Face:
There is truth to that hypothesis, but it is unnecessary to pretend to be something you are not in order to develop your functions. It is essentially like pretending to be a fish so you can learn how to swim. It could work, but it is a round about method. For instance, trying to act like an ENTJ won't develop Te and Ni, because I don't use Ni or Te to begin with. Instead, serving the same purpose as Te and Ni I have Fe and Si, so the latter functions would end up being developed in that scenario. So it would be much more efficient to zoom into Si and Fe and work on them specifically instead of trying to gain more functions through method acting. The best idea is to have a clear understanding of what you have, what you can do with it, how much energy it will cost, and approach accordingly to how you will "Peak"
Dormouse:
There are so many factors along with what you brought up that also go into skewing the accuracy of an MBTI test, you really can't blame a person for answering in the way they do at all.
I don't understand why you are still taking the test if you already understand your functions? I mean, if you can actually recognize that you are drawn to and stimulated by Ti and Ne, you're an INTP, and that is all there is to it.
Never rely on MBTI to tell you how developed you are. I say this for two reasons:
A.) MBTI is ill equipt to give accurate reads on how strong each individual function is.
B.) It doesn't matter how many questions you answer, you cannot quantify the psyche.
So either you are going to have to recognize it in yourself, or I suppose have someone else recognize it for you. Being able to utilize all of your functions will not make you an Effective XXXX type. The hierarchy of functions will always exists, and it is really that which defines what type you are, not how well developed each individual function is. For instance, I have pretty well developed Fe for an INTP, but it is still by far my most draining function for me. On top of that, it still has the lowest priority of use, I'll never be able to use Fe like an ESFJ uses Fe, because my Fe is meant to serve as a slave to my Ti. Ti (In favor of Ne) calls the shots, Ti creates our sense of identity, and Ti is the source of our energy, this is always constant. This is what makes Me, you, and every other INTP, an INTP.
