Personality type for dummies: Part 1 – the basics

Something that’s been part of my life for a while now (some 5-6 years I’d estimate) is the personality type system variously called Myers-Briggs, MBTI, Jungian typology, or just “typology”. You know, INTJ’s, ENFP’s, ESTJ’s, etc. When I say “part of my life”, I mean “stuck in my head”. I used to be extremely interested in typology, reading deep into the theory and spending a lot of time trying to figure out the personality types of every person I met and fictional character I watched. Read my previous post about why and how I use typology.

My interest in typology has waned, but it’s something that sticks in my head. I still type people (and fictional characters). At this point it’s like a reflex rather than a conscious thought process. Once a user of typology, always a user of typology, etc.

If typology interests or has ever interested you, I’m writing this post to give you a crash course in the theory and practice of typing others and yourself. Why? That it’s an amusing trainspotting exercise aside, understanding typology is worthwhile for the sake of understanding how people’s brains work differently, exactly how other people’s brains are different from yours, and why people act the way they do. Ultimately, by better understanding others and yourself, you can use it to improve your relationships—which is an eminently worthwhile end. Also, it’s really fun to guess the Twelfth Doctor’s MBTI type.

This post ended up being a lot longer than I anticipated, so here’s a table of contents of sorts to signpost what’s ahead:

  1. What’s this about
  2. The cognitive functions
  3. Function pairs
  4. Function preferences & the dominant function
  5. The function stack
  6. The four-letter code
  7. What the cognitive functions do
  8. Typing yourself and others
  9. Part 2

What’s this about?

The typology system I’m talking about here is the Myers-Briggs Type Indicator (MBTI) system which derives from Carl Jung, was developed by Katharine Briggs and Isabel Briggs Myers, and was perfected by teenagers on Tumblr. It’s dangerous using the term “personality type” (although I use it anyway for convenience) because what we colloquially undersand by “personality” are things that MBTI has nothing to do with: characteristics, attributes, traits and behaviour.

MBTI is not about behaviour, but cognition, which can be boiled down to two things: how you gather information, and how you make decisions, referred to in MBTI terminology as perceiving and judging. As you’ll appreciate, perceiving and judging have little to do with a person’s sense of humour, gregariousness, confidence, snobbishness, excitability and other attributes and behaviours we colloquially associate with “personality”.

Remember: this is about how a person gathers information and makes decisions.

The cognitive functions

If you have a passing familiarity with typology, you would know about the four-letter code that represents each of the 16 personality types: INTJ, ENFP, etc. For each of the letters in the four-letter code, there are two alternatives:

  • Introversion (“I”) or Extraversion (“E”)
  • Intuition (“N”) or Sensing (“S”)
  • Feeling (“F”) or Thinking (“T”)
  • Judging (“J”) or Perceiving (“P”)

You may have learned, or been told, that you pick which of the two alternatives for each of the four letters matches you, and that’s your personality type. While that’s technically correct, and for practical purposes will be accurate 70% – 80% of the time, that’s not actually how it works. In type theory, the letters in the four-letter code are not actually what make up a personality type; they are actually shorthand for something else: the function stack.

Every type has a function stack. A “function stack” is a set of four “cognitive functions”. It is the cognitive functions, not the actual letters in the four-letter code (and the concepts they represent, e.g. Introversion, Sensing, etc.), that are what make up a personality type. The cognitive functions are the central concepts of typology.

There are eight cognitive functions in total, and of those eight, each type has four cognitive functions, but not the other four. The eight cognitive functions are:

  • Extraverted Intuition (or “Ne” for short)
  • Introverted Intuition (“Ni”)
  • Extraverted Sensing (“Se”)
  • Introverted Sensing (“Si”)
  • Extraverted Thinking (“Te”)
  • Introverted Thinking (“Ti”)
  • Extraverted Feeling (“Fe”)
  • Introverted Feeling (“Fi”)

These functions can be grouped into two categories: “perceiving” and “judging” functions:

  • The perceiving functions are the intuition and sensing functions (Ne, Ni, Se, Si). Perceiving functions are about information-gathering. They determine how you take in information, and what kind of information you take in.
  • The judging functions are the thinking and feeling functions (Te, Ti, Fe, Fi). Judging functions are about decision-making. Once you’ve gathered information via the perceiving functions, the judging functions interpret the information and come to conclusions about it & make decisions. What kind of judging functions you have determines the basis on which you make decisions.

Function pairs

You need both perceiving functions and judging functions, otherwise you can’t function properly. As mentioned above, each type has a “function” stack comprising four of the eight functions: two perceiving functions and two judging functions. The two perceiving functions you have will be opposites of each other: for example, you will either have Introverted Intuition and Extraverted Sensing, or you will have Extraverted Intuition and Introverted Sensing. Ditto for the judging functions: you will either have Introverted Thinking and Extraverted Feeling, or you will have Extraverted Thinking and Introverted Feeling. I’ll explain what the “introverted” and “extraverted” part of the functions is later on.

The two perceiving and judging functions you have are opposites because, in addition to needing to be able to both perceive and judge, you need to both intuit and sense, and both think and feel. That’s because, as a human with an evolved human brain, you have the capacity to do both; it’s not one or the other.

To use an example, take my type, INTP. My cognitive functions are Introverted Thinking, Extraverted Feeling, Introverted Sensing and Extraverted Intuition. I have both thinking and feeling functions, and both sensing and intuition functions.

Function preferences & the dominant function

However, while each person has the capacity to use thinking, feeling, intuition and sensing, in reality you will prefer one of either thinking or feeling, and one of either intuition or sensing. One will feel more comfortable than the other, and you will use it more than the other and become better at it than the other. It’s similar to the way you are either right- or left-handed: you still have two hands, but through preference and greater use of one hand over the other, one becomes stronger and more dextrous than the other.

In addition to preferring one of each of your perceiving functions and judging functions to the other, you will have a function you lean on significantly more than the other three, called your “dominant function”. It’s probably the function you took to first, or most, when you were a child, and interacted with the world predominantly through the use of that function, drawing on your other functions only when you needed to. Even as you grow up and develop your other functions with increased use of them, you still lean heavily on your dominant function over the others, both through habit and because it becomes the function that’s most comfortable and effortless for you.

Not only is your dominant function effortless, you scarcely notice yourself using it—it becomes like a sixth sense, and you don’t understand why others can’t use it as effortlessly as you do; it’s the lens through which you experience the world, and the water you swim in. It’s absolutely central to your identity.

The function stack

This brings me to the “function stack”. It’s called a “stack” because the functions in the function stack are grouped in order from strongest to weakest, as if they were stacked on top of each other. Going back to my type, INTP, my function stack is (in order):

  1. Introverted Thinking (Ti)
  2. Extraverted Intuition (Ne)
  3. Introverted Sensing (Si)
  4. Extraverted Feeling (Fe)

Introverted Thinking (Ti) is my dominant function. You’ll see that its pair or opposite, Extraverted Feeling (Fe), is at the bottom of my function stack. The pair/opposite of your dominant function will always be your weakest function and at the bottom of your function stack; therefore it’s called the “inferior” function.

The pair of your dominant function is weakest and “inferior” because, with such heavy use of your dominant function, you scarcely exercise its pair. That’s because you can’t use two types of judging simultaneously, or two types of perceiving, because they are diametrically opposed ways of judging or perceiving. Using one function at a given moment necessarily means you are not using its pair, and so the more you use one of a pair, the less you use the other. If you use a function so much that it’s your dominant function, its pair, your “inferior” function, will be severely underused, weak, underdeveloped, immature, and you will be extremely clumsy and uncomfortable in using it.

The second and third functions are known as your “auxiliary” and “tertiary” functions, respectively. If your dominant and inferior functions are judging functions, your auxiliary and tertiary functions will be your pair of perceiving functions, and vice versa. Your auxiliary will be the preferred function of that pair, and the tertiary the non-preferred. So, for INTP again, as my dominant and inferior functions are judging functions, my auxiliary and tertiary are perceiving functions: Extraverted Intutition (Ne) and Introverted Sensing (Si), respectively.

The role of the auxiliary function is to support the dominant function. Because, in interacting with the world, you need to both judge and perceive, if your dominant function is a judging function, your auxiliary function will be a perceiving function (and vice versa). And because you interact with an external (objective) world and an internal (subjective) world, if your dominant function is an extraverted function, your auxiliary function will be an introverted function (and vice versa).

The latter is the reason your auxiliary function will always be the opposite orientation to your dominant function—your dominant and auxiliary can’t be both introverted functions, or both extroverted functions, because you need to relate to both the external and internal worlds, both the world of things and people outside you, and the world of ideas, impressions, thoughts and feelings inside you. As your dominant function already does one (either extraversion or introversion), your auxiliary will do the other.

So, your dominant and auxiliary functions together will be your primary ways of both perceiving and judging, and both extraverting and introverting. The role of the tertiary and inferior functions is to supply the needs that the dominant and auxiliary can’t supply. I’m an INTP, I mainly judge with Introverted Thinking (Ti) and perceive with Extraverted Intuition (Ne); but I also sense and feel, albeit less and not very well. For my sensing and and feeling needs, I use Introverted Sensing (Si) and Extraverted Feeling (Fe).

The four-letter code

So, the function stack converts into the four-letter code you’re familiar with, as so:

  1. The 1st letter (“E” or “I”) represents the orientation (extraverted or introverted) of the dominant function.
  2. The 2nd letter (“N” or “S”) represents which type of perceiving function you use primarily: intuition or sensing.
  3. The 3rd letter (“T” or “F”) represents which type of judging function you use primarily: thinking or feeling.
  4. The 4th letter (“P” or “J”) represents which category of function you primarily extravert with: perceiving or judging.

So, for an INTP, my first letter is “I” because my dominant function, Ti, is introverted. My second letter is “N” because I primarily use intuition over sensing. My third letter is “T” because I primarily use thinking over feeling. My fourth letter is “P” because I primarily extravert with a perceiving function: Extraverted Intuition (Ne).

Taking any type, you can reverse-engineer its function stack. Let’s take ESFP, for example:

  1. The “S” and “F” indicate that ESFP uses sensing and feeling as its modes of perceiving and judging, respectively.
  2. The “P” indicates that ESFP extraverts with a perceiving function, which will be its sensing function, so, ESFP’s sensing is extraverted: Extraverted Sensing (Se).
  3. The “E” indicates that ESFP’s dominant function is extraverted. Since Se is ESFP’s extraverted function, ESFP’s dominant function will be Se.
  4. As ESFP’s dominant function is an extraverted perceiving function (Se), its auxiliary function will be an introverted judging function. ESFP’s primary mode of judging is feeling, which makes its auxiliary function Introverted Feeling (Fi).
  5. ESFP’s tertiary function will be the opposite of its auxiliary function: Extraverted Thinking (Te).
  6. ESFP’s inferior function will be the opposite of its dominant function: Introverted Intuition (Ni).
  7. ESFP’s function stack, therefore, is: Se-Fi-Te-Ni.

What the cognitive functions do

So, after all that, the fun part: this is where I explain what the cognitive functions actually do.

First, I need to explain what sensing and intuition, and thinking and feeling, are. As you now know, sensing and intuition are two ways of perceiving (information-gathering), and thinking and feeling are two ways of judging (decision-making).

Taking the perceiving functions first, sensing gathers information that can be gathered with the five senses, and information that is “concrete”, material and verifiable. Intuition gathers information that is abstract and conceptual, and relies on seeing patterns and making connections between data points. Sensing takes things as they are in reality and focusses on the material, “real” facts and data in front of it, whereas intuition attempts to peer around the corner, see how things relate to other things and envision the possibilities of what things could be.

As for the judging functions, while thinking and feeling can be (not unfairly) stereotyped as “logic” versus “emotion”, it’s not as simple as that. It’s really the difference between evaluating things, and making decisions, based on standards that are impersonal and empirical/system-based (thinking), or standards that are values- and people-based, i.e. values about how people should relate to each other (feeling).

As foreshadowed above, the “extraverted” and “introverted” aspects of the functions is about whether, in using the function, you are directing your attention and energy toward the objective world of people and objects outside of you (extraverted), or toward the subjective world of thoughts, ideas, feelings, impressions, memories, consciousness and personal experience inside of you (introverted).

So, here we go:

Extraverted Sensing (Se) is highly attuned to the physical and material world around it. It takes in sensory information from its physical surroundings in real time—objects and people, and changes in its surroundings—and reacts fluently and confidently in the moment. Se seeks out stimulation from the physical and sensory world, which is why you will find many Se-users among sportsmen, artistic people, cooks and foodies, outdoorsy types, party animals and accomplished flirts.

Types that use Se as a dominant function are ESFP and ESTP. Types that use Se as an auxiliary function are ISFP and ISTP.

Introverted Sensing (Si) is highly attuned to its own, personal, subjective experience, i.e. how an experience is affecting the Si-user personally & how it is making the Si-user feel. Si then takes these subjective impressions and stores them, and creates a vast store of such subjective experiences, impressions and memories. It uses that store as a framework for interpreting new experiences, by way of comparison and reference. Because of this, Si-users tend to develop a very unique and personal way of looking at the world, because they view present experiences through the lens of their past experiences. This can make them hidebound and tied to what they know, and uncomfortable with new things and things that challenge what they know from their past experiences.

Types that use Si as a dominant function are ISFJ and ISTJ. Types that use Si as an auxiliary function are ESFJ and ESTJ.

Extraverted Intuition (Ne) sees new possibilities and opportunities about what can be. It does this mainly by seeing connections and patterns between ideas. It is always seeing new patterns and throwing up new possibilities for how reality can be changed. Ne-users tend to generate a lot of novel, unconventional and original ideas, and quickly see unexpected and apparently random connections between ideas and things.

Types that use Ne as a dominant function are ENFP and ENTP. Types that use Ne as an auxiliary function are INFP and INTP.

Introverted Intuition (Ni) stores subjective patterns and interpretations in much the same way Si stores subjective experiences. This store of patterns and interpretations creates a framework for interpreting new events and phenomena that the Ni-user encounters. Ni-users are therefore highly attuned to (how they interpret) things will play out, and (what they interpret to be) the “essence” and “deeper meaning” of things. They use their tendency to visualise the future in order to guide their actions.

Types that use Ni as a dominant function are INFJ and INTJ. Types that use Ni as an auxiliary function are ENFJ and ENTJ.

Extraverted Thinking (Te), a judging (decision-making) function, evaluates and makes decisions based on objective rational standards, being rules, procedures, external systems, empirical data, and results. Ultimately Te asks “what works? what gets the best results?” Te wants to organise and rationalise the external world by imposing procedures and systems, and Te-users will often be meticulously organised in their own personal and work/study lives.

Types that use Te as a dominant function are ENTJ and ESTJ. Types that use Te as an auxiliary function are INTJ and ISTJ.

Introverted Thinking (Ti) evaluates and makes decisions based on its own, subjective understanding of how things work. Whereas Te asks “what works (in practice)/gets the best results?”, Ti asks “what makes sense (to me)?”. Ti wants to boil things down to first principles and understand on a conceptual level how things work. Ti constructs a logical framework for understanding things/the world that is ultimately based on its own subjective reasoning (“what makes sense to me?”) rather than objective standards and evidence.

Types that use Ti as a dominant function are INTP and ISTP. Types that use Ti as an auxiliary function are ENTP and ESTP.

Extraverted Feeling (Fe) evaluates and makes decisions based on interpersonal standards, i.e. what promotes interpersonal harmony, what makes everyone feel good, what’s best for others. Similar to the way Te puts stock in external impersonal systems and procedures, Fe attributes importance to external personal systems and procedures, such as social norms and rules, forms of social organisation and status, social traditions and social authorities, because such things, Fe sees, promote interpersonal harmony and reduce conflict. Fe-users tend to be highly attuned to the way other people feel, and tend to be naturals at empathising, dialogue, bringing people together, and leadership.

Types that use Fe as a dominant function are ENFJ and ESFJ. Types that use Fe as an auxiliary function are INFJ and ISFJ.

Introverted Feeling (Fi) evaluates and makes decisions based on the Fi-user’s own personal values and understanding of good and bad & right and wrong. Fi-users are highly in touch with their own feelings and will always know how they feel about things. Authentically expressing one’s own feelings, values and identity, and remaining true to one’s own values, is extremely important to Fi-users. Fi-users will not care for interpersonal harmony and social norms and organisation the way Fe-users do if those things conflict with the Fi-user’s personal values.

Types that use Fi as a dominant function are INFP and ISFP. Types that use Fi as an auxiliary function are ENFP and ESFP.

Typing yourself and others

Now that you know what goes into a personality type (cognitive functions in a particular order), and what cognitive functions go with what types, you should be equipped to go out and do some type-spotting (starting with yourself!). To be fair, there’s more to type theory than what I’ve written in this post—this is “MBTI for dummies” after all—but, with a knowledge of the basics, you should be able to type people with decent accuracy.

What you’re looking for, above all, is a person’s dominant function. What’s the function that dominates their personality? What do they do so effortlessly it’s like a sixth sense? With extraverts, whose dominant function is extraverted, it shouldn’t be difficult to determine this, as their extraverted dominant function is out there in the open for all to see. With introverts, whose dominant function is introverted, it can be a bit trickier. The side of themselves introverts show to the world will often be their auxiliary function, which is extraverted, whereas their introverted dominant function can be quieter in their interactions with most people. It’ll take getting to know some introverts to see their dominant function more clearly.

One way to determine an elusive dominant function is to look for a person’s inferior function, which you do by asking “what do they really suck at? what do they suck at so much it causes them anxiety and stress? what’s the thing they run away from because of how uncomfortable it makes them?” Once you’ve pinned down an inferior function, you can deduce their dominant function (which is the inferior function’s opposite).

Determining between intuition and sensing can sometimes be a source of confusion. To be clear, not every person who has ever had an abstract thought, or enjoys talking about abstract things, is an intuitive. Sensors can intuit and intuitives can sense. Look for what they’re better at and more comfortable with. Look for how they express themselves: in concrete, straightforward language (sensors), or in generalisations and analogies (intuitives). Look for what they’re interested in: abstract things like personality theory, particle physics, philosophy and Doctor Who fanfiction, or sensory things like sport, arts, food, fashion and all-night raves.

Also don’t make the mistake of assuming that being intellectual means a person is a thinker, or that being emotive means a person is a feeler. Thinking and feeling (judging) is about a person’s underlying motivations for making decisions and evaluating things, rather than their abilities or behaviour. Do they make their decisions based on impersonal, “rational” standards, or with reference to people, their feelings, and people-focussed values.

Ultimately you can get away with using the “dichotomous” method of picking which letters in the four-letter code most applies to a person, which will be accurate 70-80% of the time, but it’s best to verify by identifying a person’s cognitive functions. Moreover, “extravert sensor feeler perceiver” just doesn’t tell you much. Knowing how the cognitive functions work allows you to understand so much more about why a person is the way they are, than the dichotomous four-letters method.

If you’re interested in reading my thought process in identifying a person’s type, you can look at any of my Typing Doctor Who blog posts, where I type Doctor Who characters and show my reasoning. So far I’ve done Clara Oswald, the Eleventh Doctor, Sarah-Jane Smith, Rose Tyler, Amy Pond and Victorian Clara.

Part 2 – Going deeper

When I began writing this post, I didn’t intend it to be more than a single part. However, in the process of organising all this information in what has hopefully been a clear and simple way, I was reminded of how much more there is to type theory. To properly accurately type people, and genuinely understand how they work using type theory, requires knowledge of the deeper aspects of type theory.

I’m going to go deeper into type theory in a Part 2 post. This will cover subjects such as inferior grips, dominant-tertiary loops, function dynamics, type maturity and growth, the significance of types of functions in different positions, and anything else relevant I think of in the meantime.

Happy typing!


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