ISTJ Development

To understand the ISTJ’s development, we have to understand the hierarchy of mental functions for the ISTJ. The hierarchy of mental functions for the ISTJ is about which mental function (Sensing, Intuiting, Thinking or Feeling) the ISTJ is most comfortable with using and which they are least comfortable in using.

Without going too much into Type dynamics, let’s look at the ISTJ’s hierarchy of mental functions:

The ISTJ is most comfortable with using the Dominant Function, Introverted Sensing and least comfortable with using the Inferior Function, Extraverted Intuition.

Childhood to Puberty


As a child, ISTJs will develop Introverted Sensing. They will show their preference for the world of activity and games rather than the world of fairy tales and stories.

They will be interested in the real world, preferring to see and touch something rather than hear about it from a storybook.

They will also usually be in tune with what is going on around them in the classroom and at home, responding to detail in colour, shape, size and showing awareness when interacting with people.

If they have not properly developed this function, they may make judgments or take action too quickly without first considering the facts.

Puberty to Age 30


At puberty, the ISTJ will start developing the auxiliary function, Extraverted Thinking.

They will develop the ability to make judgment calls and decisions according to external, objective criteria that are easily observable to all. They become straightforward, frank and objective teenagers who are not concerned at all about popularity or peer pressure.

They may also start to develop intellectual curiosity, desiring to break things down to understand how they work.

If they have not been allowed to develop this function, they may not know how to use their experiences and stored data to engage the world effectively.

Areas of Development

Assuming the environment is supportive of their development of the Dominant and Auxiliary functions, most ISTJs would have developed Extraverted Thinking and Introverted Sensing by 20 years old or so. 

Their areas of improvement will likely come from the underdeveloped sides of Extraverted Intuition and Introverted Feeling. Below are some suggestions for improvement for the ISTJ:

• Be more sensitive toward the feelings of others

• Share your personal side with others occasionally

• Learn to be more comfortable with uncertainty

• Socialize and network with people more

• Consider long-term implications of short-term decisions

• Be patient with and see the positives of spontaneity

Age 30 to Midlife


If these behaviours are not developed by the age of 30, the ISTJ will feel the tension to continue growing, firstly to start developing the tertiary function Introverted Feeling.

The ISTJ may start to show compassion and sensitivity toward those around them; they may even surprise their loved ones with their new-found expressions of love and emotion.

The ISTJ can further develop the Introverted Feeling function through these simple exercises:

• Think about a good quality of another person; find an appropriate time to praise and appreciate that person.

• If you have a conflict with another person, think about what is important to that person in that particular situation and ask yourself if you can suspend your need to be right to preserve the relationship.

• In a group meeting, observe the verbal and non-verbal cues of others and try to gauge the thoughts and feelings of people by observing their body language.

From Midlife


From midlife onward, the ISTJ’s focus turns toward the inferior function, Extraverted Intuition. Their underdeveloped Extraverted Intuition function comes out in a childish and undeveloped way when they are under stress, causing them to over-worry or catastrophize.

But in midlife, there is an unconscious shift and desire to develop that inferior function to achieve wholeness and continual growth. It is an uncomfortable but necessary transition.

Here are some simple exercises to consciously develop the Extraverted Intuition function:

• Brainstorm ideas for activities you can do over the weekend; make a list of things that you have never done before, with people you do not usually meet.

• Read into world affairs across countries and consider global patterns and trends that may link all of these together.

• Write a poem about something from nature without using physical attributes to describe it. (i.e. don’t talk about its colour or shape or size)