The Personality Test Industrial Complex: The MBTI Problem
Welcome back to PsyberSpace. I'm your host, Dr. Leslie Poston. This week, we're talking about why the most popular personality test in the world became a multimillion dollar industry despite decades of research showing it doesn't do what it claims to do, and what personality science looks like outside of the MBTI. If you've worked in a corporate environment at any point in the last forty years, there's a reasonable chance someone has asked you to take the Myers Briggs Type Indicator or the MBTI.
Leslie Poston:Then you answered an incredibly long list of questions, got assigned your four letters, and maybe sat through a workshop where your team talked about how INTJs and ESFPs bring different strengths to the table. It probably felt useful or even felt reasonably accurate, and there's some specific psychological reasons it felt that way that have nothing to do with whether it measured your personality correctly. Let's take a look at how a personality quiz built by two people with no psychology training became a fixture of corporate America, why it stuck despite evidence against it, and what we're losing by using that instead of the tools personality researchers have actually validated over the last three decades. The origin story of the MBTI starts in the early 1900s with Catherine Cook Briggs, a fiction writer and dedicated homeschooling advocate who had a long standing interest in personality differences and who had developed her own informal typology before she encountered Carl Jung's book Psychological Types in 1921. She mapped her ideas onto Jung's framework, and over the following decades, her daughter, Isabel Briggs Myers, turned that mapping into a standardized questionnaire, developing the indicator during World War II with the original intention of helping women entering the wartime workforce find jobs that suited their temperaments.
Leslie Poston:Neither Catherine nor Isabelle had graduate training in psychology or psychometrics. That's not inherently disqualifying, but that type of training makes a difference because the test they built makes claims about personality structure that are at their core empirical claims that require the kind of evidence psychometric instruments are supposed to provide before they're used to make decisions about people's careers, management focus, team placements, or hiring. When the test was first submitted for publication in 1943, the academic psychology establishment largely rejected it. And while sexism was certainly part of that rejection, the real methodological concerns have never been fully resolved. Let's look at their inspiration for just a moment.
Leslie Poston:Jung's typology was speculative and theoretical. He described his personality types as rough conceptual tools for thinking about how people orient to the world, And he specifically warned against using them to sort or label people in rigid ways. The MBTI takes Jung's tentative framework and treats it as something measurable, stable, and categorical, which goes considerably further than Jung intended or would have endorsed. The test was briefly published by Educational Testing Service before being picked up by what's now called the Myers Briggs Company, formerly ECPP, and that company has built a substantial revenue model around the MBTI test. Individual assessments run between $15 and $50 per person.
Leslie Poston:Practitioner certification programs cost thousands of dollars, and corporate training contracts can run much higher than that. The company's estimated annual revenue was around $70,000,000 last I checked, and they operate in more than 115 countries. That certification pipeline creates a professional class of people with direct financial incentive to keep using and promoting this tool, regardless of what research says about it. Once you've spent thousands of dollars becoming MBTI practitioner, your livelihood has been partially built on the premise that this instrument is valid. And that's a hard thing to walk away from, even if the evidence starts making you uncomfortable.
Leslie Poston:There are several well documented problems with the MBTI as a psychometric instrument. The test retest reliability problem is probably the most straightforward. If the MBTI measures something stable about your personality, you should get the same result when you take it again a few weeks later because your personality hasn't changed in that shorter timeframe. Researchers found that as many as seventy six percent of people receive a different four letter type when they retake their test after just five weeks. The Myers Briggs company itself acknowledges that about fifty percent of people don't get the same overall type on retest.
Leslie Poston:For a tool that's supposed to reveal something fundamental about who you are, the fact that it gives you a different answer half the time is a significant consistency problem. And it becomes especially hard to defend when organizations are making hiring, team composition, or leadership development decisions based on a result that might have been different if the person had taken the test on a Tuesday instead of a Thursday or on a payday instead of during a hiring process. The distribution problem challenges whether the categories themselves make sense. Jung's type theory assumes that people fall into distinct compartments. You're either an introvert or an extrovert, a thinker or a feeler, with a genuine dividing line between those two.
Leslie Poston:If that were how personality actually worked, you'd expect to see a bimodal distribution when you plot people's scores on each dimension. Two distinct clusters with a gap in the middle. Instead, researchers like McRae and Costa found that MBTI scores on each dimension follow a normal bell curve, with most people landing near the center and fewer people at the extremes. What that means in practice is that someone who scores just barely on the thinking side and someone who scores just barely on the feeling side get assigned to different types, given different labels, and walk away with different stories about who they are, even though their actual scores are nearly identical. The categorization is effectively arbitrary for the large number of people clustered around the midpoint, which turns out to be most people.
Leslie Poston:The predictive validity problem is ultimately what matters most within the context where the MBTI is most often used. A personality measure earns its keep to the extent that it predicts real outcomes like job performance, leadership effectiveness, or which team compositions actually produce better work. The MBTI has weak predictive validity for all of these, which means the tool is weakest in precisely the context where organizations spend money to administer it. McRae and Costa also showed that four of the MBTI's dimensions loosely correspond to four of the big five personality traits, which we'll talk about in a moment. The forced binary categorization, the thing that makes the MBTI feel so clean and simple, is exactly what throws away the most useful information.
Leslie Poston:It's like measuring someone's height in feet and then rounding to the nearest whole number. You've made your data simpler, but you've also made it wrong. The research on the lack of validity of the MBTI is fairly settled, yet the MBTI continues to feel accurate and meaningful to millions of people despite the evidence. Part of the reason comes from a 1948 experiment by psychologist Bertram Forrer. He gave each of his students what he said was a personalized personality analysis based on a test that they'd taken, and then asked them to rate how accurately the description captured who they are on a scale of zero to five.
Leslie Poston:The average rating was 4.26 out of five. Then he told them the truth. Every student had received the exact same description, which he had assembled from a newsstand astrology book. This is the Barnum effect, sometimes called the Forrer effect, and it's one of the most replicated findings in psychology. When you give people personality descriptions that are broad enough to apply to most people, but specific enough to feel personal, people rate those descriptions as highly accurate reflections of who they are.
Leslie Poston:MBTI type descriptions do exactly this using language like you value authenticity and deep connection, or you prefer to think things through before acting. Statements that feel revealing but describe tendencies that are common across the population. And because you filled out a long questionnaire beforehand, the experience carries an empirical feel that a horoscope does not. You did the work and answered the questions, so you feel that the output must reflect your real answers. Once someone has adopted a type label as part of their self-concept, once they've started introducing themselves as an INFJ, an ENTP, or building their understanding of their relationships around the type dynamics, a second mechanism kicks in.
Leslie Poston:Kunda's work on motivated reasoning demonstrated that people evaluate evidence in ways that protect beliefs they're invested in. If your MBTI type has become part of how you explain yourself to other people, research showing the test is unreliable isn't just an abstract finding. It becomes a challenge to something that feels personal. And the brain's response is to find reasons to discount that challenge rather than change a belief about identity. There's also a cognitive piece to this.
Leslie Poston:Our brains prefer categories over continuums because categories are easier to store and use. I am an introvert is a simple, portable piece of self knowledge that you can carry into any conversation. I score at the forty third percentile on extroversion, which means I'm slightly below average on sociability and positive emotionality, but within the normal range is more accurate but far less useful in conversation or as a frame for understanding why your last meeting drained you. The MBTI works with this cognitive tendency rather than against it. While that's a design advantage, it's certainly not a scientific one.
Leslie Poston:And then there's the social layer, which does most of the work here to keep this test in circulation. MBTI types function as identity markers. There are subreddits organized around MBTI type, meme accounts, dating app bios built on the four MBTI letters, and entire online communities where people sort fictional characters, bond with strangers over shared types, and use type language to narrate their relationships. This maps onto social identity theory, something we've talked about on several episodes, showing that people derive part of their self-concept from group membership. Typed communities provide belonging, shared language, and a sense of being understood.
Leslie Poston:None of which depends on the test being scientifically valid. The community reinforcement makes the framework stickier even if the framework's results are wrong. When you add all of these together, the bardom effect, motivated reasoning, categorical cognition, and social identity, you get a picture of why the MBTI persists. The things that make the MBTI feel true are structurally the same things that make astrology feel true, wrapped up in institutional packaging. A Fortune 500 company won't hire an astrologer for a team building retreat, but the psychological dynamics at play in both contexts are comparable.
Leslie Poston:The MBTI isn't the only personality assessment on the market. And the Big Five isn't the only alternative. To understand what's actually available, it helps if we look at the full range of tools that organizations are using and where they fall on the spectrum between commercial appeal and psychometric rigor. The Big Five Model, sometimes called OCEAN, measures five broad personality dimensions: openness to experience, conscientiousness, extraversion, agreeableness, and neuroticism. It came out of lexical studies by researchers like Saussure and Goldberg who analyzed which personality descriptive words appear consistently across languages.
Leslie Poston:Working from the logic, if a personality dimension is real and important to human social life, people will have developed words for it independently across cultures. When they factor analyzed these word lists across multiple languages, five consistent clusters kept emerging. And that cross cultural convergence is a large part of why the model has held up as well as it has. The big five treats each trait as a continuous dimension rather than a binary. It has strong test retest reliability, and it has genuine predictive validity.
Leslie Poston:Meta analysis found that conscientiousness showed a consistent positive correlation with job performance across virtually every occupation studied. Neuroticism predicts vulnerability to anxiety and depression. And degreeableness predicts relationship quality, all replicated across cultures and across decades. For a long time, the knock on the big five was that nobody had packaged it for the commercial market, the way that CPP originally packaged the MBTI. And that's changed.
Leslie Poston:There are many companies out there that now sell Big Five based assessment products to organizations, with pricing that ranges from around $70 a candidate to 2,000 for unlimited use. One in particular has built a successful business around assessments grounded in Big five research, complete with the kind of commercial packaging, practitioner training, and organizational support materials that the raw Big Five originally lacked. The global psychometric testing market hit an estimated $6,100,000,000 in 2025, and big five based tools are a recognized part of that market now. So the gap between the MBTI's commercial presence and the big five's availability has narrowed considerably. Even if the MBTI still has stronger brand recognition from its decades long head start.
Leslie Poston:There are other tools in the mix now too. DiSC measures behavioral tendencies across four dimensions, and it's popular in sales and management training, though its psychometric backing is weaker than the big fives. Gallup's CliftonStrengths assessment, which identifies a person's top strengths from a list of 34, has a large corporate following and substantial marketing behind it as well. The Enneagram has gained traction in some organizational and coaching contexts, although it has even less empirical support than the MBTI. Each of these occupies a different spot on the trade off between scientific validity and ease of use.
Leslie Poston:And psychometric rigor doesn't appear to be the primary factor driving most adoption decisions by organizations. The HEXACO model adds a sixth dimension to the Big Five called honestyhumility after cross linguistic personality research found that the Big Five didn't fully capture this trait related to sincerity, fairness, and modesty. HEXACO is an example of personality science doing what science is supposed to do: revising a good model when new data requires it. The MBTI hasn't meaningfully changed since the forties. Longitudinal research has also demonstrated that personality isn't fixed in the way the MBTI implicitly suggests.
Leslie Poston:People tend to become more conscientious and more agreeable as they age, particularly in response to new roles and new responsibilities. Modern personality science treats traits as tendencies that interact with situations rather than as permanent stamps, which is a more complicated picture than you're an ENTJ, but one that has the advantage of actually being supported by evidence. So if there are now commercially available alternatives with stronger science behind them, we have to ask ourselves why the MBTI still holds the position it does. And the answer is really less about market asymmetry and more about market entrenchment. The MBTI gives you four simple letters, while the big five gives you five percentile scores.
Leslie Poston:DiSC gives you a behavioral profile. CliftonStrengths gives you kind of a ranked list. And in a one hour corporate workshop, four simple letters are just easier to work with than percentile scores or ranked list. And they translate directly onto easy team exercises. The MBTI also produces a result that feels empowering and positive since every type has strengths and nobody walks away having been told they scored high on neuroticism.
Leslie Poston:That's a useful piece of information, but it doesn't make for a pleasant team building afternoon. And a pleasant experience makes the HR department that administers the test look good, which is its own kind of institutional incentive. There's also decades of institutional inertia working in the MBTI's favor. Organizations that have built certification programs, training curricula, internal language, and entire team building traditions around MBTI types aren't evaluating the MBTI against alternatives on a regular basis. They're just continuing to use what they've already invested in.
Leslie Poston:Changing a framework means retraining your facilitators, replacing your materials, and asking your employees to let go of a vocabulary they've been using for years. That kind of institutional friction protects the MBTI from competition in ways that have nothing to do with whether the science supports it. The MBTI also benefits from something the better validated alternatives haven't fully replicated: Cultural saturation. When someone puts INFJ in a dating profile or a social media bio or sorts their favorite TV characters by MBTI type, that's unpaid marketing for the entire framework. The big five doesn't generate that kind of organic cultural presence because percentile scores don't lend themselves to identity and community building in the same way an easy four letter label does.
Leslie Poston:The MBTI's stickiness comes from its ability to function as a social identity. That's a competitive advantage that psychometric rigor does not address. What you end up with is a market where the best validated tools are now commercially available, but they're still fighting an uphill battle against a product that's got a huge head start, deep institutional roots, and a cultural footprint that goes well beyond a corporate workshop where it gets administered. By the time the science shows up in a commercially viable package, MBTI's already part of how organizations think and talk about their people. So what does all of this mean for you?
Leslie Poston:If you've taken the MBTI and found it useful for thinking about yourself, that act of self reflection that comes from any personality assessment can still be valuable even if the tool prompting it has serious problems. Just thinking about whether you tend toward introversion or extroversion is a perfectly reasonable thing to do. Issues come when that reflection gets locked into a category that data doesn't support. And when organizations are using those categories to make decisions about your career and your team assignments, as if all these labels rested on solid evidence. If you're interested in personality science that holds up under scrutiny so you can do more self reflection, the big five is freely available online in validated forms at no cost.
Leslie Poston:And several commercial versions now exist that are designed for organizational use. Their results will give you something more useful than just a type. They'll give you a little profile of where you fall on five continuous dimensions, each of which has a documented relationship to real outcomes. So if your organization is evaluating personality assessment tools, tools built on the big five or the HEXACO framework are where the strongest psychometric evidence currently sits. And the commercial options have matured to the point where nobody sells it is no longer an accurate reason to default to the MBTI.
Leslie Poston:And if your company is still paying for MBTI workshops, one question worth asking is what they're getting for that money compared to what's now available. Based on the evidence, the answer is a pleasant experience for participants. Some useful conversations about working styles, but very little in the way of prediction or actionable insight about how people will actually perform and perform together. That test generates conversation, and that conversation can be valuable. But there are better tools now that will generate conversation and predict outcomes.
Leslie Poston:A broader takeaway can extend past personality testing. When something is widely adopted, commercially successful, and hits that sweet spot where it feels right, those things together can function as a substitute for evidence. And the longer that substitution goes unchallenged, the harder it becomes to displace, even when better options arrive on the scene. The MBTI is one of the clearest examples of that dynamic playing out across the industry that has had access to better data for years now. Thanks for listening to PsyberSpace.
Leslie Poston:This is your host, Dr. Leslie Poston. According to the MBTI and ENTP. Signing off as always. Until next time, stay curious.
Leslie Poston:And don't forget to subscribe so you never miss an episode.
Creators and Guests
