I noticed something very interesting about these two types, and pretty much and two types separated only be the difference between extraversion and introversion. Even before I knew about mbti, I recognized that my ability to behave as an extravert and move through conversations and social interaction effectively pretty much hinged on my intuition (my ability to come up with appropriate responses to the group I'm with, toward eliciting a desired response out of them). I recognized my ability to be outgoing was very much dependent on how well I could pull subject matter out of a hat in such a way that will increase my popularity and standing in the group, vs. taking the time to think about everything I do and say beforehand.
Well apparently, that is the correct and natural approach toward extroversion for the NTP's. Looking at the INTP and ENTP, the difference is only in whether their judging or perceiving functions are dominant, with the other being secondary. For INTP's, we use our introverted thinking as the primary function, to contemplate the world within our own minds. Extraverted intuition is our secondary function, and the function we use in the domain of the outer world. That is primarily what extroversion is played through.
ENTP's have the same two functions, introverted thinking and extraverted intution, except extraverted intuition is their primary mode of functioning while introverted thinking is secondary. So it would seem that the differences between E's and I's CAN be quite small (there are other differences to consider as well). I just thought it was interesting that it was noticeable without actually knowing the MBTI mechanics. Since the difference between the E's and I's of the same type has much to do with which of their functions takes the lead, and is thus more developed, then for one to switch between the two could really be as simple as recognizing the difference between those two functions, and choosing one to use consciously and develop. I'm sure most people here already know what I've mentioned, but what are your thoughts?