Clearly, personality quizzes have some sort of perennial appeal. Facebook newsfeeds are filled with BuzzFeed quizzes and other oddball questionnaires that tell you which city you should actually live in, which ousted Arab Spring ruler you are, and which Hogwarts house you belong in. But these new online quizzes have a dark edge that their analog predecessors didn’t. In the wake of the U.S. election, a secretive data firm hired by Donald Trump’s campaign boasted that it has been using quizzes for years to gather personal information about millions of voters. Its goal: the creation of digital profiles that can predict—and possibly exploit—Americans’ values, anxieties, and political leanings.

Whether this firm, Cambridge Analytica, has actually used predictive profiles to influence people isn’t certain; reports suggest it hasn’t, at least not directly. But the company’s methods nonetheless expose the growing scale of personality analysis online—and the dangers that come with it. On the internet, anything you do is like taking a personality quiz: Everywhere you click reveals something about you. And you’re not the only one who sees the results.

On Meet Yourself’s spine, a silver-painted mirror depicts the personality quiz’s allure: See yourself as you really are. What happens when the mirror is two-way?

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No one seems to know when the personality quiz first gained a foothold in popular culture. The journalist Sarah Laskow has traced its origin in America at least as far back as the late 19th century, “when ladies’ magazines started gaining traction and the yellow press would try anything to sell papers.” But the quiz has persisted with remarkable consistency since, with spikes in popularity during a quick magazine boom immediately post-WWII, the Cosmopolitan quizzes of the 1960s and ’70s, and today’s ubiquitous BuzzFeed quizzes.

This stretch neatly overlaps with the history of the popular quiz’s buttoned-up, high-achieving sibling: the personality test. In-depth psychological assessments like the Myers-Briggs Type Indicator began popping up in the first half of the 20th century for the purpose of scanning and sorting employees in industrial workplaces. While many of these tests, including the Myers-Briggs, have since been dismissed by the scientific community as unreliable—if not dangerously discriminatory—they, too, have persisted, perhaps in part because they at least provide a framework for otherwise-difficult office conversations. Somewhere around 10,000 companies, 2,500 colleges and universities, and 200 government agencies still use the Myers-Briggs in the U.S. today, including the majority of Fortune 500 companies.

Affiliation with these more legitimate-seeming forms of personality analysis has always given the personality quiz a vague air of authority. Indeed, if there’s any one way to characterize quizzes’ mystique, it’s probably that, through all their many iterations, they have somehow managed to tightrope-walk the line between entertainment and science, or at least something approaching science. “BuzzFeed quizzes are crafted to create the illusion of truth, or potential truth,” writes the journalist Caroline O’Donovan, in explaining the fad. She quotes Summer Anne Burton, one of BuzzFeed’s editors: “You sort of write them like horoscopes, with tidbits people can relate to.”