What if the MBTI types were given a third option for each axis that is slight to mild?
Introvert, Extrovert, Ambivert.
iNtuitive, Sensing, Biperceptual.
Feeling, Thinking, Conscientious.
Judging, Perceiving, Discerning.
So then I realized that what I proposed here is a great indicator of type for those who are ambiguous...
If your I and E are close to equal, your dominant and secondary functions are close to equivalent, but also your tertiary and inferior functions are close to equivalent each other, though less than the former.
If your Perceptual functions are close to equivalent, then you're perception functions are likely your secondary and tertiary.
If your Judging functions are close to equivalent, then you're perception functions are likely your secondary and tertiary.
If your J and P are close to equal, your extroverted reasoning and your introverted reasoning functions are close to equivalent.
Also notice that many people who have ambiguous I and E, also have ambiguous J and P, due to balanced cognitive functions.
For an example of how to use this to help determine your closest type fit... in my case, my Ni and Fe are almost equal, and score around 40 on the cognitive functions test. My Ti and Se are also almost equal and score around 30. This leaves me with no doubt that I am an NF, but my I/E and J/P have always been indecisive, so I am an
ANFD. In my case, the J/P is more clear, which means that my J functions have slightly more weight, and therefore my dominant J function is an extroverted function, making me an
ANFJ. But, because I can rule this factor out, it means that my J functions are my dominant and (by proxy) inferior functions. Since F is my lead J, this means I am an
ENFJ.
Therefore, according to this, all the
INCJs are normal
INFJs, because you have roughly balanced secondary and tertiary J functions, Fe and Ti respectively.
Also, the
INCDs are also likely
INFJs because if you have balanced J functions, your Ni and Se equal the weight of them, resulting in ambiguity between J and P. But, because you're not ambiguous about your I and N dominance, you're very likely Ni dominant, making you
INFJs.
In both respects, you're well developed cognitively.