I was very quiet as a child.
I watched people carefully, to figure them out, not interacting... just observing.
I explored my world thoroughly, always wanting to see what was around the bend, so I could understand how it worked. (And I would play around with things to figure it out.)
I read voraciously, bringing home shopping bags of books weekly. Went through the whole local library, basically.
Fascinated by processes, by the concepts underlying mechanical behavior. I loved Wile E. Coyote cartoons, and the Mousetrap game, and any sort of "systematic behavior" -- I wanted to see how it all worked together to result in a particular outcome. This eventually spilled out into more "human-oriented" systems ... like culture, religion, philosophy, psychology, etc... systems with more ambiguity.
I loved critiquing things -- movies, books, ideas, behavior (judging people by their spoken values versus their actual behavior), religious systems, etc.
The drive/focus towards all that was pretty much instinctive, not learned. It's what I did naturally.
So no, I don't think being an INTP is a choice; we're damned from birth.