MBTI and Age

How Your Personality Type Develops With Your Age

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Have you ever looked back on your life and cringed at mistakes you made or the way you behaved? I know I have, and still do. As a teenager I lived like there was no tomorrow, making a multitude of mistakes, taking risks, and trying hard to fit in with a group of teenagers that I had absolutely nothing in common with. I’d grown up in a fairly solitary way; a dorky homeschooled kid who never got up the nerve to make many friends. As a teenager, I switched gears, remade myself into what I thought was the socially ‘cool’ thing to be, and created a completely false persona that I tried to pass off as “me.”

Not sure what your personality type is? Take our new personality questionnaire here. Or you can take the official MBTI® here.

The truth is that a lot of people have a time in their life when they’ve had to ask themselves “What was I thinking?” For some people their age of ‘crazy’ is the teenage years, for others it’s a mid-life crisis, others find themselves feeling as if their whole identity has changed in their 60’s or 70’s. I’ve often wondered what happens to people or what changes to make them go through these stages in their lives. Obviously, a lot has to do with factors like environment, health, changes in stress, or hormones. But does your personality type have anything to say about these changes? I wanted to find out.

You have to have a relatively good understanding of the cognitive functions to understand what the rest of this post is about; you can find out more about these here

Your Age and the Development of the Cognitive Functions

Your Dominant and Auxiliary Functions

From birth to about age 13, you will develop your dominant function. This function will be the most obvious in children and will be the one they develop the most control of in their lives. You will see glimpses of their auxiliary function as well, but it will still be underdeveloped and not quite balanced.

From 13 to about age 21, you will develop your auxiliary function. This function will support your dominant function. If you’re an introvert, your auxiliary function will be the one you show to the outside world while your dominant function will be more hidden.  

The dominant and auxiliary functions are the most powerful facets of your personality and are generally where you have the most natural strength and ability to grow.

How do these cognitive functions affect teenagers?


The teenage years are tumultuous for almost everyone in some way. Part of this has to do with your brain development. Research has shown that the human brain doesn’t fully mature to adulthood until the early 20s. In the teen years, the parts of the brain responsible for controlling impulses and planning ahead are the last to mature. Along with this, you have hormonal changes, the pressures of life (figuring out where you’ll go to college, getting a good score on the SAT, fitting in with your peers) and you have a breeding ground for stress and chaos. Don’t get me wrong, the teenage years can be full of magic, wonder, and possibility. Being a teenager can feel like being on a roller coaster of highs and lows. When it comes to your personality type and the teenage years, you really haven’t fully developed your auxiliary, tertiary, or inferior functions well enough to be fully balanced. You are still relying very heavily on your dominant function and are just learning how to balance that out with your auxiliary function.

The Tertiary and Inferior Functions

From the age of 21 to the mid-40s, you will develop your tertiary function. While this will never be as strong as your dominant or auxiliary functions, it will help to balance them out if developed properly. 

From your 40s through your 70s, you will develop your inferior function more completely. This function will always be a weak point in your personality because it is never going to be nearly as easy to use as your dominant or auxiliary function. However, with proper practice, you can use it with much greater ease than you did in earlier life. 

Complete Development of All the Functions

When you’ve reached the age where your inferior function is developing, you may be surprised by a new side of yourself you haven’t seen before. A staunch, logical thinker suddenly finds himself weeping over an insurance advertisement. A woman who has always been highly emotional and people-oriented suddenly develops an interest in mechanics or a more ‘thinker’ type activity.  This doesn’t mean that they disregard their dominant and auxiliary functions, but that now they have developed good control over all their functions and they are able to use them all effectively. The dominant and auxiliary functions will always be the major players in your personality, but now you can enjoy a new sense of balance with the aid of your tertiary and inferior functions.

When Problems Arise

There will always be those who don’t focus on developing their functions well. Some people are so in love with their dominant functions that they focus on them to the complete exclusion of their other functions. This is why it’s important to work at using and considering all your functions. Of course, you will be most comfortable with your dominant function, and by all means, find activities and pursuits which utilize that great strength you have. Just make sure to take some time to notice and exercise your other functions to achieve a healthier, more balanced life. 

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Find out more about your personality type in our eBooks, Discovering You: Unlocking the Power of Personality Type,  The INFJ – Understanding the Mystic, and The INFP – Understanding the Dreamer. You can also connect with me via Facebook, Instagram, or Twitter!

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  1. As a nearly 21 yr old ENFP I am just waiting for that tertiary extroverted thinking process to start kicking so I can finally get something done effectively lol 😆

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