Coffee tastes less sweet in a white mug; a chip tastes fresher when its crunch is louder. Illustration by Olimpia Zagnoli

Sitting in a pub one night a dozen years ago, Charles Spence realized that he was in the presence of the ideal experimental model: the Pringles potato chip. Spence, a professor of experimental psychology at Oxford University, runs the Crossmodal Research Lab there, which studies how the brain integrates information from the five human senses to produce a coherent impression of reality. Very often, these modes of perception influence one another on the way to becoming conscious thought. For instance, scientists have long known that whether a strawberry tastes sweet or bland depends in no small part on the kinds of organic molecule detected by olfactory receptors in the nose. Spence had been wondering whether taste might be similarly shaped by sound: Would a potato chip taste different if the sound of its crunch was altered? To explore that question, he needed a chip with a reliably uniform crunch. The Pringle—that thin, homogeneous, stackable paraboloid—was perfect.

Over the next few weeks, Spence invited twenty research subjects to his basement lab and sat them in front of a microphone in a soundproof booth. There they were handed a pair of headphones and instructed to bite, one by one, into nearly two hundred Pringles original-flavor chips. After a single crunch, each subject spat out the chip and gave it a rating: crisper or less crisp, fresh or less fresh. The subjects could hear each crunch as it looped from the mike into the headphones. But, without letting the participants know, Spence funnelled the crunching noises through an amplifier and an equalizer, allowing him to boost or muffle particular frequencies or the over-all volume. About an hour later, released from the booth, each subject was asked whether he or she thought all the chips were the same.

The chips were identical, of course, but nearly all the volunteers reported that they were different—that some had come from cans that had been sitting open awhile and others were fresh. When Spence analyzed his results, he saw that the Pringles that made a louder, higher-pitched crunch were perceived to be a full fifteen per cent fresher than the softer-sounding chips. The experiment was the first to successfully demonstrate that food could be made to taste different through the addition or subtraction of sound alone. Spence published his results in the Journal of Sensory Studies, in 2004. The paper, written with a post-doc, Massimiliano Zampini, was titled “The Role of Auditory Cues in Modulating the Perceived Crispness and Staleness of Potato Chips.”

Within the small group of scientists interested in multisensory integration, the paper heralded a new direction for the field, a shift from teasing out the mechanics of audio-visual interaction to what Paul Breslin, an experimental psychologist at Rutgers University, described as “the new frontier” of oral perception. Outside the academy, the paper failed to generate any interest until 2008, when its authors were awarded the Ig Nobel Prize for Nutrition. The Ig Nobels are intended to “honor achievements that make people laugh, and then think,” but media coverage of Spence’s win focussed mostly on the former, with headlines that ranged from “BOFFIN GIVES EATERS SOUND ADVICE” to “WHY RESEARCH THAT?!” At first glance, the “sonic chip” experiment, as Spence fondly refers to it, does seem trivial. In reality, it was an elegant psychological trick, offering insight into the way the brain combines two separate sensory inputs—the crunching sound and the tactile oral sensation of a potato chip—into one multisensory perception. Spence lists the honor at the top of his curriculum vitae.

Before the sonic-chip breakthrough, Spence had worked almost exclusively on how an understanding of the neuroscience of audio and visual stimuli could help design better warning signals for drivers. (One of his insights—that sounds originating from behind a driver’s head will direct attention forward more quickly than sounds that come from the side—has found its way to market with the introduction of headrest-mounted speakers in 2015 Volvo FH trucks.) Afterward, Spence’s lab began studying the crunch of apples, the fizz of carbonated water, and the rustle of potato-chip bags. The vast majority of research into human sensory perception has been unimodal—focussed on understanding how each sense operates in isolation. Alongside sex, eating is one of the most multisensory of our activities; scientists have long claimed that much of what is perceived as flavor is actually filtered through the olfactory receptors, with taste buds playing a much smaller role. Spence goes further, arguing that in most cases at least half of our experience of food and drink is determined by the forgotten flavor senses of vision, sound, and touch.

Over the past decade, Spence has conducted a series of experiments that illustrate exactly that. Other researchers have joined him in exploring this new territory, but “Charles is a pioneer,” Francis McGlone, a neuroscientist at Liverpool John Moores University, told me. “His contribution to the field of cognitive psychology is seminal.” Breslin said, “He’s pushing the frontier in all kinds of ways that I wouldn’t have predicted.” In 1997, at the age of twenty-eight, Spence was invited to set up his own research lab at Oxford, and his Ig Nobel is just one in a long list of accolades, including a 2003 award from the European Society for Cognitive Psychology, in recognition of his “outstanding contribution to cognitive psychology in Europe.”

Along the way, Spence has found that a strawberry-flavored mousse tastes ten per cent sweeter when served from a white container rather than a black one; that coffee tastes nearly twice as intense but only two-thirds as sweet when it is drunk from a white mug rather than a clear glass one; that adding two and a half ounces to the weight of a plastic yogurt container makes the yogurt seem about twenty-five per cent more filling, and that bittersweet toffee tastes ten per cent more bitter if it is eaten while you’re listening to low-pitched music. This year alone, Spence has submitted papers showing that a cookie seems harder and crunchier when served from a surface that has been sandpapered to a rough finish, and that Colombian and British shoppers are twice as willing to choose a juice whose label features a concave, smile-like line rather than a convex, frown-like one.

It does not require an enormous leap of imagination to see how these kinds of cognitive insights could be incorporated into commercial packaging design, and, gradually, this is exactly what is happening. Americans derive a sizable proportion of their daily calories from food or drinks that are consumed directly from the package, and that is only expected to rise in tandem with the “snackification” of the Western diet. Marketing departments and product-design agencies have an extra incentive to enlist Spence’s findings in the cans, packets, tubs, and squeeze tubes that populate grocery-store shelves. We are accustomed to thinking of food and its packaging as distinct phenomena, but to a brain seeking flavor they seem to be one and the same.

“Dad always says, ‘Not the crisps again!’ ” Spence groaned, when I mentioned the Pringles experiment. We were walking back to his lab after lunch, during which he had criticized everything from the color of the rubber O-ring on the sparkling-water bottle to the sound of the Nespresso maker. Spence gives his family background the credit for his focus on finding practical applications for his research. “My parents never went to any school,” he said. “They always want to know, ‘What’s it for?’ ”