One of the lesser enigmas of life is why so many people order tomato juice on aeroplanes. Like Pavlov’s dog, I often start craving it myself the minute I do my seatbelt up. Lemon, Worcester sauce, no ice (which I find dilutes the salty thickness too much).
In the general run of things, few of us sip tomato juice for breakfast or as an aperitif, yet this savoury beverage forms 27% of all drinks orders on planes, with or without added vodka. According to one survey of more than 1,000 passengers, nearly a quarter of people will choose tomato juice when flying, even though they never drink it under other circumstances. This is exactly the kind of puzzle that interests Charles Spence, a professor of experimental psychology. In Gastrophysics, Spence notes that the “really special thing about tomato juice and Worcester sauce (both ingredients in a good bloody mary) is umami, the proteinaceous taste”. When Spence and colleagues investigated, they found that the blaring sound of being on an aeroplane – around 80-85 decibels of background noise – interferes with our ability to taste sweetness. That gin-and-tonic which tastes so sweet back on land is dulled in the air. By contrast, the noise actually increases our perception of the intensity of savoury umami flavours such as tomato juice. As we merrily ask the flight attendant to pour us a bloody mary, we have little notion that we may be driven to do so by what is happening to our ears as much as to our mouths.
The book argues that eating is a far more multi-sensory experience than we usually recognise. Spence – who has worked extensively with Heston Blumenthal at his restaurant the Fat Duck – proposes a “new science of eating” to systematically observe the ways our behaviour around food are affected by all of our senses, as well as by factors such as the eating environment and even cutlery. It transpires that, to most people, meals taste better when served with heavy, expensive knives and forks. Or with no cutlery at all (Spence cites research suggesting that eating food with our hands enhances the way it feels in the mouth). Gastrophysics is about the quirks of human perception and how they play out at mealtimes: the way that red plates oddly make food taste worse, for example, whereas bowls can make it taste better. At its best, the book is wonderfully curious and thought-provoking, throwing the whole question of why we eat the way we do wide open.
Spence argues that when we reduce eating to taste or nutrition, we miss half the story. Some of his most interesting experiments – such as the tomato juice one – have shown the degree to which sound affects our enjoyment of eating. Food has a certain music, whether we are tuned into it or not. One study found that people enjoy a cup of coffee less if the coffee machine emits a horrible high-pitched noise. As Spence writes, “many of the food properties that we all find highly desirable – think crispy, crackly, crunchy, carbonated, creamy, and of course, squeaky (like halloumi cheese) – depend, at least in part, on what we hear”. His most famous experiment is his work on the “sonic chip” – winner of the Ig Nobel prize for improbable research – which could be summarised as: loud crisps taste better. He found that increasing the volume of the crunch when eating potato crisps made eaters believe they were around 15% crunchier and fresher. “You can play exactly the same sonic tricks,” Spence claims, “with apples, celery, carrots or, in fact, with any other noisy food.” He aspires to be like the Italian futurist Marinetti, who in the 1920s and 30s threw experimental dinners that used different colours and sounds and perfumes to change the mood at table.
Another aspect of our eating experience that gets neglected, in Spence’s view, is the role of expectation. Our enjoyment of food is far from objective. Call a piece of fish “Patagonian toothfish” and it may not sound appetising, but the same fish repackaged as “Chilean seabass” becomes suavely aspirational. It’s possible to make someone believe that the same piece of meat is saltier, greasier and less pleasant simply by calling it “factory farmed” instead of “free range”. Similarly, when served food on a larger plate, our natural reaction is to eat up to 40% more. Some of the strangest examples that Spence gives concern the way that the look of something changes the way it tastes. A detail as tiny as changing the latte art on a cappuccino from an angular star to a rounded “bouba” can make the drink appear less bitter to consumers. When in 2013 Cadbury updated its Dairy Milk bar by rounding off the edges, customers complained that the chocolate tasted sweeter than before and became convinced that the formula must have changed. But Spence’s work confirms that serving food in a rounder shape – “be it a beetroot jelly or a chocolate confection” – often makes it taste sweeter.
He admits that certain culinary experts dislike this kind of trickery, and see it as irrelevant to the more important task of making good, nutritious meals. His research is regularly dismissed by some Michelin-starred chefs, who say that good food “should speak for itself”. Spence’s riposte to this is that, however much you may believe in simplicity and provenance and an honest plate of food, “there is always a multisensory atmosphere”. Even a chef who claims to let food do all the talking will go to the trouble of buying good heavy cutlery, he observes, because a plastic or aluminium fork would “spoil the experience”. Whether we like it or not, we are all affected by these manipulations. Spence’s point is that “there is no such thing as a neutral context” for eating. The flavour in our mouths at dinnertime is affected by the company we keep, by the music playing in the room (he suggests that, for most consumers, Nina Simone enhances appetite and Justin Bieber kills it), by how expensive the ingredients were and whether we are consuming them from a hospital bed.
But eating – this most complex of human activities – is also affected by a host of factors that Spence pays less attention to. In common with other experimental psychologists, he sometimes seems to treat human beings as if they were homogeneous amalgams of sense-organs, unaffected by culture or economic circumstances. Spence does not always interrogate the assumptions behind the studies he cites. For example, he reports, uncritically, that a recent survey of 2,000 people shows that “if you are a man hoping to make a good first impression on the ladies, the top tip was to make sure not to order a salad for your main course”. He does not seem to recognise that this “finding” is less about food and more about culture and gender.
Addressing the growing number of people who eat alone, he suggests jauntily: “Next time you get peckish, why not invite someone to eat with you?” For a book on psychology, there is remarkably little here on the manifold ways that eating can become dysfunctional, from bulimia to picky eating. There are people whose problems with eating go far beyond whether their plate is the right colour. Gastrophysics is brilliant when demonstrating how much the environment of the table affects our eating – particularly at high-end restaurants – but it has less to say about what we as humans bring to the table.
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