In one of the most famous scenes from the Harry Potter series, a group of kids, new to the Hogwarts School of Witchcraft and Wizardry, line up before an old and crumpled wizard's hat. It is the sorting hat. The hat will tell them which house they'll belong to during their Hogwarts education.

There is something deeply appealing about the sorting hat. It is wise. It seems to know people better than they know themselves.

We humans love this kind of insight. And our drive to better understand ourselves and the people around us has led to the creation of a multi-billion dollar industry built around personality testing.

Probably the most famous of all personality tests is the Myers-Briggs Type Indicator, or MBTI. But there are plenty of others, too. These tests categorize people based on personality traits. Are you an introvert or an extrovert? Someone who likes unexpected challenges, or someone who prefers structure and calm? Many of America's most successful companies use personality tests to gain a better understanding of their workers. Many individuals use them to gain a better understanding of themselves.

One Hidden Brain listener, Ally Adler, took the Myers-Briggs test when she was 26 and miserable in her job.

"It really helped me understand myself in a way that I hadn't before so I could work around and manage challenges both in my personal and professional life," she says.

But other people say tests like these are deeply flawed. Listener Matthew Gale says the Myers-Briggs got him completely wrong.

"My experience with Myers-Briggs played no small part in ruining me emotionally for years," he says.

While the effectiveness of these tests can be endlessly debated, one thing is clear. With a few exceptions, most do not stand up to scientific scrutiny. They typically aren't peer reviewed and usually fail basic standards of validity and reliability. Adam Grant, a psychology and management professor at the University of Pennsylvania, has written of his concerns with the Myers-Briggs, particularly when companies use the results to guide hiring and firing decisions.

"It's a great way to weed out diversity," Grant says.

Allen Hammer, the former chair of the Myers-Briggs Foundation, disagrees. He believes the Myers-Briggs is as reliable as other personality tests. And he says Grant is wrong when it comes to evidence that the Myers Briggs cannot predict real world outcomes; for example, he says, "when people matched roommates on their psychological type they got a 65 percent decrease in request for roommate changes," he says.

This week, we delve into the world of personality tests, and discover new research that suggests the power of personality assessments may not be in pinpointing the person you are, but the person you have the potential to become.

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