Poor food and rude waiters can create a restaurant experience that is literally traumatic, scientists have discovered.
A US study of almost a million restaurant ratings by diners found that the language of "bad" reviews was strikingly similar to that used by people recalling terrorist attacks or horrific accidents.
In fact, survivors of awful restaurant visits appeared to be mildly traumatised.
Professor Dan Jurafsky, language and computer scientist from Stanford University, who led the research based on downloads from the Yelp review website, said: "We found that the language of one-star reviews was very specific language. It was in the past tense rather than the present, it was a lot of pronouns and mentions of other people, a lot of negative words like 'terrible and awful', and, unusually, a lot of first-person plural pronouns, words like 'we', 'us' and 'our'.
"It turns out that there's previous scientific literature showing exactly that characteristic constellation of linguistic features characterising a particular genre, and that genre is the genre of people writing after they've been traumatised.
"So people writing after 9/11, or students writing in the campus paper after a campus tragedy, use exactly this language.
"In particular they use the first person plural, they say this bad thing happened to us as a group and we're going to get through it together. This idea of getting through suffering collectively is there in these one-star reviews. These are minor traumas."
Significantly, one-star reviews made very little mention of food. Instead, people reminisced about the "small trauma that happened to them".
Prof Jurafsky recalled a review he posted of his own after an especially unpleasant restaurant visit.
He said: "It was a case where I thought the waiter was rude to me; I felt cheated, I was upset, I talked about with my family for weeks afterwards.
"No-one died. But we're very sensitive to personal interaction and can be really injured by things that are not going to kill us but really affect us."
Prof Jurafsky's team sifted through 887,658 reviews from 6,548 restaurants in six American cities - New York, Los Angeles, San Francisco, Chicago, Philadelphia, and Boston.
The same study, presented during a session on "Big Data" at the American Association for the Advancement of Science (AAAS) annual meeting in San Jose, California, shed new light on the psychology of eating.
In particular, it revealed that posh food is perceived as sensuous and sexy while pizzas and French fries are associated with drugs and addiction.
For men and women alike, sexual appetite appeared to be on the menu when they recalled savouring carefully prepared, costly dishes produced by skilled chefs.
"We found a really interesting difference by price," said Prof Jurafsky. "If you like a very expensive restaurant you use words like 'orgasmic', 'sensual', 'sexy'. My favourite phrase is 'a very naughty deep fried pork belly'.
"The more expensive the restaurant the more likely you are to describe the food by sex. By contrast, the cheaper the restaurant, the words we found were words like crave, drugs, crack and heroin. So people talking about cheap foods - pizza, French fries - use the language of drugs."
Other examples of sexual connotations included "orgasmic pastry" and "seductively seared fois gras".
The drugs association - highlighted in phrases such as "addicted to fries" and "craving cupcakes" - could be explained by people having guilt feelings about enjoying less than healthy food, said Prof Jurafsky. They shifted the blame on to the food, with the message: "It's not my fault, I was addicted to it".
He added that a direct link was found between the price of dishes and the length of words used on the menu.
"For every extra letter in a word describing a dish the dish was 18 cents (10p) more expensive," he said.