Introverted and Extroverted Cognitive Functions
What is the difference between introverted and extroverted cognitive functions? The speed at which they fire.
Imagine your brain is constantly sending impulses and is in a constant dialogue with itself. It is constantly processing stimulation and information. Now, imagine that there are introverted and extroverted cognitive functions.
The primary difference between a cognitive function is the speed at which it is used. Actually, you can use any cognitive function, so yes, an INFJ can use Extroverted iNtuition or Extroverted Thinking, it is just not that comfortable for them to do so without external tools or help.
Both Introverted iNtuitives and Extroverted iNtuitives are really doing the same thing, just at a different speed and in a different way. Introverted iNtuitives need to make less connections and need less stimulation to start processing and formulating theories about what is happening, while the Extroverted iNtuitive needs to make more connections, and faster, in order to gain a grasp of what is happening. But both functions are trying to do the same, explain the abstract world, the unknown, and solve mysteries and understand theories.
When you engage in a cognitive function more slowly, you also do so more elaborately. You have more time to sift through and think about the connections you make. You are in less of a rush to reach a conclusion, and can make sure that you are following a linear path. Your process is more methodical and careful. But you need more time to get started and to reach the conclusion. The speed at which you use your dominant function can be indicative of if it is extroverted or not.
"But I'm an Introvert and I can think fast in certain ways!"
It needs to be said that Introverted types can still think very quickly, especially in areas where they have already spent a long time doing research. If an Introverted iNtuitive is talking about a field which is in their comfort zone, they can quickly access relevant insight and input to share that relates to this specific field, but if you take them outside their comfort zone, you will find that they are much more slow and take much longer time to follow.
It doesn't mean one is smarter or better than the other. We live in a fast-paced world, but fast doesn't always win the race.