Personal Growth using Myers Briggs Theory

The Mental Muscle Diagram

The Mental Muscle Diagram is a graphical way of representing the dynamics of each Myers Briggs personality type.

The dotted line divides the use of the functions between introversion (to the left) and extraversion (to the right). The size of the ellipse represents how much the function is consciously used, and the order or sequence of the ellipses down the page represents the preferred order of use.

Individual MMDs

Even where two people share the same type code, their uses of the functions can differ greatly. This can be illustrated using the examples (below) of Peter and Alice, two hypothetical INFPs. (Whilst they are not real people, the content of the case studies is a collage of experiences of real people I have encountered).

Case study 1 - Peter

Peter is in his late forties, and although he is clear about his preferences being INFP, his work colleagues were under the impression that he was ENFP or ENTP.

This anomaly can be explained by looking at his Mental Muscle Diagram (left). From this, it is clear that he uses Feeling more than any other function, and Thinking is used least - which is consistent with his type code of INFP. The MMD also shows that Peter uses all the functions in both attitudes, and the overall amount of time he spends introverting (to the left of the line) is only a little more than the time spent extraverting (to the right).

To understand how others might perceive Peter, it can be helpful to hide the left-hand side of the diagram, which highlights the extraverted functions.. This shows that Peter tends to use iNtuition most when dealing (spontaneously) with people, as this function occupies the biggest area to the right of the line. Some Feeling and some Thinking can also be seen, in roughly equal measure, and Sensing appears the least. On this basis, casual acquaintances, who try to work out Peter's type, might be tempted to think that he is ENFP or ENTP.

This view seemed to be supported by the fact that when Peter was introduced to the MBTI on a course at work, the result was ENTP (which included corridor scores on 3 out of the 4 dimensions: E/I, T/F and J/P). On a second workshop, a couple of years later, he realised that, when he had completed the first questionnaire, he had been thinking only about his work persona. He completed the questionnaire a second time, trying to think about his true preferences, and the result was INFP. He felt more comfortable with this as a indicator of the "real" Peter.

Case study 2 - Alice

Alice is a single female in her twenties who has developed use, primarily, of just her dominant and, to some extent, her auxiliary function. Alice is more clearly an introvert than Peter, because she spends more time in the inner world, using her preferred function - Feeling.

However, she has extraverted all the other functions, and she uses iNtuition primarily to deal with other people. Thinking and Feeling are also used, but only to a small degree.

At first meeting, other people usually have the impression that Alice is an extremely quiet but very flexible person. In fact, they sometimes think that she is a bit odd - lacking in direction, easily distracted, and occasionally suggesting some rather odd ideas.

The I, N and P aspects of Alice's character are easy to see, but the Thinking and Feeling preference isn't so clear. This sometimes seems anomalous to people who have a working knowledge of Myers Briggs: for an INxP, either Thinking or Feeling is supposed to be dominant, yet the preference on this one dimension isn't very clear. Alice is usually aloof and reserved, so people most often opt for Thinking, on the basis of her being so apparently detached from others.

However, Alice is very clear about her own type - and when she completed the MBTI, all four dimensions were clear, with scores above 25 on each dimension.

Case study comparisons

Peter and Alice have the same Myers Briggs type, but they are like chalk and cheese in personality terms. Peter demonstrates use of all the functions, but is often typed (incorrectly) as ENFP or ENTP. In fact, it is so clear that he looks like a dominant extraverted iNtuitive, that people are surprised when he declares himself to be an introvert.

Alice, on the other hand, is readily identified as INxP, but is seen as a bit of an enigma. She seems to be clear about which is her own dominant function, but other people are surprised at her conviction, and privately wonder whether she might have got it wrong.

These personality differences are manifest because Peter and Alice have developed their use of the functions to different degrees. Whilst they share the same four-letter type code, their dynamics of type are very different, as their MMDs illustrate. The MMD, therefore, is different for every individual.

Charting Personal Growth

In addition to our MMDs being unique, they are also dynamic - i.e. they change throughout life, as the following case study will demonstrate (again, this is hypothetical, but based on real experiences).

Case Study 3 - William

William is a married male in his thirties who is a middle manager in a professional organisation. He has sought counseling because he is experiencing a great deal of stress in work. At one stage in the counseling, he is introduced to MB/Jung concepts, and the MBTI is administered. Over the course of the next few years, the MBTI is administered on a few occasions again, and the changing results are noted: he started out as INTJ, then INFJ, then ENFP and finally INFP. Although he had not completed the MBTI when in his early twenties, he thinks that he would probably have reported ENTP.

William had been experiencing some of the stages of mid-life, and had come to realise that he had accommodated his personality so much, to suit the demands of the world, that his real personality and preferences had been hidden from his conscious awareness. Towards the end of the counseling period, he charts his personal development through life using the Mental Muscle Diagram.

William identified that, in his early childhood, the functions were probably quite undeveloped and undifferentiated. As in the picture (left) it may have been difficult to distinguish the functions from each other.

As William developed and grew as a child, there were various parental expectations and cultural factors that influenced his development. Two of these were the expectations that:

William's basic need for love and attention would therefore only be met by the use of an extraverted function. Although the process was not conscious, there were two main choices that William faced, as a young child. He could either extravert Feeling, which was his preferred function, or he could develop the use of iNtuition, which is his preferred auxiliary.

However, the culture in which he was being brought up tended to associate T behaviour with masculinity, and F behaviour with femininity. The expectations of acting as a male therefore had the effect of suppressing the development of his Feeling function.

Therefore, William invested the majority of his effort into developing his use of iNtuition, so that his basic needs were met. . This theme continued throughout the majority of his childhood. By the time William reached the late teenage years, his development of the functions was markedly different from that expected of an INFP:

In his teenage years, William's preferences (or, at least, those that he discussed openly with others) seemed to lie in the use of N and T. With the encouragement of careers advisors and others, he studied science subjects in school and at University, and entered into a scientific career.

After several years working in scientific and managerial roles, he presented himself for counseling after experiencing significant stress in a job that was demanding more and more use of his extraverted Thinking function. After a few years of counseling, which also included addressing other mid-life issues apart from type development, William decided to give up his job and start a new career. He is now making decorative glass bottles at a tourist site in the North of England and, whilst poorer, he is undoubtedly happier.

In type development terms, he has set himself the goal of becoming more proficient in his use and understanding of his long-neglected dominant function, and using all the functions in their opposite attitudes. The final MMD (right) represents the goal towards which he is now working.


The Mental Muscle Diagram provides a pictorial way of showing how each individual uses the four functions, and in what attitudes. It is a snapshot in time, because conscious use of the functions changes and develops. Drawing the MMD for various key stages of life can help increase self-awareness and understanding of how one's personal growth has responded to cultural or environmental demands.

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