Väänänen stayed on but soon became restless. One day, he described his old feedback idea to Ville Levaniemi, who’d been a colleague in both of his previous ventures. Levaniemi thought the idea was so simple that someone must have done it already, and said he’d investigate. “The next day, he came back to me and said, ‘Let’s resign immediately and start this business,’ ” Väänänen recalled. They installed the first HappyOrNot terminal in December, 2009, in a small grocery store in Tampere. “It was very exciting,” Väänänen said. “But when we left the store I told Ville, ‘Shit, what if, like, no one gives feedback?’ So we were guessing—maybe ten? maybe twenty?” By the end of the day, more than a hundred and twenty customers had used the terminal. “We saw that, if you make it easy, people will give feedback every day, even if you don’t give them a prize for doing it.”

Finland is a good place to start a technology company. The semi-collapse of Nokia—the Finnish telecommunications giant, which once dominated the global mobile-phone market—left a pool of unemployed but highly capable hardware and software engineers. “When we came to the United States to do trade shows,” Väänänen said, “we saw that maybe thirty per cent of the people were Finnish, and it was, like, ‘Why are we meeting here instead of in Finland?’ ” A Finnish national program, called Tekes, gives grants to entrepreneurs. The grants start very small but grow as the recipients meet targets. HappyOrNot eventually received about a million euros in Tekes grants, and grew very fast.

In early 2012, Väänänen and Levaniemi hired Todd Theisen to help with international sales, an area in which they’d been having trouble. Theisen had grown up in the United States, and majored in international politics and German studies. He then ran an English-language school in Germany for half a dozen years, married a Finn, and worked in sales and marketing for a Finnish educational-technology company. He saw immediately what HappyOrNot was doing wrong. He told me, “Selling in Finland is a different proposition from selling abroad, and it’s very different from selling in America. Finnish culture is extremely modest and humble.” There’s an old joke that a Finnish introvert looks at his shoes when he talks to you, and a Finnish extrovert looks at your shoes.

HappyOrNot’s international breakthrough came at Heathrow Airport. Passengers had been complaining that security workers there were rude and incompetent, and, as the 2012 Summer Olympics approached, the airport’s executives worried about the imminent influx of international visitors. They positioned HappyOrNot terminals so that passengers could use them as they cleared security. The executives were now able to identify problem locations in real time, and security workers in low-rated areas could see when they were viewed as more annoying than colleagues in other parts of the airport. Very quickly, Theisen told me, Heathrow security’s over-all passenger-satisfaction scores rose by more than half.

The Heathrow contract has been extremely important for HappyOrNot, since even today new clients often say that they first noticed the terminals either there or at an airport that installed them after one of its officials noticed them at Heathrow. The terminals haven’t reached the security area at Palm Beach International Airport, however—as I saw when I flew back to New York after my visit to the company. I did see a single sign, with a message from the Transportation Security Administration which asked for feedback about T.S.A. Precheck: “Scan the code to tell us about your experience.” But the sign was pushed back against a wall, and no one who didn’t understand how to scan a QR code would have known what to do. What’s more, anyone who scanned the code, as I did, would end up with just a link to the T.S.A.’s general customer-service Web page, on which, if they scrolled down far enough and clicked through enough options, they’d be able to find and fill out an (endless) online form, on which they would be required to include their full name and e-mail address. As if!

An episode in the third season of the TV show “Black Mirror” portrays a world in which people spend nearly all their time using their phones to rate virtually everyone else on a five-star scale. Lacie—a young woman whose obsession with her own rating is so extreme that she practices giggling in a bathroom mirror, while using gadgets installed in her eyes to click selfies—is trying to boost her rating in order to win a discounted rent on a fancy apartment. Soon, though, her rating plummets, following an argument with her brother, a temper explosion at an airport, and other stress-related misfortunes. In the end—after mug shots, eye-gadget removal, and confinement in what appears to be a prison for people with zero stars—she rediscovers the meaning of life by engaging in an unfettered fuck-you fight with another inmate.

The social satire in the episode is pretty broad, but Lacie’s world is enough like ours to be thought-provoking. Nowadays, it’s probably impossible for a reasonably with-it American to get through an entire twenty-four hours without being asked to rate someone or something, or feeling compelled to give five stars and a tip to a Lyft driver who was actually pretty terrible but clearly needed the work, or deciding to give a perfect score to a lousy online seller out of fear that otherwise the seller might give a less than perfect score in return.

HappyOrNot is satisfying because you can use it effortlessly and anonymously, without condemning yourself to a lifetime of targeted ads, and without adding still more monetizable information about yourself and your family to the world’s exponentially growing online hoard of permanently lost privacy. But Väänänen, Levaniemi, and Theisen have bigger ambitions. “Think of an airport,” Theisen told me. “If you’re a passenger and you’ve a bad experience in security, it can cloud your day. You’re pissed off, so you speak nastily to the salesperson at Starbucks, and they speak nastily to the next customer—it’s like a chain of events.”

Studies have shown that patients have better health outcomes when the medical professionals who care for them listen thoughtfully and explain what they’re doing, and even that flu shots are more effective if people are in a good mood when they receive them. Many medical facilities have signed on with HappyOrNot, because the data generated by the terminals make it easy for them to identify problem areas. “Patients who are treated well stick to their treatment plans more,” Theisen said. “And doctors who admit their mistakes and apologize for them are less likely to be sued for malpractice.” It’s also reasonably certain that, no matter what you do for a living, becoming less aggravating to others while you’re on the job is likely to make you and your co-workers more contented as well. “At the end of the day, we all care about how we’re treated,” Theisen said.

Väänänen told me, “Basically, every time a customer uses our service, we can say that, based on the data, we are making the world a happier place.” This assumes, of course, that happiness is quantifiable, and that the human supply of it rises and falls, like oil in a tank. There’s some evidence to the contrary, since even people with no objective reason to complain about anything somehow manage to find new ways to make themselves and others miserable. There are also situations in which measurement itself can lead to bad results. The Times recently published a story about a Veterans Administration medical center in Oregon that had boosted its “quality of care” ratings, as measured on a five-star scale, by turning away the sickest patients. Gathering those ratings had nothing to do with HappyOrNot, but the underlying issue applies to assessments of many kinds. Life wouldn’t necessarily be better if we all did the equivalent of teaching to the test.