Personality tests are everywhere.
You've seen them online, where they promise to tell you which character from Buffy the Vampire Slayer you most resemble, or try to pigeonhole you into one of three or four possible political ideologies.
You've encountered them at work, where 89 of the Fortune 100 companies -- and thousands of firms across the country -- use them to file people into neat little boxes based on how they answer repetitive questions about things like teamwork and honesty.
They pop up in career counseling offices, self-improvement retreats, self-help books, magazines, and sometimes even in college applications.
But there's one thing all personality tests have in common, experts say: They're nonsense.
The most famous personality test, the Myers-Briggs Type Indicator (MBTI), "is about as useful as a polygraph for detecting lies," according to psychologist and author Adam Grant.
Or, in the words of author Annie Murphy Paul, personality testing "is an industry the way astrology or dream analysis is an industry: slippery, often underground, hard to monitor or measure."
Paul wrote "The Cult of Personality Testing," a 2004 book aimed at debunking the sketchy -- or nonexistent -- science of personality tests. Paul says she was inspired to write the book so managers and corporations would stop using personality tests to help determine who gets hired and who gets promoted.
But in a June 25 piece for NPR, she admits her book barely made a dent in the personality testing industry, and bemoans the "Carl Jung-inspired load of nonsense" that can supposedly distill the totality of a person's mind into one of a handful of pre-determined templates.
One clear way to illustrate that personality tests are bunk science is to simply retake the tests, Grant says.
"A test is reliable if it produces the same results from different sources," Grant wrote in Psychology Today. "If you think your leg is broken, you can be more confident when two different radiologists diagnose a fracture. In personality testing, reliability means getting consistent results over time, or similar scores when rated by multiple people who know me well."
But personality tests aren't consistent.
"The interesting -- and somewhat alarming -- fact about the MBTI is that, despite its popularity, it has been subject to sustained criticism by professional psychologists for over three decades," author Roman Krznaric writes. "One problem is what statisticians call 'low test-retest reliability.' So if you take the test after only a five-week gap, there's around a 50 percent chance that you will fall into a different personality category compared to the first time you took the test."
The veracity of personality tests suffered another blow when researchers from the University of Mississippi and Florida State University published a peer-reviewed study of corporate managers broken down by MBTI personality type. The 1996 study compared the MBTI results with with "managerial attributes, behaviors and effectiveness," and came to a straightforward conclusion.
"Few consistent relationships between type and managerial effectiveness have been found,” the study's authors wrote.
Critics point out that tests like the MBTI rely on binary choices, allowing for no middle ground or shades of gray. They also point out that the test was created by two Carl Jung-obsessed housewives during World War II, and while a science degree or formal science training isn't a prerequisite for scientific discovery, the majority of Jung's work isn't supported by science.
For critics like Paul, Grant and others, the goal isn't to eliminate personality tests. That'll never happen. But by providing hard facts on the slippery practice of personality testing, they hope people who make serious decisions about other people's futures -- hiring managers, judges, college admissions counselors -- recognize personality testing for the unreliable endeavor it is.
While it might seem like personality tests provide insight, especially to the person getting the results, there's no proof that the tests provide any consistently useful information.
"Palm readings and horoscopes can spark insights too," Grant wrote. "That doesn’t mean we should talk about them in our work teams."