I did discuss the varying Function Order Models in the forums before, but I figured I'd create a thread just for this topic. For the sake of clarity, I will simply list the models in this post and save any opinions I have on these models for subsequent posts in this thread.
For the examples in this post I will use ISTP, just for the sake of convenience.
Dominant and Auxiliary Functions
In his book Psychological Types (first published in 1921), Carl Jung discusses eight functions. The Rational functions are Thinking and Feeling, both of which can be Extraverted or Introverted. The Irrational functions are Sensing and Intuitive, which again can be Extraverted or Introverted.
For each type, there is both a Dominant function and an Auxiliary function. The Auxiliary function is of the opposite rationality and attitude, so someone with a dominant Introverted Rational Function (Ti or Fi) would have an auxiliary Extraverted Irrational Function (Se or Ne).
Myers-Briggs Four Function Model, and The Four-Letter Type Code
The Myers-Briggs Type Indicator was first published in 1962. It was with this instrument that the 4-letter type code, and in particular the J/P designation (something Jung did not mention in his work), was introduced.
For Extraverts, ExxPs have an Irrational function (Se or Ne) as their dominant function, while ExxJs have a Rational function (Te or Fe) as their dominant function.
For Introverts, IxxPs have a Rational function (Ti or Fi) as their dominant function, while IxxJs have an Irrational function (Si or Ni) as their dominant function.
The four-function model also features tertiary and inferior functions. The tertiary function is the "opposite" of the auxiliary function, while the inferior function is the "opposite" of the dominant function. When I refer to "opposites" in this sense, I mean the following:
Ti is the opposite of Fe
Fi is the opposite of Te
Se is the opposite of Ni
Ne is the opposite of Si
So, for our ISTP example:
John Beebe's Eight-Function Model
But the four-function model only accounts for half of Jung's eight functions. So what about the other four?
John Beebe, who first published about his model in the 1980s, came up with "Shadow" functions, which are arranged like this:
Ti is the shadow of Fi
Te is the shadow of Fe
Se is the shadow of Ne
Si is the shadow of Ni
The Dominant, Auxiliary, Tertiary, and Inferior functions are the first four (Beebe refers to them as Hero/Heroine, Father/Mother, Puer/Puella, and Anima/Animus). The last four functions, which Beebe calls Opposing Personality, Senex/Witch, Trickster, and Demonic Personality, are the same functions with opposite attitudes. So for our ISTP example, the functions are arranged in the following order:
Lenore Thomson's Brain Hemisphere-Based Model
Research on brain lateralization has shown that behaviors that correspond to Thinking, Feeling, Sensing, and Intuition are in both hemispheres of the brain, with the left brain being more sequential and verbally oriented and the right brain being more holistic and visually oriented. Extraversion has been associated with the front of the brain, while Introversion has been associated with the back of the brain.
Thus, Jonathan Niednagel has associated left-brain dominance with Judging (Js have Te or Fe and Si or Ni as their main functions) and right-brain dominance with Perceiving (Ps have Ti or Si and Se or Ne as their main functions).
Lenore Thomson took this one step further, associating each of the eight functions with a specific part of the brain.
Front-Left: Te, Fe
Front-Right: Se, Ne
Back-Left: Si, Ni
Back-Right: Ti, Fi
In her book, Personality Type: An Owner's Manual (1998), Thomson introduced the idea of Alternatives and Double-Agents. The Alternatives are on the same side of the brain as your dominant and auxiliary functions, while the Double-Agents are on the opposite side. So for our ISTP (right-brain dominant) example, it looks like this:
Right-brain Alternative 1: Fi
Right-brain Alternative 2: Ne
Left-brain Double Agent 1: Te
Left-brain Double Agent 2: Si
Socionics Model A
Unlike Beebe and Thomson, who developed their models based on the work of Myers-Briggs, Aušra Augustinavičiūtė developed her model independently of Myers-Briggs, first publishing at some point between 1978 and 1980.
Model A is difficult for me to explain in words, so I'll just use an example of LSI (ISTj).
- Leading function: Ti
- Creative: Se
- Role: Ni
- Vulnerable: Fe
- Suggestive: Ne
- Mobilizing: Fi
- Observant or Ignoring: Si
- Demonstrative: Te