I guess since I have the "deep" thinking function and not the "deep" intuitive function, I feel compelled to go Ti nitpicky here and say that Ni doesn't do critical thinking; it does extremely uncritical intuiting. Ni doms have always struck me as people who are so open-minded that their minds seem liable to fall out at any moment.
This can result in really effective critical thinking when paired properly with Judging functions, but on its own it doesn't do this. I think you kind of generally overestimate how much can attributed to Ni on its own because you really like being dominant in the dominant function most correlated with giftedness...which is fair enough, but you kind of unwittingly promote the popular misperception of Ni as some kind of superpower meta-function, etc. when you approach it this way.
I also think your Ni and Te are generally so well integrated that you don't know how to separate them, which is another example of why Ni doesn't really do critical thinking any more than any other Perception function. It's not programmed for that because too much critical thinking makes Ni feel cramped and unable consider interpretive angles that aren't necessarily logically consistent with themselves. Seriously, pure Ni on its own interprets critical thinking as too limiting. Even adding the inherent judgment associated with critical thinking is already moving out of the realm of what Perception functions can do on their own.
What you're referring to from your self-experience and experience with other INTJs is a smooth combination of Ni and Te that you seem to continually misinterpret as just Ni being some meta-superfunction on its own. The critical thinking part kinda has to at least partially involve the, y'know, Thinking function.
Yeah, I mean, I pretty much agree with all this.
[MENTION=9811]Coriolis[/MENTION] said it before, and I didn't respond, but I agree with pretty much everything she said.
Ni, as I have said here many times, has to be "pared down" by a judging function (and preferably a Je one).
So, yeah, without that, it can lose any and all objectivity, and, well, that's not really good for critical thinking.
But, that being said, I said what I said - albeit, imprecisely - for a reason.
See, in the NiTe combination, Ni does the majority of the critical thinking (at least for me).
I'd say it's responsible for something like 80% of my critical thinking.
Now, obviously, I'm an Ni dom, so maybe that explains why it's so high, but...
If you listen to ENTJs talk about their aux Ni, they often sound like they're saying the same thing.
Like, it's the Ni that serves the function of doing what we might call NiTe/TeNi-styled critical thinking.
[MENTION=857]FDG[/MENTION] mentioned it above when he answered Ti and Ni, and said Ni does "skeptical investigation".
See, the way Ni does critical thinking: it basically bends the mind around the concepts.
Imagine concepts were physical things that existed on their own plane.
Ni is like, it's like the silver time travel stuff from Donnie Darko.
It sorta snakes around, peers around the corners of walls, etc.
Now, the peering around the corners: that's Ni's form of a logical deduction.
It does so differently than, let's say, Ti though.
It does the "logical deduction" by peering around the conceptual corner to see what's there.
Upon observing, it "knows" what's there, and proceeds accordingly.
Now, granted, Te plays a role there (as does Se, et al).
But that whole moving thru conceptual space, that's Ni.
And that is the majority of what's going on in that action.
Now, as I said before, granted, I am an INTJ.
I have checked with an ENTJ on this, and, as suspected, that description was sorta beyond him.
He doesn't have that much Ni, and as such, that whole conceptual plane of existence was foreign to him.
For him, Ni is basically this function that figures shit out for his Te imperatives and what not.
Like, he's Teing 80% of the time, or whatever, but then will run into a roadblock.
That's when he'll use Ni, to figure out how to get around that roadblock.
Or to see the roadblock be for it got there, etc.
So there's this function that Ni serves, whether it's NiTe or TeNi cognition.
It seems to be a bit different for each, but it does seem to revolve around problem-solving.
Like, when the solution needs to be found, Ni is the thing that is breaking ground, finding the novel way of looking at things, in order to solve whatever problem, or question, that has come up.
Which corroborates well with Dario Nardi's research about Ni doms: that, for whatever reason, their brains seem to go into a state of flow when they are attempting to solve a novel problem with which they are unfamiliar; whereas other types only really experience this same state of flow when they are doing something they are very familiar with.
I mean, that's a very interesting observation.
It basically seems to be saying that Ni's primary domain is in figuring out and solving novel, not previously seen problems and questions.
And that squares pretty well with what one would imagine Ni's primary function should be: figuring out novel ("Aha!") solutions.
(Btw, I hate that whole "Aha!" moment - Ni connection thing. I know why it's there, but it's just so shallow a take on it.)
Anyway, obviously I'm then associating this novel problem-solving/question-considering with critical thinking.
Which is fine, cuz that kind of cognition should indeed be highly associated with critical thinking.
But Te is inherently, as Coriolis pointed to, and as I have before, wrapped up in the whole thing.
It would look different coming from an INFJ.
And, obviously, this NiTe/TeNi-styled critical thinking is not the only form of critical thinking.
Obviously, all functions can be used to engage in critical thinking.
But that answer is so obvious and boring, it doesn't really get us anywhere interesting.
The question asked which cognitive function is
most associated with critical thinking.
Now, cognitive functions, imo, don't tend to work solely by themselves.
Perhaps they can and do to some extent.
But I tend to think of them as working in pairs (or sometimes more).
And usually as one Perceiving function, and one Judging function.
So NiTe, TiNe, FiNe, TeNi, NeTi, NeFi, etc.
So, in light of that, since I don't think Ti acts alone (usually), nor Fi...
But I was going to be answering for each function acting
as if it did...
I just threw out the ones that I think most contribute to critical thinking, in and of themselves.
I said Ti, Fi, Ni, and Ne.
Notice, I did not say Te.
And it's not cuz I don't think it doesn't aid in critical thinking.
And, maybe, in its way, it does so just as much as these others (perhaps it and Ne are closer to one another, in this regard).
But I was kinda just throwin shit out there that sorta makes sense to me, not setting by-laws of how this shit necessarily works.
Rarely do I explain anywhere close to my entire thinking on a matter, cuz doing so just takes too much time (I'd say I rarely explain more than 20%).
But see, that other 80%, the part of the iceberg under the water... most all of that is Ni.
Granted, it might have a Te flavor (or veneer, or coating, if you will).
But Ni is the primary engine comin up with all that shit.
It's peakin around conceptual corners, zooming in and out, going 50,000 feet up, then comin back down within an inch of the object of observation (I.e., the concept being examined) and examining the finer details.
All of this is mostly unseen by those looking at an Ni dom.
But it is what we're doing when we go into that weird state y'all see where it seems like we're no longer really there.
The purpose of this state is to do those inner conceptual landscape mental gymnastics in order to come to understand, to accurately/properly "see" what it is that's in front of us, what it is we're dealing with.
And, considering we do this a lot, and I think it's actually a pretty effective method of figuring shit out purely via thinking about it...
I figured I'd say "hell, it's Ni", rep a few other functions I think also do a good job at critical thinking (albeit in different ways), and see where the thread might take us.
All things considered, I do actually think that what [MENTION=10654]Noon[/MENTION] said hit the bullseye most accurately.
"Any function can fly or fail, depending on the intelligence of the individual."
(Sorry if that's not a perfect rendition; I'm paraphrasing, and on my phone)
Anyway, I think that hits the nail on the head, but, unsurprisingly, the functions (in combination, especially, for the INPs [TiSe/SeTi and FiSe/SeFi are not]) I mentioned also happen to be those most correlated with intelligence (as measured via IQ/giftedness).
As for your last line, as you already know well, these are all cognitive functions.
I considered whether a thinking function would be necessary for critical thinking.
But I think going down that path would, ironically, lead you to some erroneous thinking.
There's some NiTe critical thinking for ya.
<- I seriously haven't done that for years; couldn't help myself; for old time's sake 
I like that concept a lot. I'd like to think I have the capability to fix everything.. maybe it truly is that I pick and choose skills vs not actually taking the time to find out what I am truly incapable of.. But patience is a big part of the equation either way.
