The Full Form of ISFJ is Introversion (I), Sensing (S), Feeling (F), Judgment (J).

According to Carl G. Jung’s theory of psychological types [Jung, 1971], people can be characterized by their preference of general attitude:

• Extraverted (E) vs. Introverted (I),

their preference of one of the two functions of perception:

• Sensing (S) vs. Intuition (N),

and their preference of one of the two functions of judging:

• Thinking (T) vs. Feeling (F)

The three areas of preferences introduced by Jung are dichotomies (i.e. bipolar dimensions where each pole represents a different preference). Jung also proposed that in a person one of the four functions above is dominant – either a function of perception or a function of judging. Isabel Briggs Myers, a researcher and practitioner of Jung’s theory, proposed to see the judging-perceiving relationship as a fourth dichotomy influencing personality type [Briggs Myers, 1980]:

• Judging (J) vs. Perceiving (P)

The first criterion, Extraversion – Introversion, signifies the source and direction of a person’s energy expression. An extravert’s source and direction of energy expression is mainly in the external world, while an introvert has a source of energy mainly in their own internal world.

The second criterion, Sensing – Intuition, represents the method by which someone perceives information. Sensing means that a person mainly believes information he or she receives directly from the external world. Intuition means that a person believes mainly information he or she receives from the internal or imaginative world.

The third criterion, Thinking – Feeling, represents how a person processes information. Thinking means that a person makes a decision mainly through logic. Feeling means that, as a rule, he or she makes a decision based on emotion, i.e. based on what they feel they should do.

The fourth criterion, Judging – Perceiving, reflects how a person implements the information he or she has processed. Judging means that a person organizes all of his life events and, as a rule, sticks to his plans. Perceiving means that he or she is inclined to improvise and explore alternative options.

All possible permutations of preferences in the 4 dichotomies above yield 16 different combinations, or personality types, representing which of the two poles in each of the four dichotomies dominates in a person, thus defining 16 different personality types. Each personality type can be assigned a 4 letter acronym of the corresponding combination of preferences: