An Introduction To The Introduction
Interested in what makes others "tick"? Wonder why people think differently to you? Feel like your mind is in an endless, torturous loop where nothing you try seems to work and you can feel your sanity unravelling? You might be interested in learning about MBTI.
Chances are, if you've been on the internet lately, you'll have seen MBTI on people's profiles. "INTP", "ENFJ", "ISTJ"... but what the hell do any of these letters mean? MBTI stands for "Myers-Briggs Type Indicator", and is a form of categorisation or personality typology system. The theory was built on Carl Jung's work, though initially more focused on personality rather than psychology. This is the form of MBTI that you're likely more familiar with — "E" or "I" for extroversion or introversion, "N" or "S" for intuition or sensing, "T" or "F" for thinking or feeling, and "J" or "P" for judging or perceiving. This is known as "letter typing" within online communities, and is regarded by some (including myself) as a rather vague measure of personality, and not very useful outside of that.
Applying Cognitive Functions to MBTI
To remedy this issue, Jung's original model of cognitive functions was applied to MBTI. In my opinion, this creates a much more specific model of MBTI where the separate functions can be applied to everyday scenarios, as well as being useful for self-improvement. This version of MBTI suggests that each MBTI type uses four functions making up their "orientation". A dominant, auxiliary, tertiary and inferior function. These consist of a thinking, intuition, sensing and feeling function that may be extroverted (focusing on the world and environment around oneself) or introverted (focusing inwards on one's body, mind and self).
Thinking — Objective and logical thought used to make decisions.
- Te (Extroverted Thinking) — Established facts and principles, logic and reason. E.g. reading up on something and using those established facts as your truth. Preferring clear-cut rules, guidelines and efficiency.
- Ti (Introverted Thinking) — Information analysis to come up with meaning or a framework. E.g. reading up on something, mulling over that information in your mind and using that to come up with your own version of truth. Preferring reasoning that makes sense to oneself, even if it isn't conventional or efficient.
Feeling — Values, morals and their impact, used to make decisions.
- Fe (Extroverted Feeling) — Social harmony and ethics. E.g. having to make a difficult decision and focusing on what would best benefit everyone and harm the least people. The focus is on other's wellbeing instead of oneself.
- Fi (Introverted Feeling) — Subjective values and beliefs. E.g. making a difficult decision based on what you think is right, what you value and what you want. The focus is on oneself, though this may not necessarily manifest as selfishness but rather strong internal values.
Sensing — The concrete, tangible world and details, used to process information.
- Se (Extroverted Sensing) — The external environment and senses (the external world). E.g. taking notice of physical sensations and using those to process information, preferring hands-on experiences.
- Si (Introverted Sensing) — Past experiences and memory (the internal world), as well as internal feelings. E.g. comparing the present with past events and established patterns. Preferring routine and safety.
Intuition — Abstract patterns and possibilities, used to process information.
- Ne (Extroverted Intuition) — Various possibilities, novel ideas and abstract connections. E.g. viewing a seemingly mundane object and being able to imagine all the different ways it could be used and what it could represent (be associated with). Likely good with metaphors.
- Ni (Introverted Intuition) — An internal vision, planning and strategy. The long-term. E.g. being able to visualise one's long-term path or goal, and what should be done to get there. Cause and effect. This function is commonly associated with chess.

The dominant function comes first in the stack, and is what the rest of the functions "serve". It is developed first in life and will likely be the strongest function and the one you rely on in everyday life. The auxiliary function balances the dominant, typically developing during adolescence. Think of it as a sort of advisor to the dominant function. The tertiary function is less developed than the dominant and auxiliary, and is not as "comfortable" to use. It is the opposite of the auxiliary type (Thinking vs Feeling and Sensing vs Intuition). It is activated during periods of stress. which will be covered in the next section. This function is usually developed in the middle of one's life. Finally, the inferior function is the least developed and emerges during moments of incredible stress.
What's Wrong With Me?? (A.K.A. Loops, Grips and Self-Improvement)
When an individual is under stress, the use and presentation of their cognitive functions can change. This was mentioned briefly in the previous section.

One example of this is a loop — the exaggeration or overuse of two introverted or two extroverted functions within one's function stack. This is commonly between the dominant and tertiary functions, causing the auxiliary function to become "ignored". This can lead to mental instability or seemingly irrational thought processes, as the balancing or mediating nature of the auxiliary function is no longer in effect. This manifests differently depending on the MBTI type.

A grip refers to resorting to the underdeveloped inferior function in a stressful situation where the higher functions have failed. Due to the underdeveloped nature of the inferior function, this leads to immaturity that often worsens the situation at hand.
A Conclusion and Further Reading Material
Learning about MBTI allows you to take a step back and observe yourself and your thought patterns, and decide if what you are doing is really healthy, or if you are struggling in a loop or grip due to stress. Oftentimes we do not realise our harmful behaviour until the damage is done — and so, being able to recognise when you are in a loop or a grip is incredibly useful. Nobody is ever perfect, and we will all have moments in our lives where we do not take the most logical or mature approach to a problem. However, I am a strong believer that everyone has the free will to improve themselves and break out of these cycles of psychological pain — and that knowledge gives us the power to do so. Learning about MBTI was my first step towards my recovery journey, and I hope that this will be useful for someone else, too.
If you want to learn more about MBTI, I recommend checking out the official Myers-Briggs website, my favourite website Type In Mind for further descriptions of cognitive functions in specific MBTI types, and the Sakinorva Cognitive Functions test (though I stand by the opinion that you know yourself better than tests do, and that looking into cognitive functions and deciding for yourself is probably more accurate).
I'll also state as a disclaimer that MBTI is often referred to as a pseudo-psychology or proto-psychology (depending on who you ask) for a reason. Many theories within it are conflicting and there is a significant lack of empirical evidence — a fairly common issue with theories concerning the subconscious or vague ideas such as "personality". Take everything here with a grain of salt — especially as it has been written by someone who is by no means an expert.