According to Carl G. Jung's theory of psychological types, human consciousness is characterized by its preference of the general attitude:
- Extraverted (E) vs. Introverted (I)
It is also characterized by its preferences within the two pairs of its mental functions:
- Sensing (S) - Intuition (N)
- Thinking (T) - Feeling (F)
The three parameters introduced by Jung are dichotomies (i.e. bipolar dimensions where each pole represents an opposite preference). Jung proposed that
in a person one of the mental functions is dominant.
Isabel Briggs Myers proposed that a fourth dichotomy, with the opposite poles of judging and perceiving,
also influences the characteristics of personality type:
- Judging (J) – Perceiving (P)
All possible permutations of the 4 criteria above yield 16 different combinations representing which of the opposite poles in each of the four dichotomies dominates in a person, thus defining 16 different personality types.
The 16 personality types can be assigned a combination of 4 letters (an acronym) corresponding to the opposite poles in each of the four dichotomies.
The first letter in a personality type name corresponds to the first letter of the attitude preference (“E” for extraversion and “I” for introversion).
The second letter in a personality type name corresponds to the preference within sensing-intuition pair: “S” stands for sensing and “N” stands for intuition (to distinguish from “I” for introverted attitude).
The third letter in a personality type name corresponds to preference within the thinking-feeling pair: “T” stands for thinking and “F” stands for feeling.
The forth letter in a personality type name corresponds to a person’s preference within the judging-perceiving pair: “J” for judging and “P” for perception.
- ISTJ stands for an Introvert, Sensing, Thinking, Judging
- ENFP stands for an Extravert, iNtuitive, Feeling, Perceiving
And so on.
What do the percentages next to the personality type letters mean?
Humanmetrics Jung Typology Test™ (JTT™) and Jung Typology Profiler for Workplace™
(JTPW™) instrument determine the expressiveness of each of the four personality type
dimensions (Extraversion vs. Introversion, Sensing vs. Intuition, Thinking vs. Feeling,
and Judging vs. Perceiving.
In JTT™ and JTPW™, the scales of these four dimensions represent a continuum between two opposite poles, from 100 at one pole to 100 at another pole. I.e. Extravert-Introvert dimension is a continuum from 100 on Extraversion (i.e. a respondent is a 100% extravert) to 100 on Introversion (i.e. a respondent is a 100% introvert). In other words the scale is 200 units long:
Extravert [100% - - - 0% - - - 100%] Introvert
People may reveal features of both poles but typically have a preference of one way over the other. The letter indicates the preference and the percentage indicates the extent of it.
The E-I score of 0% means the respondent is at the borderline between being an extravert and an introvert. Having Extraversion score of greater than 0 - e.g. 20% - means being 20% more slanted toward Extraversion over Introversion. Having Introversion score of greater than 0 - e.g. 20% - means being 20% more slanted toward Introversion over Extraversion.
The same pertains to the S-N, T-F, and J-P dichotomies.