The 8 Cognitive Functions
Psychologist Carl Jung was first to observe that our brains have 8 basic, fundamental functions that it performs and that these express themselves differently in each of us.
Each of us has a "dominant" function that is our strongest function and the one that comes most naturally. For discussion sake, assume it describes about 75% of who we are.
Your strong points and the things you are really good at doing will usually be a direct result of what your dominant function is.
Each of us has an "auxiliary" function. It is our second strongest function and it supports the dominant function. Assume the auxiliary function describes about 15% of who we are.
Together the dominant and auxiliary describe about 90% of us. By age ~20, both of these functions are normally well developed.
Thus if you know someone's dominant and auxiliary function you can predict many things about their behavior and their preferences.
This is the key to understanding people who are different than us.
The 3rd and 4th function develop later in life and tend to represent areas where we are challenged. Areas where you might be weak or troubled can be predicted by knowing your 3rd and 4th function.
The 5th through 8th cognitive functions are considered to be unconscious. Meaning that you aren't normally aware of them. They are weak sometimes negative functions that tend to pop up and surprise you when under stress.
The 4 letter personality type code, is simply a way to identify what order the functions appear in each of us. For example, an INTJ will have a Introverted iNtuition as a dominant, with Extraverted Thinking as the auxiliary.
An ESFP will have a dominant function of Extraverted Sensing and an auxiliary of Introverted Feeling.
To see how all 8 functions play out for each of the 16 Types, click here.