste of food, but other than making for some really cool party tricks - why are these relationships important? What are the broader applications?

Charles: I've seen interesting examples of people taking research and running with it. One would be from British Airways. The airline who, a couple of years ago, took our findings and for their long-haul passengers offered one channel on the headset with music designed to match the meals that you could choose from the menu. A bit of sonic seasoning for the passengers given the deleterious effects of that background noise. Putting on those headphones with the noise cancellation and then bringing in music to match the taste of the food seems like a good idea.

We have earlier this year a café in Vietnam, where they are playing sweet music 24 hours a day with the idea that that will allow them to put a little bit less sugar into their cakes, pastries, and drinks, but keep the perception in the mind of those who go to the café the same. You're eating, drinking something a little bit less unhealthy, but it tastes just as good as always and that may be down to the music in the background.

Who knows, maybe sonic seasoning will become more of a diet trend in the coming years... but...until that happens, the application of Charles’ research can most often be found in advertising campaigns.

Charles: I know of companies over in the Netherlands who are selling bitterballen. These little fried snacks that go with your beer, a very Dutch treat. They're accentuating the sound of the crunch in the adverts on TV.

You might think of something like Magnum ice cream, a chocolate-covered ice cream lolly. Again when the model on the TV set in the advert bites into that ice cream you'll hear a crunch, a crack, the chocolate may be louder than is really the case because the advertisers are now understanding the importance of sound and conveying a certain expectation.

If this kind of commercial manipulation sounds familiar, it’s because we’ve heard it before. Take this Pringles commercial from the 90’s:

[Prinples commercial]

Or more recently, this TV ad by KitKat.

[Kit Kat commerical]

Many food companies utilize sonic branding as a way to convince customers that their products are fresh and delicious. Think of the pop of a Snapple cap [Snapple cap pop], or the fizz of an ice cold Coca Cola [Coca Cola fizz].

But not all sonic branding is intentional, or even desired for that matter. In 2010, SunChips developed a new 100% compostable chip bag, with one unfortunate design flaw - the bag was way too loud. [loud bag crunch SFX] After numerous complaints and a dip in market share, SunChips later released a modified, quieter bag. [quieter bag crunch SFX]

For better or worse, the snack industry has been keen to crossmodal relationship for quite some time. But all these real world examples beg the question - what makes them work?

Charles: We don't know for sure where these cross-sensory associations between taste and sound come from. If you think about that sweet taste being higher in pitch, bitter tastes being associated with lower-pitched sounds, where might that come from? Well, if you look at birth in humans, in rats, in chimpanzees, that all species, when you put a sweet taste on their tongue at around birth will stick their tongue out and up to kind of lick and ingest the goodness, the calories they need for growth. [baby giggle SFX]

Put a bitter taste on a newborn's tongue, be it a human, be it a rat, be it a chimpanzee and the tongue will immediately kind of go out and down because we're all born ejecting bitter tastes [baby whine SFX] because that's something that signals quite often poison...If you think about the kind of gurgles that a newborn would make with a tongue in different positions or you might make now if you try and stick your tongue out up and down, you'll hear a slight difference in the sonic qualities. Maybe that it's there from birth, and our brains pick up the statistics of the world.

Even if these multisensory relationships have been with us since birth, they aren’t without limitations.

Charles: If I gave you a glass of water it's not really magic. There's no music I could play that would make you think that water was wine. … but what I can do if I give you a complex taste like that spicy salad, like a rich creamy chocolate or a glass of wine, a cup of coffee, a soft drink. Then I can accentuate something in that tasting experience.

It may not be turning water into wine, but enhancing an existing taste through sound is still a remarkable discovery.

Charles: It's kind of nice almost to talk to people, to share your findings and to try and bring them into this new space that initially they think is bizarre, is bonkers, is ridiculous. Then maybe they come away thinking, "Wow. I never realized that sound had that kind of effect."

Food is often considered one of the great joys of life, and for good reason. Eating involves all of our senses. And while sound influences how our food tastes, it may not be as obvious as the alluring sight of a bright red apple or the delicious smell of a fresh-baked cookie - but learning to appreciate its sonic nuances can open a whole new world of flavor.

Twenty Thousand Hertz is produced out of the studios of Defacto Sound, a sound team dedicated to making the world sound better. Find out more at defacto sound dot com.

This episode was written and produced by Dave Parsons...and me, Dallas Taylor. With help from Sam Schneble. It was sound designed and mixed by Jai Berger.

Thank you to our guest Charles Spence from the Crossmodal Research Laboratory at Oxford University. His incredible work in the field of crossmodal relationships is what made this episode possible. If you’re interested in the work Charles and his team are doing, check out his new book - Gastrophysics: The New Science of Eating.

This episode was inspired by two other great podcasts. The first was 99% Invisible’s episode called "the sizzle" and the second was GastroPod's Crunch Crackle Pop show. Both are worth a listen.

Like the music you hear on this episode of Twenty Thousand Hertz? Each song is provided by our friends at Musicbed! You can listen to all of them, including this one, "Off White33" by "Tangerine", on our exclusive playlist. Start listening now at music.20k.org.

You can get in touch with me at hi at 20k dot org. You can also connect with us on Facebook and Twitter. If you tried our taste experiment earlier, please let me know if it worked for you.

You’ll find all of the links I mentioned in the show description.

Thanks for listening.