According to Myers Briggs Educator Danielle Poirier, the dominant mental function is the most distinctive marker of a person’s personality type (aka mbti type). Following this principle, she organizes the 16 Myers Briggs Personality Types in four clusters:
If you examine the MBTI Type letters within each of the four family groups, you’ll note the Personality Types within a given cluster sometimes share only one letter with another member of their group. Some would find this odd, yet none-the-less all the types within a cluster have a solid basis for collaboration and communication because they share the same dominant mental function or mental process.
These four primary Type groups can be further sub-divided based on their energy orientation or attitude (Extraversion vs. Introversion):
Organizing or ordering the Personality Types in this manner flows into a more recent extrapolation of the Myers-Briggs -Jung mental functions. The original four (Intuition, Sensing, Thinking, and Feeling) now become eight when one considers the attitude or direction of the mental function (either Introverted or Extraverted). Thus the mental function of Intuition is divided into two: one mental function is Introverted Intuition and the second is Extraverted Intuition. While the two are related, Type educators who hold to this model believe the differences are enough to warrant the distinction. Some educators, like Hartzler and Nardi (see references and sources at this end of this article), have developed coaching models on these 8 functions - helping people learn to sharpen skills associated with one of more of the 8 mental functions (most typically those skills associated with mental functions that are less favored by a given type)
How you can use the "new" 8 mental functions to determine "Your Best Fit" Personality Type
While the MBTI ® meets the conventional test standards for reliability and validity, accurately measuring something extremely complex like the whole of a person's personality type is beyond the power of our traditional psychometric tools. A whole host of conditions impact the "test taking" situation, including mood, life situation, aspirations, work implications, degree of self-insight, gender expectations, level of psychological maturity, to name just a few. Then add the fact that the human mind is constantly evolving, learning and unlearning things, and maturing-growing. All of these factors are why Isabel Myers originally called her instrument an "indicator." The instrument points in a direction - gives a clue - but not a definitive answer; the MBTI and other similar instruments attempting to measure Personality Type (including my own - the Cognitive Style Inventory) are not tests. They can only point the way; give a general direction.
Sometimes this directional pointing is spot on. At other times, a course adjustment is needed; the identified MBTI Type letters may be close but not correct in identifying which of the 16 Personality Types is a person's best fit. For this reason, an important part of the accredited MBTI administration process involves having the client verify the score through a variety of processes that assist in better understanding key concepts related to psychological type and in doing a degree of self-reflection in understanding (and appreciating) one's own inner workings.
As an MBTI Administrator, one of the most common "type score" uncertainties I've encountered is when the score on the MBTI personality type instrument is close to the borderline between two type letters. For example, a person might score close to the borderline between ENTJ and ENTP. Too frequently they remain uncertain when they employ the accepted practice of reading the respective Personality Type descriptions of the two competing types; they will find a number of phrases in each of the descriptions of characteristics of the two Personality Types that seem to fit.
This is understandable as the two Types do share 3 of the 4 MBTI letters. But if you look at the core mental function of these two types in the above example, they are quite different. ENTJ has at its core Extraverted Thinking; ENTP has at its core Extraverted Intuition. So while the two types share a number of characteristics, the "primary engine" driving each type is different. So what needs to be explored in this case to determine the proper Type affiliation is the nature of these two different mental functions and to what degree each fits the person exploring their Personality Type fit.
Another example. Sometimes the the uncertainty between two type affiliations is not around the core mental function. Perhaps the Type score is near the borderline between INFJ and INTJ - both sharing the core Introverted Intuition as their dominant mental function. Here the distinction is between Extraverted Feeling and Extraverted Thinking. The person may indeed feel equally drawn to Feeling and Thinking - but Type Dynamics theory suggests most typically each would be more comfortably oriented in opposite energy dimensions. A sensitive INTJ will more comfortably Introvert his Feeling nature; a logical INFJ will more comfortably Introvert her Thinking nature . . . and visa-versa.
So it is my belief that by better understanding the nature of the 4 mental functions in their attitudes (Extraverted and Introverted forms) one can determine with greater certainty the best fit within the 16 Personality Types. These are illustrated in more detail on the next page - Understanding the Mental Process Functions of the 16 MBTI Personality Types
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If you are person who is uncertain of your type preferences examine which of the descriptions in the next section seem to best fit your experience and then look at the MBTI type letters aligned with that description.
According to the model, one of the 8 basic styles should seem a natural fit as your core essence and perhaps another one or two styles that act as an auxiliary or complement to your core function. Some of the other functions will seem quite a stretch - being that way would feel foreign. Yet within each of us is a template for better developing all the mental functions (a total of 8 when you consider both the Introverted and Extraverted forms of the 4 basic functions of Thinking, Feeling, Sensing, and Intuition). To the extent you can learn to stretch yourself enough to experience how it is to operate on these functions that are opposite your natural preferences, you’ll find it easier to bridge the gap with those Personality Types who naturally operate on those opposite preferences and mental functions.
Continued - DESCRIPTIONS OF THE JUNG-MYERS-BRIGGS MENTAL FUNCTIONS
THE 16 MBTI PERSONALITY TYPES
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* While commonly called a "test" the MBTI ® is not a test but a personality inventory in which there are no right or wrong answers.