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 pretty solitary; 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’. I know, you’re probably thinking I sound like a complete loser – and you wouldn’t be wrong! I’m embarrassed even writing about this.

In my efforts to be what I thought was “cool” I lost a bunch of weight, wore the trendy clothes, and went along with whatever my friends wanted, to an extent. I couldn’t let go of some of my stronger ideals, which turned off my friends, and always left me feeling like an outsider. I came out of my teenage years pregnant, leaving an abusive relationship, and completely confused about who I was. While not everyone goes quite as crazy as I did in my teenage years, a lot of people have a time in their life when they have 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 their environment, medical issues, 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 make up about 90% of your personality ‘type’ and are going to consistently be your most relied-upon functions. 

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 till the early 20’s. 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 dreams. Being a teenager can feel like being on a roller coaster of high’s and lows. When it comes to your MBTI 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 functions. 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 can 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. 

My Story

I’m 31-years-old now. I’m in the middle of developing my tertiary function, introverted thinking. I find myself being more logical, not as vulnerable to overpowering emotions (although they do still hit me a lot), and I take care of myself better than I did as a teenager. I feel more comfortable using my extraverted feeling around other people, can finally be true to myself around my family and friends, and I’m looking forward to getting to know my inferior function, extraverted sensing, sometime soon. For now I still walk into door frames, trip over my feet, and am pretty bad at using extraverted sensing very well. I’m looking forward to getting a handle on that soon! I hope that learning about the development of these functions can help you to better understand yourself and where you are in life right now. I’d love to hear your thoughts in the comments section!

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Susan Storm

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