Everyone has an opinion about food. You can’t go on the internet without stumbling over someone’s lengthy review of a bistro, bar or banana slicer. As Alexis de Tocqueville wrote of the United States in 1835, “Public opinion is divided into a thousand minute shades of difference upon questions of very little moment.”

But food writing, to a linguist like me, isn’t just about food. The words you use when you write a restaurant review say as much about your own psychology as they do about which dish to order.

In a recent study at Stanford and Carnegie Mellon University my colleagues and I examined 900,000 restaurant reviews on the web of 6,500 restaurants, across seven US cities. Large-scale reading of this sort is beyond the abilities of even the most indecisive restaurant-goer, and so we used techniques from computational linguistics, writing software to count automatically the number of words, their complexity and the number of times certain words occurred, such as specific pronouns or particular nouns or adjectives.

We found that when people write a “1-star” review, they use the language of trauma: precisely the same words used by people writing about a tragedy such as the death of a loved one. Trauma victims, for instance, use the pronouns “we” or “us” to emphasise a collective sense of grief and solidarity, and this word and other linguistic manifestations of trauma were similarly over-represented in bad reviews (“we were ignored”, “yelled at us”, “none of us will ever go back”). These terrible reviews are not complaints about bad food or atmosphere but rather a coping mechanism for dealing with minor trauma caused by face-to-face interactions. People felt attacked, and their instinctive response underlines the importance of personal interactions for commerce, whether we’re asking people to choose a restaurant or a doctor.

Money also matters. Reviewers of expensive restaurants relied on multisyllabic words such as “commensurate”, “unobtrusively”, “sumptuous” and “vestibule”, and wrote long-winded reviews to depict themselves as well educated or sophisticated. We eat high-class food not only because it tastes good but also to signal that we’re high-class ourselves and have the “commensurate” language.

When a review of an expensive restaurant was positive, writers tended to use metaphors of sex and sensual pleasure, talking about “orgasmic pastry” or “seductively seared foie gras”, cake that is “creamier and more voluptuous” or “very naughty deep-fried pork belly” – perhaps a way of demonstrating their sensuous, hedonistic nature.

But positive reviews of cheap restaurants and foods instead employed metaphors of drugs or addiction: “the chocolate in their cookies must have crack”, “the wings are addicting” or “in desperate need for a fix [of curry]” or “craving it [pizza] pretty badly right now”.

When a review of an expensive restaurant was positive, writers tended to use metaphors of sex and sensual pleasure

Why the difference? We’re embarrassed about eating chips and chocolate. Foods that we “crave” aren’t vegetables. We talk about food as an addiction when we’re feeling guilty. By placing the blame on the food we’re distancing ourselves from our own “sin” of eating fried or sugary snacks. It’s not my fault I couldn’t resist that addictive cupcake. The cupcake made me do it! In fact, women are more likely than men to use these drug metaphors, suggesting that they are especially likely to feel the pressure to conform by eating healthy or low-calorie food.

In another study, my student Josh Freedman and I looked at the advertising text on the back of packets of crisps. As with reviews, we found that the more expensive the crisp, the fancier the language. We also found expensive crisps more likely to use the language of comparison (“less fat”, “best in America”, not like “any other chip”) or negation (“never fried”, “no fluorescent orange”). In fact crisps cost 4 cents more per ounce for every additional “no” on the packet. This use of distinguishing language supports French sociologist Pierre Bourdieu’s theory that upper-class taste in food has the role of “distinguishing” the rich from other classes – “We’re not like those other chips.”

Menu language is equally instructive. In a study for my forthcoming book, we computationally analysed thousands of US menus and found we could predict prices just from the words on the menu. Again, the more expensive the restaurant, the fancier the words. Difficult foreign words (“tonnarelli”, “choclo”, “bastilla”, “persillade”, “oyako”) are an implicit signal of the high-educational status of the menu writer and, by extension, the customer. But we also found that expensive menus were shorter and more implicit. By contrast, the wordy menus of middle-priced restaurants were stuffed with adjectives (“fresh”, “rich”, “mild”, “crisp”, “tender”, “golden brown”), while positive but vague words such as “delicious”, “tasty” and “savoury” were used by the cheapest restaurants.

High-status restaurants want their customers to presuppose that food will be fresh, crisp and delicious. The surfeit of adjectives on middle-priced menus is thus a kind of overcompensation, a sign of status anxiety, and only the cheapest restaurants, in which the tastiness of the food might be in question, must overly protest the toothsomeness of their treats.

We are surrounded by the language of food, words that offer a window into our psyche, our finances and our society. Next time you choose an entrée or tear open that packet of crisps, read carefully – you may just be putting words in your mouth.

Dan Jurafsky is professor of linguistics and computer science at Stanford University. His book, ‘The Language of Food: A Linguist Reads the Menu’, is published on September 15 by WW Norton (£18.99)