A critical look at the world's most popular psychological metric, the Myers-Briggs Type Indicator.

by Brian Dunning

Filed under Fads, General Science

Skeptoid Podcast #221

August 31, 2010

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Today we're going to delve into the murky depths of Jungian psychology, and examine one of its most popular surviving manifestations. The Myers-Briggs test is used all over the world, and is the single most popular psychometric system, with the full formal version of the test given more than 2,000,000 times a year. But is it a valid psychological tool, is it just another pop gimmick like astrology, or is the truth somewhere in between?

The Myers-Briggs Type Indicator, called MBTI for short, more properly owes the bulk of its credit to the great Swiss analytical psychologist Carl Jung. In 1921, Jung published his book Psychological Types, in which he laid out all the same concepts found in the MBTI, but he had them organized quite differently. Jung had everyone categorized as either a "perceiver" or a" judger". Perceivers fell into one of two groups: sensation and intuition; while judgers also fall into two groups: thinking and feeling. So everyone fits into one of those four buckets. Finally, each bucket is divided into two attitude types: introversion and extraversion. Thus, the scale proposed by Jung divided us all into one of eight basic psychological types.

An American woman, Katherine Briggs, bought Jung's book and was fascinated by it. She recommended it to her married daughter, Isabel Briggs Myers, who had a degree in political science. The two of them got hooked on the idea of psychological metrics. Together they sat down and codified their own interpretation of Carl Jung, making a few important changes of their own. Jung had everyone fitting into one of four basic buckets. Myers and Briggs decided that each person probably combined elements, so they modified Jung's system and made it a little more complex, ending up with four dichotomies, like binary switches. Any combination of the four switches is allowed, and Myers and Briggs reasoned that just about every personality type could be well described by one of the sixteen possible ways for those switches to be set. Basically, according to Myers and Briggs, we're all represented by a four-digit binary number.

The first dichotomy is called your Attitude, and according to the MBTI, you're either an E for Extravert or an I for Introvert. Extraverts prefer action, frequent interaction, focus outward, and are most relaxed when interacting with others. Introverts prefer thought, less frequent but more substantial interaction, and are most relaxed spending time alone.





The second dichotomy is your Perceiving function, and you're either S for Sensing or N for Intuition. Sensing is the scientific, tangible data-driven approach to gathering information, preferring to deal in concrete, measurable information. The Intuition approach prefers theoretical, abstract, hunch-driven information, finding more meaning in apparent patterns and context.





The third dichotomy is your Judging function, and you're either a T for Thinking or an F for Feeling. This is basically how you make decisions. Thinking makes the logical decision, what's best for the situation, based on rules and pragmatism. Feeling decides based on empathy for the people whom the decision affects, seeking balance and harmony.





The fourth and final dichotomy is your Lifestyle, and you're either a J for Judgment or a P for Perception. This one gets a little confusing. Judgment types prefer to use the third dichotomy, Judging, when relating to the outside world, while Perception types prefer the second Perceiving dichotomy; but how that preference is determined is based on whether you're an Introvert or an Extravert. Suffice it to say, for the purpose of this light overview, that this last of the four dichotomies, Lifestyle, is the most complicated; and it's where Myers and Briggs most creatively expanded upon Jung on their own.

The basic test, of which there are several variations and revisions, is called the MBTI Step I and it's a series of almost 100 questions, each with two possible answers. Each question consists of two short statements or word choices, and you simply choose which of the two you prefer. When the results are tabulated, you should ideally have your preference established for each of the four dichotomies; and congratulations, you are now identified by one of sixteen possible personality types. Myers and Briggs gave names and descriptions to all sixteen, names such as the Executive, the Caregiver, the Scientist, and the Idealist.

Perhaps the most common misconception about the MBTI is that it shows your aptitude, helping you determine what kinds of things you'd be good at. This is not the case. Myers-Briggs is only about determining your preference, not your ability. There might be things that you're good at that you don't enjoy, and there might be things you enjoy that you're not good at. The MBTI helps your find your comfort zone, the types of activities you'll like and be most content with; not necessarily those at which you'll be especially competent.

Even though neither had any background in psychology, Myers and Briggs enjoyed great success with their system. As Mrs. Briggs was getting quite old, Isabel Myers was the main driving force. Her initial idea was that certain personality types would more easily excel at different jobs, and the tool was intended to be used by women entering the workforce during World War II. However, it was not published until 1962, but since that time, it's become the most widely used basic psychology test. It's most often used outside of the psychological profession, and is employed in career counseling, sports coaching, marriage counseling, dating, professional development, and almost every other field where people hope to be fit with a role that would work best for them.

So the MBTI's practical use is overwhelmingly unscientific, and it's often criticized for this. Criticism ranges from the pragmatic fact that neither Jung nor Myers and Briggs ever employed scientific studies to develop or test these concepts, relying instead on their own observations, anecdotes, and intuitions; all the way to charges that your MBTI score is hardly more meaningful than your zodiac sign.

One obvious trait that the MBTI has in common with horoscopes is its tendency to describe each personality type using only positive words. Horoscopes are so popular, in part, because they virtually always tell people just what they want to hear, using phrases that most people generally like to believe are true, like "You have a lot of unused potential." They're also popular because they are presented as being personalized based on the person's sign. This has been called the Forer Effect, after psychologist Bertram Forer who, in 1948, gave a personality test to his students and then gave each one a supposedly personalized analysis. The impressed students gave the analyses an average accuracy rating of 85%, and only then did Forer reveal that each had received an identical, generic report. Belief that a report is customized for us tends to improve our perception of the report's accuracy.

I notice this right away when I read Isabel Myers' description for my own personality type, ISTJ, the Duty Fulfiller: "Practical, matter-of-fact, realistic, and responsible." Basically it's a nice way to say "Dry, boring, and punctual," which hits my nail pretty squarely on the head. From that alone, I might conclude that the MBTI is extraordinarily insightful. But if I look at her description of my opposite counterpart, an ENFP, the Inspirer, that person is "Warmly enthusiastic and imaginative. Sees life as full of possibilities." Who wouldn't like to believe that about his or her self? If I'd taken the test and been handed that result, I might be equally inclined to embrace it, probably thinking something like "Wow, I'm even more awesome than I thought I was."

Due to these legitimate criticisms of the MBTI and its unscientific underpinnings, the test is rarely used in clinical psychology. I did a literature search on PubMed and discovered that, interestingly, many of the published studies of its practical utility come from nursing journals. Many of the other publications pertain to relationship counseling and religious counseling. Normally, this is a red flag. When you see a topic that purports to be psychological being used in practically every professional discipline except psychology, you have very good reason to be skeptical of its actual value. Should we dismiss the Myers-Briggs Type Indicator as a psychometric?

The test does have some severe inherent problems. It's been found that 50% of test takers who retake it score differently the second time. This is because nobody is strictly an E or an I, for example, but somewhere in between. Many people are right on the border for some of the four dichotomies, and depending on their mood that day or other factors, may answer enough questions differently to push them over. Yet the results inaccurately pigeonhole them all the way over to one side or the other. This makes it possible for two people who are very similar to actually end up with completely opposite scores. Isabel Myers was aware of this limitation, and did her best to eliminate questions that did not push people away from the center when the results were studied in aggregate. It was a hack.

From the perspective of statistical analysis, the MBTI's fundamental premise is flawed. According to Myers & Briggs, each person is either an introvert or an extravert. Within each group we would expect to see a bell curve showing the distribution of extraversion within the extraverts group, and introversion within the introverts. If the MBTI approach is valid, we should expect to see two separate bell curves along the introversion/extraversion spectrum, making it valid for Myers & Briggs to decide there are two groups into which people fit. But data have shown that people do not clump into two separately identifiable curves; they clump into a single bell curve, with extreme introverts and extreme extraverts forming the long tails of the curve, and most people gathered somewhere in the middle. Jung himself said "There is no such thing as a pure extravert or a pure introvert. Such a man would be in the lunatic asylum." This does not support the MBTI assumption that people naturally separate into two groups. MBTI takes a knife and cuts the bell curve right down the center, through the meatiest part, and right through most people's horizontal error bars. Moreover, this forced error is compounded four times, with each of the four dichotomies. This statistical fumble helps to explain why so many people score differently when retaking the test: There is no truly correct score for most people, and no perfect fit for anyone.

And this has been borne out in observation. A number of studies have found that personality types said to be most appropriate for certain professions, notably nursing or teaching, turn out to be no more prevalent among that profession than among the general population. The Army Research Institute commissioned one such study to determine if the MBTI or similar tests could be used to improve the placement of personnel in different duties, and firmly concluded that the results of such tests did not justify their use in career counseling.

From reviewing the literature, I do find one common theme among mainstream psychotherapists where the use of the MBTI is advised, and that's as a conversation starter. It's a fine way to give people a quick snapshot of what their strengths and weaknesses might be, and of those with whom they interact. To get the dialog going, this is a perfectly valid tool. But as a tool for making career decisions, relationship decisions, or psychiatric assessment, no. Although it would be nice to have a magically easy self-analysis tool that can make your decisions for you and be your crystal ball, the Myers-Briggs test is not it. It is interesting and it does have value as a starting point for meaningful dialog, but that's where the line should be drawn.



By Brian Dunning

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