In the 1920s, Swiss psychiatrist Carl Jung wrote Psychological Types. His work become one of the most widely used personality models in the world today: Type Theory.

You might be familiar with the Myers-Briggs Type Indicator® (MBTI®), a self-report questionnaire that helps people locate where they best fit in Jung’s theory.

After decades of published studies, researchers have confirmed sixteen basic personality types, each of which can be named by a four-letter Type Code (“INFP”, “ESTJ”, etc). Each personality type can also be represented as a cluster of related themes.

This application allows you to quickly assess which of the Sixteen Types fits best for you or an acquaintance, and provides useful information about each Type such as: contributions to teams, what kind of input gets a positive response, and so forth.

Why are there sixteen Types? Here is the full story:

First, Dr. Jung identified four mental functions — today known as cognitive processes. We focus our attention and gather information using Sensing (“S”) and iNtuiting (“N”), and we organize our experiences and make decisions using Thinking (“T”) and Feeling (“F”). These are technical terms; for example, “feeling” here does not mean emotion — it refers to cognition based in values.

Jung then described how each of these four processes plays out in a person’s “internal world” (“I”) of thoughts, feelings, memories and imagination; the “external world” (E) is one of actions, people, tools and organizations. Thus, there are eight cognitive processes:

1. •Extraverted Sensing
   

2. •Introverted Sensing
   

3. •Extraverted Intuiting
   

4. •Introverted Intuiting
   

5. •Extraverted Thinking
   

6. •Introverted Thinking
   

7. •Extraverted Feeling
   

8. •Introverted Feeling
   

By the way, people are familiar with the term “extroversion”, but Jung coined the term and originally spelled it “extraversion” — a spelling still used by practitioners today.

People have potential access to all eight cognitive processes, but in practice develop a preference for only two. Everyone can perceive and make decisions; everyone also has a conscious experience of their personal, internal world as well as the external world around them. A minimal of two processes is needed to cover all of these bases.

For example, someone might have a preference for “Extraverted Thinking” and “Introverted Sensing” — the Thinking process affords decision-making while Sensing affords perception; together, the person has both an Extraverted and an Introverted side.

Of the two preferred processes, one is Dominant: it plays the lead role. If the Dominant process is Extraverted then the person tends to extravert; if the Dominant process is Introverted then the person tends to introvert.

When we take into account the presence of a Dominant process, the result is sixteen personality Types.

In the 1940s, Isabel Myers and her mother created a pencil-and-paper questionnaire to help identify which of the Sixteen Types best describes someone. To keep it simple, the Myers-Briggs Type Indicator® asks people to select from two options along four dimensions of personality, like this:

1. •Extraverting or Introverting?
   

2. •Sensing or Intuiting?
   

3. •Thinking or Feeling?
   

4. •Judging or Perceiving?
   

Myers created the Judging / Perceiving dimension in order to locate which cognitive process a person preferred to show to the outside world. If a Type has a “J” in its Code then the Type shows either Thinking or Feeling to the outside world. Conversely, if a person has a “P” in its Code then the Type shows either Sensing or Intuiting to the outside world.

Since the original questionnaire, many professional statisticians and psychological assessment designers have improved it; creating what is now the most-used assessment today. As of 2008, there are over six-thousand published research studies on Type Theory.

Here is an example that explains the “INFP” Type Code:

1. •The middle two letters in the Code (“NF”) indicate a preference for the Intuiting and Feeling cognitive processes.
   

2. •The first letter (“I”) indicates that the Dominant (Lead) process is Introverted (kept to oneself).
   

3. •The fourth letter (“P”) indicates the process shown to the world is Intuiting (Extraverted Intuiting).
   

Thus, INFP’s dominant cognitive process is: “Introverted Feeling”.

Types share commonalities and differences. As you read about each Type, you will sometimes find similar language. For example, both “ISFP” and “INTJ” share a preference for Introverting; this is apparent from their four-letter Type Codes. You will also find qualities that go beyond the Code; “ISFP” and “INTJ” both take a pragmatic approach to problem solving and feel free to do “whatever it takes to get the job done” — for both, accommodating others’ standards and expectations takes a backseat to getting a useful result. Commonalities are bridges to getting along better on teams — and one-on-one.

Myers hoped that improved self-knowledge would allow people to better choose a job they would enjoy; creating a climate suitable to a more peaceful world. Today, Type Theory is used by counselors, consultants, educators and managers all around the world. The ethical use of this theory demands that people view Type Theory as only one data point about themselves, rather than as a “box” or a “label”.

Improved knowledge of ourselves and others encourages several positives:

1. •We spend less time expecting others to be like us.
   

2. •We spend less time trying to be like others.
   

3. •We spend more time being ourselves; doing what we do best.
   

4. •We find we can flex more often and grow more easily.
   

Remember: everyone is unique. Type Theory is just a model — a convenient fiction. It provides a language or a lens; a start to better understand someone — even when that someone is you!