About the MBTI® Instrument
Exploring Type beyond the Four Letters
Myers’ J-P dichotomy completed the structure for Jung’s psychological types; it provided a formula for identifying our dominant and auxiliary functions. The formula also established a preference order for use and development of the four basic functions
within each of the 16 types, and the attitude
in which each function appears within a type. In other words, Myers provided us with a theoretical order for how we prefer to use each of Jung’s functions
– how we naturally distribute our energy between these eight mental functions to operate in the world. Although we use all eight, we will concentrate on the first four – keeping in mind that we can use and do use all eight.
The dominant (or leading) function is the first of the eight mental processes (Functions-in-Attitude) in the type hierarchy of each of the 16 types. It appears as one of two middle letters of the type code.
The dominant function is the mental process that guides the personality; the one that we habitually use more than the other seven mental functions. The dominant function provides the overall direction to the personality and is the way in which we most comfortably adapt to the world; we rely on it the most to guide us through life’s situations, especially during the first half of life.
The second function in the type code hierarchy is the auxiliary (or supporting) function. It is represented by the other middle letter in the type code. The auxiliary function guides the dominant function; it is the function we use the most after our dominant. The auxiliary also provides balance for the dominant in both function and attitude.
The Tertiary Function
The tertiary function is opposite the auxiliary on the same dichotomy; it is used in either the same OR the opposite attitude of the dominant function. The tertiary function does not appear in the four letters of the MBTI® type code.
Theoretically, our tertiary function is easier for us to access and use than our inferior function, but harder to access and use than our dominant and auxiliary. We use the tertiary function, like the auxiliary function, to help the dominant function navigate in a different direction.
The Inferior Function
The inferior function (also known as the fourth function) is opposite the dominant function on the same dichotomy and is in the opposite attitude of the dominant.
We have a harder time accessing, using and becoming comfortable with this function than we do with the other three mental processes in our type hierarchy. The inferior function can be the most problematic of the functions in our type code as it is inherently contradictory to the dominant function that is leading the personality. When we are stressed or tired, the inferior function is the one that is bound to “erupt,” causing us to become “out- of- sorts” or unlike ourselves, or “in the grip” (Naomi Quenk). The inferior function does, however, have its purpose, which is to provide us with an entirely different perspective than is afforded by our dominant function. The inferior function can teach us valuable life lessons, and is considered by Jungians to be the function that bridges the personality to the world of the unconscious