SHANKAR VEDANTAM, HOST:

This is HIDDEN BRAIN. I'm Shankar Vedantam.

(SOUNDBITE OF JOHN WILLIAMS' "ENTRY INTO THE GREAT HALL AND THE BANQUET")

VEDANTAM: It's one of the most famous scenes in the "Harry Potter" series. Two lines of kids, newly arrived at the Hogwarts School of Witchcraft and Wizardry, march into a vast and glorious dining hall. The air glows with light from hanging torches and graceful flying candles. The ceiling looks like the night sky full of stars.

(SOUNDBITE OF FILM, "HARRY POTTER AND THE SORCERER'S STONE")

EMMA WATSON: (As Hermione Granger) I read about it in "Hogwarts: A History."

VEDANTAM: The endless dining tables glitter with silver plates and golden goblets. Young students make their way to the front of the hall, where an old and crumpled wizard's hat awaits them. It is the Sorting Hat.

(SOUNDBITE OF FILM, "HARRY POTTER AND THE SORCERER'S STONE")

MAGGIE SMITH: (As Professor Minerva McGonagall) Now, when I call your name, you will come forth. I shall place the Sorting Hat on your head, and you will be sorted into your houses.

VEDANTAM: The hat peers into the minds of the youngsters.

(SOUNDBITE OF FILM, "HARRY POTTER AND THE SORCERER'S STONE")

LESLIE PHILLIPS: (As Sorting Hat) Hmm, difficult.

VEDANTAM: After judging their personality traits and potential, it decides which house they'll belong to during their Hogwarts education. Will it be brave Gryffindor, gentle Hufflepuff, smart Ravenclaw or ambitious Slytherin?

(SOUNDBITE OF FILM, "HARRY POTTER AND THE SORCERER'S STONE")

PHILLIPS: (As Sorting Hat) But where to put you?

DANIEL RADCLIFFE: (As Harry Potter) Not Slytherin. Not Slytherin.

PHILLIPS: (As Sorting Hat) Not Slytherin, eh? Are you sure? You could be great, you know. It's all here in your head. And Slytherin will help you on the way to greatness. There's no doubt about that. No.

RADCLIFFE: (As Harry Potter) Please.

PHILLIPS: (As Sorting Hat) Well...

RADCLIFFE: (As Harry Potter) Please...

PHILLIPS: (As Sorting Hat) If you're sure...

RADCLIFFE: (As Harry Potter) ...Anything but Slytherin.

PHILLIPS: (As Sorting Hat) ...Better be Gryffindor.

(CHEERING)

VEDANTAM: There is something deeply appealing about the Sorting Hat. It's wise. It knows people better than they know themselves. It tells them who they are and to which tribe they belong. Are they courageous, loyal, curious or cunning? All humans, old and young, love this kind of insight.

MICHAELA BLACKBURN: Hi, my name's Michaela Blackburn (ph), and the house I'm in is in Gryffindor.

VEDANTAM: I ran into a 10-year-old Michaela and a group of her friends at PotterVerse, a "Harry Potter" convention in Baltimore.

HAILEY: I'm Hailey (ph), and I'm in Ravenclaw.

LILY: I'm Lily (ph), and I'm in Gryffindor.

RILEY: I'm Riley (ph), and I'm in Ravenclaw.

VEDANTAM: I'd come to the conference to learn more about the Hogwarts houses and the appeal of the Sorting Hat. Michaela and her friends are huge "Harry Potter" fans.

And do you all know each other really well?

MICHAELA: Yeah.

LILY: Yeah.

VEDANTAM: OK, good.

RILEY: Yeah.

VEDANTAM: All right, so here's a little test that I want to do, OK? We're going to pick Michaela. And you're not going to say it, but the rest of your friends on the count of three are going to call out and say what house you think she should be in, not what she says she's in or what she wants to be in, but based on what you know of her, what house you think she should be in, all right? So on the count of three - ready? One, two, three.

HAILEY: Slytherin.

RILEY: Slytherin.

LILY: Slytherin.

UNIDENTIFIED CHILD #1: Hufflepuff.

VEDANTAM: And what had you said?

MICHAELA: I said I was in Gryffindor.

VEDANTAM: Wait, your friends got you completely wrong.

MICHAELA: Well, we went to this camp, and it sorted me into Slytherin, but I am sort of cunning. So yeah, they're right. And she's right as well because I am sort of nice.

RILEY: Yes, you are loyal to your friends, I would think.

MICHAELA: Yeah.

VEDANTAM: Why do you think she's a Slytherin?

HAILEY: Because me and her went to a camp and we - a "Harry Potter" camp called Hogwoods (ph), and we got sorted into Slytherin. And I got Ravenclaw.

VEDANTAM: And why did you think she was a Slytherin?

RILEY: Because my sister's actually a Slytherin, and she kind of has the same personality as my sister.

VEDANTAM: Even among these young girls, it's easy to see how the question - what house are you in? - flows into a larger question - what kind of person are you? Your Hogwarts house is a window into your identity. Walking around the convention, I met Brittany Overman (ph) and Devon Valverde (ph).

DEVON VALVERDE: All right. Yeah, well, we met on a social media app.

VEDANTAM: Brittany spotted a line on Devon's profile that she liked. It said, talk "Harry Potter" to me. She responded with the inevitable question.

BRITTANY OVERMAN: What's your Hogwarts house (laughter)?

VALVERDE: She actually helped me discover my house. I was with her when I discovered that I'm a Hufflepuff.

OVERMAN: Yeah. And I'm a Slytherin, so it's actually a very unlikely pairing, but it's a very sweet one.

VEDANTAM: Got it. And what was the social media website?

(LAUGHTER)

VALVERDE: It's a little embarrassing, but it was Tinder.

OVERMAN: Yeah (laughter).

VALVERDE: It's a app (inaudible).

OVERMAN: Who knew, right?

VEDANTAM: So wait, you're on Tinder, and someone says, talk "Harry Potter" to me. That's what happened.

OVERMAN: Oh, my God, but it was like the best thing ever because, obviously, people on Tinder don't look for people to talk about "Harry Potter." And I was, like, really worried because I initially did not want to join the app at all just because I was like, I know what people look for on there. And I was like, that's not what I'm looking for. But I know that there's a lot of people on there. So I was like, chances are, I might find somebody who doesn't want what's usually asked for on Tinder. So, like, I saw the "Harry Potter" thing. I was like, OK, I got try to talk to him. Hopefully he talks back to me. And it worked out pretty well.

VEDANTAM: The desire to find our tribe is universal. We do it all the time. If it's not Hogwarts houses, then it's whether we are night people or morning people, dog people or cat people, Aquarius or Leo.

(SOUNDBITE OF YOUTUBE VIDEO, "ASTROLOGY: UNDERSTANDING LEO MEN")

JANET SCIALES: Hi. I'm the star goddess, and here's how to spot a Leo. You can spot a Leo because they're right in the center of the room, standing...

(SOUNDBITE OF YOUTUBE VIDEO, "CAT PEOPLE VS. DOG PEOPLE")

EUGENE LEE YANG: Are you a dog person? OK, dog people are way better than cat people.

(SOUNDBITE OF YOUTUBE VIDEO, "ASTROLOGY: UNDERSTANDING LEO MEN")

SCIALES: ...Mane of flowing hair like Bill Clinton and Monica Lewinsky.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED WOMAN #1: This is going to be country versus city.

(SOUNDBITE OF YOUTUBE VIDEO, "CAT PEOPLE VS. DOG PEOPLE")

ANDREW ILNYCKYJ: Dog people are conformists.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED WOMAN #1: I was actually born in the city.

VEDANTAM: And so it goes.

(SOUNDBITE OF YOUTUBE VIDEO, "CAT PEOPLE VS. DOG PEOPLE")

ILNYCKYJ: Cat people, on the other hand, are more abstract.

VEDANTAM: All these categories, just like Hogwarts houses, offer insight into why we behave the way we do. They offer us guidance on how to navigate a complex world. This need to understand ourselves has fostered a thriving industry built on the marketing and sale of personality tests. These tests promise to tell you who you are, why you are the way you are and what it all means. Some of these tests are long. Some are short. Some are free. Some cost a lot of money. Some categorize you by your favorite color.

(SOUNDBITE OF ARCHIVED RECORDING)

MARY MISCISIN: And today, you'll discover your True Colors, the unique combination of traits that make up your personality.

VEDANTAM: If you like to be prepared, according to the True Colors test, you must be a gold. Innovative people are green. And blues...

(SOUNDBITE OF ARCHIVED RECORDING)

MISCISIN: Blues pay attention to their emotions, and one of their favorites is romance.

VEDANTAM: There are personality tests that promise to match you with the perfect job.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED MAN #2: Find your purpose and be successful in work you enjoy.

VEDANTAM: Others promise that discovering your personality will guide you to love.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED MAN #3: Ever hear of the term hopeless romantic? Ever wonder if it happens to describe you? Well, welcome to ItsAllViral. And today we're going to be seeing if you are, indeed, a hopeless romantic.

VEDANTAM: There are even personality tests to help you shed weight.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED WOMAN #4: There is some new research in a book out that says the key to losing weight is avoiding the foods that clash with your personality type. Health and fitness expert...

VEDANTAM: These tests may seem silly, but there's something unsettling about them. They make me uneasy because there's been a long history of classifying people by their personalities. This history hasn't always been as benign as labeling someone a hopeless romantic.

There was a time when scientists would openly, without any discomfort, classify people's personality by their race. Asians were meek or awkward. Europeans were ambitious and brave, Africans - wild and animalistic. Or think about the associations people have long had about gender. Men's personalities are supposed to be dominant, women submissive.

There's a reason many of us feel horror today about personality classifications that were once considered scientific. We recognize now that they were just simply racist or sexist. As we fought to eliminate these old systems, why is it we keep coming up with new ways to classify ourselves? For one thing, there's something enormously seductive about such tests. They offer quick and easy insights into the messy and complicated problems we face every day. And as I heard at the PotterVerse convention, classifying people can be a source of joy.

All right, so let's play this with her now. On the count of three - one, two, three.

UNIDENTIFIED PEOPLE: Slytherin.

(LAUGHTER)

VEDANTAM: But as fun as they can be, personality tests can also lead to serious outcomes. Many corporations today are using such tests to make important decisions. When we asked listeners to share their experiences of personality testing in the workplace, we got a huge response. The most famous of these workplace personality tests is the Myers-Briggs Type Indicator, or the MBTI. It sorts people into 16 personality types, and it's hugely popular. It's used by most of America's Fortune 100 companies. And some 2 million people take the test each year.

The test categorizes you along four axes. Each describes a way of seeing or dealing with the world. For example, if you're an ENFP, that means you're an extrovert rather than an introvert, you rely on intuition more than facts, you're emotional rather than cerebral, and you prefer to go with the flow rather than have a highly structured life. We had lots of people call in about the Myers-Briggs. Many praised the test for helping to improve their lives. Some said it helped them find love.

HAILEY JONES: I took the personality test as part of a Christian club that I was in as an undergraduate in college and discovered that I am what Myers-Briggs calls an ENFP.

VEDANTAM: This is listener Hailey Jones (ph). She says she didn't think much about her Myers-Briggs category until she made a discovery.

JONES: The last three guys who I dated have all had the same Myers-Briggs Type Indicator.

VEDANTAM: They were all INTJs. Once she realized this, she began to use this pattern as a screening tool.

JONES: And I absolutely look for them. It's one of the first questions I ask people. And on all my dating profiles, it says ENFP seeks INTJ. And I know that that sounds kind of funny, but it's just been true for me.

VEDANTAM: Ally Adler took the Myers-Briggs during a hard time in her career. She was 26 and miserable in her job. The test told her that she was an ENFJ. This was a surprise because Ali didn't think of herself as driven by emotion. But she soon began to see things about herself that told her the test was right.

ALLY ADLER: And it really helped me understand myself in a way that I hadn't understood myself before so that I could work around and manage challenges both in my personal and my professional life related to the emotionally, feelings-driven person and part of my personality that I hadn't really acknowledged before and it turns out is really central to who I am. So learning about my personality type has actually been, I think, critical to my happiness and my success since then, and I am really glad I did it.

VEDANTAM: Some listeners said their test results had even shaped their very identity.

CHRISTINA HEALY: In college, my best friend and I both took the Myers-Briggs personality test. And we both wound up getting ENFP.

VEDANTAM: This is Christina Healy (ph).

HEALY: And we both were just so excited about it. We read the description of what that meant for us and the types of job we were most likely to get and just different personality traits. And that really helped solidify a lot of our personality during that time.

VEDANTAM: Christina says those last years of college were an important time of self-discovery.

HEALY: And that did a lot of the hard work for us - being able to just read and agree with and then, therefore, live the rest of our lives that way.

VEDANTAM: What Christina is saying is that the test played the role that a friend or a teacher or a mentor might have played. The test told her - Christina, this is who you are. This is your destiny. She had a mold, and she was happy to shape herself to it.

Years later, Christina was asked to take the test again. A lot had happened in her life since she and her roommate learned that they were both ENFPs. She'd gone to graduate school, relocated to a new city, matured. She'd changed, and she worried her Myers-Briggs category would change, too. She didn't want that. So when she retook the test, she made sure to give answers that would allow her to remain an ENFP. She'd found her tribe. She didn't want to be kicked out.

For all those who love the Myers-Briggs and other personality tests, there are plenty of people who don't. They feel that rather than helping, these tests can be deeply destructive.

MATTHEW GALE: And I started feeling like "Dr. Jekyll and Mr. Hyde" - like, there was this person that would come out, and I had no idea that it was there.

VEDANTAM: When we come back, we look at how personality tests are being used for more than dating advice and career counseling. Increasingly, they've turned into a tool to decide who should do what in the workplace, who should get a promotion, who should get fired. You're listening to HIDDEN BRAIN. I'm Shankar Vedantam. Stay with us.

(SOUNDBITE OF MUSIC)

VEDANTAM: I'm Shankar Vedantam. You're listening to HIDDEN BRAIN. Today we're talking about the power of personality tests. These tools tap into a deep desire we have to discover our place in the world. For some people, they offer comfort and relief. But that's not always the case.

GALE: Hello, HIDDEN BRAIN friends. My name is Matthew. I am in Westminster, Colo. And my experience with Myers-Briggs played no small part in destroying my life, ruining me emotionally for years.

VEDANTAM: Matthew Gale says that after being promoted to technical director at a theater he worked that, he and other managers went on an overnight retreat. Among other team-building activities, they all took the Myers-Briggs.

GALE: And - now my job required that I be organized and have ideas and do math and all these sort of technical and intellectual things. And when we did the Myers-Briggs, I came out to be, like, this INFJ.

(SOUNDBITE OF MUSIC)

GALE: I was mystic and quiet and...

VEDANTAM: An introvert who relies on feelings rather than facts.

GALE: After that moment, any time I made a mistake or I said something or had an idea, either my co-workers or myself would say - but that's just because you're this personality type. Maybe there's a job better suited to your personality type. And it made it so people didn't trust my opinion, didn't trust my ideas, didn't trust my conclusions, didn't trust what - any action that I took throughout the day.

VEDANTAM: Matthew began to doubt his own skills.

GALE: I thought I was this sort of organized and logical person. And I started feeling like "Dr. Jekyll and Mr. Hyde" - like, there was this person that would come out, and I had no idea that it was there, that I was really this artsy-fartsy, head-in-the-clouds guy who couldn't get anything done, who really just needed to have a pottery studio and sit around and smoke pot all day. That's kind of how people were treating me.

VEDANTAM: Matthew says his colleagues stopped trusting him, and he stopped trusting himself.

A veterinarian I spoke with also felt that the personality test she took at work had gotten her completely wrong. Cynthia (ph) works for a private animal emergency hotline. We're not using her last name or the name of her company to protect her privacy. Cynthia says her job is very stressful. Often, people call in panicked. She remembers one call from a person whose Labrador retriever had eaten rat poison.

CYNTHIA: The owner was really, really anxious, said the dog had just gotten into it five minutes earlier. And they all - when they're really anxious, they say, usually at the end, is my dog going to die?

VEDANTAM: Often, Cynthia takes 30 calls like this from around the country in an eight-hour shift. It's work that requires a combination of knowledge, and patience and empathy. Cynthia and her colleagues rely on one another for support.

CYNTHIA: We're all very conscientious of each other. We have a good group there. We don't have any scheduled breaks when we're at work. We only take breaks when it's not too busy and the other person isn't going to be swamped by too many calls. We are just very considerate of each other, and everybody in the team tends to be real good, hard workers and considerate of each other that way.

VEDANTAM: To Cynthia, it was obvious her team was good at what it did. But she says that didn't stop the company's human resources department from conducting personality tests to draw out deeper truths about the employees.

CYNTHIA: Our company, which is a smaller company, was purchased by another company. And the HR department for the larger company sent an email out to all of us in the new company, asking us just to do a personality test. And they said the reason they wanted us to do it was just to help our managers better manage us.

VEDANTAM: Cynthia says she and her colleagues were in a bind.

CYNTHIA: We were concerned that if we refused to do it, that maybe - I don't know. Maybe they would fire us or something like that. And they were sending out a number of reminders to do the test.

VEDANTAM: So she took it. The test was called the Culture Index. It was very short. On the first page, Cynthia was asked to pick adjectives that described her. On the second page, she had to pick adjectives that described her on the job. That was it.

What kind of words were they on these two? When you saw the pages - describe the test to me.

CYNTHIA: Yeah. So the words were things like calm, patient, knowledgeable, logical, friendly, outgoing, attractive.

VEDANTAM: Cynthia remembers picking words that she felt reflected who she was - calm, patient, resourceful, logical, friendly. A couple days later, she says, HR emailed her the results. They rated people in seven categories.

CYNTHIA: Autonomy, social ability, pace, conformity, logic, ingenuity and energy units.

VEDANTAM: Most of the scales ran from 1 to 10, with 10 being the best. Cynthia learned she'd scored a 1 for all the categories except energy. That category had a maximum score of 100. She got 12.

(SOUNDBITE OF MUSIC)

CYNTHIA: And then there's a write-up. So they have a graph when you get your results. So there's two very scientific-looking graphs, and then they have a write-up. And the write-off - write-up for me said - let's see. Let me just - it says, this individual has very little energy and may require more breaks during the workday than most individuals. And most people - a lot of my co-workers got kind of similar comments, some not quite as severe. Some said, this person runs out of energy by the afternoon and will need breaks in the afternoon. And so...

VEDANTAM: So what - and what was your interpretation when the scale of - when the energy scale runs from 2 to 100 and you were rated at 12? What was your reaction to that?

CYNTHIA: Oh, I thought it was ridiculous. Like, I had no idea how they calculated that. And it really is - of all the things that they said about me, that is the most blatantly wrong, and anybody who knows me would actually know that's true. I mean, honestly, I think if you make it through veterinary school, you have to have a certain amount of energy. Just - I mean, and I just - you know, I just always work very hard, and I always have. That's really been kind of the defining characteristic of my life, I would say.

VEDANTAM: Cynthia says the experience felt insulting.

CYNTHIA: So I looked into the test. Honestly, it was my reaction. I - you know, I had gone into it assuming that it was an accepted test by the psychological community, and then when I looked into it, I saw that they have no peer-reviewed published data at all. And actually, they don't call themselves a test. They insist on calling themselves a personality survey. So I just couldn't believe that any company would put any validity to this.

(SOUNDBITE OF MUSIC)

VEDANTAM: Gary Walstrom is the founder of the Culture Index, the test that Cynthia took. He declined to do a recorded interview, but spoke to us by phone. He says that Cynthia, quote, "doesn't know what she's talking about." Gary's not a psychologist but says the survey was developed in consultation with a psychology professor. He agreed that the Culture Index has not been through a scientific peer review process, but he has confidence that it helps companies manage and motivate people based on their personality. He says it helps with hiring decisions. It allows managers to make sure the personality of the individual fits the personality of the position. The Culture Index is one of many personality assessments that companies can choose from - as advertising and infomercials make abundantly clear.

(SOUNDBITE OF AD)

UNIDENTIFIED WOMAN: For most of the positions we create...

VEDANTAM: They're being used all the time in important decisions.

(SOUNDBITE OF AD)

UNIDENTIFIED WOMAN: So instead of me attracting 100 people for one job, I'm going to get 50 that will be naturally more successful in that specific role, so...

VEDANTAM: In fact, job applicants are so aware of how seriously companies take these tests that services have popped up to tell people how to hack the tests. We searched YouTube and found homegrown videos like this one.

(SOUNDBITE OF YOUTUBE VIDEO, "HOW TO PASS A PRE-EMPLOYMENT PERSONALITY TEST PART 1")

UNIDENTIFIED MAN: Let us go through a couple of example true-or-false questions.

VEDANTAM: Despite the poor audio quality, this video, "How To Pass A Pre-Employment Personality Test," has racked up nearly 300,000 views.

(SOUNDBITE OF YOUTUBE VIDEO, "HOW TO PASS A PRE-EMPLOYMENT PERSONALITY TEST PART 1")

UNIDENTIFIED MAN: I always love to be in large, noisy crowds. You may not always like to be in a large, noisy crowds, so you might answer false. What they are really asking is whether or not you like people and can deal with it at work when it is busy. That makes the answer true.

VEDANTAM: Most companies use the Myers-Briggs, which is widely considered to be an industry standard. This test has an interesting history. It originated in the ideas of a contemporary of Sigmund Freud, Carl Jung.

ALLEN HAMMER: He identified three dimensions of personality.

VEDANTAM: This is Allen Hammer, a psychologist and former chair of the Myers-Briggs Foundation (ph).

HAMMER: One was where you tend to focus your attention. And he said that there are two opposite ways you can focus your attention. One is on the external world. He called that extroversion. And one is on the internal world, and he called that introversion.

VEDANTAM: Category two is about how people perceive the world. Some people focus on details, on facts. Others are more intuitive, imaginative. The third category is whether people are driven by thinking or by emotion.

HAMMER: Thinking is a way of objectively looking at a situation, making a detached, objective, logical, analytical decision or judgment about something. Whereas the opposite of that is what he called feeling, the subjective, interpersonal way of making a decision.

VEDANTAM: In the 1940s, an American woman named Isabel Myers became interested in Jung's ideas.

HAMMER: Her mother, actually, was interested in Jung first, and then Isabel, who was a housewife at the time and a writer - she got interested in type and then started looking at applications in - particularly around careers.

VEDANTAM: Isabel Myers, along with her mother, Katharine Cook Briggs, turned Jung's theories into a test. She also added her own ideas into the mix.

HAMMER: And Isabel Myers added a fourth dimension, which she described as which of those two processes you tend to use in the outer world. So she said you either tend to use a judging function in the outer world or a perceiving function in the outer world. And that's represented by the letters J and P. So those are the four dimensions, and when you combine the four dimensions and the two opposites on each dimension, you get 16 different types.

VEDANTAM: Even though Isabel Myers and her mother were self-taught, many of the researchers who have worked on the tests since then are psychologists. Nonetheless, despite the widespread popularity of the Myers-Briggs test, it's generally not held in high regard by top psychologists who study personality. Adam Grant is a professor of psychology and management at the University of Pennsylvania. When he first took the Myers-Briggs, he learned that he was an INTJ - in other words, an introvert, an intuiter, a thinker and a judger. Fine, he said. But then a few months later, he took the test again.

ADAM GRANT: I got opposite scores on every dimension. I scored - now I was ESFP.

VEDANTAM: Adam says fans of the Myers-Briggs tend to shrug off such discrepancies.

GRANT: Well, they say, either, you know, you're gaming the test and you want a different answer. I could not have wanted something more opposite. I wanted consistency. I wanted to know who I was. I was trying really hard to answer them the same way. I began to question whether this test had any validity and reliability whatsoever.

VEDANTAM: Validity and reliability - these are two of the most important scientific factors to consider when judging the value of any psychological test.

GRANT: Reliability is about whether the test measures what it claims to measure. And so you could look at that in terms of, do you get the same result over time or if different people rate you, did they give similar answers?

VEDANTAM: So if you have a test for HIV, does the test actually give you the answer that you have HIV every time you use the test?

GRANT: Exactly. Does it give you an accurate score? And then validity is essentially, does the test predict anything? So, you know, can it predict what kind of jobs I'll be happy in or what kind of person I should marry?

VEDANTAM: And your thesis about the Myers-Briggs test is what?

GRANT: Well, it doesn't do very well in reliability or validity. It falls well short of most conventional reliability standards, and the Myers-Briggs proponents themselves will tell you that it doesn't predict anything.

VEDANTAM: The thing that concerns me about personality tests is less the stuff that might be inaccurate but is mostly just fun, and more the stuff that is increasingly being used to gauge who should be doing what in the workplace, who is best suited for which career to select the people who you want to rise within an organization.

GRANT: It's a great way to weed out all kinds of diversity. There was a company in Canada not long ago where there was a major acquisition made, and the CEO gave every single person who was acquired the Myers-Briggs and then fired everyone who didn't match his type.

VEDANTAM: Good grief.

GRANT: That's terrifying.

VEDANTAM: Many personality researchers put greater stock in a test known as the Big Five. It measures things like how much you care about the opinions of others versus your own judgment. It also measures qualities such as introversion and extroversion. At first glance, there are similarities between this test and the Myers-Briggs and other personality tests. But Adams says the Big Five has large amounts of peer-reviewed data to back it up. That data, he argues, makes for better predictions.

And what you're saying is that scores on this Big Five personality test do what compared to the Myers-Briggs?

GRANT: We can predict your job performance, your effectiveness in a team with different collaborators, your likelihood of sticking around in a job versus leaving as well as your probability of your marriage surviving, depending on the personality fit between you and your spouse.

VEDANTAM: But Allen Hammer, the psychologist who is a proponent of the Myers-Briggs test disagrees with that him. He believes the Myers-Briggs is as reliable as other personality tests. And he says that Adam's wrong when it comes to the evidence that the Myer-Briggs cannot predict real world outcomes.

HAMMER: When people matched roommates on their psychological type, they got a 65 percent decrease in requests for roommate changes.

VEDANTAM: Where Allen agrees with Adam is that the Myers-Briggs is often used in ways it should not be used.

HAMMER: I don't think the MBTI should ever be used to either select people into an occupation or to promote them. And I've worked in large corporations for - with large corporations for the past, I guess, 25 years. And we've never ever used it that way.

VEDANTAM: I hear what Allen is saying. But I would argue that these tests are popular precisely because they purport to give us a quick snapshot of who someone is and what they're good at. If you're a manager, and you learn one of your employees is an introvert, according to the test, it's absurd to think this won't shape the way you decide whether that employee should have a public-facing role.

JESSICA COMSTOCK: By show of hands or wands, how many people are familiar with the Myers-Briggs Type Indicator?

VEDANTAM: Back at the "Harry Potter" conference, I stopped by a panel discussion. It was called Hogwarts Houses as Personality Types. It was packed, standing-room only. People were even sitting in the aisles. The panel leader Jessica Comstock was listing off the personality traits that made people suited for each of the different houses.

COMSTOCK: The people who are extroverts are people who like to be the center of attention, people who like to have things go, go, go all the time and people who recharge by being around others - Gryffindors.

VEDANTAM: Jessica is a self-described "Harry Potter" nerd. She spends much of her free time researching, analyzing and lecturing on various themes in the books. She saw a graphic on the Internet one day that correlated "Harry Potter" characters to the Myers-Briggs. It was cute, but she felt misguided.

(SOUNDBITE OF MUSIC)

VEDANTAM: She thought the houses rather than individual characters made for a better correlation.

COMSTOCK: How many people know their personality type?

VEDANTAM: So Jessica designed a detailed chart to show how closely Hogwarts Houses align with Myers-Briggs categories.

COMSTOCK: I'm going to do a little experiment with the first few people. So what is your MBTI?

UNIDENTIFIED WOMAN #1: ISTP.

VEDANTAM: Jessica looks at her chart. ISTP matches to Slytherin.

COMSTOCK: What is your house?

UNIDENTIFIED WOMAN #1: Slytherin.

COMSTOCK: Yes, it is.

(LAUGHTER)

COMSTOCK: Somebody from another section - yellow.

UNIDENTIFIED WOMAN #2: ESFJ.

COMSTOCK: You said ESFJ? You're a Hufflepuff.

VEDANTAM: Right again, the audience soaks it in.

COMSTOCK: And if anybody thinks I'm cheating, you're welcome to come and look at my notes.

VEDANTAM: To the folks at PotterVerse, the fact that there's a connection between being an ESFJ and a Hufflepuff is proof that the Hogwarts Houses are real science. But as I sit and listen...

COMSTOCK: What is your house?

VEDANTAM: ...I find Jessica's chart dumbfounding.

COMSTOCK: Yes, it is.

VEDANTAM: If "Harry Potter" houses can replicate personality tests that companies are using to determine which employees get jobs or get fired, as I said earlier, good grief.

(SOUNDBITE OF MUSIC)

VEDANTAM: By this point, you know where my head is at. I was disturbed by the multibillion-dollar industry that has been created around personality tests. But then as often happens, I heard a mind-bending story that made me think about these tests in a different way. I'm Shankar Vedantam. This is HIDDEN BRAIN. We'll be right back.

(SOUNDBITE OF MUSIC)

VEDANTAM: As I talked to Adam Grant about personality tests, I became convinced it was a terrible idea to use such tests to hire and fire people. But then as we were reporting the story, I came across some research that made me think about personality classifications in a different way. Now, it's absolutely true that many personality tests are unscientific and unreliable. But does that mean they're useless? At Louisiana State University, the economist Naci Mocan was looking at how beliefs shape economic choices. His subject wasn't the "Harry Potter" Sorting Hat but a more ancient way to classify personality - the Chinese zodiac.

(SOUNDBITE OF MUSIC)

VEDANTAM: Our story begins in Anhui province in China in 1987. A young Chinese couple had decided to start a family. Xiao-Qi (ph) and his wife Yangcheng (ph) were happily married and the timing was right. It was soon going to be 1988. As hundreds of millions of Chinese knew, this was a most-significant year. After 11 years of rats, and roosters, and snakes and sheep, it was finally going to be the Year of the Dragon.

(SOUNDBITE OF MUSIC)

VEDANTAM: According to Chinese tradition, there's no better year for a child to be born than the Year of the Dragon. Dragon kids are destined for greatness. Xiao-Qi was a doctor at one of the province's largest hospitals. He knew it was going to be a crazy year. Pregnant women were already pre-booking rooms at the hospital. Births were going to skyrocket. It was the same all across the country. It seemed that pregnant women were everywhere, dreaming of the greatness of their coming Dragon babies.

Xiao-Qi and Yangcheng lived in Hefei, a city with a famous history for producing brilliant minds and well-educated people. So when their son arrived as planned in that most auspicious year, they already had big plans for him. They named him Han Yu. Xiao-Qi wanted Han Yu to be even better educated than himself - ideally, at a top-ranked university in the United States. And so mother and father quickly instilled in the very young child the conviction that great things were expected from him.

HAN YU: This idea is kind of indoctrinating my mind, so one day when people ask me what I want to do, when I think about it, I really think that I want to be a Ph.D. in the future. I want to be a doctor.

VEDANTAM: That was the beginning of a long march. Han recalls that when he was in middle school, his father came home one day at lunchtime bearing an armful of textbooks.

YU: And he just came back at noon one day and put some books in my bookcase. And I asked him, hey, Dad, what did you buy? He told me that those are some textbooks for master degree students to practice their English. You know, at that time, I was 13.

VEDANTAM: Master's degree books for a 13-year-old. Xiao-Qi explained to Han that mastering English would be essential if he was to do well at that fancy university in America. He and Yangcheng spared their child from doing any household chores. All Han had to do was to achieve his parents' dreams.

YU: When I was at home, my father always said, hey, Son, I don't want you to do any housework at home. You just need to focus - perhaps - and that's not sounds right. But he said that we just need you to focus on study.

VEDANTAM: Han finished college and his master's degree in China, and then, as planned, he went off to the United States for even more education. Han enrolled in an economics Ph.D. program at Louisiana State University, where he met a mentor whose expectations of him were every bit as high as those of his own parents.

NACI MOCAN: My name is Naci Mocan. I am a professor of economics at Louisiana State University and a research associate of the National Bureau of Economic Research.

VEDANTAM: Naci is Han's Ph.D. adviser. When Han told Naci about life in China, they talked about the Chinese zodiac and the power of the Year of the Dragon. They were sure that belief in the Zodiac was just superstition. In fact, they were certain that anyone who was born in the Year of the Dragon would actually be at a great disadvantage.

MOCAN: If there is half a million extra kids born in the Year of the Dragon, those kids will have more peers in the classrooms. There's going to be - there would be fewer resources per child in the schools. The classrooms will be a little more crowded, et cetera. You would expect worse educational outcomes rather than better.

VEDANTAM: They decided to prove their hypothesis that Dragon kids would fare worse than other kids at school. As it turned out, the Chinese government has a treasure trove of data - the academic performance of middle schoolers, demographic surveys, interviews with parents about their own education and household income. And so the two economists collected all the data, controlled for different variables and crunched the numbers. And they found that in middle school, Dragon kids did better than their peers.

MOCAN: They actually have higher test scores in middle school.

VEDANTAM: These kids also outperform their peers in high school.

MOCAN: Even at the standardized nationwide university entrance exams, Dragon kids score better.

VEDANTAM: And they did better in college.

MOCAN: Individuals who were born in the Year of the Dragon - they are 14 percent more likely to have earned at least a bachelor's degree.

VEDANTAM: This was not the outcome that the economists expected to find.

MOCAN: Yes, it was really unexpected, frankly.

VEDANTAM: At first, Naci and Han came up with a straightforward explanation. Middle and high school teachers in China probably also believe in the Zodiac. They were just granting high grades to Dragon kids. But that account fell apart because college-level entrance exams are graded by a computer, not by a superstitious human being. Also, Dragon kids were outperforming peers in the same classroom, kids who are born right before and right after the auspicious year.

YU: According to our results, it seems that Dragon - when Dragons compared with other zodiacs, on average, they are really doing better.

VEDANTAM: OK, Dragon kids were doing better because they had higher self-esteem.

MOCAN: So if everybody tells them, oh, you are superior, you are smarter than everybody, you are destined for greatness and good fortune, you know, they may believe that this is the case. And their self-esteem - you know that from other research that self-esteem is important in learning. People - kids who have more self-esteem, they do better in school.

VEDANTAM: But when they looked at how children reported their own beliefs about their IQ, there was no difference between Dragon kids and kids born right before and right afterwards.

MOCAN: And Dragon kids are not more confident about their own abilities or about their own future.

VEDANTAM: In fact, the Dragon kids weren't really smarter. They scored the same on IQ tests. So what explained their success at school?

(SOUNDBITE OF COMPUTER BEEP)

YU: Yeah, it's just software. Basically, every Chinese used this - uses this thing.

VEDANTAM: From his office at Louisiana State University, Han Yu calls his parents in China.

YANGCHENG: (Speaking Chinese).

YU: (Speaking Chinese).

VEDANTAM: It turns out, the success of Dragon babies doesn't lie with the schools, or the teachers or even with the kids themselves. It's because of parents like Xiao-Qi and Yangcheng.

YU: (Speaking Chinese).

VEDANTAM: From the moment Han was born, his parents had sky-high expectations for him. That turns out to be the case with many parents of Dragon babies.

MOCAN: The parents of these Dragon children, they are actually more likely to believe, in comparison to other parents, that their children will obtain at least a high school education, at least a college degree. And Dragon parents are more likely to believe that their children will become a leader in professional life in the future. So Dragon parents are different from other parents in the way they sort of believe in their kids' future.

VEDANTAM: These beliefs become a self-fulfilling prophecy. Parents who believe their kids are destined for greatness act in ways that help their kids achieve greatness. Han's parents pushed him, giving him master's-level textbooks in middle school and telling him as a toddler that his goal in life was to get a Ph.D. in America. As Han chatted with his parents, I asked if he could translate a question for me.

Could you ask your parents whether they think that your success is partly because you were born in the year of the Dragon?

SHAOQI: (Speaking Chinese).

YU: He said that during those years when I grew up, perhaps this also affect - potentially affect their behaviors, their invest on me.

VEDANTAM: Han's own parents, in other words, were the living embodiment of the research that Han was doing. Life had folded back on itself. Here was Han in America getting his doctorate and publishing research about Dragon kids that validated his parents' belief in his own Dragon potential.

And could you ask him, then, what is his reaction or feeling upon seeing that that dream has come true?

YU: (Speaking Chinese).

SHAOQI: (Speaking Chinese).

YU: My father said that actually, his dream has not completely become true because - and he wish - he expects that I should have more and better achievements, accomplishment, and also, he expects me to have - to continue study in the U.S. So I guess, for me, it's going to be a postdoc. Yeah.

VEDANTAM: And what's your reaction to that, Han?

YU: Well, I guess I'll work harder. I don't want to my parents to - I don't want to let them down, I think. And to get a postdoc in a good, better university is also my dream. So...

VEDANTAM: So yeah, tests that purport to tell you who you are nonsense until they're not.

That brings us back to "Harry Potter." Jessica Comstock, the woman who connects "Harry Potter" houses with the Myers-Briggs test tells me the story of Neville Longbottom.

(SOUNDBITE OF FILM, "HARRY POTTER AND THE SORCERER'S STONE")

MATTHEW LEWIS: (As Neville Longbottom) You're sneaking out again, aren't you?

RADCLIFFE: (As Harry Potter) Now, Neville, listen. We were...

LEWIS: (As Neville Longbottom) No, I won't let you. You'll get Gryffindor into trouble again.

COMSTOCK: In Harry's year, you had Neville Longbottom, who actually turns out to be a really important character to the story. He starts off as kind of this bumbling weird kid.

VEDANTAM: When it's Neville's turn with the sorting hat, it turns out the hat has a very hard time deciding where to put him.

COMSTOCK: In Neville, the hat took like three minutes to figure out where to put it, which is a really long time considering that for some characters the hat barely touches their hair, and it knows. And Neville was almost a hatstall between Gryffindor and Hufflepuff. And Neville argued with the hat that he wanted Hufflepuff. And the hat put him in Gryffindor. So the hat kind of listens to you. But if it's - if you're - it depends on what your potential is because, you know, Neville grows to be one of the bravest characters in the books. And the hat knew that.

VEDANTAM: And is that because the hat knew that or because the hat put Neville in Gryffindor, and Neville learned to be brave as a result?

COMSTOCK: That's the magic. Does the hat put you because it knows you have the house? Or do you become the house it puts you in?

(SOUNDBITE OF MUSIC)

VEDANTAM: Does the hat put you in the house in which you belong? Or do you become the house the hat puts you in? Throughout our lives, we evaluate our children, our students, our friends and our colleagues. We enthusiastically look at tests that supposedly reveal the aptitudes and interests of others. What isn't always clear, to them or to us, is the power of these expectations to transform people's lives. Sometimes, our beliefs lift people up - make them run harder, reach for more. Other times, our expectations attach leaden weights to wings and keep dreams from taking flight. I can't say I have much confidence in personality tests. But I've come to understand there is huge power in the faith we have in them.

(SOUNDBITE OF MUSIC)

VEDANTAM: This week's show was produced by Jenny Schmidt and mixed by Parth Shah. It was edited by Tara Boyle. Our team includes Rhaina Cohen, Maggie Penman and Renee Klahr. Original music by Ramtin Arablouei. Anya Grundmann is NPR's vice president for programming. For more HIDDEN BRAIN, please follow us on Facebook, Twitter and Instagram. And make sure to subscribe to our podcast. While personality tests are not foolproof, here's one thing I can guarantee. Talking to a friend about HIDDEN BRAIN is a clear indicator of your good taste and personality.

As we've seen throughout this episode, it's extremely tempting to pigeonhole people. It makes the lives of teachers, colleagues and managers so much easier. Some of us have the great good fortune to know teachers, colleagues and managers who haven't done this to us. Far from pigeonholing, the best friends and mentors do what the sorting hat did for Neville Longbottom. They see potential in us that we may not see ourselves. I'd like to nominate three co-workers who have played that role in my life as our unsung heroes today - Rob Stein, Madhulika Sikka and Tracy Wahl. In different ways and at different times, they each opened doors for me, encouraged me to reinvent myself and helped to create HIDDEN BRAIN. I'm so grateful to each of them.

(SOUNDBITE OF MUSIC)

VEDANTAM: One last thing before we go, my colleague Tara Boyle was mentioning a term she knew from French the other day. Tara's in the studio with me right now. What was the term, Tara?

TARA BOYLE: It's l'esprit de l'escalier, which is a very classy French term which means the idea or thought that comes to you as you're walking down the staircase from a party far too late to use it in witty conversation.

VEDANTAM: So the reason we are mentioning this term to you is that we're working on an episode about how language shapes the way we see the world. Can you think of a time in your life - a story where you wished there was an English term for this phrase you knew in another language? If so, please tell us about it. How can people get in touch with us, Tara?

BOYLE: They can record a voice memo and send it to hiddenbrain@npr.org. Or you can call and leave a message at 661-772-7246. That's 661-77-BRAIN.

VEDANTAM: Thanks so much.

BOYLE: Et merci.

Copyright © 2017 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.