Here's a possible clue to F or T preference we should look at. In daily annoyances, including in our interaction here, how do you tend to judge people? Or what is the kneejerk judgment you make? "Stupid", "dumb", "silly", etc.? Or is it more along the lines of ethics? Like maybe "inappropriate", "bad person", etc. I'm not even sure of kneejerk F judgments. Maybe they don't even come out like that. Or maybe it comes across as questioning the value/worth of things (rather than the people who make them like T tends to go after)?
I say kneejerk, because it is often hard to sort out T/F by conventional means, such as "how you make your decisions". It is often ambiguous. or both are even involved, and it is hard to tell what the actual preference is. However, in a more kneejerk response, your true primary mode of judgment is likely what comes up, almost unconsciously. You don't have time to consult the other processes.
Now, it can't be a too much stressed out reaction, as the more stressed out it is, the further down you will go in the processes. But a normal quick judgment will most likely reflect the true preference.
I had noticed I always tend to think what people do is stupid, dumb, etc. I don't usually think "bad" immoral, etc. (I did when a child, and stuff like cursing, or smoking/drinking, etc were said to be "bad" when kids did it, so then I saw such kids as "bad". When I grew up, I began, on my own thinking, developing a more relativistic morality until becoming Christian, and even then, I thought many were judging others too self-righteously, and when someone did something I didn't like; I would not label them "bad". When others did things that really disturbed me, like some teachings in other schisms of the church, which placed some sort of burden on us, I would always attack it with logical analysis).
So how do others tend to react? Do you find it matches your T/F preference? And those unsure of T/F, do you think this idea might work as a possible clue?