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Like most quizzes on the internet, personality tests aren't what you would call "reliable."

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Hey, what type of sandwich are you? How 'bout which fast food chain?

And what piece of furniture best represents you as a person? These are all real quizzes on the Internet, and they're fun, but most people know not to take them too seriously. The Myers-Briggs Type Indicator, or MBTI test, is a different story.

It's probably the most popular personality test on the Internet, and it claims to tell you your personality type. If anyone's ever told you that, "You're such an INFJ." or whatever, that's the MBTI. People tend to take the results of that test more seriously because, for a while, a lot of psychologists took it seriously too.

But for decades, we've known that there are other better ways to measure personality traits. Because those 4-letter personality types... They don't mean very much.

Psychologists define your personality as your characteristic thoughts, emotional responses and behaviors. And a lot of them study personality by looking at the individual traits people have. The parts of personality that seem to be stable over time and apply in different contexts.

Back in the 1940s, Katherine Cook Briggs and her daughter, Isabel Briggs Myers, who were both interested in psychology research, tried to measure personality by identifying traits like this. One trait they tested was whether people were extroverted or introverted, which to them meant whether you were focused on the outside world or focused on yourself. They also asked whether people preferred to trust their senses as opposed to relying on their intuition or gut feelings, whether they approach the world by thinking, meaning logical reasoning, or by feeling, meaning that they were more subjective, and finally, whether they were judging, which meant that they preferred to come to conclusions about things, or perceiving, which meant that they were open to new information.

Myers and Briggs picked these 4 traits because they were inspired by well-known psychologist Carl Jung. He developed these ideas from working with patients but didn't really test the ideas in a scientific way. Myers and Briggs wanted to create a test that applied those ideas so people can learn about different personality types, and understand their own thoughts, emotions and behaviors based on their personality type.

The test would assign you one trait from each pair so there were 16 possible personality types you could have. These days, if you take a Myers-Briggs test online, you'll probably get a result like, "Congratulations! You're an INTJ!" "This means that you're vision-oriented, quietly innovative, insightful..." ...and so on.

It might even tell you what kind of career you're suited for, or what personality type you should look for in a life partner. But what those tests are telling you is about as scientific as what kind of sandwich you are. When psychologists measure, well, anything, they want their measurements to be both reliable and valid.

Reliability mostly just means that if you give people the same tests over time, they'll get a similar score. That's called retest reliability. There's also another kind of reliability called internal consistency reliability, which means that psychologists want to measure 1 thing at a time.

You don't want questions about personality mixing with questions about, say, intelligence. Validity means that the test should have something to do with real life. Like, if I know your test result, can I predict what you'll do?

Does your type help me figure out whether you'll go to a party or just stay home? The MBTI shows room for improvement in all of these things. First, it's not especially reliable.

That's because most people aren't extreme extroverts or introverts; they're somewhere in the middle. If a test forces you into one category or the other, it's really easy for all those people in the middle to switch sides. It has some problems with internal consistency too.

For example, the MBTI treats thinking and feeling as opposites. But in other tests, people are more likely to be good at both, rather than just one or the other. When it comes to validity, the evidence is mixed.

So that's part of the problem... There's a spectrum when it comes to personality traits. But a bigger issue is that most of the traits the MBTI looks at just aren't good choices.

Because in most people, these traits tend to change in different situations. So in the past few decades, researchers have developed new and better ways of looking at personality that solve some of the issues with Myers-Briggs. Instead of just relying on theory, they started from the ground up, asking people hundreds of questions, and coming up with key, consistent personality traits based on the answers.

Lots of different research teams independently landed on the same 5 personality traits, which are now called the Big Five. Personality tests that measure where you fall on the spectrum of each of these traits... tend to have much better reliability and validity than the MBTI. The results are consistent and they're good at predicting what you'll do in a real-life situation.

So personality researchers have been relying on the Big Five for years. If you're looking for a scientific, evidence-based personality test, that's the one to take. The Big Five won't assign you an actual personality "type" though.

It just tells you about the individual aspects of your personality, which researchers use to learn how people with different levels of certain traits, or combinations of traits, might think, feel and behave. Even the best personality tests aren't the last word on what people are like though. There are lots of different factors that affect what goes on in our brains, and researchers are always finding new connections.

But one thing's for sure, your MBTI personality type doesn't actually say very much about you, no matter how popular the test is. Thanks for watching this episode of SciShow Psych, which was brought to you by our patrons on Patreon. If you wanna help support this show, just go to

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