Basic MBTI Theory

Many people have taken the MBTI (Myers–Briggs Type Indicator) test and received their own four-letter code and corresponding personality type description. But what do these letters actually mean? How are they related to each other? How are personality type descriptions determined? How can we infer the type description from the letters, or deduce the letters from someone’s behavior?

This tutorial approaches MBTI from a Ti perspective, drawing on authoritative English MBTI materials. It explains the underlying theory in a clear, logical, and easy-to-understand way, while pointing out common misunderstandings about MBTI online. The tutorial ends with a diagram summarizing its content.

1. The Four Dimensions of MBTI

MBTI consists of 4 dichotomies. The first and fourth reflect orientation, while the second and third represent functions. The four dimensions are:

• E-I: Energy orientation

  • Extraversion (E): Focuses primary energy on people and things in the external world

  • Introversion (I): Focuses primary energy on experiences and ideas in the internal world

    E does not mean sociable, and I does not mean shy. E-I reflects where one directs energy.

• S-N: Perceiving functions

  • Sensing (S): Perceives specific details through senses and memory

  • Intuition (N): Perceives abstract meanings through exploration and insight

    For example, when perceiving an apple, someone using S might describe its color and taste; someone using N might talk about its health benefits.

• T-F: Judging functions

  • Thinking (T): Analyzes things logically and makes objective, rational decisions

  • Feeling (F): Understands others’ needs and makes value-based decisions

    For example, when interviewing candidates, a T-type person might set objective scoring criteria and rank applicants by score; an F-type person might subjectively assess value based on personal circumstances and team impact. F does not mean emotional.

• J-P: Orientation toward the outer world

  • Judging (J): Prefers decisiveness and closure, dealing with the outer world using judging functions

  • Perceiving (P): Prefers flexibility and spontaneity, dealing with the outer world using perceiving functions

    J does not mean judgmental, and P does not mean perceptive in the casual sense. J-P reflects one’s outward lifestyle.

Based on preferences across these four dimensions, there are 16 distinct personality types, each labeled with four letters. For example, INFP means Introverted, Intuitive, Feeling, Perceiving.

2. Cognitive Functions

Behind the four dimensions are 8 mental functions, derived from the perceiving and judging functions combined with the energy orientation (E/I). They are:

• Perceiving functions

  • Extraverted Sensing (Se): Gains immediate concrete details from the external world through sensory experience

    High-Se types often react quickly to external changes, have strong rhythm and hands‑on skills, and enjoy sensory experiences.

  • Introverted Sensing (Si): Recalls past memories and details from the internal world by storing facts

    High-Si types tend to be reliable, stable, traditional, responsible, and rely on experience when deciding.

  • Extraverted Intuition (Ne): Discovers future opportunities and possibilities in the external world through exploration

    High-Ne types often think divergently, excel at association, pursue possibilities, and dislike routine.

  • Introverted Intuition (Ni): Understands abstract connections from the internal world through foresight and insight

    High-Ni types are sensitive to abstract and mysterious ideas, sense patterns, and grasp the big picture.

• Judging functions

  • Extraverted Thinking (Te): Organizes the external world efficiently and logically through direct, clear reasoning

    High-Te types are direct, decisive, good at leadership, efficient problem‑solvers, and focus on optimization.

  • Introverted Thinking (Ti): Builds internal logical frameworks by objectively analyzing things

    High-Ti types are objective, logically rigorous, curious about fundamentals, and often think in ways others struggle to follow.

  • Extraverted Feeling (Fe): Maintains harmony in the external world by understanding others’ values and needs

    High-Fe types are empathetic, responsive to emotional needs, and considerate in communication.

  • Introverted Feeling (Fi): Builds core personal values internally by listening to one’s inner self

    High-Fi types are introspective, sincere, and emphasize that their authentic values should not be controlled by others.

If we compare cognition to a computer receiving input and producing output, the 8 functions can be illustrated as:

Based on the J-P dimension (outer world orientation), the eight functions can be regrouped:

• Extraverted perceiving functions (Se, Ne) and introverted judging functions (Ti, Fi) correspond to P (perceiving the outer world).
• Extraverted judging functions (Te, Fe) and introverted perceiving functions (Si, Ni) correspond to J (shaping the outer world).

From this, we can see: if J-P were defined by inner-world orientation, perceiving the outer world would mean judging the inner world, and judging the outer world would mean perceiving the inner world. J types, who are decisive outwardly, may be less structured internally; P types, flexible outwardly, may strongly defend their inner logic or values when challenged.

3. Type Dynamics

Everyone has all 8 cognitive functions, but with different preferences. Among the 16 types, functions are ranked by preference into: Dominant, Auxiliary, Tertiary, and Inferior. This is Type Dynamics.

• The Dominant function is used most often.
  • E types have a dominant function with subscript e; I types have i.
  • P types’ dominant is among Se, Ne, Ti, Fi.
  • J types’ dominant is among Te, Fe, Si, Ni. Example: INFP dominant = Fi; ESTJ dominant = Te.
• The Auxiliary function is second-most used and balances E/I.
  • E types have auxiliary i; I types have auxiliary e. Example: INFP auxiliary = Ne; ESTJ auxiliary = Si.

In type dynamics, E types show their dominant function outwardly; I types show their auxiliary outwardly and keep dominant inward. Thus, I types are often underestimated in daily interaction.

The Tertiary function is partially reversed from the Auxiliary; the Inferior is reversed from the Dominant. The tertiary and inferior are less preferred and may be overused under stress or neglected. The method for identifying these four functions is summarized below.

4. The 16 Personality Types

Using type dynamics (Section 3) and cognitive function descriptions (Section 2), we can derive the function stack and typical traits for each type, as shown below.

Note 1: According to the reference materials, the tertiary function includes both introverted and extraverted forms. The widely circulated “full 8-function order” found online is not cited in this manual or other academic literature.

Note 2: “Key Associated Traits” are translated directly from selected textbook descriptions; some nuance may be lost.

When understanding the 16 types, keep in mind:

• Each type is more than a combination of four letters; it reflects the interaction of cognitive function preferences in type dynamics.
• Scores on MBTI results reflect preference, not skill, ability, or proficiency.
• Although society often favors ESTJ traits, no type is “better” or “worse.” Each type’s strengths are a gift to the world.
• You may use type to understand or forgive yourself, but not as an excuse to avoid action. Type does not limit your career, activities, or relationships.
• Every individual is unique; personality is complex, and MBTI cannot explain everything.

5. Personality Type Development

Type theory holds that people are born with innate preferences among the 8 cognitive functions. Personality type is determined at birth and does not change over time.

During development, the dominant and auxiliary functions are strengthened, while opposite functions are somewhat neglected, leading to differentiation. This produces the typical traits associated with the dominant and auxiliary functions.

In adolescence, the innate dominant and auxiliary develop first, helping one find a comfortable place in the world. In middle age, people often develop the previously neglected functions to become more whole, without changing their innate type or preferences. They simply become more flexible.

The ideal goal of type development is not equal use of all functions, but early differentiation of dominant and auxiliary, acknowledgment of the inferior, and later conscious use of non-preferred functions when appropriate.

Environment and major events may distort or suppress natural type development, leading someone to become skilled at non-preferred functions but feeling unsatisfied or incompetent when using them. Thus, MBTI results may not always reflect one’s true, innate best-fit type.

6. Summary

References

• MBTI manual: A guide to the development and use of the Myers-Briggs Type Indicator, Third Edition. Isabel Briggs Myers, et al.
• Introduction to Type, Sixth Edition. Isabel Briggs Myers.
• Introduction to Jungian Cognitive Functions, Jung Psychological Assessment, https://mp.weixin.qq.com/s/KR-6adxKueOq1mwjHMBnpw