How reliable is the Myers-Briggs personality type indicator?

Not only that, but it might just be a disturbing world if we could discriminate by personality accurately. The human soul is a complexflowingchanging entityimpossible to capture on a sheet of paper with little bubbles to fill in.

Myer-Briggs personality tests

In Western society, whether you’re at school, at work, in the military, filling out a dating profile, or sometimes even just sitting at home surfing the web, one thing is certain: You will be asked at some point to fill out a personality assessment test, which is usually the Myers-Briggs personality test or some derivative from the same idea. The “Myers-Briggs Type Indicator” (MBTI) has propagated throughout culture until it’s almost a cult on its own. But it’s based on nothing but a pseudo-scientific theory! 

The test itself involves answering a series of non-intuitive multiple-choice questions, often with vague phrasing and answers. These answers are then scored to produce a personality inventory, in which the individual is rated on four different metrics: 

  • Intuition/Sensing
  • Introversion/Extraversion
  • Feeling/Thinking
  • Perception/Judging

…producing a coded letter score. Leaning heavier toward Intuition or Sensing will produce an “I” or “S” in that slot, for instance. This produces one of sixteen possible codes, which is then assigned as the test-taker’s personality. Because “introversion” also starts with “I,” it’s designated by the letter “N” instead. By the way, the labels don’t mean their conventional definitions; while “introversion” might suggest a person who prefers to be alone, in this context, it’s supposed to mean “thought-oriented” while its complement “extraversion” means “action-oriented.” 

However, there are many different configurations and definitions of Myers-Briggs inventories and their derivatives. 

Astrology For Nerds

That’s how one Quora poster thought to pose it. To be sure, it’s a handy metaphor. Back in the swinging 1970s, astrology was hugely popular as part of the cultural sway towards New Age beliefs. Astrology is the belief that each person has a unique personality and destiny, which can be divined from their date of birth related to the positions of the stars and planets, grouped into twelve constellations. These were known as “star signs,” collectively known as the “zodiac.” 

During that decade, it was common for people to casually ask each other, “What’s your sign?” at cocktail parties and similar events. Singles in the dating scene would be heard to mutter things like, “Of course we get along; he’s a Sagittarius and I’m a Libra, so we’re both fire signs!” or “He cheated on me, but what do you expect from a Libra?” We’re actually going to come back to astrology because it has bearing on our topic – in fact, they share some common roots! 

Astrology has faded in popularity in recent decades, albeit an astrology column forecasting the future for each “star sign” is still faithfully printed in virtually every newspaper in the world. Other popular methods of personality divination have also come along over the years: biorhythmsthe Enneagram of Personality, and too many more to list here. Again, we’ll circle back to the whole sphere of personality theories to dig into their common root. 

How saturated into the culture is the MBTI? 

whole forums devoted to typology systems like MBTI

  • There are whole forums devoted to typology systems like MBTI, segregated by the code.

dating services based on MBTI

  • There are dating services based on MBTI.

MBTI tattoos for each type

  • There are – wait for it – MBTI tattoos. Yes, for each type.

despite the Myers-Briggs Foundation itself recommending against that usage

  • It is a staple of employment screening, despite the Myers-Briggs Foundation itself recommending against that usage, albeit merely on ethical grounds.


  • It’s brought up in contexts like parenting, so there are impacts on children too.

by the US military

  • Unsurprisingly, it’s used by the US military as an instrument of divining leadership potential.

Apparently so!

  • Do people use the MBTI to decide what kind of pet to adopt? Apparently so!

As is always the case with pseudo-scientific typology systems, the MBTI is often defended as “just for fun” or a harmless group exercise during employee orientation. And yet, if people are using the MBTI as a starting point for getting tattoos and making life-altering decisions impacting their career, parenting, and even pet ownership, clearly, somebody’s taking it seriously. 

The Origins Of The MBTI

The time was the year 1944, World War II. In the United States, the war effort impacted the home front in many ways. Citizens were called on to buy war bonds, save scrap metal, ration foods, so the front lines ate heartily, and of course, volunteered to enlist. But every man who left his factory job to go fight the Axis powers left a vacancy, while legions of idle housewives sat at home with little to do. Women, informally, were recruited into the workforce in droves by businesses desperate for raw manpower. 

Cue Rosie the Riveter

But there was a problem: In the early 20th century, it was uncommon for women to work, so most of these women had never had a job before. Pressed to apply for jobs they’d really rather not have if they’d had a choice, women often took the opportunity to stall, saying they just couldn’t make up their minds about which position to take. Even if they did genuinely want a job, many more were just clueless as to what went on in this unfamiliar world of employment. Human resources, meanwhile, needed these answers fast because these positions had to be filled fast, and didn’t care if it was the correct answer as long as it happened right now. Something, anything, was needed to convince these women that, yes indeed, they’d be just perfect for cleaning out the grease pit at the poultry plant – why, if they give it a chance, they just might love it! All they needed was a snappy expert analysis that looked scientifically convincing. 

Enter Katherine Briggs, and her daughter and chief research subject, Isabel Briggs-Myers. Neither of them had any formal psychological training, but they’d scanned a book by Carl Jung and could dash together an ad-hoc “test” that would pass muster long enough to convince that privileged social butterfly to get her hands dirty in the grease pit. Katherine, a stay-at-home mom from Michigan, had raised her own daughter in what she later touted as “a cosmic laboratory of baby training,” from which she had formulated her personality assessment methods. 

About Carl Jung… 

That book was an English translation of Carl Jung’s 1921 Psychological Types. In it, Jung put forth an untested theory that humans could be separated into two types and those two further into two types more, for four total. Even Jung himself cautioned against reading too much into his admitted pipe-dream, and surmised, “every individual is an exception to the rule.” Jung’s motivation in writing this work was an attempt to reconcile the theories of his own mentor, Sigmund Freud, and other psychology theorists. 

While both Freud and Jung are still respected today in science, it has to be mentioned that both of them produced work that has since become obsolete from modern research. They were pioneers in a field nobody thought to establish previously, so hats off to them anyway. But the Swiss psychiatrist Jung, particularly, leaned to the mystic side along with his science side. He had spiritual beliefs and exercised them by, for example, recommending religious practice as a cure for alcoholism. He had an interest in the paranormal, conducted seances, and even delivered lectures on psychic phenomena. 

But the “aha!” comes when we learn he was interested in alchemy, too. Alchemy was the early Medieval attempt at the hard sciences, fraught with misguided forays into trying to transmute base metals into gold and trying to find a panacea for all diseases. Within its field of discipline lies both astrology and humorism. Humorism defined four “humors” – blood, yellow bile, black bile, and phlegm – which were supposed to be liquids in the body controlling our health and determining our temperament into four types: phlegmatic, choleric, sanguine, and melancholic. 

Sound familiar? Yes, we’re back to four basic personality types, and the balance of the same makes a mixture of sixteen combinations that were alleged to determine one’s personality. In fact, those same temperaments have an additional one along for the ride, “supine,” in five-temperament personality, yet another personality-assessment theory based on humorism. So not only are we tying in astrology and humorism, but we’re also seeing the roots of the Asian version of Myers-Briggs, blood type personalities, which is a comparable theory that cuts out all that bile and phlegm to focus on just blood, which is sorted into four types


Getting back to Katherine Briggs and Isabel Briggs-Myers, they started with Jung’s book but applied a highly altered version of Jung’s ideas to their assessment test. It was good enough for the time. Women went to work in the factories, and the Axis powers were defeated. 

Debunking The MBTI And Its Peers

Thanks to the immense emphasis the Myers-Briggs theory has been given in the years since WWII, in no short part due to the marketing of the Myers-Briggs Foundation itself as it’s a $20 million dollar per year industry, it’s been the subject of increasingly harsh scrutiny. 

First off, about half the tested subjects have different results on different days, suggesting that the assessment measures mood more than personality. One subject, an organizational psychologist at Wharton, shared this experience on his Linked-In profile 

One book debunking personality testing is The Cult of Personality: How Personality Tests Are Leading Us to Miseducate Our Children, Mismanage Our Companies, and Misunderstand Ourselves, by a mental health journalist and former senior editor at Psychology Today

“In personality testing, reliability means getting consistent results over time, or similar scores when rated by multiple people who know me well. As my inconsistent scores foreshadowed, the MBTI does poorly on reliability. Research shows ‘that as many as three-quarters of test takers achieve a different personality type when tested again’, writes Annie Murphy Paul in The Cult of Personality Testing, ‘and the sixteen distinctive types described by the Myers-Briggs have no scientific basis whatsoever‘. In a recent article, Roman Krznaric adds that ‘if you retake the test after only a five-week gap, there’s around a 50% chance that you will fall into a different personality category’.”

Given these observations, it’s surprising to see how widely used these type of “tests” are in recruiting and other endeavours that really should be done with more solid scientific support.

Another book debunking personality testing as a whole is House of Cards: Psychology and Psychotherapy Built on Myth, by Robyn Dawes, who tackles a whole host of pseudo-science practices besides. 

STP (Foundation for Applied Psychology), examined the quality of some of the personality tests available on the market. The majority of tests are criticized for lack of scientific evidence that they work. One example is Myers-Briggs, one of the world’s largest occupational psychological tests, and as described by STP’s reviewer as a “collegial game”. Another test, Thomas PPA, has been used by 10’s of thousands of companies, STP writes that the deficiencies in the theoretical foundation of the test are: “unacceptable and tends to overthrow the credibility of the instrument.”

In total, criticisms of the MBTI itself (which also applies to many tests like it) sum up to: 

  • No evidence that human personality works in dichotomies.
  • Limited concurrence with other tests – only the “intuition/sensing” scale seems to measure anything predicted by any other model; everything else seems to be static.
  • It depends on self-reporting. As do some 90% of assessments out there.
  • It exploits the Forer / Barnum effect (explained below).
  • Low reliability. No known study has ever taken something predicted by an MBTI and validated it with the subject’s behaviour.
  • Severe deficiencies in the theoretical foundation of the tests, including Myers-Briggs and PPA.

Scientist Robert Hogan calls it “little more than an elaborate Chinese fortune cookie.” 

What about other personality model theories? 

There are of course a host of other personality typologies, many of which we’ve covered above, but the best we can say about them is that they’re unproven but, to varying shades, possibly viable. 

The Big Five is one touted as the closest to a scientifically accurate assessment. However, this is because it measures very obvious factors like curiosity and empathy, traits easily diagnosed with more precise tools. It’s not aimed so much at finding your dream date as it is at diagnosing huge deficiencies resulting from things like PTSD or a stroke. Its chief critique is the lack of scope. 

There is also the realm of other psychological assessment tools, called “psychometrics,” ranging from IQ tests to the DiSC profile to the Adult ADHD Self-Report Scale. These naturally are attempts to qualify intelligence, conceptualize behaviour, or diagnose a disorder, respectively. Even these instruments have their proponents and detractors. The fact is, analyzing a big, complex human brain is just too complicated a task for any single sheet of paper. The best we can do is pin down observational data like “Does the patient laugh when you tell them a joke?” We’re continuously evolving our collective understanding of how much of the human mind we can even map, and what that map might look like. 

Why People Want To Believe In Personality Typing

Humans have a common flaw in the way our brains are wired: We really, really want the universe to be sorted into discrete categories. We want a tidy calendar that’s consistent and is divided into whole months, weeks, and days, but the universe gives us a planet that orbits its sun every 365.256 days and says “LOL Deal with it!” This human prejudice towards the orderly mapping of reality, in opposition to the inherent chaos and messiness of nature, leads to psychological hiccups ranging from conspiracy theories to Obsessive-Compulsive Disorder. 

Humans, social animals, also have a strong need for self-validation. This means we want labels for people because labels sort us into nice neat bins and simplify social relations. expresses this perfectly right in the banner: “It’s so incredible to finally be understood!” We all want this badly, and for some, it’s worth putting on a mask and being misunderstood as a false stereotype, rather than force others to deal with all your psychological nooks and crannies.

But the big reason we’re likely to fall for personality assessment tests is when the results trigger the Forer effect, also called “the Barnum effect.” Briefly, it’s the tendency for people to read a general, generic assessment and assign it personal value. It was first discovered in 1947 by psychologist Ross Stagner, who gave some managers a personality test and then showed them “results,” which were actually the same copy given to each manager regardless of the test, and based on newspaper horoscopes. Each of the managers, when questioned, said the results matched them perfectly! 

In 1948, psychologist Bertram R. Forer did a more formal experiment, testing his class of 39 students with the “Diagnostic Interest Blank.” For results, each student got back the same answers, all composed of bland, vague sentences like “You have a tendency to be critical of yourself” and “Security is one of your major goals in life.” Again, each of the students rated the test as being a magnificent crystal ball, thrilling them with its piercing insight into their unique gifts. 

This same trick is exploited in every shade of fortune-telling you could name, from psychic “cold readers” to astrologers. “You try to be neat most of the time.” “You feel you could be more successful financially if you set your mind to it.” “Sometimes you feel like your romantic partner doesn’t understand you.” “You think puppies are cuter than tarantulas.” Next time you’re worried about being surrounded by idiots and how to understand them, take any broad, general statement about humanity at large and personalize it down to one person, then watch them go:

“Hey, that’s me!” 

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