[Caveat: The below is a reflection of my Ni running crazy with ideas and creating connections that might or might not be there. So take it as a grain of salt; these are just my opinions. My choice of words is intuitive and arbitrary and does not reflect any canonical source.]
So, Ni-doms are able to create characters in their mind, and then
flawlessly take on that character in the real world, to such a high
degree that any observer would think that they are in fact really
like that.
Would you say that other types are unable to do this and that this
behaviour therefore indicates that one has strong Ni? Or can other
types achieve a similar sort of thing, as far as an observer can tell,
but with the construction of the character being different?
I'm sure other types are
able to do this, but Ni-doms are most
likely to do it.
My sense is that it has to do with the nature of Intuition. The dominant function is one we associate with the most, and therefore, it is reasonable to call it the strongest indicator of our "Identity". If we take this to be true, then Feeling and Thinking dominant persons are most likely to be stable and consistent with their Identity, as the judging preference would have the strongest pull over their overall personality. Even as they develop their lower functions, their priorities ultimately remain the same, as the lower functions are shaped according to the dominant functions. The "sense of self" is easy to see and measure.
With Perceiving functions, it is a little different. My understanding is that Sensing has to do with experience of the concrete, and so I'm guessing, Sensing dominants would have their Identity associated with their experiences and their environments. As they develop further, they let themselves be swayed by what they experience and what they see, feel, sense, etc. Again, the "sense of self" is measured by the experiences the person has had.
Compared to these, Intuition is almost alien. Intuition dominants associate with the connections, abstractions and patterns
behind the concrete world, which makes them slightly detached from the concrete reality. Pair it with Introversion, and you have a function that is set up for complete disassociation from the external world.
This, I reckon, makes Ni-doms most
likely to be able to switch between different personae, and find it least troublesome to method-act, because their dominant function doesn't have an pull that pertains to external or concrete details over their Identity. The pull exists, but it is very internal, and pertains to
ideals (e.g. in my case, symmetry, design, conclusions). So Ni-doms seek to fulfill these ideals, ultimately, while letting their lower functions (Fe/Te, Fi/Ti, Se) help the individual reach the dominant function's agenda.
For that matter, it's not necessarily that
all Ni-doms method act, it's just they are more likely to do it, for any number of reasons. It's the kind of thing Louis CK (INFJ) does in his comedy; he pushes people. He purposely says mean and ugly things, just to make a point. However, you can tell he's a genuinely nice person and isn't evil or racist or any number of adjectives you can describe him as. Same with Bill Hicks (INxJ), Norm Macdonald (INxJ), et al. [I have similar examples of some members here, but I'm not sure if I can post them with their consent].
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Another perspective to this is that Intuition is the least likely function to get validation from the external world, so Intuition dominant types often create personas to better "fit in".
It may however be the case that it is the Ni's alone who are able to
completely create the image of a character and take it on, essentially
becoming Ali G. What are the implications of this? Does this mean
that the best method actors are of these types? Are the best authors
- or at least, the ones best at creating complete characters, and then
playing out their interaction in achieving the goal of the story - also
going to be Ni's?
I'm not sure the sample size is adequate to make these assumptions, but theoretically, yes. Although I'm sure other types can achieve results of the same artistic merit, but with completely different methods of operation.