The most complicated aspect of Myers-Briggs® personality types is also one of the things that makes it a useful theory. It’s the answer to criticisms like “But people aren’t 100% introverts or extroverts” and “Sometimes I use thinking and sometimes feeling, so the test must be wrong.”
Myers-Briggs® theory describes complex, nuanced, dynamic personalities using something called “function stacks.” That term refers to mental processes (functions) that people use in a certain order (stack) of preference. But when you start trying to study function stacks and people are throwing around phrases like “Extroverted Intuition” and “Introverted Thinking” it starts getting confusing, especially after you learn ENxJs don’t even use Extroverted Intuition and IxTJ types don’t use Introverted Thinking. What on earth is going on?
I’ve written about cognitive functions before, but I feel like I’ve always fallen short of explaining the concept both simply and concisely. I’ll link to those more in-depth posts at the end of this article, but right now let’s try and break this topic down for the simplest function stack guide on the Internet.
What J and P Really Mean
Contrary to popular opinion, Judging and Perceiving aren’t a sliding scale. They aren’t even meant to stand on their own as an aspect of your personality — they’re just in your four-letter type to describe how you use the other letters. Thinking and Feeling are both Judging functions because they’re involved in how you make decisions. Sensing and Intuition are both Perceiving functions because they’re about how you learn information.
When you have a J in your Myers-Briggs® type, that simply means you use your Thinking/Feeling process to interact with the outer world. If you’re a P type, then you use your Sensing/Intuition process in the outer world. That’s why we describe an NP type as using Extroverted Intuition and a TJ type as using Extroverted Thinking.
Start Stacking Up
We don’t just have an extroverted side to our personalities, though. We’re a mix of both (though there is one we’ll prefer). If you extrovert your perceiving side (S/N) then your judging side (T/F) is introverted.
That means that an xSFP type uses Extroverted Sensing and Introverted Feeling as their two “favorite” mental functions. An xNTJ type would use Extroverted Thinking and Introverted Intuition. Now that we’ve found our first two functions, we can start talking about how they stack.
Introverts and Extroverts Explained
People with an E in their Myers-Briggs® type lead with their extroverted function. If you’re an ENFP, then you’re leading with Extroverted Intuition. If you’re an ESTJ, you’re leading with Extroverted Thinking. That makes your introverted side the co-pilot (also called the secondary or auxiliary function).
Introverts, on the other hand, lead with their introverted mental process. This means that an IxxP type actually leads with their introverted judging function. Similarly, IxxJ types are dominant perceivers. They use the J/P preference as their co-pilot to interact with the outer world, but it isn’t their favorite mental process 
Rounding Things Out
Once you know a type’s top two functions, the others are easy to find. Your tertiary process is opposite your co-pilot (e.g. types using co-pilot extroverted intuition have tertiary introverted sensing). Your inferior process is opposite your dominant (e.g. dominant introverted feeling types have inferior extroverted thinking). The best way to visualize this is with Personality Hacker’s car model:
And there you have it. Function stacks explained. Now that you know how functions relate to your four-letter type, you can see how powerful this theory is. Your Myers-Briggs® type doesn’t just say whether you’re an introvert or an extrovert, a feeler or a thinker, etc. It’s describing the different ways your mind works, which mental processes you use most comfortably, and allows for every type using both introversion and extroversion, intuition and sensing, and thinking as well as feeling.
Function stacks also help explain things like why ENFPs use intuition differently than INFJs (for example). The ENFP’s intuition is pointed toward the outer world, while the INFJ’s is pointed inward. To learn more about that, check out these posts:
- Introduction To Cognitive Functions: The Learning Processes
- Introduction To Cognitive Functions: The Decision-Making Processes
Featured image credit: ElisaRiva via Pixabay
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Thank you! This is very helpful. And one of the best presented guides I read so far.
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Thanks 🙂
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If you could explain how function stacks work for introverts in more detail, it’d be helpful. I’ve read over it a few times but I still don’t fully understand. This has definitely helped more than any other article has, though!
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I’m glad to hear this article is helpful! Here’s a more complete explanation of what’s going on with introverts’ function stacks:
To briefly recap, if you’re looking at the letters for a person’s type, S/N refers to the Perceiving function and F/T refers to the judging function. If someone is a J-type, then that means their Judging function (either F or T) is extroverted. If someone is a P-type, then that means their Perceiving Function is extroverted. Here are a few examples:
An xNFP type uses Extroverted Intuition (since P tells us their N is extroverted) and Introverted Feeling (since whichever of the two middle letters is not extroverted is introverted).
Same thing for an xSTP type—Sensing (the perceiving function) is Extroverted and Thinking (the judging function) is introverted.
For an xSFJ type, their judging function is extroverted, so they’d use Extroverted Feeling and Introverted Sensing. Similarly, a xNTJ type would use Extroverted Thinking and Introverted Intuition.
For introverts, their dominant function is whichever of those first two functions is introverted. So an INFP leads with Introverted Feeling, an ISTP with Introverted Thinking, an ISFJ with Introverted Sensing, and an INTJ with Introverted Intuition.
The thing that makes an introvert’s function stack a little strange is that their dominant function does not match their J/P preference. Even though an INFP has “P” in their four-letter type, their favorite function is actually their judging function, Introverted Feeling. Similarly, even though an INTJ has “J” in their name, their favorite function is their perceiving Introverted Intuition.
Hope this helps! If you have any other questions that I might be able to answer, let me know 😊
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thank you! this definitely cleared things up a lot.
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