In the world of personality type enthusiasts, there are three main camps: those who believe that type dynamics are an essential part of understanding personality types, those who think type dynamics lack legitimate support, and those who are sitting there right now wondering “What in the heck are type dynamics?”

We’re going to begin this multi-part series by addressing that final question. Before we can delve into the conflict over the theory of type dynamics, we must first move everyone out of the third camp and make sure that we’re all on the same page about what the theory of type dynamics actually is. First and foremost we should remember that it is, in fact, a theory.

The theory of type dynamics is based on psychologist Carl Jung’s theory of cognitive functions. According to Jung, we each have four basic ways of taking in information and making decisions. Jung called these cognitive functions sensation, intuition, thinking, and feeling—which should sound familiar to anyone who’s studied personality typology. In Jung’s framework, thinking and feeling are defined as judging functions, because they help us make decisions; sensing and intuition, on the other hand, are perceiving functions, because they define how we perceive information. If that all sounds a bit convoluted, hang in there—it will become more clear.

The seeds of the theory of type dynamics lay in Jung’s assertion that each type has an “auxiliary function which is in every respect different from the nature of the primary function.” In other words, one cognitive function—the primary—takes the driver’s seat in influencing thinking and behavior, while the auxiliary function plays a helper role. If the primary function is the driver, the auxiliary function is the copilot.

In 1962, Isabel Briggs Myers extrapolated on Jung’s original idea, creating the core of what is now the theory of type dynamics. She took Jung’s concept of primary and auxiliary functions and ran with it, using the word “dominant” rather than “primary.” She decided that Jung’s statement that, for any given person, these two functions would be different in all respects meant that one would be extraverted and the other introverted. Similarly, one would be a judging function and the other a perceiving. A person’s dominant and auxiliary functions would be opposite in both direction (extraverted or introverted) and nature (judging or perceiving). If a person’s dominant function was Extraverted Feeling, then their auxiliary function might be Introverted Intuition.

In the 1980s, W.H. Grant and Alan Brownsword, among others, expanded this theory to further describe the dominant and auxiliary functions, as well as add two more functions to the “stack.” The so-called “Grant-Brownsword model” specifies that the primary function is, as one might expect, extraverted for Extraverts and introverted for Introverts. The auxiliary function is the reverse: introverted for Extraverts and extraverted for Introverts.

In this model, the J or P portion of the four-letter type serves as a “pointer variable” that indicates which function will be directed outwards—that is, extraverted. Grant and Brownsword proposed that Judgers extravert their dominant judging function (T or F) and Perceivers extravert their dominant perceiving functions (N or S).

The extraverted functions are those which are most apparent to an observer. For example, the most noticeable quality of an ESTP is the way she lives in the moment and focuses on what’s happening now—which is also called Extraverted Sensing. Meanwhile, an ESTJ uses his sense of logic and reason to put his surroundings in order—demonstrating Extraverted Thinking. As a Perceiver, the ESTP shows us her perceiving function (Sensing). As a Judger, the ESTJ shows us his judging function (Thinking).

Grant, Brownsword, and their contemporaries went on to decide that there was a tertiary function that was the opposite of the auxiliary in both direction and nature, as well as an inferior function that was the opposite of the dominant. The direction (extraverted or introverted) of the functions from dominant to inferior would thus alternate between extraverted and introverted.

Eventually, each type’s specific combination of dominant, auxiliary, tertiary, and inferior functions became known as the type’s “cognitive functions” or “cognitive stack.” Later editions of the MBTI Manual endorsed this position, and type dynamics were described in detail in the 1985 and 1998 editions.

So, how does this theory actually apply to the 16 personality types that we’re all familiar with? First, let’s look at the eight cognitive functions. According to the theory of type dynamics, each type primarily uses four of the following functions:

  • Extraverted iNtuition (Ne) – Notices patterns and connections, generates possibilities.
  • Introverted iNtuition (Ni) – Identifies probable outcomes, conceptualizes new ways of seeing.
  • Extraverted Sensing (Se) – Experiences and takes action in immediate context.
  • Introverted Sensing (Si) – Stores and categorizes information, reviews past experiences.
  • Extraverted Feeling (Fe) – Adjusts to and accommodates others, maintains social norms
  • Introverted Feeling (Fi) – Adheres to personal beliefs, searches for deeper meaning
  • Extraverted Thinking (Te) – Imposes order on external environment, applies logic
  • Introverted Thinking (Ti) – Understands systems, looks for internal inconsistencies in a model or framework

To determine the order of your cognitive stack, you would first look at the first and last letters of your four-letter personality type, in order to determine the direction and nature of your dominant function. If you are an Extravert, then your dominant function will be extraverted and of the same nature of the last letter of your type: an extraverted Judger’s dominant function will be Te or Fe, and an extraverted Perceiver’s dominant function will be Ne or Se.

However, if you are an Introvert, your J-P preference will be displayed in your first extraverted function, which will actually be your auxiliary function. Your dominant function will be introverted, and it will be of the opposite nature of the last letter of your type. That is, if you are a Perceiver, then your dominant function will actually be a judging one (Ti or Fi), and if you are a Judger, then your dominant function will be a perceiving one (Si or Ni). For an Extravert, it is their auxiliary function that will be introverted and opposite in nature to the J-P preference.

For a concrete example, let’s use me and my type. I am an INTJ, so according to type dynamics, my dominant function is Introverted iNtuition (Ni). It is introverted because I am an introvert, but it is a perceiving function because—according to Grant and Brownsword’s extrapolations on Briggs Myers’ theory—my judging function must be extraverted, and therefore is my auxiliary function.

The theory holds that Introverts conceal (or introvert) their dominant functions and reveal (or extravert) their auxiliary functions, while Extraverts do the opposite. Thus, my auxiliary function is Extraverted Thinking (Te), which is opposite in both direction and nature from my dominant function of Ni. Then, it follows that my tertiary function is Introverted Feeling (Fi) and my inferior function is Extraverted Sensing (Se).

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If you would like to avoid the mental gymnastics of figuring out your own cognitive stack according to the theory of type dynamics, you can use the following chart.


After figuring out your cognitive stack based on type dynamic theory, you can finally set about figuring out what that means about you. Jung believed that the dominant function was the one over which a person had the most conscious control over and to which a person directed most of his or her “psychic energy.” In turn, the other functions in a person’s cognitive stack are under a decreasing amount of conscious control.


A standard part of the theory of type dynamics is that the functions develop in order of decreasing conscious control. Many people believe that the dominant function develops early in life, the auxiliary function develops in one’s young adulthood, the tertiary function develops in one’s 30s or 40s, and the inferior function does not become well-developed until one is in or past middle-age. However, it is also theorized that we use the inferior function more—no matter our age or state of development—in times of stress and/or fatigue.

When reading a description of a cognitive function that is a part of your stack, it would theoretically be most representative of you if it is your dominant or even auxiliary function, as they would be the most developed. Earlier, I provided a simple, one-line description for each function, based on a synthesis of several sources and my own understanding of the functions. For a more comprehensive picture of each function, you may want to read multiple sources. I have found that some sources seem to be weak in their descriptions of particular functions, possibly because the author does not have that particular function in his or her cognitive stack. That said, some good descriptions of the functions can be found here, here, and here.

In the next part of this series on cognitive functions and type dynamics, we will look at the arguments in favor of the validity of type dynamics.

Rachel Suppok
Rachel holds a B.S. in Neuroscience and usually a cup of coffee. She is an INTJ, but she is not a super-villain. Yet. Folow Rachel on Twitter @rsuppok.