Many people think that a Myers-Briggs personality type is simply their score on four different dimensions: Introvert—Extrovert, Intuitor—Sensor, Feeler—Thinker, and Perceiver—Judger. They view these as independent, surface-level variables that are each a spectrum and believe that no person is "100% introvert or 100% extrovert" and the same for the other variables. This is, however, a fundamental misunderstanding of the theory of cognitive functions that the Myers-Briggs personality type system is based on.

The Myers & Briggs foundation spreads misinformation about their theory by oversimplifying it, which not only misrepresents the ideas but also takes away an opportunity for people to better understand the way that they and others experience the world. After explaining what a Myers-Briggs personality type actually is, I will explain in more detail how utterly and dismally the official proponents of Myers-Briggs types have failed to accurately present and use their theory.

The theory states that our thoughts are based on four cognitive processes: two for processing information (Perceiving), and two for making decisions (Judging). The Perceiving functions are Sensation, which handles sensory inputs from the real world and concrete truths, and Intuition, which handles concepts, ideas, and underlying patterns. The Judging functions are Thinking, which looks at the facts impartially, and Feeling, which bases decisions primarily on emotions and values. These four functions are further split into eight, as each can be directed inwardly and intensively (introverted) or externally and extensively (extroverted). Together, all of the functions are Fe (extroverted Feeling), Fi (introverted Feeling), Te (extroverted Thinking), Ti (introverted Thinking), Se (extroverted Sensing), Si (introverted Sensing), Ne (extroverted Intuition), and Ni (introverted Intuition).

While what the cognitive functions are and do is fairly complicated, they can be roughly summarized like this: Fe is using emotions socially and seeking group harmony, Fi is one’s personal individual passion, Te is authoritative leadership that brings order and gets things done, Ti is pure logic and critical analysis, Se is in-the-moment real-world experience, Si is memory and detailed information storage, Ne is brainstorming of many different ideas and possibilities and Ni is long-term abstract thinking. For more information on cognitive functions, check out some of these resources: ThoughtCatalog, UnderstandMyersBriggs and FunkyMBTIinFiction explain the functions in much more detail.

Everyone tends to trust and prefer certain functions more than others. This forms a hierarchical “function stack,” in which the functions are ordered from the most to least used/preferred/trusted. As a general rule, the lowest four functions are unconscious (they are referred to as “shadow functions”), so the top four are the most important. In order from most to least trustworthy, those are the dominant, the auxiliary, the tertiary, and the inferior function. The functions alternate between introverted and extroverted.

This stack explains the four-letter “code” of a Myers-Briggs type. The I/E letter tells if the first function is introverted, making someone an “introvert,” or extroverted, making someone an “extrovert.” The J letter tells if the first two functions are extroverted Judgment and introverted Perceiving, or the other way around for P. The middle two letters say what kind of Judgment or Perception they are: N or S, and T or F. Hence, the four letter code: I/E, N/S, F/T, P/J.

For example, here are the cognitive functions of an INFJ based on the letters. “N” is the Perceiving function, which “J” says is introverted: Ni. “F” is the Judging function, which “J” says is extroverted: Fe. “I” says that the introverted function is dominant, thus Ni dominant and Fe auxiliary. The tertiary function is the opposite of the auxiliary, and the inferior function is the opposite of the dominant; thus Ni dominant, Fe auxiliary, Ti tertiary, and Se inferior.

For this reason, it makes no sense to say that someone is “55% introverted” or “kind of ESTP but kind of ESTJ” while talking about Myers-Briggs personality types. If someone is an “I” type, they are 100% an introvert, but for every introvert, the second-favorite cognitive function is extroverted, so of course an introvert can “act extroverted” when they use their extroverted functions. In Myers-Briggs, you cannot be “stuck between” two types such as ESTP and ESTJ because the function order of these types is completely different.

However, if you have heard that Myers-Briggs personality types are just scores on four scales, then it is not your fault. The Myers & Briggs Foundation is to blame because they spread misinformation about their own subject. Instead of giving even a rudimentary explanation of cognitive functions, their presentations of the theory rely exclusively on the four letters, which oversimplifies the theory and leads to misconceptions about how it works. The worst way that the Myers & Briggs Foundation misrepresents their own theory, though, is through the Myers-Briggs test.

The Myers-Briggs test uses the letter-by-letter method to determine one’s personality type, which is a very poor and inaccurate method. It does not take into account cognitive functions, and finding personality type by figuring out one’s cognitive function stack is the best method to determine one’s personality type. More specifically, though, it has many other flaws. The Myers Briggs Type Indicator (MBTI) only offers yes or no questions without any “maybe” options or grey areas. The person taking the test cannot ask the test what a question means. The MBTI only tests a person’s self-concept and not what their personality actually is, so people often will shape their results to fit what they like to think about themselves. Worst of all, though, the MBTI gives the results in terms of percentages of each letter, so people come to see a Myers-Briggs personality type as scores on four independent spectra. In reality, those percentages only represent the test’s confidence that you are each letter—but even with a high confidence percentage, the test can easily be wrong due to the aforementioned flaws in the testing method.

If someone actually wants to figure out their personality type, there are several ways to do so that do not suffer from all of the same problems as the test. One can do independent research on each type and figure out which description is the most like them, although online descriptions can be flawed because they are often based on stereotypes. Oftentimes, the more “official” a resource is that offers information about Myers-Briggs personality types, the more it oversimplifies and stylizes the information, and thus the less accurate it is.

A better way to do this is to research cognitive functions and see which type’s cognitive function order fits them the best. One way that takes less time is to ask an expert or at least someone who knows enough about the workings of the Myers-Briggs system to figure out others’ personality types. None of these methods, however, involves taking a Myers-Briggs test.